Date: Wed, 5 Dec 2001 09:03:18 +0200 From: titus manea <titus@edc.dnttm.ro> To: freebsd-security@FreeBSD.ORG Subject: OpenSSH UseLogin problem Message-ID: <20011205090318.A7617@unix.edc.dnttm.ro>
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II. Problem Description
OpenSSH includes a feature by which a user can arrange for
environmental variables to be set depending upon the key used for
authentication. These environmental variables are specified in the
uthorized_keys' (SSHv1) or `authorized_keys2' (SSHv2) files in the
user's home directory on the server. This is normally safe, as this
environment is passed only to the user's shell, which is invoked with
user privileges.
However, when the OpenSSH server `sshd' is configured to use
the system's login program (via the directive `UseLogin yes' in
sshd_config), this environment is passed to login, which is invoked
with superuser privileges. Because certain environmental variables
such as LD_LIBRARY_PATH and LD_PRELOAD can be set using the previously
described feature, the user may arrange for login to execute arbitrary
code with superuser privileges.
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ls -l `which login`
-r-sr-xr-x 1 root wheel 22020 Oct 25 13:06 /usr/bin/login
LD_ env vars like LD_LIBRARY_PATH and such do not work for setuid binaries.
(ld.so man page)
programs. Here is an example ( i did it as root).
Ok, i moved libmysqlclient.so.10 from its place to my ~. and copied
mysql to ~ too.
[08:52:11] [titus!root]~#./mysql
/usr/libexec/ld-elf.so.1: Shared object "libmysqlclient.so.10" not found
[08:52:19] [titus!root]~#export LD_LIBRARY_PATH=/home/titus
[08:52:35] [titus!root]~#./mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5 to server version: 3.23.41
Type 'help;' or '\h' for help. Type '\c' to clear the buffer.
mysql> Bye
[08:52:49] [titus!root]~#chmod +s mysql
[08:52:54] [titus!root]~#./mysql
/usr/libexec/ld-elf.so.1: Shared object "libmysqlclient.so.10" not found
[08:52:55] [titus!root]~#
--
__________________________________________________________________________
Titus Manea <titus@2edc.com> | Eastern Digital Inc.
Lab owner | http://2edc.com
| +40-56-192091
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