IMP 2.x SQL injection vulnerabilities

IMP is a popular webmail package written in PHP. It ships with some UNIX
systems and is also used on Windows servers. The version 2 of the program
contains some SQL injection flaws which allow any remote user to access
the webmail system's database. Valid user authentication is not required
in order to exploit the flaws.

The error happens in some database functions in PHP files named
lib/db.<databasename>. An example from db.pgsql, function check_prefs:

$sql="select username from $default->db_pref_table where username='$user@$server'";

Including user-supplied strings directly in an SQL query is a mistake.
The fix is to use something like the addslashes() PHP function.

As a proof of concept:

$ lynx
"http://webmail.server/imp/mailbox.php3?actionID=6&server=x&imapuser=x&#39;;somesql+--&pass=x&quot;

IMP would try to execute "somesql" and the result would be this kind
of PHP error (presuming the PHP configuration allows displaying error
messages on web pages):

Warning: PostgreSQL query failed: ERROR: parser: parse error at or near "somesql" in
/usr/share/horde/imp/lib/db.pgsql on line 127

Even though SQL query results aren't directly readable from the screen
in the above example, the attacker might e.g. update his/her mail
signature to contain wanted query results and then view it on the
preferences page of IMP. This requires a valid login, but isn't a
problem for an attacker because IMP allows the use of any remote IMAP
server. Use of the server_list option doesn't affect this behaviour; the
attacker-controlled IMAP server may be still passed to mailbox.php3 in the
URL.

The impact of SQL injection depends heavily on the underlying database
and its configuration. If PostgreSQL is used, it's possible to execute
multiple complete SQL queries separated by semicolons. The database
contains session id's so the attacker might hijack sessions of people
currently logged in and read their mail. In the worst case, if the
hordemgr user has the required privilege to use the COPY SQL command
(found in PostgreSQL at least), a remote user may read or write to any
file the database user (postgres) can. The attacker may then be able to
run arbitrary shell commands by writing them to the postgres user's
~/.psqlrc; they'd be run when the user starts the psql command which
under some configurations happens regularly from a cron script.

If other database servers are used, the exploitation possibilities may
be more limited.

The vendor has been informed about this bug last month. Although there
hasn't been any direct reply, there was a comment on this on the IMP
mailing list: "2.2.x is officially deprecated/unsupported. This does not
apply to 3.x.".

Versions up to and including 2.2.8 seem vulnerable. According to the
author, version 3 isn't affected so upgrading to IMP 3 is recommended.
This, and more information about IMP is available at http://horde.org/imp/.

Jouko Pynnönen
[email protected]