MySQL Anonymous Login Handshake - Information Leakage.

2006-05-03T00:00:00
ID SECURITYVULNS:DOC:12527
Type securityvulns
Reporter Securityvulns
Modified 2006-05-03T00:00:00

Description

~.oOOo. Anonymous Login Handshake .oOOo.~

MySQL Server (<= 4.1.18, 5.0.20 ) has an information leakage in the way mysql parses login packets on anonymous users (blank password).

Author: Stefano Di Paola Vulnerable: Mysql <= 4.1.18, 5.0.20 Type of Vulnerability: Local/Remote - input validation - Information Leakage Tested On : Debian 3.1 - IA32. Vendor Status: Notified on April, 25th 2006, Confirmed on April, 26th 2006, New versions released on 2nd May 2006. Fixed: Update to 4.0.27, 4.1.19, 5.0.21, 5.1.10 versions.

A Proof of Concept is Attached for this issue. Tested on: Debian 3.1 - IA32.

A little Note: To take advantage of these flaws an attacker should have direct access to MySQL server communication layer (port 3306 or unix socket). But if used in conjuction with some web application flaws (i.e. php code injection) an attacker could use socket programming (i.e. php sockets) to gain access to that layer.

-- Description

By crafting a specifically malformed login packet, initial db name is filled with uninitialized memory content.

Let's suppose MySql Server has anonymous access.

Infact, if we want to use 'wisecdb' database as user 'wisec' and password 's' a normal client would send a packet like this:


43 00 00 01 0d a6 03 00 00 00 00 01 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 77 69 73 65 63 00 14 aa 69 23 07 2a ff 99 61 a3 c4 5f 04 66 3b 32 ef a1 f2 b6 59 77 69 73 65 63 64 62 00 C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . w i s e c . . . i # . * . . a . . _ . f ; 2 . . . . Y w i s e c d b .


but if we look at the code (MySQL <= 5.0.20) on sql_parse.cc line ~ 993 function check_connection(THD thd): --
char
user= end; char passwd= strend(user)+1; char db= passwd; char db_buff[NAME_LEN+1]; // buffer to store db in utf8 char user_buff[USERNAME_LENGTH+1]; // buffer to store user in utf8 uint dummy_errors;

uint passwd_len= thd->client_capabilities & CLIENT_SECURE_CONNECTION ? passwd++ : strlen(passwd); db= thd->client_capabilities & CLIENT_CONNECT_WITH_DB ? db + passwd_len + 1 : 0; [1] / Since 4.1 all database names are stored in utf8 */ if (db) { db_buff[copy_and_convert(db_buff, sizeof(db_buff)-1, system_charset_info, db, strlen(db), thd->charset(), &dummy_errors)]= 0; db= db_buff; }

--

It can be noticed a check for packet construction is missing here[1].

Just replace the null byte at the end of username 'wisec\0' with any other byte like this 'wisec0'. What happens?

user is assigned to some part of the packet content, and db is assigned with some (internal) memory beyond packet_length.

so if we send a specifical packet we'll get an error message like this:

Access denied for user ''@localhost to database 'lqt'

By changing packet lenght (db length) and with a little bit of luck a malicious user could get sensitive informations such as parts of queries and or response executed by some previously logged user.

-

The fix:

bugs are fixed in 4.0.27, 4.1.19, 5.0.21, 5.1.10. You can download them on http://dev.mysql.com/downloads/

=================================================

==Anonymous packet information leakage poc :

my_anon_db_leak.c

Compile with: gcc my_anon_db_leak.c -o my_anon_db_leak

usage: my_anon_db_leak [-s path/to/socket] [-h hostname_or_ip] [-p port_num] [-n db_len]

Example $ my_anon_db_leak -s /tmp/mysql.sock -n 20

Regards,

Stefano

--

......---oOOo--------oOOo---...... Stefano Di Paola Software Engineer Email: stefano.dipaola_at_wisec.it Email: stefano.dipaola1_at_tin.it Web: www.wisec.it ..................................