Forge Web Credentials: SAML Tokens

ID Name
T1606.001 Web Cookies
T1606.002 SAML Tokens

An adversary may forge SAML tokens with any permissions claims and lifetimes if they possess a valid SAML token-signing certificate.[1] The default lifetime of a SAML token is one hour, but the validity period can be specified in the NotOnOrAfter value of the conditions ... element in a token. This value can be changed using the AccessTokenLifetime in a LifetimeTokenPolicy.[2] Forged SAML tokens enable adversaries to authenticate across services that use SAML 2.0 as an SSO (single sign-on) mechanism.[3]

An adversary may utilize Private Keys to compromise an organization's token-signing certificate to create forged SAML tokens. If the adversary has sufficient permissions to establish a new federation trust with their own Active Directory Federation Services (AD FS) server, they may instead generate their own trusted token-signing certificate.[4] This differs from Steal Application Access Token and other similar behaviors in that the tokens are new and forged by the adversary, rather than stolen or intercepted from legitimate users.

An adversary may gain administrative Azure AD privileges if a SAML token is forged which claims to represent a highly privileged account. This may lead to Use Alternate Authentication Material, which may bypass multi-factor and other authentication protection mechanisms.[4]

ID: T1606.002
Sub-technique of:  T1606
Platforms: Azure AD, Google Workspace, Office 365, SaaS, Windows
Permissions Required: Administrator
Data Sources: Logon Session: Logon Session Creation, Web Credential: Web Credential Creation, Web Credential: Web Credential Usage
Contributors: Blake Strom, Microsoft 365 Defender; Oleg Kolesnikov, Securonix
Version: 1.1
Created: 17 December 2020
Last Modified: 14 April 2021

Procedure Examples

ID Name Description
G0016 APT29

APT29 created tokens using compromised SAML signing certificates.[5]

Mitigations

ID Mitigation Description
M1015 Active Directory Configuration

For containing the impact of a previously forged SAML token, rotate the token-signing AD FS certificate in rapid succession twice, which will invalidate any tokens generated using the previous certificate.[6]

M1047 Audit

Enable advanced auditing on AD FS. Check the success and failure audit options in the AD FS Management snap-in. Enable Audit Application Generated events on the AD FS farm via Group Policy Object.[7]

M1026 Privileged Account Management

Restrict permissions and access to the AD FS server to only originate from privileged access workstations.[7]

M1018 User Account Management

Ensure that user accounts with administrative rights follow best practices, including use of privileged access workstations, Just in Time/Just Enough Administration (JIT/JEA), and strong authentication. Reduce the number of users that are members of highly privileged Directory Roles.[4]

Detection

This technique may be difficult to detect as SAML tokens are signed by a trusted certificate. The forging process may not be detectable since it is likely to happen outside of a defender's visibility, but subsequent usage of the forged token may be seen. Monitor for anomalous logins using SAML tokens created by a compromised or adversary generated token-signing certificate. These logins may occur on any on-premises resources as well as from any cloud environment that trusts the certificate.[4] Search for logins to service providers using SAML SSO which do not have corresponding 4769, 1200, and 1202 events in the Domain.[8]

Consider modifying SAML responses to include custom elements for each service provider. Monitor these custom elements in service provider access logs to detect any anomalous requests.[8]

References