Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Cloud

2/27/2018
03:00 PM
Connect Directly
Twitter
LinkedIn
Google+
RSS
E-Mail
50%
50%

SAML Flaw Lets Hackers Assume Users' Identities

Vulnerability affects single sign-on for SAML-reliant services including OneLogin, Duo Security, Clever, and OmniAuth.

A newly discovered vulnerability lets attackers take advantage of single sign-on (SSO) systems relying on Security Assertion Markup Language (SAML) and authenticate as another user without knowing his or her password.

Duo Security's Duo Labs discovered the flaw and coordinated with the CERT/CC on disclosures from the affected vendors, which include Duo Security. The CERT/CC published an advisory on the flaw today.

SAML is an XML markup language used to authenticate to third-party applications. When a user authenticates to an application such as Office 365 or Salesforce, SAML redirects the browser to a company login page. After a successful login, the browser redirects to the third-party app and grants the user access. SAML is popular among SSO services.

Step one of SSO authentication is via the Identity Provider (IdP), which checks usernames and passwords, verifies account status, and prompts two-factor authentication. The IdP generates a signed SAML response, which it forwards to the service provider for validation. If the signature is valid, a string identifier in the SAML response identifies which user to authenticate.

Researchers at Duo Labs discovered many open-source libraries incorrectly use the results of XML DOM traversal and canonicalization APIs. An attacker can change SAML responses without altering the cryptographic signature and authenticate to applications as a legitimate user.

"Single sign-on simplifies authentication by letting you log into one service which, in turn, grants access to multiple services," explains Kelby Ludwig, senior application security engineer at Duo. "If an attacker has access to one of the single sign-on systems, they can tamper with SAML in such a way they can log in as different users."

The vulnerability is in the XML comments inserted into SAML response requests. In most cases, the XML canonicalization algorithm will remove comments while validating the signature. This means any attacker can add comments to a SAML response without invalidating the signature.

All an attacker needs is an account on the same network as the target. They can change the content of their own SAML requests so a different user's name appears as their own and bypass the primary authentication for the affected SAML provider.

Duo Labs identified the following affected vendors. CVEs have been assigned for:

  • OneLogin - python-saml - CVE-2017-11427
  • OneLogin - ruby-saml - CVE-2017-11428
  • Clever - saml2-js - CVE-2017-11429
  • OmniAuth-SAML - CVE-2017 - 11430
  • Shibboleth - CVE-2018-0489
  • Duo Network Gateway - CVE-2018-7340

This vulnerability affects each service relying on SAML in different ways. SAML IdPs and service providers are very configurable and there's room for greater or lesser impact. For example, service providers that use email addresses and validate their domain against a whitelist are less likely to be exploited than those allowing arbitrary strings to identify users, researchers explain.

It's important to emphasize this flaw doesn't only affect IdPs but SAML libraries. In the case a vendor wants to add single sign-on, they may add one of these libraries, which would increase the number of people affected. Anyone who uses one of these libraries should check whether they're affected, says Steve Manzuik, director of security research at Duo Labs.

"Enterprises running products will have patches to install and vendors using affected libraries will have to issue patches as well," says Manzuik. Remediation depends on the type of relationship a business has with SAML.

This vulnerability only lets an attacker bypass the first factor of authentication, so it helps if your SAML service provider uses two-factor authentication. However, if your IdP handles both first- and second-factor authentication, the flaw likely bypasses both.

Related Content:

 

 

 

Black Hat Asia returns to Singapore with hands-on technical Trainings, cutting-edge Briefings, Arsenal open-source tool demonstrations, top-tier solutions and service providers in the Business Hall. Click for information on the conference and to register.

Kelly Sheridan is the Staff Editor at Dark Reading, where she focuses on cybersecurity news and analysis. She is a business technology journalist who previously reported for InformationWeek, where she covered Microsoft, and Insurance & Technology, where she covered financial ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
ragediver24
50%
50%
ragediver24,
User Rank: Strategist
2/28/2018 | 12:08:15 PM
SAML Flaw
Does this flaw also allow attackers to assume user identities and login on mobile devices as well?
7 Tips for Infosec Pros Considering A Lateral Career Move
Kelly Sheridan, Staff Editor, Dark Reading,  1/21/2020
For Mismanaged SOCs, The Price Is Not Right
Kelly Sheridan, Staff Editor, Dark Reading,  1/22/2020
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: This comment is waiting for review by our moderators.
Current Issue
IT 2020: A Look Ahead
Are you ready for the critical changes that will occur in 2020? We've compiled editor insights from the best of our network (Dark Reading, Data Center Knowledge, InformationWeek, ITPro Today and Network Computing) to deliver to you a look at the trends, technologies, and threats that are emerging in the coming year. Download it today!
Flash Poll
How Enterprises are Attacking the Cybersecurity Problem
How Enterprises are Attacking the Cybersecurity Problem
Organizations have invested in a sweeping array of security technologies to address challenges associated with the growing number of cybersecurity attacks. However, the complexity involved in managing these technologies is emerging as a major problem. Read this report to find out what your peers biggest security challenges are and the technologies they are using to address them.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-16029
PUBLISHED: 2020-01-26
A vulnerability in the application programming interface (API) of Cisco Smart Software Manager On-Prem could allow an unauthenticated, remote attacker to change user account information which can prevent users from logging in, resulting in a denial of service (DoS) condition of the web interface. Th...
CVE-2020-3115
PUBLISHED: 2020-01-26
A vulnerability in the CLI of the Cisco SD-WAN Solution vManage software could allow an authenticated, local attacker to elevate privileges to root-level privileges on the underlying operating system. The vulnerability is due to insufficient input validation. An attacker could exploit this vulnerabi...
CVE-2020-3121
PUBLISHED: 2020-01-26
A vulnerability in the web-based management interface of Cisco Small Business Smart and Managed Switches could allow an unauthenticated, remote attacker to conduct a cross-site scripting (XSS) attack against a user of the interface. The vulnerability is due to insufficient validation of user-supplie...
CVE-2020-3129
PUBLISHED: 2020-01-26
A vulnerability in the web-based management interface of Cisco Unity Connection Software could allow an authenticated, remote attacker to perform a stored cross-site scripting (XSS) attack. The vulnerability is due to insufficient input validation by the web-based management interface. An attacker c...
CVE-2020-3131
PUBLISHED: 2020-01-26
[CVE-2020-3131_su] A vulnerability in the Cisco Webex Teams client for Windows could allow an authenticated, remote attacker to cause the client to crash, resulting in a denial of service (DoS) condition. The attacker needs a valid developer account to exploit this vulnerability. The vulnerability i...