martin f krafft
2009-Jun-28 08:14 UTC
[Secure-testing-team] Bug#534908: possibly symlink attack due to client-connect script
Package: openvpn
Version: 2.1~rc15-1
Severity: important
Tags: security
OpenVPN''s --client-connect option is described as follows:
--client-connect script
Run script on client connection. The script is passed the
common
name and IP address of the just-authenticated client as
environmen-
tal variables (see environmental variable section below).
The
script is also passed the pathname of a not-yet-created
temporary
file as $1 (i.e. the first command line argument), to be used
by
the script to pass dynamically generated config file
directives
back to OpenVPN.
Since the script and it''s argument should be visible in the process
table, and client connect scripts might just be simple shell
scripts, it could be possible for an attacker to launch a symlink
attack:
1. monitor process table for connect script
2. create symlink, e.g. to overwrite /etc/shadow
3. watch the connect script clobber /etc/shadow
I don''t think this is a big threat, it''s a problem that can
easily
be solved by using a proper tempfile (and ensuring that it gets
deleted when no longer needed).
-- System Information:
Debian Release: squeeze/sid
APT prefers unstable
APT policy: (500, ''unstable''), (500,
''stable''), (1, ''experimental'')
Architecture: i386 (i686)
Kernel: Linux 2.6.30-1-686 (SMP w/1 CPU core)
Locale: LANG=en_GB, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages openvpn depends on:
ii debconf [debconf-2.0] 1.5.26 Debian configuration management sy
ii libc6 2.9-18 GNU C Library: Shared libraries
ii liblzo2-2 2.03-1 data compression library
ii libpam0g 1.0.1-9 Pluggable Authentication Modules l
ii libpkcs11-helper1 1.07-1 library that simplifies the intera
ii libssl0.9.8 0.9.8k-3 SSL shared libraries
ii openssl-blacklist 0.5-2 list of blacklisted OpenSSL RSA ke
ii openvpn-blacklist 0.4 list of blacklisted OpenVPN RSA sh
Versions of packages openvpn recommends:
ii net-tools 1.60-23 The NET-3 networking toolkit
Versions of packages openvpn suggests:
ii openssl 0.9.8k-3 Secure Socket Layer (SSL) binary a
ii resolvconf 1.44 name server information handler
-- debconf information excluded
--
.''''`. martin f. krafft <madduck at d.o> Related
projects:
: :'' : proud Debian developer http://debiansystem.info
`. `''` http://people.debian.org/~madduck http://vcs-pkg.org
`- Debian - when you have better things to do than fixing systems
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