Debian Security Advisory: fsh symlink attack

Nov 30, 2000, 00:06 (0 Talkback[s])
(Other stories by Wichert Akkerman)

Date: Thu, 30 Nov 2000 00:46:36 +0100
From: Wichert Akkerman wichert@cistron.nl
To: debian-security-announce@lists.debian.org
Subject: [SECURITY] [DSA-002-1] fsh symlink attack

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Debian Security Advisory DSA-002-1                              security@debian.org
http://www.debian.org/security/                           Wichert Akkerman 
November 30, 2000

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Package        : fsh
Problem type   : symlink attack
Debian-specific: no

Colin Phipps found an interesting symlink attack problem in fsh (a tool to quickly run remote commands over rsh/ssh/lsh). When fshd starts it creates a directory in /tmp to hold its sockets. It tries to do that securely by checking of it can chown that directory if it already exists to check if it is owner by the user invoking it. However an attacker can circumvent this check by inserting a symlink to a file that is owner by the user who runs fhsd and replacing that with a directory just before fshd creates the socket.

This has been fixed in version 1.0.post.1-3potato.

wget url
        will fetch the file for you
dpkg -i file.deb
        will install the referenced file.

Debian GNU/Linux 2.2 alias potato

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Potato was released for alpha, arm, i386, m68k, powerpc and sparc.

Source archives:
http://security.debian.org/dists/stable/updates/main/source/fsh_1.0.post.1-3potato.diff.gz
MD5 checksum: 278a82a3899974ec60b4f92d3a2d53d7
http://security.debian.org/dists/stable/updates/main/source/fsh_1.0.post.1-3potato.dsc
MD5 checksum: d2e6eee08ba39ed82b756f39da2a1587
http://security.debian.org/dists/stable/updates/main/source/fsh_1.0.post.1.orig.tar.gz
MD5 checksum: d0ade4d65da92256c110a042479109f1

Alpha architecture:
http://security.debian.org/dists/stable/updates/main/binary-alpha/fsh_1.0.post.1-3potato_alpha.deb
MD5 checksum: 729414dcde81ef4d50681839a8df62a2

ARM architecture:
http://security.debian.org/dists/stable/updates/main/binary-arm/fsh_1.0.post.1-3potato_arm.deb
MD5 checksum: 5543a9a61b7af9b48c277f4aca83c75a

Intel ia32 architecture:
http://security.debian.org/dists/stable/updates/main/binary-i386/fsh_1.0.post.1-3potato_i386.deb
MD5 checksum: 6d6dd446e87bff6ed57c7176813609c8

Motorola 680x0 architecture:
http://security.debian.org/dists/stable/updates/main/binary-m68k/fsh_1.0.post.1-3potato_m68k.deb
MD5 checksum: 50bce3a431b141e68a3dfdae1b71f5a9

PowerPC architecture:
http://security.debian.org/dists/stable/updates/main/binary-powerpc/fsh_1.0.post.1-3potato_powerpc.deb
MD5 checksum: 8e99a4a3657fee8d9545099d02526c5b

Sun Sparc architecture:
http://security.debian.org/dists/stable/updates/main/binary-sparc/fsh_1.0.post.1-3potato_sparc.deb
MD5 checksum: fe3de98286cb7d5e83ca00631785adbe

These files will be moved into
ftp://ftp.debian.org/debian/dists/stable/*/binary-$arch/ soon.

For not yet released architectures please refer to the appropriate directory ftp://ftp.debian.org/debian/dists/sid/binary-$arch/ .

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apt-get: deb http://security.debian.org/ stable/updates main
dpkg-ftp: ftp://security.debian.org/debian-security dists/stable/updates/main
Mailing list: debian-security-announce@lists.debian.org