- cross-posted to:
- [email protected]
- cross-posted to:
- [email protected]
Found the error Not allowed to load local resource: file:///etc/passwd while looking at infosec.pub’s communities page. There’s a community called “ignore me” that adds a few image tags trying to steal your passwd file.
You have to be extremely poorly configured for this to work, but the red flags you see should keep you on your toes for the red flags you don’t.
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If you find something, report it. Don’t experiment on the public.
https://www.bugcrowd.com/resources/guide/what-is-responsible-disclosure/
My first thought was that a Javascript library pulled from a CDN got spiked.
Is this, by any chance, originated from the sub called
ignore? In that case is probably my bad because is set as the image of the channel. (I was playing with lemmy in the previous version and forgot about it, sorry. It will not work since your browser can’t access local file that easily without breaking the sandbox :))Edit: I removed it so you shouldn’t see the alert anymore. What I wasn’t expecting is that apparently every sub is loaded even if you don’t visit it.
But… why? Why even put that URL there? Even if it was most likely harmless for all users, this still looks like an attempt at data exfiltration.
Because I wanted to try if others URI schemas were supported instead of http / https. file:// was a valid one. Don’t worry, the day an attempt of data exfil will happen, you will not see it though your console logs.
I doubt this person ever expected anyone to find it or to read that much into it lol
Holy shit this is kind of unsettling. Though I would expect ALL major browsers to reject reading any local files like this… would this kind of thing actually succeed somewhere/somehow?
If you ran your browser as root and configured your browser to load local resources on non-local domains maybe. I think you can do that in chrome://flags but you have to explicitly list the domains allowed to do it.
I’m hoping this is just a bad joke.
Yeah, seems highly unlikely to ever yield any results. Even if you did manage to read a file, you have to get lucky finding a password hash in a rainbow table or the password being shit enough to crack.
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you don’t need to be root to read
/etc/passwdThat’s because passwd doesn’t store the password hashes. Just user names.
Are you sure? What do you get when you run
cat /etc/passwdin terminal? Just paste the results here 😇Edit: to anyone reading this on the future, don’t actually do this, it was a joke
yup pretty sure
$ cat /etc/passwd fox:hunter2:1000:1000::/home/fox:/usr/bin/zsh😉
Weird, all I see is *******
Since you told me not to. There isn’t a risk on most linux systems; passwords were moved to /etc/shadow a long time ago. It only leaks the names of your users and largely useless info for most attackers:
root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin mail:x:8:8:mail:/var/mail:/usr/sbin/nologin news:x:9:9:news:/var/spool/news:/usr/sbin/nologin uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin proxy:x:13:13:proxy:/bin:/usr/sbin/nologin www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin backup:x:34:34:backup:/var/backups:/usr/sbin/nologin list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin irc:x:39:39:ircd:/run/ircd:/usr/sbin/nologin gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin _apt:x:100:65534::/nonexistent:/usr/sbin/nologin systemd-network:x:101:102:systemd Network Management,,,:/run/systemd:/usr/sbin/nologin systemd-resolve:x:102:103:systemd Resolver,,,:/run/systemd:/usr/sbin/nologin messagebus:x:999:999:System Message Bus:/:/usr/sbin/nologin systemd-timesync:x:998:998:systemd Time Synchronization:/:/usr/sbin/nologin systemd-coredump:x:997:997:systemd Core Dumper:/:/usr/sbin/nologin delial:x:1000:1000:,,,:/home/delial:/bin/bash sshd:x:103:65534::/run/sshd:/usr/sbin/nologin xrdp:x:104:110::/run/xrdp:/usr/sbin/nologin dictd:x:105:111:Dictd Server,,,:/var/lib/dictd:/usr/sbin/nologin nm-openvpn:x:106:112:NetworkManager OpenVPN,,,:/var/lib/openvpn/chroot:/usr/sbin/nologin sssd:x:107:113:SSSD system user,,,:/var/lib/sss:/usr/sbin/nologinWell it’s not completely useless. It offers some insights into the system. Which service accounts exists, what usernames are used.
If an attacker finds a valid username they can then start bruteforcing the password.
From your account list we can see you have sshd and xrdp. Do they both provide the same kind of bruteforce protection? Are there any recent exploits for either?
Can confirm it’s still there for the
ignore mecommunity.Nice share, thanks for the information. Definitely need to be careful both as a server operator with Lemmy, and a user of it.
honestly, this feels more like a proof of concept than an actual hack. passwords are almost universally encrypted and stored in /etc/shadow nowadays and when I was on the security CoP at my old job cat’ing /etc/passwd was how we proved basic read access to a system but nothing more.
It is possible that something like this could exfil the file as well, which might leak info about what daemons a given system is running. An attacker could possibly then do some research to find vulnerabilities for a given service version and try the real attack later. Generally complex kill chains like this aren’t viable for mass scanning though, much more likely that they would just automate an attempt at a few common exploits than force themselves to do actual recon.
While this is concerning, I wonder what the author(s) of this were thinking would happen. I assume it’s supposed to be an attempt at stealing the server’s passwords, since I at least know of no browser that freely allows access to local files.
FWIW,
/etc/passwditself contains no passwords (the name exists for historical reasons) but it definitely is a globally accessible file that can give you clues about the target system. Given this, it’s more likely the user is attempting to find out if arbitrary disk reads are possible by using a well known path on many servers.
