Wow, I did not realize that SSH did that. Good to know, and it makes sense as a default, because the people who need it need to have it on by default. But I think I'm going to be turning that off, because it's a security measure that doesn't make sense for my particular environment:
1) I'm pretty much never typing secrets into an SSH tunnel; these days if there's a secret I need to transmit over SSH I'm going to be copying and pasting it, which will not reveal info from keyboard timing. (Or rsync'ing a file, which ditto).
2) I'm not in a high-security environment where nation-states have an interest in sniffing my keystrokes.
3) I often open SSH connections to servers in other continents. Those underwater cables have massive bandwidth, but they're also in constant use by thousands upon thousands of people. So anything I can do to reduce my bandwidth by 100x is probably worth doing.
Any reason you can think of why I should not be setting ObscureKeystrokeTiming=no in my ~/.ssh/config?
> Obviously forking go’s crypto library is a little scary, and I’m gonna have to do some thinking about how to maintain my little patch in a safe way
This should really be upstreamed as an option on the ssh library. Its good to default to sending chaff in untrusted environments, but there are plenty of places where we might as well save the bandwidth
I come from a world (yesteryear) where a computer had 1KB of RAM (ZX80). I've used links with modems rocking 1200 bps (1200 bits per second). I recall US Robotics modems getting to speeds of 56K - well that was mostly a fib worse than MS doing QA these days. Ooh I could chat with some bloke from Novell on Compuserve.
In 1994ish I was asked to look into this fancy new world wide web thing on the internet. I was working at a UK military college as an IT bod, I was 24. I had a Windows 3.1 PC. I telnetted into a local VAX, then onto the X25 PAD. I used JANET to get to somewhere in the US (NIST) and from there to Switzerland to where this www thing started off. I was using telnet and WAIS and Gopher and then I was apparently using something called "www".
I described this www thing as "a bit wank", which shows what a visionary I am!
Fellow old here, I had several 56k baud modems but even my USR (the best of the bunch) never got more than half way to 56k throughput. Took forever to download shit over BBS...
Yes, because at that time, a modem didn't actually talk to a modem over a switched analog line. Instead, line cards digitized the analog phone signal, the digital stream was then routed through the telecom network, and the converted back to analog. So the analog path was actually two short segments. The line cards digitized at 8kHz (enough for 4kHz analog bandwidth), using a logarithmic mapping (u-law? a-law?), and they managed to get 7 bits reliably through the two conversions.
ISDN essentially moved that line card into the consumer's phone. So ISDN "modems" talked directly digital, and got to 64kbit/s.
In case anyone else is curious, since this is something I was always confused about until I looked it up just now:
"Baud rate" refers to the symbol rate, that is the number of pulses of the analog signal per second. A signal that has two voltage states can convey two bits of information per symbol.
"Bit rate" refers to the amount of digital data conveyed. If there are two states per symbol, then the baud rate and bit rate are equivalent. 56K modems used 7 bits per symbol, so the bit rate was 7x the baud rate.
It sort of already is. This behavior is only applied to sessions with a TTY and then the client can disable it, which is a sensible default. This specific use case is tripping it up obviously since the server knows ahead of time that the connection is not important enough to obfuscate and this isn't a typical terminal session, but in almost any other scenario there is no way to make that determination and the client expects its ObscureKeystrokeTiming to be honored.
What's a concrete threat model here? If you're sending data to an ssh server, you already need to trust that it's handling your input responsibly. What's the scenario where it's fine that the client doesn't know if the server is using pastebin for backing up session dumps, but it's problematic that the server tells the client that it's not accepting a certain timing obfuscation technique?
The behavior exists to prevent a 3rd party from inferring keystrokes from active terminal sessions, which is surprisingly easy, particularly with knowledge about the user's typing speed, keyboard type, etc. The old CIA TEMPEST stuff used to make good guesses at keystrokes from the timing of AC power circuit draws for typewriters and real terminals. Someone with a laser and a nearby window can measure the vibrations in the glass from the sound of a keyboard. The problem is real and has been an OPSEC sort of consideration for a long time.
The client and server themselves obviously know the contents of the communications anyway, but the client option (and default behavior) expects this protection against someone that can capture network traffic in between. If there was some server side option they'd probably also want to include some sort of warning message that the option was requested but not honored, etc.
Yes, but I wouldn't be surprised if the change is rejected. The crypto library is very opinionated, you're also not allowed to configure the order of TLS cipher suites, for example.
Threats exist in both trusted and untrusted environments though.
This feels like a really niche use case for SSH. Exposing this more broadly could lead to set-it-and-forget-it scenarios and ultimately make someone less secure.
+1... Given how much SSH is used for computer-to-computer communication it seems like there really should be a way to disable this when it isn't necessary.
In practice I've never felt this was an issue. But I can see how with extremely low bandwidth devices it might be, for instance LoRa over a 40 km link into some embedded device.
Once upon a time I worked on a project where we SSH'd into a satellite for debugging and updates via your standard electronics hobbiest-tier 915mhz radio. Performance was not great but it worked and was cheap.
I haven't heard much about the ArduCopter (and ArduPilot) projects for a decade, are those projects still at it? I used to run a quadroter I made myself a while back until I crashed it in a tree and decided to find cheaper hobbies...
Well at least crashing drones into trees has never been cheaper hahaha. So it's super easy to get into nowadays, especially if it's just to play around with flight systems instead of going for pure performance.
Because TCP interprets packet loss as congestion and slows down. If you're already on a slow, lossy wireless link, bandwidth can rapidly fall below the usability threshold. After decades of DARPA attending IETF meetings to find solutions for this exact problem [turns out there were a lot of V4 connections over microwave links in Iraq] there are somewhat standard ways of setting options on sockets to tell the OS to consider packet loss as packet loss and to avoid slowing down as quickly. But you have to know what these options are, and I'm pretty sure the OP's requirement of having `ssh foo.com` just work be complicated by TCP implementations defaulting to the "packet loss means congestion" behavior. Hmm... now that I think about it, I'm not even sure if the control plane options were integrated into the Linux kernel (or Mac or Wintel)
Very interesting, I hadn't heard of this obfuscation before so it was well worth clicking.
Another good trick for debugging ssh's exact behavior is patching in "None" cipher support for your test environment. It's about the same work as trying to set up a proxy but lets you see the raw content of the packets like it was telnet.
For terminal games where security does not matter but performance and scale does, just offering telnet in the first place can also be worth consideration.
I don't see how Claude helped the debugging at all. It seemed like the author knew what to do and it was more telling Claude to think about that.
I've used Claude a bit and it never speaks to me like that either, "Holy Cow!" etc. It sounds more annoying than interacting with real people. Perhaps AIs are good at sensing personalities from input text and doesn't act this way with my terse prompts..
Even if the chatbot served only as a Rubber Ducky [1], that's already valuable.
I've used Claude for debugging system behavior, and I kind of agree with the author. While Claude isn't always directly helpful (hallucinations remain, or at least outdated information), it helps me 1) spell out my understanding of the system (see [1]) and 2) help me keep momentum by supplying tasks.
A rubber ducky demands that you think about your own questions, rather than taking a mental back seat as you get pummeled with information that may or may not be relevant.
I assure you that if you rubber duck at another engineer that doesn't understand what you're doing, you will also be pummeled with information that may or may not be relevant. ;)
AIs are exceptional at sensing personalities from text. Claude nailed it here, the author felt so good about the "holy cow" comments that he even included them in the blog post. I'm not just poking this, but saying that the bots are fantastic sycophants.
3. If you uncork the socket, or if the buffer hits MSS, the kernel sends the packet
Basically, the kernel waits until it has a full packet worth of data, or until you say you don't have any more data to send, and then it sends. Sort of an extreme TCP_YESDELAY.
Oh wow - I've never heard of TCP_CORK before. Without disabling pings I'd still pay the cost of receiving way more packets, but maybe that'd be tolerable if I didn't have to send so many pongs. This is super handy; excited to play around with it.
I am aware of TCP_NODELAY (funny enough I recently posted about TCP_NODELAY to HN[1] when I was thinking about it for the same game that I wrote about here). But I think the latency hit from disabling it just doesn't work for me.
I missed that thread originally, the post and the comments where a good read, thank you for sharing.
I got a kick out of this comment [0]. "BenjiWiebe" made a comment about the SSH packets you stumbled across in that thread. Obviously making the connection between what you were seeing in your game and this random off-hand comment would be insane (if you had seen the comment at all), but I got a smile out of it.
Can you explain how TCP_CORK helps here? The chaff packets are spaced 20ms apart and sent per socket, so I don’t see how TCP_CORK could help unless it coalesced across 20ms intervals? But coalescing is clearly not an option for the intended obfuscation effect of the original feature.
The reliance on LLMs is unfortunate. I bet this mystery could gave been solved much quicker by simply looking at the packet capture in Wireshark. The Wireshark dissectors are quite mature, SSH is covered fairly well.
> I bet this mystery could gave been solved much quicker by simply looking at the packet capture in Wireshark.
For some people who are used to using Wireshark and who know what to look for, probably yes. For the vast majority of even technical people, probably not.
In my case, I did a packet capture of a single keystroke using tcpdump and imported it into Wireshark and I get just over 200 'Client: encrypted packet' and 'Server: encrypted packet' entries. Nothing useful there at all. If I tcpdump the entire SSH connection setup from scratch I get just as much useful information - nothing - but, oddly, fewer packets than my one keystroke triggered.
So yeah, I dislike LLMs entirely and dislike the reliance on LLMs that we see today, but in this case the author learned a lot of interesting stuff and shared it with us, whereas without LLMs he might have just shrugged and moved on.
And thats a huge downside when people howl about "Encryption everywhere! ".
Try debugging that shit. Thats right, debugging interfaces aren't safe, by some wellakshually security goon.
You want a real fun one to debug, is a SAML login to a webapp, with internal Oauth passthrough between multiple servers. Sure, I can decrypt client-server stuff with tools, but server-server is damn near impossible. The tools that work break SSL, and invalidate validation of the ssl.
I used to share that opinion but after decades in industrial automation I find myself coming down much more on the "yeah, encryption everywhere" because while many vendors do not provide good tools for debugging, that's really the problem, and we've been covering for them by being able to snoop the traffic.
Having to MITM a connection to snoop it is annoying, but the alternative appears to be still using unencrypted protocols from the 1970s within the limitations of a 6502 to operate life-safety equipment.
Sounds like blaming a tool on a problem it did not cause. Either way, solvable and encryption is important. Badly designed systems and or lack of tooling isn't really an encryption problem.
Anyway, VMs should not have authentication, it makes access sooo much easier. Also drop your IPs while you're at it. Might be useful for debugging later.
Unfortunately with SSH specifically, the dissectors aren't very mature - you only get valid parsing up to the KeX completion messages (NEWKEYS), and after that, even if the encryption is set to `none` via custom patches, the rest of the message flow is not parsed.
Seems because dumping the session keys is not at all a common thing. It's just a matter of effort though - if someone put in the time to improve the SSH story for dissectors, most of the groundwork is there.
Interesting, I thought it was possible to decrypt SSH in Wireshark a la TLS, but it seems I'm mistaken. It still would have been my first goto, likely with encryption patched out as you stated. With well documented protocols, it's generally not too difficult deciphering the raw interior bits as needed with the orientation provided by the dissected pieces. So let me revise my statement: this probably would have been a fairly easy task with protocol analysis guided code review (or simply CR alone).
My thoughts exactly. The OP used AI to get a starting point to their investigation, then used their skills to improve their game, with actual (I guess according to the article itself) proof of that, as opposed to just approving changes from the LLM.
This looks like an actual productivity boost with AI.
Not even remotely accurate. While the dissector is not as mature as I thought and there's no built-in decryption as there is for TLS, that doesn't matter much. Hint: every component of the system is attacker controlled in this scenario.
>Is that because wireshark can't do that just from packet captures?
Well, not quite. I think it's more that nobody has taken the time to implement it. That's not to say such an implementation would automatically decrypt the traffic from a capture with no extra leg work, of course. Wireshark dissectors have user configurable preferences, and presumably this would be where captured secrets could be set for use. This is how it handles TLS decryption [1], which works beautifully.
obviously OPs empirical and analytical rigor are top notch. He applied LLMs in the best way possible: fill gaps with clumsy command line flags or protocol implementations. Those aren't things one needs to keep in their head all the time.
Well, I spent a good part of my career reverse engineering network protocols for the purpose of developing exploits against closed source software, so I'm pretty sure I could do this quickly. Not that it matters unless you're going to pay me.
What are you even trying to say? I suppose I'll clarify for you: Yes, I'm confident I could have identified the cause of the mysterious packets quickly. No, I'm not going to go through the motions because I have no particular inclination toward the work outside of banter on the internet. And what's more, it would be contrived since the answer has already shared.
I think the point they're making is that "I, a seasoned network security and red-team-type person, could have done this in Wireshark without AI assistance" is neither surprising nor interesting.
That'd be like saying "I, an emergency room doctor, do not need AI assistance to interpret an EKG"
Sure, but that is aside from my original point. If somebody:
a) Has the knowledge to run tcpdump or similar from the command line
b) Has the ambition to document and publish their effort on the internet
c) Has the ability identify and patch the target behaviors in code
I argue that, had they not run to an LLM, they likely would have solved this problem more efficiently, and would have learned more along the way. Forgive me for being so critical, but the LLM use here simply comes off as lazy. And not lazy in a good efficiency amplifying way, but lazy in a sloppy way. Ultimately this person achieved their goal, but this is a pattern I am seeing on a daily basis at this point, and I worry that heavy LLM users will see their skill sets stagnate and likely atrophy.
I'm still waiting for a systems engineering tool that can log every layer, and handle SSL the whole pipe wide.
Im covering everything from strafe and ltrace on the machine, file reads, IO profiling, bandwidth profiling. Like, the whole thing, from beginning to end.
Real talk though, how much would such a tool be worth to you? Would you pay, say, $3,000/license/year for it? Or, after someone puts in the work to develop it, would you wait for someone else to duct tape something together approximately similar enough using regexps that open source but 10% as good, and then not pay for the good proprietary tool because we're all a bunch of cheap bastards?
We have only ourselves to blame that there aren't better tools (publicly) available. If I hypothetically (really!) had such a tool, it would be an advantage over every other SRE out there that could use it. Trying to sell it directly comes with more headaches than money, selling it to corporations has different headaches, open-sourcing it don't pay the bills, nevermind the burnout (people don't donate for shit). So the way to do it is make a pitch deck, get VC funding so you're able to pay rent until it gets acquired by Oracle/RedHat/IBM (aka the greatest hits for Linux tool acquisition), or try and charge money for it when you run out of VC funding, leading to accusations of "rug pull" and development of alternatives (see also: docker) just to spite you.
In the base case you sell Hashimoto and your bank account has two (three!) commas, but worst case you don't make rent and go homeless when instead you could've gone to a FAANG and made $250k/yr instead of getting paid $50k/yr as the founder and burning VC cash and eating ramen that you have to make yourself.
I agree, that would be an awesome tool! Best case scenario, a company pays for that tool to be developed internally, the company goes under, it gets sold as an asset and whomever buys it forms a compnay and tries to sell it directly and then that company goes under but that whomever finally open sources it because they don't want it to slip into obscurity but if falls into obscurity anyway because it only works on Linux 5.x kernels and can't be ported to the 6.x series that we're on now easily.
Or you could use anycasting to terminate SSH sessions on the moral equivalent of one of a number of geography based reverse proxies and then forward the packet over an internal network to the app server over a link tuned for low latency. The big guys already do something similar with HTTP over TLS for DDoS protection and to limit end to end latency on TLS.
Granted... it would increase the cost (since you're adding reverse proxies) but it would be a quick way to get acceptable latency, rudimentary DDoS protection, and you could try different connection options independent of the main app's logic.
It would be hard to estimate how much latency you're adding with a SSH2 reverse proxy in this case, but it's probably lower than one might think.
The idea of letting Claude loose on my crypto[graphy] implementation is about the most frightening thing I've heard of in a while [though libnss is so craptastic, I can't see how it would hurt in that case.] But I loved this write-up. It was readable and explained the problem the OP was encountering and proposed solutions well.
> Or you could use anycasting to terminate SSH sessions on the moral equivalent of one of a number of geography based reverse proxies and then forward the packet over an internal network to the app server over a link tuned for low latency.
I've been thinking about some stuff like this! Not being able to put my game behind Cloudflare[1] is a bummer. Substantial architectural overhead though.
> The idea of letting Claude loose on my crypto[graphy] implementation is about the most frightening thing I've heard of in a while [though libnss is so craptastic, I can't see how it would hurt in that case.]
I hear you, but FWIW the patch I was reverting was trivial (and it's also in the go crypto library, which is pretty easy to read). It's a couple-of-line change[2], and Claude did almost exactly what I would have done (I was tired and would have forgotten to shrink the handshake payload).
[1] This isn't strictly true, Cloudflare spectrum exists, but its pricing is an insane $1/GB last I checked.
Funny to see this fixed in 2023 and the side effects. Back in 2004, before I focused on performance, I did some security work including inter-keystroke latency analysis of captured SSH sessions to estimate the commands typed:
In 2023, ssh added keystroke timing obfuscation. The idea is that the speed at which you type different letters betrays some information about which letters you’re typing. So ssh sends lots of “chaff” packets along with your keystrokes to make it hard for an attacker to determine when you’re actually entering keys.
Now that's solving the problem the wrong way. If you really want that, send all typed characters at 50ms intervals, to bound the timing resolution.
Wouldn't this just change the packet interval from 20ms to 50ms? Or did you mean a constant stream of packets at 50ms intervals, nonstop?
I think the idea behind the current implementation is that the keystrokes are batched in 20ms intervals, with the optimization that a sufficiently long silence stops the chaff stream, so the keystroke timing is obfucated with an increased error bar of 20ms multiplied by number of chaff packets.
I assume the problem, such as it is, relates to the fact that a real human typing in 20-50ms would generate a few characters at most but a program could generate gobs of data. So automatically you know what packets to watch. Then you know if there were more the likely keys were in set X, while if there were fewer the likely keys were in set Y.
So a clock doesn't solve the problem. The amount of data sent on each clock pulse also tells you something about what was sent.
The Chaff packets already fire on a timer. They inject random extra fake keystrokes so you can't tell how many keystrokes were actually made. The only other way I can think of to solve that is by using a step function: Send one larger packet (fragmented or the same number of individual packets) on each clock pulse if the actual data is less than some N where N is the maximum keystrokes ever recorded with some margin. Effectively almost every clock pulse will be one packet (or set of packets) of identical size. Of course if you do that then you'll end up consuming more data over time than sending random amounts of packets.
> That 20ms is a smoking gun - it lines up perfectly with the mysterious pattern we saw earlier!
Speaking of smoking guns, anybody else reckon Claude overuses that term a lot? Seems anytime I give it some debugging question, it'll claim some random thing like a version number or whatever, is a "smoking gun"
Yes! While this post was written entirely by me, I wouldn't be surprised if I had "smoking gun" ready to go because I spent so much time debugging with Claude last night.
Serious question though, since AI seems to be so all capable and intelligent. Why wouldn't it be able to tell you the exact reason that I could tell you just by reading the title of this post on HN? It is failing even at the one thing it could probably do decently, is being a search engine.
It's not just a coincidence, it's the emergence of spurious statistical correlations when observations happen across sessions rather than within sessions.
Or the "Eureka! That's not just a smoking gun, it's a classic case of LLMspeak."
Grok, ChatGPT, and Claude all have these tics, and even the pro versions will use their signature phrases multiple times in an answer. I have to wonder if it's deliberate, to make detecting AI easier?
Without knowing how LLM's personality tuning works, I'd just hazard a guess that the excitability (tendency to use excided phrases) is turned up. "smoking gun" must be highly rated as a term of excitability. This should apply to other phrases like "outstanding!" or "good find!" "You're right!" etc.
They love clichés, and hate repeating the same words for something (repetition penalty) so they'll say something like "cause" then it's a "smoking gun" then it's something else
You might see certain phrases and mdashes ;-) rather often, because … these programs are trained on data written by people (or Microsoft's spelling correction) which overused them in the last n years? So what should these poor LLMs generate instead?
smoking gun, you're absolutely right, good question, em dash, "it isn't just foo, it's also bar", real honest truth, brutal truth, underscores the issue, delves into, more em dashes, <20 different hr/corporate/cringe phrases>.
That's the point though, it doesn't reflect human usage of the word. If
delve were so commonly used by humans too, we wouldn't be discussing
how it's overused by LLMs.
Maybe we need a real AI which creates new phrases and teaches the poor LLMs?
Looking back we already had similar problems, when we had to ask our colleagues, students, whomever "Did you get your proposed solution from the answers part or the questions part of a stackoverflow article?" :-0
I seem to hit this logic often recently for some reason.
There are two issues with it:
- a primary is not a totality: if "security is the #1 consideration for SSH", that implies there's a #2, maybe even a #3 and so on consideration. So the question that follows becomes tautological: "but if the author doesn't need security, why use ssh?" -> surely for one or more of the #2, #3, etc. considerations, right?
- overabstraction (*): you ended up strawmanning the author. What they had issue with was keystroke timing obfuscation, which is a privacy feature. Timing attacks are (in part) a privacy concern, and privacy is a security concern, yes, but security is not just privacy concern, and privacy concerns are not just about timing attacks; these groups are not equal. For example, they might very well want the transmitted keypresses themselves to remain confidential, or they might very well want to retain cryptographic assurance of their integrity. These are security features they can continue to utilize by sticking with SSH.
All of this is to say, it's not even necessarily them using SSH for a hypothetical #2 or #3 (...etc...) reason, but likely because they still very much want to make use of large chunks of #1, which disabling keypress obfuscation does not actually rid SSH of, only at most weakens it in ways they clearly seem to be okay with.
(*) although if I zoom out enough, this is once again just "a primary is not a totality", just implicitly
> I am working on a high-performance game that runs over ssh.
Found your problem.
But it is an interesting world where you can casually burrow into a crypto library and disable important security features more easily than selecting the right network layer solution.
Yea UDP is technically more performant, but then you need a crypto layer + reliable message delivery layer + bespoke client. Using a plain old SSH client is cool.
its not really a question of 'udp performs better'. in tcp we have to live to head-of-line blocking on losses and congestion control. if you don't care about receiving every packet, but only the most recent, then udp is a good choice.
running without congestion control means that you avoid slowstart. but at a certain rate you run into poorly defined 'fairness' issues where you can easily negatively impact other flows. past that point, you can actually self-interfere and cause excessive losses for yourself.
quic uses congestion control, but uses latency estimates and variance as a signal to back off. it still imposes an ordering on a per-stream basis. so it might not be ideal either.
sctp has a mode which supports reliable and unordered, which might be something to consider
so really - if you care about latency and have a different reliability model, its worth unpacking all these considerations and using them to select your transport layer or even consider writing a minimal one yourself
Not related to SSH, but does the eieio.games website make anyone else's monitor flicker? When the website is fullscreen it overwhelms something. I thought my monitor's backlight was going.
The really mysterious part is how ~10,000 packets per second costs ~20% of a core. That would mean SSH is bottlenecking in its code at ~50,000 packets per second per core which would be ~500 Mbps per core (assuming full packets) which is ludicrously slow. It is trivial to do 10x that packet per second rate. Is SSH really that poorly designed?
I do not know where people get the idea that encryption is that slow. Standard AES hardware acceleration instructions do ~25 Gbps per core (on a 2023 CPU) which is ~50x that rate [1]. I have heard modern cores can do ~40-50 Gbps, but I have not been able to find any independent benchmarks of that. Even the Intel i5-2500, a CPU from 2011, averages ~10 Gbps which is ~20x that rate. Even unaccelerated encryption can do ~2-5 Gbps in pure software which is 4-10x the SSH rate.
And in this situation, the amount of encrypted payload in each packet is 36 bytes which is ~40x less than a full packet of ~1500 bytes. You would almost surely hit packet per second limits before you hit payload throughput limits at these small sizes.
Encryption is slow when compared to data throughput you can get with a properly designed transport stack, but that is because it is in comparison to 100 Gbps per core even with no hardware offload. Anything less than ~10 Gbps/1 million packets per second (ignoring other bottlenecks, so only the software transport is the limit) is not merely unoptimized, it is pessimized.
I wonder if this is the same reason why Microsoft's Remote SSH plugin on VS Code is so flaky even with a decent internet connection. Every couple of months I try to give it another go and give up due to the poor keyboard latency I inevitably experience. And the slow reconnects whenever I glance away from my computer monitor briefly. This is on a fiber connection with a 20ms ping to the remote machine.
You surely mean the latency in its embedded terminal and not the code editor, right? I use VSCode’s remote SSH specifically so that code editing doesn’t suck. It really does not.
> Keystroke obfuscation can be disabled client-side.
please never do that (in production)
if anyone half way serious tries they _will_ be able to break you encryption end find what you typed
this isn't a hypothetical niche case obfuscation mechanism, it's a people broke SSH then a fix was found case. I don't even know why you can disable it tbh.
That doesn't sound right to me. This obfuscation isn't about a side-channel on a crypto implementation, this is about literally when your keystrokes happen. In the right circumstances, keystroke timing can reduce the search space for bruteforcing a password [1] but it's overstating to describe that as broken encryption.
I'm baffled about this "security feature". Besides from this only being relevant to timing keystrokes during the SSH session, not while typing the SSH password, I really don't understand how can someone eavesdrop on this? They'd have to have access to the client or server shell (root?) in order to be able to get the keystrokes typing speed. I've also never heard of keystroke typing speed hacking/guessing keystrokes. The odds are very low IMO to get that right.
I'd be much more scared of someone literally watching me type on my computer, where you can see/record the keys being pressed.
Anyone who can spy on the network between the client and server can see the timing. This includes basically anyone on the same LAN as you, anyone who sets up a WiFi access point with a SSID you auto-connect to, anyone at your ISP or VPN provider, the NSA and god knows who else.
And the timing is still sensitive. [1] does suggest that it can be used to significantly narrow the possible passwords you have, which could lead to a compromise. Not only that, but timing can be sensitive in other ways --- it can lead to de-anonymization by correlating with other events, it can lead to profiling of what kind of activity you are doing over ssh.
So this does solve a potentially sensitive issue, it's just nuanced and not a complete security break.
It is to prevent timing attacks but there are many ssh use cases where it is 100% computer to computer communications where there is no key based timing attack possible.
- you are listening to an SSH session between devices
- and you know what protocol is being talked over the connection (i.e. what they are talking about)
- and the protocol is reasonably predictable
then you gain enough information about the plaintext to start extracting information about the cipher and keys.
It's a non-trivial attack by all means but it's totally feasible. Especially if there's some amount of observable state about the participants being leaked by a third party source (i.e. other services hosted by the participants involved in the same protocol).
this only works for manually typed text, not computer to computer communication where you can't deduce much from what is being "typed" as it's not typed but produced by a program to which every letter is the same and there is no different delay in sending some letters (as people have when typing by hand)
I agree it is more nuanced than a simple 'good for computer-to-computer' and 'bad for person-to-computer'. I'm sure there are cases where both are wrong but I don't think that necessarily changes that it makes a reasonable baseline heuristic.
I'd love to hear more about this kind of attack being exploited in the wild. I understand it's theoretically possible, but...good luck! :)
You're guessing a cipher key by guessing typed characters with the only information being number of packets sent and the time they were sent at. Good luck. :)
I haven't given this more than 5 seconds of thought, but wouldn't it make sense to only enable the timing attack prevention for pseudo-terminal sessions (-t)?
The fix seems kind of crazy though, adding so much traffic overhead to every ssh session. I assume there's a reason they didn't go that route, but on a first pass seems weird they didn't just buffer password strokes to be sent in one packet, or just add some artificial timing jitter to each keystroke.
I'm just guessing but this chaff sounds like it wouldn't actually change the latency or delivery of your actual keystrokes while buffering or jitter would.
So the "real" keystrokes are 100% the same but the fake ones which are never seen except as network packets are what is randomized.
Hey, if ECHELON snuck a listener into my house, where six devices hang out on a local router... Good for them, they're welcome to my TODO lists and vast collection of public-domain 1950s informational videos.
(I wouldn't recommend switching the option off for anything that could transit the Internet or be on a LAN with untrusted devices. I am one of those old sods who doesn't believe in the max-paranoia setting for things like "my own house," especially since if I dial that knob all the way up the point is moot; they've already compromised every individual device at the max-knob setting, so a timing attack on my SSH packet speed is a waste of effort).
And of course it totally doesn't work if the client doesn't have JavaScript at all. I read the HN front-page through an AI summary and it also got censored when it scraped the article.
One thing you notice if you have ADSL is that some services are built as if slower connections matter and others are not. Like Google's voice and audio chat services work poorly but most of the others work well. Uploading images to Mastodon, Bluesky, Facebook, LinkedIn, Instagram and Nextdoor is reliable, but for Tumblr you have to try it twice. I don't what they are doing wrong but they are doing something wrong and not finding out what they're doing wrong because they're not testing and they're not listening to users.
Nobody consulted me about their decision not to run fiber by my house. If some committee decides to make ssh bloated they are, together with the others, conspiring to steal my livelihood and I think it would be fair for me to sue them for the $50k it would take to run that fiber myself.
It's OK if you work for Google where there is limitless dark fiber but what about people in African countries?
It's the typical corporate attitude where latency never matters: Adobe thinks it is totally normal that it takes 1-5s for a keystroke to appear when you are typing into Dreamweaver.
I agree with your general point that most companies/projects do a terrible job optimizing for slow computers/networks, but OpenSSH is from the OpenBSD people, who are well-known for supporting ancient hardware [0]. Picking a random architecture, they fully support a system with only 64MB of memory [1], and the base install includes SSH. So I suspect that OpenSSH is fairly well tested on crappy computers/networks.
There's a good chance you have other options. Regardless of how you feel about the company's head, Starlink would probably be one of them, with likely better performance than you're dealing with on ADSL.
But you cannot just sue a company because their network connected software doesn't work well on slow networks. Let alone a project like OpenSSH. It would be like me suing a game studio because my PC doesn't meet their listed minimum requirements to play the game.
Hey, it is one thing to buy a new computer, it is another thing to ask people to move.
A better analogy is a bank redlining neighborhoods. The cost to run fiber to difficult rural locations pays itself easily if you look at a 25-year time span and is an order of magnitude less than building a new housing unit on the West Coast.
You just opened a huge nostalgia portal, never thought that Dreamweaver would still be around, I used that somewhere around 2003 I believe. Good memories
Frankly I wish there was an HTML editor that delivers on what it promised. I mean, markdown is almost as rife with edge cases as YAML and somehow the link syntax still eludes me. If we could “just” template by merging at the DOM level and had decent HTML editors the world would be a different place. But yeah, Adobe probably thinks Dreamweaver isn’t worth maintaining just as they seem to think Photoshop is barely worth maintaining (they keep adding AI features that sorta work but the foundations seem to be much worse than Illustrator)
>>> That makes a lot of sense for regular ssh sessions, where privacy is critical. But it’s a lot of overhead for an open-to-the-whole-internet game where latency is critical.
Switching to telnet instead of SSH might be an option.
> I am working on a high-performance game that runs over ssh.
Step one, run https://www.psc.edu/hpn-ssh-home/introduction/ instead
Step two, tune TCP/IP stack
Step... much later: write your own "crypto". (I'm using quotes because, before someone points out the obvious, packets-per-keystroke isn't, itself, a cryptographic algorithm, but because it's being done to protect connections from being decrypted/etc, mess with it at your own peril.)
Telnet nowadays typically isn’t available by default for security reasons, and OP wants people to be able to play the game just by typing “ssh thegamehost”.
Wow, I did not realize that SSH did that. Good to know, and it makes sense as a default, because the people who need it need to have it on by default. But I think I'm going to be turning that off, because it's a security measure that doesn't make sense for my particular environment:
1) I'm pretty much never typing secrets into an SSH tunnel; these days if there's a secret I need to transmit over SSH I'm going to be copying and pasting it, which will not reveal info from keyboard timing. (Or rsync'ing a file, which ditto).
2) I'm not in a high-security environment where nation-states have an interest in sniffing my keystrokes.
3) I often open SSH connections to servers in other continents. Those underwater cables have massive bandwidth, but they're also in constant use by thousands upon thousands of people. So anything I can do to reduce my bandwidth by 100x is probably worth doing.
Any reason you can think of why I should not be setting ObscureKeystrokeTiming=no in my ~/.ssh/config?
> Obviously forking go’s crypto library is a little scary, and I’m gonna have to do some thinking about how to maintain my little patch in a safe way
This should really be upstreamed as an option on the ssh library. Its good to default to sending chaff in untrusted environments, but there are plenty of places where we might as well save the bandwidth
"where we might as well save the bandwidth"
I come from a world (yesteryear) where a computer had 1KB of RAM (ZX80). I've used links with modems rocking 1200 bps (1200 bits per second). I recall US Robotics modems getting to speeds of 56K - well that was mostly a fib worse than MS doing QA these days. Ooh I could chat with some bloke from Novell on Compuserve.
In 1994ish I was asked to look into this fancy new world wide web thing on the internet. I was working at a UK military college as an IT bod, I was 24. I had a Windows 3.1 PC. I telnetted into a local VAX, then onto the X25 PAD. I used JANET to get to somewhere in the US (NIST) and from there to Switzerland to where this www thing started off. I was using telnet and WAIS and Gopher and then I was apparently using something called "www".
I described this www thing as "a bit wank", which shows what a visionary I am!
> I've used links with modems rocking 1200 bps
Yo, 300 baud, checking in.
Do I hear 110?
+++ATH0
Ah, the good old days. I remember dialing up local BBSes with QMODEM.
AT&C1&D2S36=7DT*70,,,5551212
Fellow old here, I had several 56k baud modems but even my USR (the best of the bunch) never got more than half way to 56k throughput. Took forever to download shit over BBS...
> several 56k baud modems
These were almost definitely 8k baud.
Yes, because at that time, a modem didn't actually talk to a modem over a switched analog line. Instead, line cards digitized the analog phone signal, the digital stream was then routed through the telecom network, and the converted back to analog. So the analog path was actually two short segments. The line cards digitized at 8kHz (enough for 4kHz analog bandwidth), using a logarithmic mapping (u-law? a-law?), and they managed to get 7 bits reliably through the two conversions.
ISDN essentially moved that line card into the consumer's phone. So ISDN "modems" talked directly digital, and got to 64kbit/s.
In case anyone else is curious, since this is something I was always confused about until I looked it up just now:
"Baud rate" refers to the symbol rate, that is the number of pulses of the analog signal per second. A signal that has two voltage states can convey two bits of information per symbol.
"Bit rate" refers to the amount of digital data conveyed. If there are two states per symbol, then the baud rate and bit rate are equivalent. 56K modems used 7 bits per symbol, so the bit rate was 7x the baud rate.
It sort of already is. This behavior is only applied to sessions with a TTY and then the client can disable it, which is a sensible default. This specific use case is tripping it up obviously since the server knows ahead of time that the connection is not important enough to obfuscate and this isn't a typical terminal session, but in almost any other scenario there is no way to make that determination and the client expects its ObscureKeystrokeTiming to be honored.
What's a concrete threat model here? If you're sending data to an ssh server, you already need to trust that it's handling your input responsibly. What's the scenario where it's fine that the client doesn't know if the server is using pastebin for backing up session dumps, but it's problematic that the server tells the client that it's not accepting a certain timing obfuscation technique?
The behavior exists to prevent a 3rd party from inferring keystrokes from active terminal sessions, which is surprisingly easy, particularly with knowledge about the user's typing speed, keyboard type, etc. The old CIA TEMPEST stuff used to make good guesses at keystrokes from the timing of AC power circuit draws for typewriters and real terminals. Someone with a laser and a nearby window can measure the vibrations in the glass from the sound of a keyboard. The problem is real and has been an OPSEC sort of consideration for a long time.
The client and server themselves obviously know the contents of the communications anyway, but the client option (and default behavior) expects this protection against someone that can capture network traffic in between. If there was some server side option they'd probably also want to include some sort of warning message that the option was requested but not honored, etc.
Yes, but I wouldn't be surprised if the change is rejected. The crypto library is very opinionated, you're also not allowed to configure the order of TLS cipher suites, for example.
Threats exist in both trusted and untrusted environments though.
This feels like a really niche use case for SSH. Exposing this more broadly could lead to set-it-and-forget-it scenarios and ultimately make someone less secure.
Resource-constrained environments might be niche to you, but they are not niche to the world.
+1... Given how much SSH is used for computer-to-computer communication it seems like there really should be a way to disable this when it isn't necessary.
It looks like it is only applied for PTY sessions, which most computer-computer connections wouldn't be using.
https://github.com/openssh/openssh-portable/blob/d7950aca8ea...
In practice I've never felt this was an issue. But I can see how with extremely low bandwidth devices it might be, for instance LoRa over a 40 km link into some embedded device.
Hah no.
Nobody is running TCP on that link, let alone SSH.
Once upon a time I worked on a project where we SSH'd into a satellite for debugging and updates via your standard electronics hobbiest-tier 915mhz radio. Performance was not great but it worked and was cheap.
This is still done today in the Arducopter community over similar radio links.
I haven't heard much about the ArduCopter (and ArduPilot) projects for a decade, are those projects still at it? I used to run a quadroter I made myself a while back until I crashed it in a tree and decided to find cheaper hobbies...
They're alive and well and producing some pretty impressive software.
Crashing your drone is a learning experience ;)
Remote NSH over Mavlink is interesting, your drone is flying and you are talking to the controller in real time. Just don't type 'reboot'!
Well at least crashing drones into trees has never been cheaper hahaha. So it's super easy to get into nowadays, especially if it's just to play around with flight systems instead of going for pure performance.
https://github.com/markqvist/Reticulum
and RNode would be a better match.
In aerial robotics, 900MHz telemetry links (like Microhard) are standard. And running SSH over them is common practice I guess.
what's wrong with tcp, on a crappy link, when guaranteed delivery is required? wasn't it invented when slow crappy links were the norm?
Because TCP interprets packet loss as congestion and slows down. If you're already on a slow, lossy wireless link, bandwidth can rapidly fall below the usability threshold. After decades of DARPA attending IETF meetings to find solutions for this exact problem [turns out there were a lot of V4 connections over microwave links in Iraq] there are somewhat standard ways of setting options on sockets to tell the OS to consider packet loss as packet loss and to avoid slowing down as quickly. But you have to know what these options are, and I'm pretty sure the OP's requirement of having `ssh foo.com` just work be complicated by TCP implementations defaulting to the "packet loss means congestion" behavior. Hmm... now that I think about it, I'm not even sure if the control plane options were integrated into the Linux kernel (or Mac or Wintel)
Life is difficult sometimes.
It will time out before your packet gets through, or it will retransmit faster than the link can send packets.
Very interesting, I hadn't heard of this obfuscation before so it was well worth clicking.
Another good trick for debugging ssh's exact behavior is patching in "None" cipher support for your test environment. It's about the same work as trying to set up a proxy but lets you see the raw content of the packets like it was telnet.
For terminal games where security does not matter but performance and scale does, just offering telnet in the first place can also be worth consideration.
It made the front page when it was added.
https://news.ycombinator.com/item?id=37307708
Not everyone sees the HN frontpage every day, and sometimes especially-esoteric things spend a fairly short timespan on there.
I don't see how Claude helped the debugging at all. It seemed like the author knew what to do and it was more telling Claude to think about that.
I've used Claude a bit and it never speaks to me like that either, "Holy Cow!" etc. It sounds more annoying than interacting with real people. Perhaps AIs are good at sensing personalities from input text and doesn't act this way with my terse prompts..
Even if the chatbot served only as a Rubber Ducky [1], that's already valuable.
I've used Claude for debugging system behavior, and I kind of agree with the author. While Claude isn't always directly helpful (hallucinations remain, or at least outdated information), it helps me 1) spell out my understanding of the system (see [1]) and 2) help me keep momentum by supplying tasks.
[1] https://en.wikipedia.org/wiki/Rubber_duck_debugging
A rubber ducky demands that you think about your own questions, rather than taking a mental back seat as you get pummeled with information that may or may not be relevant.
I assure you that if you rubber duck at another engineer that doesn't understand what you're doing, you will also be pummeled with information that may or may not be relevant. ;)
That isn't rubber duck debugging. It's just talking to someone about the problem.
The entire point of rubber duck debugging is that the other side literally cannot respond - it's an inanimate object, or even a literal duck/animal.
Oh it can definitely be a person. I've worked with a few!
I'm not saying you should do this, but you can do this:
https://gist.github.com/shmup/100a7529724cedfcda1276a65664dc...
Lol not bad
They also don’t waste electricity, water, drive up the prices of critical computer components, or DDOS websites to steal their content.
Not to defend the extravagant power use of the AI datacenters, but I invite you to look up the ecological footprint of a human being.
The human being in this scenario exists either way.
The AI does not.
Claude is much faster at extracting fields from a pcap and processing them with awk than I am!
Have you tried wireshark?
You’re absolutely right!
AIs are exceptional at sensing personalities from text. Claude nailed it here, the author felt so good about the "holy cow" comments that he even included them in the blog post. I'm not just poking this, but saying that the bots are fantastic sycophants.
No they aren't. Current LLMs always have that annoying over-eager tone.
The comment about Claude being pumped was a joke.
It depends how much the LLM has been beaten into submission by the system prompt.
ChatGPT set to "terse and professional" personality mode is refreshingly sparse on the "you're absolutely right" bullshit
It's like I keep saying, it probably wasn't a good idea to give our development tools Genuine People Personalities...
You can also use TCP_CORK to reduce the number of packets without any increased latency.
Disabling TCP_NODELAY would also reduce number of packets + be portable & simpler to implement - but would incur a latency penalty.
Haven't heard of TCP_CORK, very interesting.
For people who don't feel like googling it:
1. You TCP_CORK a socket
2. You put data into it and the kernel buffers it
3. If you uncork the socket, or if the buffer hits MSS, the kernel sends the packet
Basically, the kernel waits until it has a full packet worth of data, or until you say you don't have any more data to send, and then it sends. Sort of an extreme TCP_YESDELAY.
See https://catonmat.net/tcp-cork for where I learned it all from.
Oh wow - I've never heard of TCP_CORK before. Without disabling pings I'd still pay the cost of receiving way more packets, but maybe that'd be tolerable if I didn't have to send so many pongs. This is super handy; excited to play around with it.
I am aware of TCP_NODELAY (funny enough I recently posted about TCP_NODELAY to HN[1] when I was thinking about it for the same game that I wrote about here). But I think the latency hit from disabling it just doesn't work for me.
[1] https://news.ycombinator.com/item?id=46359120
I missed that thread originally, the post and the comments where a good read, thank you for sharing.
I got a kick out of this comment [0]. "BenjiWiebe" made a comment about the SSH packets you stumbled across in that thread. Obviously making the connection between what you were seeing in your game and this random off-hand comment would be insane (if you had seen the comment at all), but I got a smile out of it.
[0] https://news.ycombinator.com/item?id=46366291
wow, I missed that comment, that's an incredible connection. Thank you!
Can you explain how TCP_CORK helps here? The chaff packets are spaced 20ms apart and sent per socket, so I don’t see how TCP_CORK could help unless it coalesced across 20ms intervals? But coalescing is clearly not an option for the intended obfuscation effect of the original feature.
The reliance on LLMs is unfortunate. I bet this mystery could gave been solved much quicker by simply looking at the packet capture in Wireshark. The Wireshark dissectors are quite mature, SSH is covered fairly well.
I'm anti-LLM in most cases, but:
> I bet this mystery could gave been solved much quicker by simply looking at the packet capture in Wireshark.
For some people who are used to using Wireshark and who know what to look for, probably yes. For the vast majority of even technical people, probably not.
In my case, I did a packet capture of a single keystroke using tcpdump and imported it into Wireshark and I get just over 200 'Client: encrypted packet' and 'Server: encrypted packet' entries. Nothing useful there at all. If I tcpdump the entire SSH connection setup from scratch I get just as much useful information - nothing - but, oddly, fewer packets than my one keystroke triggered.
So yeah, I dislike LLMs entirely and dislike the reliance on LLMs that we see today, but in this case the author learned a lot of interesting stuff and shared it with us, whereas without LLMs he might have just shrugged and moved on.
And thats a huge downside when people howl about "Encryption everywhere! ".
Try debugging that shit. Thats right, debugging interfaces aren't safe, by some wellakshually security goon.
You want a real fun one to debug, is a SAML login to a webapp, with internal Oauth passthrough between multiple servers. Sure, I can decrypt client-server stuff with tools, but server-server is damn near impossible. The tools that work break SSL, and invalidate validation of the ssl.
Yes, Esri products suck. Bad.
I used to share that opinion but after decades in industrial automation I find myself coming down much more on the "yeah, encryption everywhere" because while many vendors do not provide good tools for debugging, that's really the problem, and we've been covering for them by being able to snoop the traffic.
Having to MITM a connection to snoop it is annoying, but the alternative appears to be still using unencrypted protocols from the 1970s within the limitations of a 6502 to operate life-safety equipment.
Sounds like blaming a tool on a problem it did not cause. Either way, solvable and encryption is important. Badly designed systems and or lack of tooling isn't really an encryption problem.
Anyway, VMs should not have authentication, it makes access sooo much easier. Also drop your IPs while you're at it. Might be useful for debugging later.
It seems like a leap to suggest we shouldn't have widely deployed encryption...rather than just fix the debugging tools.
Particularly in today's political climate, encryption has only become more necessary.
Unfortunately with SSH specifically, the dissectors aren't very mature - you only get valid parsing up to the KeX completion messages (NEWKEYS), and after that, even if the encryption is set to `none` via custom patches, the rest of the message flow is not parsed.
Seems because dumping the session keys is not at all a common thing. It's just a matter of effort though - if someone put in the time to improve the SSH story for dissectors, most of the groundwork is there.
Interesting, I thought it was possible to decrypt SSH in Wireshark a la TLS, but it seems I'm mistaken. It still would have been my first goto, likely with encryption patched out as you stated. With well documented protocols, it's generally not too difficult deciphering the raw interior bits as needed with the orientation provided by the dissected pieces. So let me revise my statement: this probably would have been a fairly easy task with protocol analysis guided code review (or simply CR alone).
Way to gatekeep. God forbid people use tools to help them investigate instead of knowing the exact approach to take.
My thoughts exactly. The OP used AI to get a starting point to their investigation, then used their skills to improve their game, with actual (I guess according to the article itself) proof of that, as opposed to just approving changes from the LLM.
This looks like an actual productivity boost with AI.
What I suggested (mistakenly so, see my revised suggested approach in response to one of your siblings) is the exact opposite of gate keeping.
ChatGPT gaslit the OP telling it there was no such thing as keystroke chafing. So yes, in this case it would have been better to do the work oneself.
Asking an LLM about SSH (hint: the two S-es stand for security) would tell you why only having packet capture in Wireshark isn't going to reveal shit.
Not even remotely accurate. While the dissector is not as mature as I thought and there's no built-in decryption as there is for TLS, that doesn't matter much. Hint: every component of the system is attacker controlled in this scenario.
> Not even remotely accurate.
> there's no built-in decryption
Is that because wireshark can't do that just from packet captures?
>Is that because wireshark can't do that just from packet captures?
Well, not quite. I think it's more that nobody has taken the time to implement it. That's not to say such an implementation would automatically decrypt the traffic from a capture with no extra leg work, of course. Wireshark dissectors have user configurable preferences, and presumably this would be where captured secrets could be set for use. This is how it handles TLS decryption [1], which works beautifully.
[1] https://wiki.wireshark.org/TLS#tls-decryption
Wireshark can decrypt it, so I don't understand what you mean?
Not from packet captures, it can't.
obviously OPs empirical and analytical rigor are top notch. He applied LLMs in the best way possible: fill gaps with clumsy command line flags or protocol implementations. Those aren't things one needs to keep in their head all the time.
How much are you staking on that bet?
Well, I spent a good part of my career reverse engineering network protocols for the purpose of developing exploits against closed source software, so I'm pretty sure I could do this quickly. Not that it matters unless you're going to pay me.
So you are basically overqualified to tell other people how to do it, especially with the payment part.
What are you even trying to say? I suppose I'll clarify for you: Yes, I'm confident I could have identified the cause of the mysterious packets quickly. No, I'm not going to go through the motions because I have no particular inclination toward the work outside of banter on the internet. And what's more, it would be contrived since the answer has already shared.
I think the point they're making is that "I, a seasoned network security and red-team-type person, could have done this in Wireshark without AI assistance" is neither surprising nor interesting.
That'd be like saying "I, an emergency room doctor, do not need AI assistance to interpret an EKG"
Consider that your expertise is atypical.
Sure, but that is aside from my original point. If somebody:
a) Has the knowledge to run tcpdump or similar from the command line
b) Has the ambition to document and publish their effort on the internet
c) Has the ability identify and patch the target behaviors in code
I argue that, had they not run to an LLM, they likely would have solved this problem more efficiently, and would have learned more along the way. Forgive me for being so critical, but the LLM use here simply comes off as lazy. And not lazy in a good efficiency amplifying way, but lazy in a sloppy way. Ultimately this person achieved their goal, but this is a pattern I am seeing on a daily basis at this point, and I worry that heavy LLM users will see their skill sets stagnate and likely atrophy.
Sigh.
I'm still waiting for a systems engineering tool that can log every layer, and handle SSL the whole pipe wide.
Im covering everything from strafe and ltrace on the machine, file reads, IO profiling, bandwidth profiling. Like, the whole thing, from beginning to end.
Theres no tool that does that.
Hell, I can't even see good network traces within a single Linux app. The closest you'll find is https://github.com/mozillazg/ptcpdump
But especially with Firefox, good luck.
Real talk though, how much would such a tool be worth to you? Would you pay, say, $3,000/license/year for it? Or, after someone puts in the work to develop it, would you wait for someone else to duct tape something together approximately similar enough using regexps that open source but 10% as good, and then not pay for the good proprietary tool because we're all a bunch of cheap bastards?
We have only ourselves to blame that there aren't better tools (publicly) available. If I hypothetically (really!) had such a tool, it would be an advantage over every other SRE out there that could use it. Trying to sell it directly comes with more headaches than money, selling it to corporations has different headaches, open-sourcing it don't pay the bills, nevermind the burnout (people don't donate for shit). So the way to do it is make a pitch deck, get VC funding so you're able to pay rent until it gets acquired by Oracle/RedHat/IBM (aka the greatest hits for Linux tool acquisition), or try and charge money for it when you run out of VC funding, leading to accusations of "rug pull" and development of alternatives (see also: docker) just to spite you.
In the base case you sell Hashimoto and your bank account has two (three!) commas, but worst case you don't make rent and go homeless when instead you could've gone to a FAANG and made $250k/yr instead of getting paid $50k/yr as the founder and burning VC cash and eating ramen that you have to make yourself.
I agree, that would be an awesome tool! Best case scenario, a company pays for that tool to be developed internally, the company goes under, it gets sold as an asset and whomever buys it forms a compnay and tries to sell it directly and then that company goes under but that whomever finally open sources it because they don't want it to slip into obscurity but if falls into obscurity anyway because it only works on Linux 5.x kernels and can't be ported to the 6.x series that we're on now easily.
Or you could use anycasting to terminate SSH sessions on the moral equivalent of one of a number of geography based reverse proxies and then forward the packet over an internal network to the app server over a link tuned for low latency. The big guys already do something similar with HTTP over TLS for DDoS protection and to limit end to end latency on TLS.
Granted... it would increase the cost (since you're adding reverse proxies) but it would be a quick way to get acceptable latency, rudimentary DDoS protection, and you could try different connection options independent of the main app's logic.
It would be hard to estimate how much latency you're adding with a SSH2 reverse proxy in this case, but it's probably lower than one might think.
The idea of letting Claude loose on my crypto[graphy] implementation is about the most frightening thing I've heard of in a while [though libnss is so craptastic, I can't see how it would hurt in that case.] But I loved this write-up. It was readable and explained the problem the OP was encountering and proposed solutions well.
> Or you could use anycasting to terminate SSH sessions on the moral equivalent of one of a number of geography based reverse proxies and then forward the packet over an internal network to the app server over a link tuned for low latency.
I've been thinking about some stuff like this! Not being able to put my game behind Cloudflare[1] is a bummer. Substantial architectural overhead though.
> The idea of letting Claude loose on my crypto[graphy] implementation is about the most frightening thing I've heard of in a while [though libnss is so craptastic, I can't see how it would hurt in that case.]
I hear you, but FWIW the patch I was reverting was trivial (and it's also in the go crypto library, which is pretty easy to read). It's a couple-of-line change[2], and Claude did almost exactly what I would have done (I was tired and would have forgotten to shrink the handshake payload).
[1] This isn't strictly true, Cloudflare spectrum exists, but its pricing is an insane $1/GB last I checked.
[2] https://cs.opensource.google/go/x/crypto/+/833695f0a57b30373...
Funny to see this fixed in 2023 and the side effects. Back in 2004, before I focused on performance, I did some security work including inter-keystroke latency analysis of captured SSH sessions to estimate the commands typed:
https://www.brendangregg.com/sshanalysis.html
The 2023 patch should finally fix that 2004 issue.
In 2023, ssh added keystroke timing obfuscation. The idea is that the speed at which you type different letters betrays some information about which letters you’re typing. So ssh sends lots of “chaff” packets along with your keystrokes to make it hard for an attacker to determine when you’re actually entering keys.
Now that's solving the problem the wrong way. If you really want that, send all typed characters at 50ms intervals, to bound the timing resolution.
Typing with an extra 50ms latency will be fairly unpleasant.
Average is 25ms. Just put sending on a clock.
Also considering ssh tunnels.
> send all typed characters at 50ms intervals
Wouldn't this just change the packet interval from 20ms to 50ms? Or did you mean a constant stream of packets at 50ms intervals, nonstop?
I think the idea behind the current implementation is that the keystrokes are batched in 20ms intervals, with the optimization that a sufficiently long silence stops the chaff stream, so the keystroke timing is obfucated with an increased error bar of 20ms multiplied by number of chaff packets.
I assume the problem, such as it is, relates to the fact that a real human typing in 20-50ms would generate a few characters at most but a program could generate gobs of data. So automatically you know what packets to watch. Then you know if there were more the likely keys were in set X, while if there were fewer the likely keys were in set Y.
So a clock doesn't solve the problem. The amount of data sent on each clock pulse also tells you something about what was sent.
The Chaff packets already fire on a timer. They inject random extra fake keystrokes so you can't tell how many keystrokes were actually made. The only other way I can think of to solve that is by using a step function: Send one larger packet (fragmented or the same number of individual packets) on each clock pulse if the actual data is less than some N where N is the maximum keystrokes ever recorded with some margin. Effectively almost every clock pulse will be one packet (or set of packets) of identical size. Of course if you do that then you'll end up consuming more data over time than sending random amounts of packets.
> That 20ms is a smoking gun - it lines up perfectly with the mysterious pattern we saw earlier!
Speaking of smoking guns, anybody else reckon Claude overuses that term a lot? Seems anytime I give it some debugging question, it'll claim some random thing like a version number or whatever, is a "smoking gun"
Yes! While this post was written entirely by me, I wouldn't be surprised if I had "smoking gun" ready to go because I spent so much time debugging with Claude last night.
It's interesting how LLMs influence us, right? The opposite happened to me: I loved using em dashes, but AI ruined it for me.
I still love using emdashes, and people already thought I was a robot!
https://xkcd.com/3126/
Soon the Andy 3000 will finally be a reality...
I used to love using em dashes.
I still do - but I used to, too.
Hey wait, - isn't one! Did a human write this?
Serious question though, since AI seems to be so all capable and intelligent. Why wouldn't it be able to tell you the exact reason that I could tell you just by reading the title of this post on HN? It is failing even at the one thing it could probably do decently, is being a search engine.
Reminds me of ethimology nerd's videos. He has some content about how LLMs will influence human language.
Some day in the future we will complain about AIs with a 2015 accent because that’s the last training data that wasn’t recursive.
The "maybe" of yesterday is the "you're absolutely right!" of tomorrow.
shouldn't it be "human language influences human language"?
ChatGPT too. And "lines up perfectly" when it doesnt actually line up with anything
Same with Gemini.
You can absolutely see this pattern in Gemini in 2026.
Btw, is the injection of "absolutely" and "in $YEAR" prevalent in other LLMs as well, or is it just in Gemini's dialect?
It's just Gemini. I'm guessing they changes the system prompt for the new year or something, but it's pretty annoying.
"You're so right, that nice catch lines up perfectly!"
It's not just a coincidence, it's the emergence of spurious statistical correlations when observations happen across sessions rather than within sessions.
You can add an M-dash, and we completed the bs-bingo. :)
I chuckled out loud. It's funny cause it's true.
Or the "Eureka! That's not just a smoking gun, it's a classic case of LLMspeak."
Grok, ChatGPT, and Claude all have these tics, and even the pro versions will use their signature phrases multiple times in an answer. I have to wonder if it's deliberate, to make detecting AI easier?
A computational necromancer has likely figured out a way to power a data center by making Archimedes spin in his grave very fast.
I've love to delve into that.
https://pshapira.net/2024/03/31/delving-into-delve/
I'm working on a little SRE agent to pre-load tickets with information to help our on-call and I'm already tired of Claude finding 'smoking guns'.
Without knowing how LLM's personality tuning works, I'd just hazard a guess that the excitability (tendency to use excided phrases) is turned up. "smoking gun" must be highly rated as a term of excitability. This should apply to other phrases like "outstanding!" or "good find!" "You're right!" etc.
They love clichés, and hate repeating the same words for something (repetition penalty) so they'll say something like "cause" then it's a "smoking gun" then it's something else
You might see certain phrases and mdashes ;-) rather often, because … these programs are trained on data written by people (or Microsoft's spelling correction) which overused them in the last n years? So what should these poor LLMs generate instead?
I don't think claude has even once used this in my conversations (Claude Desktop, Claude Code, Voice conversations...) Sycophancy, yes absolutely!
Maybe it has something to do with your profile/memories?
Yes, it’s kind of a corpus delicti. ;)
smoking gun, you're absolutely right, good question, em dash, "it isn't just foo, it's also bar", real honest truth, brutal truth, underscores the issue, delves into, more em dashes, <20 different hr/corporate/cringe phrases>.
It's nauseating.
It's what they read on The Internets when training, so don't expect them to generate new phrases, other than what they learned from it?
That's the point though, it doesn't reflect human usage of the word. If delve were so commonly used by humans too, we wouldn't be discussing how it's overused by LLMs.
### The answer that fits everything (and what to do about it)
Maybe we need a real AI which creates new phrases and teaches the poor LLMs?
Looking back we already had similar problems, when we had to ask our colleagues, students, whomever "Did you get your proposed solution from the answers part or the questions part of a stackoverflow article?" :-0
cant wait for chatgpt to make me read about grandmas secret recipe and scroll through 6 ads to see the ingredients for my chicken teriyaki dinner
You might find this a fun read: https://en.wikipedia.org/wiki/Wikipedia:Signs_of_AI_writing
Come on...haven't we all had to deal with the crazy smart lead who was loaded with those same types of annoying tics?
Considering what these LLMs bring to the table, I think a little tolerance for their cringe phrases is in order.
At this I'm just so glad that "you're absolutely right!" phase is over.
I see it from GPT5 too a lot
It's a smoking gun of Claude usage.
> Speaking of smoking guns
Oh shoot! A shooting.
So the TL;DR of this post is: don't change this setting unless you know what you're doing.
Chastise it with a reminder that you're using smokeless powder.
Well, security is the #1 consideration for SSH, but if the author doesn't need security, why use ssh?
For example, "nc" (netcat) is pre-installed on all platforms where ssh is.
I seem to hit this logic often recently for some reason.
There are two issues with it:
- a primary is not a totality: if "security is the #1 consideration for SSH", that implies there's a #2, maybe even a #3 and so on consideration. So the question that follows becomes tautological: "but if the author doesn't need security, why use ssh?" -> surely for one or more of the #2, #3, etc. considerations, right?
- overabstraction (*): you ended up strawmanning the author. What they had issue with was keystroke timing obfuscation, which is a privacy feature. Timing attacks are (in part) a privacy concern, and privacy is a security concern, yes, but security is not just privacy concern, and privacy concerns are not just about timing attacks; these groups are not equal. For example, they might very well want the transmitted keypresses themselves to remain confidential, or they might very well want to retain cryptographic assurance of their integrity. These are security features they can continue to utilize by sticking with SSH.
All of this is to say, it's not even necessarily them using SSH for a hypothetical #2 or #3 (...etc...) reason, but likely because they still very much want to make use of large chunks of #1, which disabling keypress obfuscation does not actually rid SSH of, only at most weakens it in ways they clearly seem to be okay with.
(*) although if I zoom out enough, this is once again just "a primary is not a totality", just implicitly
> For example, "nc" (netcat) is pre-installed on all platforms where ssh is.
This is technically incorrect, because Windows now includes SSH too!
I enjoyed this write up as it touched on several topics I enjoy reading about.
Also I was unfamiliar with SSH being vulnerable in the past to keystroke timing!
https://news.ycombinator.com/item?id=37307708
2023 discussion about it here.
> I am working on a high-performance game that runs over ssh.
Found your problem.
But it is an interesting world where you can casually burrow into a crypto library and disable important security features more easily than selecting the right network layer solution.
the obtuseness is the point! This is true of a lot of my work[1][2][3].
The problems you run into when doing things you shouldn't do are often really fun.
[1] https://news.ycombinator.com/item?id=42342382
[2] https://news.ycombinator.com/item?id=37810144
[3] https://news.ycombinator.com/item?id=42674116
These were great reads, thanks for linking. The writeup around the UUID page was super interesting!
This is hackernews not consumer news
You should feel free to explore / abuse all options :)
Yea UDP is technically more performant, but then you need a crypto layer + reliable message delivery layer + bespoke client. Using a plain old SSH client is cool.
However, there are existing libraries for exactly this use case - see https://github.com/ValveSoftware/GameNetworkingSockets
I guess QUIC libraries would also work.
its not really a question of 'udp performs better'. in tcp we have to live to head-of-line blocking on losses and congestion control. if you don't care about receiving every packet, but only the most recent, then udp is a good choice.
running without congestion control means that you avoid slowstart. but at a certain rate you run into poorly defined 'fairness' issues where you can easily negatively impact other flows. past that point, you can actually self-interfere and cause excessive losses for yourself.
quic uses congestion control, but uses latency estimates and variance as a signal to back off. it still imposes an ordering on a per-stream basis. so it might not be ideal either.
sctp has a mode which supports reliable and unordered, which might be something to consider
so really - if you care about latency and have a different reliability model, its worth unpacking all these considerations and using them to select your transport layer or even consider writing a minimal one yourself
>in tcp we have to live to head-of-line blocking on losses and congestion control.
Is this not a performance consideration?
Either way, using plain old SSH means a metric bajillion computers have a client for your game built in.
Not related to SSH, but does the eieio.games website make anyone else's monitor flicker? When the website is fullscreen it overwhelms something. I thought my monitor's backlight was going.
The really mysterious part is how ~10,000 packets per second costs ~20% of a core. That would mean SSH is bottlenecking in its code at ~50,000 packets per second per core which would be ~500 Mbps per core (assuming full packets) which is ludicrously slow. It is trivial to do 10x that packet per second rate. Is SSH really that poorly designed?
> It is trivial to do 10x that packet per second rate.
When making this statement, are you taking into account that SSH encrypts the traffic by default?
I do not know where people get the idea that encryption is that slow. Standard AES hardware acceleration instructions do ~25 Gbps per core (on a 2023 CPU) which is ~50x that rate [1]. I have heard modern cores can do ~40-50 Gbps, but I have not been able to find any independent benchmarks of that. Even the Intel i5-2500, a CPU from 2011, averages ~10 Gbps which is ~20x that rate. Even unaccelerated encryption can do ~2-5 Gbps in pure software which is 4-10x the SSH rate.
And in this situation, the amount of encrypted payload in each packet is 36 bytes which is ~40x less than a full packet of ~1500 bytes. You would almost surely hit packet per second limits before you hit payload throughput limits at these small sizes.
Encryption is slow when compared to data throughput you can get with a properly designed transport stack, but that is because it is in comparison to 100 Gbps per core even with no hardware offload. Anything less than ~10 Gbps/1 million packets per second (ignoring other bottlenecks, so only the software transport is the limit) is not merely unoptimized, it is pessimized.
[1] https://calomel.org/aesni_ssl_performance.html
I wonder if this is the same reason why Microsoft's Remote SSH plugin on VS Code is so flaky even with a decent internet connection. Every couple of months I try to give it another go and give up due to the poor keyboard latency I inevitably experience. And the slow reconnects whenever I glance away from my computer monitor briefly. This is on a fiber connection with a 20ms ping to the remote machine.
You surely mean the latency in its embedded terminal and not the code editor, right? I use VSCode’s remote SSH specifically so that code editing doesn’t suck. It really does not.
You're right, the latency is in the embedded terminal. Perhaps it is trying to run SSH inside SSH. Still, the disconnects are a pain too.
> Keystroke obfuscation can be disabled client-side.
please never do that (in production)
if anyone half way serious tries they _will_ be able to break you encryption end find what you typed
this isn't a hypothetical niche case obfuscation mechanism, it's a people broke SSH then a fix was found case. I don't even know why you can disable it tbh.
That doesn't sound right to me. This obfuscation isn't about a side-channel on a crypto implementation, this is about literally when your keystrokes happen. In the right circumstances, keystroke timing can reduce the search space for bruteforcing a password [1] but it's overstating to describe that as broken encryption.
[1] https://people.eecs.berkeley.edu/~daw/papers/ssh-use01.pdf
THANK YOU!
I'm baffled about this "security feature". Besides from this only being relevant to timing keystrokes during the SSH session, not while typing the SSH password, I really don't understand how can someone eavesdrop on this? They'd have to have access to the client or server shell (root?) in order to be able to get the keystrokes typing speed. I've also never heard of keystroke typing speed hacking/guessing keystrokes. The odds are very low IMO to get that right.
I'd be much more scared of someone literally watching me type on my computer, where you can see/record the keys being pressed.
Anyone who can spy on the network between the client and server can see the timing. This includes basically anyone on the same LAN as you, anyone who sets up a WiFi access point with a SSID you auto-connect to, anyone at your ISP or VPN provider, the NSA and god knows who else.
And the timing is still sensitive. [1] does suggest that it can be used to significantly narrow the possible passwords you have, which could lead to a compromise. Not only that, but timing can be sensitive in other ways --- it can lead to de-anonymization by correlating with other events, it can lead to profiling of what kind of activity you are doing over ssh.
So this does solve a potentially sensitive issue, it's just nuanced and not a complete security break.
[1] https://people.eecs.berkeley.edu/~daw/papers/ssh-use01.pdf
They literally explain the mechanism in the post and then explain why the security tradeoff made sense for their ssh game………
It is to prevent timing attacks but there are many ssh use cases where it is 100% computer to computer communications where there is no key based timing attack possible.
There is an argument that if:
- you are listening to an SSH session between devices
- and you know what protocol is being talked over the connection (i.e. what they are talking about)
- and the protocol is reasonably predictable
then you gain enough information about the plaintext to start extracting information about the cipher and keys.
It's a non-trivial attack by all means but it's totally feasible. Especially if there's some amount of observable state about the participants being leaked by a third party source (i.e. other services hosted by the participants involved in the same protocol).
this only works for manually typed text, not computer to computer communication where you can't deduce much from what is being "typed" as it's not typed but produced by a program to which every letter is the same and there is no different delay in sending some letters (as people have when typing by hand)
I agree it is more nuanced than a simple 'good for computer-to-computer' and 'bad for person-to-computer'. I'm sure there are cases where both are wrong but I don't think that necessarily changes that it makes a reasonable baseline heuristic.
I'd love to hear more about this kind of attack being exploited in the wild. I understand it's theoretically possible, but...good luck! :)
You're guessing a cipher key by guessing typed characters with the only information being number of packets sent and the time they were sent at. Good luck. :)
I haven't given this more than 5 seconds of thought, but wouldn't it make sense to only enable the timing attack prevention for pseudo-terminal sessions (-t)?
The fix seems kind of crazy though, adding so much traffic overhead to every ssh session. I assume there's a reason they didn't go that route, but on a first pass seems weird they didn't just buffer password strokes to be sent in one packet, or just add some artificial timing jitter to each keystroke.
I'm just guessing but this chaff sounds like it wouldn't actually change the latency or delivery of your actual keystrokes while buffering or jitter would.
So the "real" keystrokes are 100% the same but the fake ones which are never seen except as network packets are what is randomized.
It's actually really clever.
SSH has no way of knowing when a password is being typed. It can happen any time within the session after SSH auth.
But they'd have to be on the same network as me to do that attack, right?
Yep, like ECHELON and friends are. The metadata recorded about your (all of our) traffic is probably enough to perform the timing attack.
Hey, if ECHELON snuck a listener into my house, where six devices hang out on a local router... Good for them, they're welcome to my TODO lists and vast collection of public-domain 1950s informational videos.
(I wouldn't recommend switching the option off for anything that could transit the Internet or be on a LAN with untrusted devices. I am one of those old sods who doesn't believe in the max-paranoia setting for things like "my own house," especially since if I dial that knob all the way up the point is moot; they've already compromised every individual device at the max-knob setting, so a timing attack on my SSH packet speed is a waste of effort).
@eieio: whatever email protection you're running is triggering on the extension info. For example I see:
> And they’re sent to servers that advertise the availability of the [email protected] extension. What if we just…don’t advertise [email protected]?
Is it possible that this is on your end?
The extension is "ping@openssh.com." It shows up in the blog reliably for me across several browsers and devices.
No, it's Cloudflare munging the HTML. Cloudflare then provides JavaScript to un-munge it, but that's not reliable.
And of course it totally doesn't work if the client doesn't have JavaScript at all. I read the HN front-page through an AI summary and it also got censored when it scraped the article.
TIL! I'll see if I can change that.
fwiw, I tcdumped between two systems running fedora43 and saw no chaff. (one packet out, one reply, one tcp ack.)
I find it disturbing.
One thing you notice if you have ADSL is that some services are built as if slower connections matter and others are not. Like Google's voice and audio chat services work poorly but most of the others work well. Uploading images to Mastodon, Bluesky, Facebook, LinkedIn, Instagram and Nextdoor is reliable, but for Tumblr you have to try it twice. I don't what they are doing wrong but they are doing something wrong and not finding out what they're doing wrong because they're not testing and they're not listening to users.
Nobody consulted me about their decision not to run fiber by my house. If some committee decides to make ssh bloated they are, together with the others, conspiring to steal my livelihood and I think it would be fair for me to sue them for the $50k it would take to run that fiber myself.
It's OK if you work for Google where there is limitless dark fiber but what about people in African countries?
It's the typical corporate attitude where latency never matters: Adobe thinks it is totally normal that it takes 1-5s for a keystroke to appear when you are typing into Dreamweaver.
I agree with your general point that most companies/projects do a terrible job optimizing for slow computers/networks, but OpenSSH is from the OpenBSD people, who are well-known for supporting ancient hardware [0]. Picking a random architecture, they fully support a system with only 64MB of memory [1], and the base install includes SSH. So I suspect that OpenSSH is fairly well tested on crappy computers/networks.
[0]: https://www.openbsd.org/plat.html
[1]: https://www.openbsd.org/landisk.html#hardware
There's a good chance you have other options. Regardless of how you feel about the company's head, Starlink would probably be one of them, with likely better performance than you're dealing with on ADSL.
But you cannot just sue a company because their network connected software doesn't work well on slow networks. Let alone a project like OpenSSH. It would be like me suing a game studio because my PC doesn't meet their listed minimum requirements to play the game.
Hey, it is one thing to buy a new computer, it is another thing to ask people to move.
A better analogy is a bank redlining neighborhoods. The cost to run fiber to difficult rural locations pays itself easily if you look at a 25-year time span and is an order of magnitude less than building a new housing unit on the West Coast.
You're not ok with a security/privacy tool using defensive techniques because of ... the lack of fiber in Africa?
My backyard but people will take Africa more seriously than anywhere in the US 2 miles from the end of cable.
The openssh team does not owe you anything.
If you want a “1990s” mode, add it yourself or pay some to do it for you.
> One thing you notice if you have ADSL
This is funny to me, because ADSL used to be the fast thing, as opposed to dialup modems.
You just opened a huge nostalgia portal, never thought that Dreamweaver would still be around, I used that somewhere around 2003 I believe. Good memories
Frankly I wish there was an HTML editor that delivers on what it promised. I mean, markdown is almost as rife with edge cases as YAML and somehow the link syntax still eludes me. If we could “just” template by merging at the DOM level and had decent HTML editors the world would be a different place. But yeah, Adobe probably thinks Dreamweaver isn’t worth maintaining just as they seem to think Photoshop is barely worth maintaining (they keep adding AI features that sorta work but the foundations seem to be much worse than Illustrator)
Because we stopped coding for performance years ago.
Tell me more about this game!
It's vibe coded
>>> That makes a lot of sense for regular ssh sessions, where privacy is critical. But it’s a lot of overhead for an open-to-the-whole-internet game where latency is critical.
Switching to telnet instead of SSH might be an option.
>very confidently told me that my tcpdump output was normal ssh behavior:
I mean, for modern version of Openssh it's not exactly wrong. The failure was to tell you why that is the normal behavior.
> I am working on a high-performance game that runs over ssh.
Step one, run https://www.psc.edu/hpn-ssh-home/introduction/ instead Step two, tune TCP/IP stack Step... much later: write your own "crypto". (I'm using quotes because, before someone points out the obvious, packets-per-keystroke isn't, itself, a cryptographic algorithm, but because it's being done to protect connections from being decrypted/etc, mess with it at your own peril.)
If security doesn’t matter then why not use telnet or something else besides ssh instead of forking a security library?
Telnet nowadays typically isn’t available by default for security reasons, and OP wants people to be able to play the game just by typing “ssh thegamehost”.
> Telnet nowadays typically isn’t available by default for security reasons
And with good reason. This CVE is from yesterday:
https://nvd.nist.gov/vuln/detail/CVE-2026-24061
> telnetd in GNU Inetutils through 2.7 allows remote authentication bypass via a "-f root" value for the USER environment variable.
Telnetd is the server though, and OP wouldn’t be using that.
ah, good point.
I loled and closed the article after 'I am working on a high-performance game that runs over ssh.'
Vibe coders man...
> I am working on a high-performance game that runs over ssh.
WAT. Please no.
Why not? If it's high-performance, it's fine.
Performing with highly elevated privileges? (Joke)
ssh the protocol doesn't imply any privileges of any kind
Unless you leave your ssh agent on, then it very much does.