Writing "/etc/hosts" breaks the Substack editor(scalewithlee.substack.com) |
Writing "/etc/hosts" breaks the Substack editor(scalewithlee.substack.com) |
If that's their idea of security...
* The product provided for blogging/content publishing did a shitty job of configuring WAF rules for its use cases (the utility of a "magic WAF that will just solve all your problems" being out of the picture for now) * The WAF product provided by the cloud platform clearly has shitty, overreaching rules doing arbitrary filtering on arbitrary strings. That filtering absolutely can (and will) break unrelated content if the application behind the WAF is developed with a modicum of security-mindedness. You don't `fopen()` a string input (no, I will not be surprised - yes, sometimes you do `fopen()` a string input - when you are using software that is badly written).
So I am wondering:
1. Was this sent to Substack as a bug - they charge money for their platform, and the inability to store $arbitrary_string on a page you pay for, as a user, is actually a malfunction and disfunction"? It might not be the case "it got once enshittified by a CIO who mandated a WAF of some description to tick a box", it might be the case "we grabbed a WAF from our cloud vendor and haven't reviewed the rules because we had no time". I don't think it would be very difficult for me, as an owner/manager at the blogging platform, to realise that enabling a rule filtering "anything that resembles a Unix system file path or a SQL query" is absolutely stupid for a blogging platform - and go and turn it the hell off at the first user complaint.
2. Similarly - does the cloud vendor know that their WAF refuses requests with such strings in them, and do they have a checkbox for "Kill requests which have any character an Average Joe does not type more frequently than once a week"? There should be a setting for that, and - thinking about the cloud vendor in question - I can't imagine the skill level there would be so low as to not have a config option to turn it off.
So - yes, that's a case of "we enabled a WAF for some compliance/external reasons/big customer who wants a 'my vendor uses a WAF' on their checklist", but also the case of "we enabled a WAF but it's either buggy or we haven't bothered to configure it properly".
To me it feels like this would be 2 emails first ("look, your thing <X> that I pay you money for clearly and blatantly does <shitty thing>, either let me turn it off or turn it off yourself or review it please") - and a blog post about it second.
It's not likely to be a WAF or content scanner, because the HTTP request is using PUT (which browser forms don't use) and it's uploading the content as a JSON content-type in a JSON document. The WAF would have to specifically look for PUTs, open up the JSON document, parse it, find the sub-string in a valid string, and reject it. OR it would have to filter raw characters regardless of the HTTP operation.
Neither of those seem likely. WAFs are designed to filter on specific kinds of requests, content, and methods. A valid string in a valid JSON document uploaded by JavaScript using a JSON content-type is not an attack vector. And this problem is definitely not path traversal protection, because that is only triggered when the string is in the URL, not some random part of the content body.
Nobody could prove that's exactly what's happening without seeing Cloudflare's internal WAF rules, but can you think of any other reasonable explanation? The endpoint is rejecting a PUT who's payload contains exactly /etc/hosts, /etc/passwd, or /etc/ssh/sshd_config, but NOT /etc/password, /etc/ssh, or /etc/h0sts. What else could it be?
It references this CVE https://github.com/tuo4n8/CVE-2023-22047 which allows the reading of system files. The example given shows them reading /etc/passwd
The author just collected a bunch of correlations and then decided what the cause was. I've been doing this kind of work for many, many years. Just because it looks like it's caused by one thing, doesn't mean it is.
Correlation is not causation. That's not just a pithy quip, there's a reason why it's important to actually find causation.
edit: Also, someone commented here "it was an irrelevant cf WAF rule, we disabled it". Assuming honesty, seems to confirm that the author was indeed right.
Yes, the people in charge probably didn't think or know of SQL comments. However, it worked well as long as input is sanitized and not concatenated, which is often the case using modern frameworks or common sense.
However, nowadays, we just put a WAF in front of everything, it's cheaper that way because common sense is hard to come by. People like Foo Bar--Baz still exist, and unless they've had their name changed, they're sometimes running into extremely wierd issues in the web software they're using.
I've worked with a WAF installation (totally different product), where the "WAF fail" tell was HTTP status 200 (!) and "location: /" (and some garbage cookies), possibly to get browsers to redirect using said cookies. This was part of the CSRF protection. Other problems were with "command injection"-patterns (like in the article, expect with specific Windows commands, too - they clash with everyday words which the users submit), and obviously SQL injections which cover some relevant words, too.
The bottom line is that WAFs in their "hardened/insurance friendly" standard configs are set up to protect the company from amateurs exposing buggy, unsupported software or architectures. WAF's are useful for that, but you still gave all the other issues with buggy, unsupported software.
As others have written, WAFs can be useful to protect against emerging threats, like we saw with the log4j exploit which CloudFlare rolled out protection for quite fast.
Unless you want compliance more than customers, you MUST at least have a process to add exceptions to "all the rules"-circus they put in front of the buggy apps.
Whack-a-mole security filtering is bad, but whack-a-mole relaxation rule creation against an unknown filter is really tiring.
The outcome is the usual one, stuff breaks and there is no additional security.
I worked on a project where we had to use a WAF for compliance reasons. It was a game of wack-a-mole to fix all the places where standard rules broke the application or blocked legitimate requests.
One notable, and related example is any request with the string "../" was blocked, because it might be a path traversal attack. Of course, it is more common that someone just put a relative path in their document.
Ahh, the modern trend of ”unalived”¹ etc. comes to every corner of society eventually.
Why would random text be parsed? I read the article but this doesn't make sense to me. They suggested directory transversal but your text shouldn't have anything to do with that and transversal is solved by permission settings
I do understand this appoach. From the defence point of view it makes sense, if you have to create a solution to protect millions of websites it doesn't make sense to tailor it to specifics of a single one
(What's below is written not as "this is how it should be done" but instead "what I understand should be done". To provide context to what I do and do not understand so that my misunderstandings can be more directly addressed)
I understand being over zealous, an abundance of caution. But what I'm confused about is why normal text could lead to an exploit in the first place. I can only understand this being a problem if arbitrary text is being executed. Which that would appear to be a HUGE security hole ripe for exploitation. But path access is handled by privileges. So even if arbitrary text is being executed, how can that lead to exploitation without already having a major security hole?
Maybe I'm not understanding substack? I've only been a reader. But why is the writer not in a container or chroot? If you want you be overly zealous why not use two vms? Put them in a vm to write, once they've edited then run tests and then use that as the image for the userspace in the ephemeral vm that is viewed by readers. Would this still be exploitable? I don't mean image for the whole vm, I really do mean a subimage so you can lock that up.
The hacky workaround which has been stably working for a while now was to encode the offending request body and decode it on the destination server.
generally think that Substack has done a good thing for its core audience of longform newsletter writer creators who want to be Ben Thompson. however its experience for technical people, for podcasters, for people who want to start multi-channel media brands, and for people who write for reach over revenue (but with optional revenue) has been really poor. (all 4 of these are us with Latent.Space). I've aired all these complaints with them and theyve done nothing, which is their prerogative.
i'd love for "new Substack" to emerge. or "Substack for developers".
He gave a talk on it at WordCamp Asia at the start of last year, although I haven’t heard of any progress recently on it.
1. It's a social media platform with a network that is still easy to extract organic growth from.
2. 99% email deliverability without configuring anything. It's whitelisted everywhere.
/etc/hosts
See, HN didn't complain. Does this mean I have hacked into the site? No, Substack (or Cloudflare, wherever the problem is) is run by people who have no idea how text input works.
There is sadly no evidence in this article that the supposed filter does protect the platform from potential attacks.
We had unending trouble with mod_security. The worst issue I can remember was that any POST request whose body contained the word "delete" was automatically rejected. That was the full rule. To this day I still can't imagine what the developers were thinking.
Writing `find` as the first word in your search will prevent Firefox from accepting the “return” key is pressed.
Pretty annoying.
For example, I worked with a client that had a test suite of about 7000 or so strings that should return a 500 error, including /etc/hosts and other ones such as:
../../apache/logs/error.log
AND%20(SELECT%208203%20FROM%20(SELECT(SLEEP(5)))xGId)
/../..//../..//../..//../winnt/system32/netstat.exe?-a
We ended up deploying a WAF to block all these requests, even though it didn't improve security in any meaningful way.
> We "failed" and were not in compliance as you could make a request containing one of those strings--ignoring that neither Apache, SQL, or Windows were in use.
this causes me pain
I guess someone was told, when compiling those strings, that they should observe this known-good implementation (that actually crashed upon receiving such things) and record whatever it returns, and then mandate it of everyone else from now on.
That's a very uncharitable view. It's far more likely that they are simply using some WAF with sane defaults and never caught this. They'll fix it and move on.
This particular rule is obviously off. I suspect it wasn't intended to apply to the POST payload of user content. Perhaps just URL parameters.
On a big enough website, users are doing weird stuff all the time and it can be tricky to write rules that stop the traffic you don't want while allowing every oddball legitimate request.
As much as this is a pain, the alternative can be more painful.
I used to have a client that would forward me an email from their security team every six weeks saying "we found a SQL injection issue with your site, can you look into this and confirm that it's fixed?" and I'd reply back saying "that not possible" and they'd go "ok, we've marked this as a false positive".
Eventually I got bored of having the same conversation over and over, so I asked them to show what they were finding. It turned out their scan would do the following:
html1 = request("https://example.com/search?query=test")
html2 = request("https://example.com/search?query=test' or 1=1--")
if (html1 != html2)
sql_injection_vulnerable = true
This is a perfect use case for a WAF, I can stick one in front and then have it return 500s for all these requests and not worry about it any more.
In our case, we didn't have a WAF, but they had a obvious User-Agent, and it turns out that blocking all of their requests passed the scan too :)
WAFs blocking the string with the filename then is the "to make sure nobody ever accidentally leaves your gate open, we've replaced it with a concrete wall" solution to this problem. You might never have this problem, and might need to actually use the gate but the vendor/security team has successfully solved their problem of checking off a blocked attack, and the consequences are now your problem
> directory transversal attack
I asked why setting permissions was not a sufficient solution. Is someone gaining root? How?
I understand there's the user visiting substack and the person editing on substack. Certainly this is about the person editing. This is why I asked about the containerization side. That's an extra layer in permissions. Not only should that editor not have permissions to edit `/etc/passwd` (or some other file), but they wouldn't be able to do so even if gaining root. They'd need to gain root, break out of the container, and gain root again (hopefully that container is being run as a user and not root!).
But even there, I'm still confused about the exploits. How is a transversal even happening? Why is text even being executed? I understand we're sending POST requests but why is that POST request able to do anything other than input string literals into a text body? Isn't this a prepared statement? Why does that POST request have permission to access those files in the first place? Like even if a malicious editor circumvented defenses and was able to write injections, accessing those files shouldn't be possible from permissions, right?
My understanding is that for this solution to be effective then several other critical security flaws have to also have happened. And how far does this thing need to go? Isn't it defeatable if I chop up the keywords into benign ones, store as variables, and then expand them? I guess it stops very low hanging fruit attackers but again, isn't that also only in the situations where there are also low hanging fruit attacks available which can cause far more damage? That's where my confusion is coming from.
But the WAF rule is not site-specific.
Almost all of your comment is asking site-specific questions, but that's barking up the wrong tree. The WAF is working under a completely different paradigm.
It especially doesn't know about specific user rules within a specific site! Or file permissions. None of those are in scope for the WAF. The WAF is trying to protect a million sites at once.
> Isn't it defeatable if I chop up the keywords into benign ones, store as variables, and then expand them?
That might work half the time, but not the other half. The filter isn't pointless, it's just being badly and annoyingly applied.
/etc/passwd is readable by design by every user in Linux. And you have it even inside the containers. If you set permissions to "readable by root only" normal programs won't be able to map user names to ids and your application might die
In modern linux this file doesn't contain any passwords, the only thing the attacker can gain by reading it is learning some usernames
If your site discusses databases then turning on the default SQL injection attack prevention rules will break your site. And there is another ruleset for file inclusion where things like /etc/hosts and /etc/passwd get blocked.
I disagree with other posts here, it is partially a balance between security and usability. You never know what service was implemented with possible security exploits and being able to throw every WAF rule on top of your service does keep it more secure. Its just that those same rulesets are super annoying when you have a securely implemented service which needs to discuss technical concepts.
Fine tuning the rules is time consuming. You often have to just completely turn off the ruleset because when you try to keep the ruleset on and allow the use-case there are a ton of changes you need to get implemented (if its even possible). Page won't load because /etc/hosts was in a query param? Okay, now that you've fixed that, all the XHR included resources won't load because /etc/hosts is included in the referrer. Now that that's fixed things still won't work because some random JS analytics lib put the URL visited in a cookie, etc, etc... There is a temptation to just turn the rules off.
And economics. Many people here are blaming incompetent security teams and app developers, but a lot of seemingly dumb security policies are due to insurers. If an insurer says "we're going to jack up premiums by 20% unless you force employees to change their password once every 90 days", you can argue till you're blue in the face that it's bad practice, NIST changed its policy to recommend not regularly rotating passwords over a decade ago, etc., and be totally correct... but they're still going to jack up premiums if you don't do it. So you dejectedly sigh, implement a password expiration policy, and listen to grumbling employees who call you incompetent.
It's been a while since I've been through a process like this, but given how infamous log4shell became, it wouldn't surprise me if insurers are now also making it mandatory that common "hacking strings" like /etc/hosts, /etc/passwd, jndi:, and friends must be rejected by servers.
We're SOC2 + HIPAA compliant, which either means convincing the auditor that our in-house security rules cover 100% of the cases they care about... or we buy an off-the-shelf WAF that has already completed the compliance process, and call it a day. The CTO is going to pick the second option every time.
I keep hearing that often on HN, however I've personally never seen seen such demands from insurers. I would greatly appreciate if one share such insurance policy. Insurance policies are not trade secrets and OK to be public. I can google plenty of commercial cars insurance policies for example.
I still have a nervous tick from having a screen lock timeout "smaller than or equal to 30 seconds".
If anything, I think this attitude is part of the problem. Management, IT security, insurers, governing bodies, they all just impose rules with (sometimes, too often) zero regard for consequences to anyone else. If no pushback mechanism exists against insurer requirements, something is broken.
I would argue that password policies are very context dependent. As much as I detest changing my password every 90 days, I've worked in places where the culture encouraged password sharing. That sharing creates a whole slew of problems. On top of that, removing the requirement to change passwords every 90 days would encourage very few people to select secure passwords, mostly because they prefer convenience and do not understand the risks.
If you are dealing with an externally facing service where people are willing to choose secure passwords and unwilling to share them, I would agree that regularly changing passwords creates more problems than it solves.
Always made me judge my company's security teams as to why they enable this stupidity. Thankfully they got rid of this gradually, nearly 2 years ago now (90 days to 365 days to never). New passwords were just one key l/r/u/d on the keyboard.
Now I'm thinking maybe this is why the app for a govt savings scheme in my country won't allow password autofill at all. Imagine expecting a new password every 90 days and not allowing auto fill - that just makes passwords worse.
I believe that this is overall a reasonable approach for companies that are bigger than "the CEO knows everyone and trusted executives are also senior IT/Devs/tech experts" and smaller than "we can spin an internal security audit using in-house resources"
Ask the CIO what actual threat all this is preventing, and you'll get blank stares.
As an engineer what incentive is there to put effort into knowing where each form input goes and how to sanitize it in a way that makes sense? You are getting paid to check the box and move on, and every new hire quickly realizes that. Organizations like these aren't focused on improving security, they are focused on covering their ass after the breach happens.
the CIO is securing his job.
No.
> aggressively
No.
>, and in this case, to the wrong content altogether.
Yes - making it not a Scunthorpe problem.
WAFs are always a bad idea (possible exception: in allow-but-audit mode). If you knew the vulnerabilities you'd protect against them in your application. If you don't know the vulnerabilities all you get is a fuzzy feeling that Someone Else is Taking Care of it, meanwhile the vulnerabilities are still there.
Maybe that's what companies pay for? The feeling?
I do wish it were possible to write the rules in a more context-sensitive way, maybe possible with some standards around payloads (if the WAF knows that an endpoint is accepting a specific structured format, and how escapes work in that format, it could relax accordingly). But that's probably a pipe dream. Since the backend could be doing anything, paranoid rulesets have to treat even escaped data as a potential issue and it's up to users to poke holes.
I might be out of the loop here, but it seems to me that any WAF that's triggered when the string "/etc/hosts" is literally anywhere in the content of a requested resource, is pretty obviously broken.
We changed auditors after that.
Oh: I resisted tooth and nail about turning on a WAF at one of my gigs (there was no strict requirement for it, just cargo cult). Turns out - I was right.
Definitely, though I have seen other solutions, like inserting non-printable characters in the problematic strings (e.g. "/etc/ho<b></b>sts" or whatever, you get the idea). And honestly that seems like a reasonable, if somewhat annoying, workaround to me that still retains the protections.
I agree. There is a business opportunity here. Right in the middle of your sentences.
Hint: Context-Aware WAF.
Many platforms have emerged in the last decade - some called it smart WAF, some called it nextgen WAF.. All vaporware garbage that consumes tons and tons of system resource and still manages to do a shit job of _actually_ WAF'ing web requests.
To be truly context-aware, you need to compute a priori about the situation - the user, the page, the interactions etc.
They shouldn't be doing that job at all. The content of user data is none of their business.
I favor the latter approach. That group of Cloudflare users will understand the complexity of their use case accepting SQL in payloads and will be well-positioned to modify the default rules. They will know exactly where they want to allow SQL usage.
From Cloudflare’s perspective, it is virtually impossible to reliably cover every conceivable valid use of SQL, and it is likely 99% of websites won’t host SQL content.
Another developer in the team decided they wanted to log what customers searched for, so if someone typed in "OutOfMemoryException" in the search bar...
How about this: don't run a dumb as rocks Web Application Firewall on an endpoint where people are editing articles that could be about any topic, including discussing the kind of strings that might trigger a dumb as rocks WAF.
This is like when forums about web development implement XSS filters that prevent their members from talking about XSS!
Learn to escape content properly instead.
But it doesn't. This case highlights a bug, a stupid bug. This case highlights that people who should know better, don't!
The tension between security and usability is real but this is not it. Tension between security and usability is usually a tradeoff. When you implement good security that inconveniences the user. From simple things like 2FA to locking out the user after 3 failed attempts. Rate limiting to prevent DoS. It's a tradeoff. You increase security to degrade user experience. Or you decrease security to increase user experience.
This is neither. This is both bad security and bad user experience. What's the tension?
This also reminded me, I think in the PHP 3 era, PHP used to "sanitize" the contents of URL requests to blanket combat SQL injections, or perhaps, it was a configuration setting that would be frequently turned on in shared hosting services. This, of course, would've been very soon discovered by the authors of the PHP site and various techniques were employed to circumvent this restriction, overall giving probably even worse outcomes than if the "sanitation" wasn't there to begin with.
[1] the second time it happened, a colleague added "if we got 403, print "HAHAHA YOU'VE BEEN WAFFED" to our deployment script, and for that I am forever thankful because I saw that error more times than I expected
Oh, I just remembered I had another encounter with the AWS WAF.
I had a Jenkins instance in our cloud account that I was trying to integrate with VSTS (imagine github except developed by Microsoft, and still maintained, nevermind that they own github and it's undoubtedly a better product). Whenever I tried to trigger a build, it worked, but when VSTS did, it failed. Using a REST monitor service I was able to record the exact requests VSTS was making and prove that they work with curl from my machine... after a few nights of experimenting and diffing I noticed a difference between the request VSTS made to the REST monitor and my reproduction with curl: VSTS didn't send a "User-Agent" header, so curl supplied one by default unless I added I think -H "User-Agent:", and therefore did not trigger the first default rule in the AWS WAF, "if your request doesn't list a user agent you're a hacker".
HAHAHA I'VE BEEN WAFFED AGAIN.
Writing about biology, finance, or geology? Shrug.
Dumb filtering is bad enough when used by smart people with good intent.
For bonus, the reverse proxy will run on a system infiltrated by Russian (why not Chinese as well) hackers.
sits quietly for a second
"Oh nnnnnnnooooooooooooooo lol!"
It turns out OpenRouter’s API is protected by Cloudflare and something about specific raw chunks of HTML and JavaScript in the POST request body cause it to block many, though not all, requests. Going direct to OpenAI or Anthropic with the same prompts is fine. I wouldn’t mind but these are billable requests to commercial models and not OpenRouter’s free models (which I expect to be heavily protected from abuse).
(Update: On the way to doing that, I decided to run my tests again and they now work without Cloudflare being touchy, so I'll keep an eye on it!)
(Update 2: They just replied to me on X and said they had fixed their Cloudflare config - happy days!)
Trying to contact support was difficult too due to AI chatbots, but when I finally did reach a human, their "tech support" obviously didn't bother to look at this in any reasonable timeframe.
It wasn't until some random person on Twitter suggested the possibility of some magic string tripping over some stupid security logic that I found the problem and could finally edit my post.
This isn't a tension. This rule should not be applied at the WAF level. It doesn't know that this field is safe from $whatever injection attacks. But the substack backend does. Remove the rule from the WAF (and add it to the backend, where it belongs) and you are just as secure and much more usable. No tension.
https://www.macchaffee.com/blog/2023/wafs/
Of course, Wordpress is basically undefendable, so I'd never ever host it on a machine that has anything else of value (including e.g. db credentials that give access to much more than the public content on the WP installation).
People will manage to circumvent the firewall if they want to attack your site. But you will still pay, and get both the DoS vulnerabilities created by the firewall and the new attack vectors in the firewall itself.
This is like spam filtering. I'm an anti-spam advocate, so the idea that most people can't discuss spam because even the discussion will set off filters is quite old to me.
People who apologize for email content filtering usually say that spam would be out of control if they didn't have that in place, in spite of no personal experience on their end testing different kinds of filtering.
My email servers filter based on the sending server's configuration: does the EHLO / HELO string resolve in DNS? Does it resolve back to the connecting IP? Does the reverse DNS name resolve to the same IP? Does the delivery have proper SPF / DKIM? Et cetera.
My delivery-based filtering works worlds better than content-based filtering, plus I don't have to constantly update it. Each kind has advantages, but I'd rather occasional spam with no false positives than the chance I'm blocking email because someone used the wrong words.
With web sites and WAF, I think the same applies, and I can understand when people have a small site and don't know or don't have the resources to fix things at the actual content level, but the people running a site like Substack really should know better.
The same application also stored my full password in localStorage and a cookie (without httponly or secure). Because reasons. Sigh.
I'm going to do a hot take and say that WAFs are bollocks mainly used by garbage software. I'm not saying a good developer can't make a mistake and write a path traversal, but if you're really worried about that then there are better ways to prevent that than this approach which obviously is going to negatively impact users in weird and mysterious ways. It's like the naïve /(fuck|shit|...)/g-type "bad word filter". It shows a fundamental lack of care and/or competency.
Aside: is anyone still storing passwords in /etc/passwd? Storing the password in a different root-only file (/etc/shadow, /etc/master.passwd, etc.) has been a thing on every major system since the 90s AFAIK?
1. Create a new post. 2. Include an Image, set filter to All File types and select "/etc/hosts". 3. You get served with an weird error message box displacing a weird error message. 4. After this the Substack posts editor is broken. Heck, every time i access the Dashboard, it waits forever to build the page.
Did find this text while browsing the source for an error (see original ascii art: https://pastebin.com/iBDsuer7):
SUBSTACK WANTS YOU
TO BUILD A BETTER BUSINESS MODEL FOR WRITING
https://substack.com/jobsIt references this CVE https://github.com/tuo4n8/CVE-2023-22047 which allows the reading of system files. The example given shows them reading /etc/passwd
SecRule REQUEST_COOKIES|!REQUEST_COOKIES:/__utm/|REQUEST_COOKIES_NAMES|ARGS_NAMES|ARGS|XML:/* "@pmFromFile lfi-os-files.data"
SecRule REQUEST_COOKIES|!REQUEST_COOKIES:/__utm/|REQUEST_COOKIES_NAMES|ARGS_NAMES|ARGS|XML:/* "@pmFromFile unix-shell.data" ...
The advantage (whack-a-mole notwithstanding) of a WAF is it orders of magnitude easier to tweak WAF rules than upgrade say, Weblogic, or other teetering piles of middleware.
Turns out the hunches were right all along.
One of the authors of the paper has said "WAFs are just speed bump to a determined attacker."
We wish. Speed bumps don't totally immobilise a pseudo-random selection of innocent vehicles.
Doors are a speedbump for a car.
Well yeah, sure, doesn't mean I'm going to have an open doorframe or a door without a lock.
This isn't like having a lock on your door, this is like having a cheap, easily pickable padlock on your bank vault. If the vault has a proper lock then the padlock serves no purpose, and if it doesn't then you're screwed regardless.
I am sharing this in relation to the WAF comments and how much the companies implementing WAF care about your case.
> "How could Substack improve this situation for technical writers?"
They don’t care about (technical) writers. All they care about is building a TikTok clone to “drive discoverability” and make the attention-metrics go up. Chris Best is memeing about it on his own platform. Very gross.
If you push back you'll always get a lecture on "defense in depth", and then they really look at you like you're crazy when you suggest that it's more effective to get up, tap your desk once, and spin around in a circle three times every Thursday morning. I don't know... I do this every Thursday and I've never been hacked. Defense in depth, right? It can't hurt...
“We need SQL injection rules in the WAF”
“But we don’t have an SQL database”
“But we need to protect against the possibility of partnering with another company that needs to use the same datasets and wants to import them into a SQL database”
In fairness, these people are just trying to do their job too. They get told by NIST (et al) and Cloud service providers that WAF is best practice. So it’s no wonder they’d trust these snake oil salesman over the developers who asking not to do something “security” related.
Resolving wildcards is trickier but definitely possible if you have a list of forbidden files
[1]: https://nodejs.org/api/path.html#pathresolvepaths
Edit: changed link because C's realpath has a slightly different behavior
Here is a WAF matching line: https://github.com/coreruleset/coreruleset/blob/943a6216edea...
Here's where that file is loaded: https://github.com/coreruleset/coreruleset/blob/943a6216edea...
It's loaded with '"@pmFromFile lfi-os-files.data"' which means "case-insensitive match of values from a file".
So yeah, the reason it can't resolve paths properly is because WAFs are just regex and substring matching trying to paper over security issues in an application which can only be solved correctly at the application level.
Be very, very careful about this, because if you aren't, this can actually result in platform-dependent behavior or actual filesystem access. They are bytes containing funny slashes and dots, so process them as such.
Edit: s/text/bytes/
It's like not allowing the filesystem to use the word "virus" in a file name. Yes, it technically protects against some viruses, but it's really not very difficult to avoid while being a significant problem to a fair number of users with a legitimate use case.
It's not that it's useless. It's that it's stupid.
It reminds me of when airports started scanning people's shoes because an attacker had used a shoe bomb. Yes, that'll stop an attacker trying a shoe bomb again, but it disadvantages every traveller and attackers know to put explosives elsewhere.
Anything else is just a fuzzy bug injector that will only stop the simplest scanners and script kiddies if you are lucky.
The problem is that generally you're breaking actual valid use cases as the tradeoff to being another layer of defense against hypothetical vulnerabilities.
Yes, discussing the hosts file is a valid use case.
Yes putting angle brackets in the title of your message is valid use case your users are going to want.
Yes putting "mismatched" single quotes inside double quotes is a thing users will do.
Yes your users are going to use backslashes and omit spaces in a way that looks like attempts at escaping characters.
(All real problems I've seen caused by overzealous security products)
I believe the exact opposite.
One (of many) reasons is that it can make your code less secure, by hiding your security mistakes from you.
If your WAF obscures escaping issues during your own testing and usage you could very easily let those escaping issues go unresolved - leaving you vulnerable to any creative attacker who can outsmart your WAF.
So is HN and every other site in the world insecure because it allows users to post "/etc/hosts" ?
Why? It obviously has an annoying cost and equally obviously won't stop any hacker with a lukewarm IQ
It is net zero for security and net negative for user experience, so having it is worse than not having it.
So it's really blocking doorknob-twisting scripts.
as far as WAFs being garbage, they absolutely are, but this is a great time for a POSIWID analysis. A WAF says its purpose is to secure web apps. It doesn't do that, but people keep buying them. Now we're faced with a crossroads: we either have to assume that everyone is stupid or that the actual purpose of a WAF is something other than its stated purpose. I personally only assume stupidity as a last resort. I find it lazy and cynical, and it's often used to dismiss things as hopeless when they're not actually hopeless. To just say "Oh well, people are dumb" is a thought-terminating cliche that ignores potential opportunities. So we do the other thing and actually take some time to think about who decides to put a WAF in-place and what value it adds for them. Once you do that, you see myriad benefits because a WAF is a cheap, quick solution that allows non-technical people to say they're doing something. You're the manager of a finance OU that has a development group in it whose responsibility is some small web app. Your boss just read an article about cyber security and wants to know what this group two levels below you is doing about cyber security. Would you rather come back with "We're gonna need a year, $1 million and every other dev priority to be pushed back in order to develop a custom solution" or "We can have one fired up tomorrow for $300/mo, it's developed and supported by Microsoft and it's basically industry standard." The negative impact of these things is obvious to us because this is what we do, but we're not always the decision-makers for stuff like that. Often the decision-makers are actually that naive and/or they're motivated less by the ostensible goal of better web app security and more by the goal of better job security.
As far as etc/passwd you're right that passwords don't live there anymore but user IDs often do and those can indicate which services are running as daemons on a given system. This is vital because if you can figure out what services are running you can start version fingerprinting them and then cross-referencing those versions with the CVE database.
Who would be that stupid?
Correction: it is not your application but someone else's Certified Stuff (TM) that you can't change, but which is still vulnerable.
We disabled this check, auditor swerved out of his lane, I spent more several hours explaining things he didn’t understand, and things resolved after our CEO had a call with him (you can imagine how the discussion went).
All in all, if the auditor would have been more reasonable it wouldn’t have been an issue, but I’ve always been wary of managed firewall rulesets because of this reason.
WAFs can have thousands of rules ranging from basic to the sophisticated, not unlike mechanisms you can deploy at a checkpoint.
Security devices like IDSes or WAFs allow deploying filtering logic without touching an app directly, which can be hard/slow across team boundaries. They can allow retroactive analysis and flagging to a central log analysis team. Being able to investigate whether an adversary came through your door after the fact is powerful, you might even be able to detect a breach if you can filter through enough alerts.
People are more likely to get dismissed for not installing an IDS or WAF than having one. Its effectiveness is orthogonal to the politics of its existence, most of the time.
The way I assume it works in practice on a real team is that after some time, most of your team will have no idea how the WAF works and what it protects against, where and how it is configured… but they know it exists, so they will no longer pay attention to security because “we have a tool for that”, especially when they should have finished that feature a week ago…
When you don’t require them to change it, you can just assign them a random 16 character string and tell them it’s their job to memorize it.
I suddenly understand why it makes sense to integrity-check a payload that is already protected by all three of TLS, TCP checksum and CRC.
https://knowyourmeme.com/memes/events/star-wars-battlefront-...
If you know what you're doing, turn these protections off. If you don't, there's one less hole out there.
It’s even dumber than that. An attacker tried and failed to use a shoe bomb, and yet his failure has caused untold hours of useless delay for over 13 years now.
Ransomware is a huge and growing problem. Very different than airline security, where attacks are extremely uncommon. If planes were constantly getting blown up, and if a majority of those attacks started with a shoe bomb, then checking everyone's shoes would seem a lot more reasonable, no?
If the insurer requested something unreasonable, you'd go to a different insurer. It's a competitive market after all. But most of the complaints about incompetent security practices boil down to minor nuisances in the grand scheme of things. Forced password changes once every 90 days is dumb and slightly annoying but doesn't significantly impact business operations. Having to run some "enterprise security tool" and go through every false positive result (of which there will be many) and provide an explanation as to why it's a false positive is incredibly annoying and doesn't help your security, but it's also something you could have a $50k/year security intern do. Turning on a WAF that happens to reject the 0.0001% of Substack articles which talk about /etc/hosts isn't going to materially change Substack's revenue this year.
It negatively impacts security, because users then pick simpler passwords that are easier to rotate through some simple transformation. Which is why it's considered not just useless, but an anti-pattern.
If your startup is on the verge of getting a 6 figure MRR deal with a company, but the company's security team mandates you put in a WAF to "protect their data"... guess you're putting in a WAF, like it or not.
Install the WAF crap, and then feed every request through rot13(). Everyone is happy!
I understand the need for security tooling, but I don’t think companies often consider the huge performance impact these tools add.
Every CIO I have worked for (where n=3) has gotten where they are because they're a good manager, even though they have near-zero current technical knowledge.
The fetishizing of "business," in part through MBAs, has been detrimental to actually getting things done.
A century ago, if someone asked you what you do and you replied, "I'm a businessman. I have a degree in business," you'd get a response somewhere between "Yeah, but what to you actually do" and outright laughter.
Finance and business grads have really taken over the economy, not just through technocratic "here's how to do stuff" advice but by personally taking all the reigns of power. They're even hard at work taking over medicine and pushing doctors out of the work-social upper-middle-class. Already did it with professors. Lawyers seem safe, so far.
Nope, lawyers are fucked too. It's just not as advanced yet: https://www.abajournal.com/web/article/arizona-approves-alte...
I wouldn't be mean about it. I'm imagining adding a line to the email such as:
> (Yes, I know this is annoying, but it's required by our insurance company.)
What is the insurance company going to do, jack up our rates because we accurately stated what their policy was?
It would've gone from the insurer to the legal team, to the GRC team, to the enterprise security team, to the IT engineering team, to the IT support team, and then to the user.
Steps #1 to #4 can (and do) introduce their own requirements, or interpret other requirements in novel ways, and you'd be #5 in the chain.
That’s what the conversation I shared is demonstrating ;)
> Good would also be,if they actually knew what they are talking about, before trying to tell the engineers what to do.
Often the people enduring the rules aren’t supposed to be security specialists. Because you’ll have your SMEs (subject matter experts) and your stockholders. The stakeholders will typically be project managers or senior management (for example) who have different skill sets and priorities to the SMEs.
The problem is that when it comes to security, it’s a complicated field where caution is better than lack of caution. So if a particular project does call on following enhanced secret practices, it becomes a ripe field for snake oil salesman.
Or to put it another way: no company would get sued for following security theatre but they are held accountable if there is a breach due to not following security best practices.
So often it doesn’t matter how logical and sensible the counter argument is, it’s automatically a losing argument
The real problem is that the domain has gotten so complicated that a traditional risk mitigation approach to is an outdated role and is now better fulfilled by technical staff who specialise in security. But that’s an organisation problem caused by senior management (C-suite and above) rather than a particular individual in that specific role not doing their job well.
the main point is you need to pay a third party
Information loss is an inherent property of large organizations.
That's such an interesting axiom, I'm curious if you would want to say more about it? It feels right intuitively - complexity doesn't travel easily across contexts and reaching a common understanding is harder the more people you're talking to.
I imagine this gets amplified in a large org. The docs are lacking, people might not read them anyway, and you get an explosion of people who don't understand very much but still have a job to do.
The underlying purpose of the rules and agency to apply the spirt rather than the letter gets lost early in the chain and trying to unwind it can be tedious.
The part that’s not said outloud is that a lot of “computer security” people aren’t concerned with understanding the system. If they were, they’d be engineers. They’re trying to secure it without understanding it.
This is such a bizarre hybrid policy, especially since forced password rotations at fixed intervals are already not recommended for end-user passwords as a security practice.
One discourse I hear is that "people will just use the same password everywhere". To which I'll answer, "but we have mfa". "yeah, but the insurance guys".
WAFs do throw false positives and do require adjustments OOTB for most sites, but you’re missing the forest by focusing on this single case.
And WAF rules can be tuned. There's no reason an apostrophe in a username or similar needs to be blocked, if it were by a rule.
(in the anti-WAF camp but playing a pedant here)
In your Django app, you indeed follow the best practices and don't concatenate strings together and so think that this security theater doesn't apply. Yet, this is precisely how Django ORM works under the hood, and SQL injections are periodically found there.
The real solution here is to subscribe to the django-announce list and update Django, or backport the fix manually.
I'm not saying you're wrong, I've never worked in a company this large (except for a brief internship), or in IT specifically. But also, like, come on people, grow up.
The long passphrase is more for the key that unlocks your password manager rather than the random passwords you use day to day.
A false positive from a conservative evaluation of a query parameter or header value is one thing, conceivably understandable. A false positive due to the content of a blog post is something else altogether.
Rules like this might very well have had incredible positive impact on ten of thousands of websites at the cost of some weird debugging sessions for dozens of programmers (made up numbers obviously).
<!DOCTYPE html>
<html lang="en">
<body>
<p>/etc/hosts is a file on Unix hosts</p>
i guess demanding "Structured logs for everything or bust" is the answer? (i'm not a big o11y guy so pardon me if this is obvious)
Numeronyms are evil and we should stop using them.
It all comes down to understanding whether the intersection of two grammars is empty.
Error: OutOfMemoryException
Search: OutOfMemoryException
Sure you could add a convention to your 'how to log' doc that specifies that all user input should be tagged with double '#' but who reads docs until things break? convention is a shitty way to make things work.
There's 100 ways that you could make this work correctly. Only restarting on a much more specific string, i.e. including the app name in the log line etc . . . but that's all just reducing the likely hood that you get burned.
I've also written a OOM-Killer.sh myself, I'm not above that, but it's one of those edge cases that's impossible to do correctly, which is why parsing and acting on log data generally considered and anti-pattern.
Let's see what's blocked:
"Division by zero" anywhere in the response body since that's a php error. Good luck talking about math ([0] and [1])
Common substrings in webshells, all matched as strings in response bodies, rather than parsing HTML, so whatever, don't comment about webshells either [2]
Unless the body is compressed, in which case don't apply the above. Security [3].
Also, read this regex and tell me you understand what it's doing. Tell me the author of it understands what it matches: https://github.com/coreruleset/coreruleset/blob/943a6216edea...
What the coreruleset is doing here is trying to parse HTML, SQL, HTTP, and various other languages with Regular Expressions. This doesn't work. This will never give you a right result.
It's trying to keep up to date with the string representation of java and php errors, without even knowing the version of Java the server is running, and without the Java maintainers, who constantly add new errors, having any say.
The only reasons attackers aren't evading the webshell rules here trivially is because so few people use these rules in practice that they're not even worth defeating (and it is quite easy to have your php webshell generate unique html each load, which cannot be matched by a regular expression short of /.*/; html is not a regular grammar).
I was ready to see something that made WAFs feel like they did _anything_ based on your comment, but all I see is a pile of crap that I would not want anywhere near my site.
Filtering java error strings and php error strings out of my rust app's responses using regexes to parse html is just such a clown-world idea of security. Blocking the loading of web-shells until the attacker changes a single character in the 'title' block of the output html seems so dumb when my real problem is that someone could write an arbitrary executable to my server.
Every WAF ruleset I've read so far has made me sure it's a huge pile of snake-oil, and this one is no different.
[0]: https://github.com/coreruleset/coreruleset/blob/943a6216edea...
[1]: https://github.com/coreruleset/coreruleset/blob/943a6216edea...
[2]: https://github.com/coreruleset/coreruleset/blob/943a6216edea...
[3]: https://github.com/coreruleset/coreruleset/blob/943a6216edea...
These rules do in fact work. Like I've said previously, these rules require tuning for your particular website. If I'm "talking about math" then I would modify or disable that rule as needed.
I think this is the forest you're missing. WAF isn't "install it and walk away". WAF needs to be tested in conjunction with your release, like any other code would.
The WAF can and does protect against attacks your code would never think of. It also /logs requests/ in a way your web server will not, making it invaluable for auditing.
And when running 3rd party software that has a function you cannot control, but need to prevent, WAFs can do that, too. I have a particular query string that must work from an internal but not external network while external/internal users leverage the same URL -- WAF can do that with a custom rule examining the query string and denying access to the outside world.
Or if I need to prevent [AI] bot scraping. WAF can do that with a couple of clicks.
WAF also unloads the web server from malicious traffic. Instead of having to size up or out a web server, I can have a WAF appliance prevent that traffic from ever reaching the server.
> Every WAF ruleset I've read so far
You don't appear to have any experience with implementation or operation of a WAF, but are attempting to be authoritative and dismiss a WAFs utility.
agree
> And you can't meaningfully measure product metrics like impact for fundamentally broken products
disagree
https://retail.direct.zurich.ch/resources/definition/product...
Questionnaire Zurich Cyber Insurance
Question 4.2: "Do you have a technically enforced password policy that ensures use of strong passwords and that passwords are changed at least quarterly?"
Since this is an insurance questionnaire, presumably your answers to that question affect the rates you get charged?
(Found that with the help of o4-mini https://chatgpt.com/share/680bc054-77d8-8006-88a1-a6928ab99a...)
I just cant imagine any outcome other than it was translated to just a "no" and increased your premium over what it would have otherwise been.
Totally bonkers stuff.
Eliminating everything but a business's industry specific apps, MS Office, and some well-known productivity tools slashes support calls (no customization!) and frustrates cyberattacks to some degree when you can't deploy custom executables.
You install software via ticket requests to IT, and devs might have admin rights, but not root, and only temporary.
This is nothing new though, back in the timesharing days, where we would connect to the development server, we only got as much rights as required for the ongoing development workflows.
Hence why PCs felt so liberating.
The worst part about cyber insurance, though, is that as soon as you declare an incident, your computers and cloud accounts now belong to the insurance company until they have their chosen people rummage through everything. Your restoration process is now going to run on their schedule. In other words, the reason the recovery from a crypto-locker attack takes three weeks is because of cyber insurance. And to be fair, they should only have to pay out once for a single incident, so their designated experts get to be careful and meticulous.
Fear of a prospective expectation, compliance, requirement, etc., even when that requirement does not actually exist is so prevalent in the personality types of software developers.
My mental model at this point says that if there's a cost to some important improvement, the politics and incentives today are such that a typical executive will only do the bare minimum required by law or some equivalent force, and not a dollar more.
counter point - people are going to use them, better to expose newbies early and often and then everyone is better off
shorthands will always be in demand. we used to say “horseless carriage”, then “automobile”, then “car”. would you rather use Light amplification by stimulated emission of radiation or just “laser”s? etc
in the new york times? sure, spell out observability. but on HN? come on. the term is 7 years old and is used all over the site. it’s earned it
If you find typing tedious just use autocomplete or other tools instead of making it the readers' problem.
In around 2011, the Defence Signals Directorate (now the Australian Signals Directorate) went through and did an analysis of all of the intrusions they had assisted with over the previous few years. It turned out that app whitelisting, patching OS vulns, patching client applications (Office, Adobe Reader, browsers), and some basis permission management would have prevented something like 90% of them.
The "Top 4" was later expanded to the Essential Eight which includes additional elements such as backups, MFA, disabling Office macros and using hardened application configs.
https://www.cyber.gov.au/resources-business-and-government/e...
At first glance that might seem a poor move for corporate information security. But crucially, the security of cloud webapps is not the windows sysadmins' problem - buck successfully passed.
It's about the transition from artisanal hand-configuration to mass-produced fleet standards, and diverting exceptional behavior and customizations somewhere else.
Alice is on Discord because half of the products the company uses now give more or less direct access to their devs through Discord
Just wait when more countries keep adopting cybersecurity laws for companies liabilities when software doesn't behave, like in any other engineering industry.
A breach can turn out into enough money being lost, in credibility, canceled orders, or lawsuits, big enough to close shop, or having to fire those that thought security rules were dumb.
Also anyone with security officer title, in many countries has legal responsibilities when something goes wrong, so when they sign off software deliverables that go wrong, is their signature on the approval.