The Security Assertion Markup Language (SAML) is a widely used standard in single sign-on systems. In a simplified version, the user authenticates to an Identity Provider which generates a signed SAML Response. This response is then forwarded to a Service Provider for validation and authentication.
If the Service Provider does not manage to properly validate the incoming SAML response message signatures, attackers might be able to manipulate the response content without the application noticing. Especially, they might be able to alter the authentication-targeted user.
By exploiting this vulnerability, an attacker can manipulate the SAML Response to impersonate a different user. This, in turn, can have various consequences on the application’s security.
Exploiting this vulnerability allows an attacker with authenticated access to impersonate other users within the SAML-based SSO system. This can lead to unauthorized access to sensitive information, resources, or functionalities the attacker should not have. By masquerading as legitimate users, the attacker can bypass authentication mechanisms and gain unauthorized privileges, potentially compromising the entire system. By impersonating a user with higher privileges, the attacker can gain access to additional resources. Privilege escalation can lead to further compromise of other systems and unauthorized access to critical infrastructure.
With the ability to impersonate other users, an attacker can gain access to sensitive data stored within the SAML-based SSO system. This includes personally identifiable information (PII), financial data, intellectual property, or any other confidential information. Data breaches can result in reputational damage, legal consequences, financial losses, and harm to individuals whose data is exposed.
The following code examples are vulnerable because they explicitly include comments in signature checks. An attacker is able to change the field identifying the authenticated user with XML comments.
import org.opensaml.xml.parse.StaticBasicParserPool;
import org.opensaml.xml.parse.ParserPool;
public ParserPool parserPool() {
StaticBasicParserPool staticBasicParserPool = new StaticBasicParserPool();
staticBasicParserPool.setIgnoreComments(false); // Noncompliant
return staticBasicParserPool;
}
import org.opensaml.xml.parse.BasicParserPool;
import org.opensaml.xml.parse.ParserPool;
public ParserPool parserPool() {
BasicParserPool basicParserPool = new BasicParserPool();
basicParserPool.setIgnoreComments(false); // Noncompliant
return basicParserPool;
}
import org.opensaml.xml.parse.StaticBasicParserPool;
import org.opensaml.xml.parse.ParserPool;
public ParserPool parserPool() {
return new StaticBasicParserPool();
}
import org.opensaml.xml.parse.BasicParserPool;
import org.opensaml.xml.parse.ParserPool;
public ParserPool parserPool() {
return new BasicParserPool();
}