rssh, scponly: Unrestricted command execution

1. Gentoo Linux Security Advisory

Advisory Reference	GLSA 200412-01 / scponly
Release Date	December 03, 2004
Latest Revision	May 22, 2006: 03
Impact	normal
Exploitable	remote

Package	Vulnerable versions	Unaffected versions	Architecture(s)
net-misc/scponly	< 4.0	>= 4.0	All supported architectures
app-shells/rssh	<= 2.2.2	>= 2.2.3	All supported architectures

Related bugreports: #72815, #72816

Synopsis

rssh and scponly do not filter command-line options that can be exploited to execute any command, thereby allowing a remote user to completely bypass the restricted shell.

2. Impact Information

Background

rssh and scponly are two restricted shells, allowing only a few predefined commands. They are often used as a complement to OpenSSH to provide access to remote users without providing any remote execution privileges.

Description

Jason Wies discovered that when receiving an authorized command from an authorized user, rssh and scponly do not filter command-line options that can be used to execute any command on the target host.

Impact

Using a malicious command, it is possible for a remote authenticated user to execute any command (or upload and execute any file) on the target machine with user rights, effectively bypassing any restriction of scponly or rssh.

3. Resolution Information

Workaround

There is no known workaround at this time.

Resolution

All scponly users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=net-misc/scponly-4.0"

All rssh users should upgrade to the latest version:

Code Listing 3.2: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=app-shells/rssh/rssh-2.2.3"

4. References

Page updated December 03, 2004

Summary: This is a Gentoo Linux Security Advisory

Security Team
Contact Address

Donate to support our development efforts.