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';somesql+--&pass=x"
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@example.com