CAPEC-21 Detail

An adversary guesses, obtains, or "rides" a trusted identifier (e.g. session ID, resource ID, cookie, etc.) to perform authorized actions under the guise of an authenticated user or service.

Execution Flow

[Survey the application for Indicators of Susceptibility] Using a variety of methods, until one is found that applies to the target, the adversary probes for cookies, session tokens, or entry points that bypass identifiers altogether.

• Spider all available pages
• Attack known bad interfaces
• Search outward-facing configuration and properties files for identifiers.

[Fetch samples] The adversary fetches many samples of identifiers. This may be through legitimate access (logging in, legitimate connections, etc.) or via systematic probing.

• An adversary makes many anonymous connections and records the session IDs assigned.
• An adversary makes authorized connections and records the session tokens or credentials issued.
• An adversary gains access to (legitimately or illegitimately) a nearby system (e.g., in the same operations network, DMZ, or local network) and makes a connection from it, attempting to gain the same privileges as a trusted system.

[Impersonate] An adversary can use successful experiments or authentications to impersonate an authorized user or system or to laterally move within a system or application

[Spoofing] Malicious data can be injected into the target system or into a victim user's system by an adversary. The adversary can also pose as a legitimate user to perform social engineering attacks.

[Data Exfiltration] The adversary can obtain sensitive data contained within the system or application.

Prerequisites

Server software must rely on weak identifier proof and/or verification schemes.
Identifiers must have long lifetimes and potential for reusability.
Server software must allow concurrent sessions to exist.

Skills Required

To achieve a direct connection with the weak or non-existent server session access control, and pose as an authorized user

Resources Required

Ability to deploy software on network.
Ability to communicate synchronously or asynchronously with server.

Mitigations

Design: utilize strong federated identity such as SAML to encrypt and sign identity tokens in transit.
Implementation: Use industry standards session key generation mechanisms that utilize high amount of entropy to generate the session key. Many standard web and application servers will perform this task on your behalf.
Implementation: If the identifier is used for authentication, such as in the so-called single sign on use cases, then ensure that it is protected at the same level of assurance as authentication tokens.
Implementation: If the web or application server supports it, then encrypting and/or signing the identifier (such as cookie) can protect the ID if intercepted.
Design: Use strong session identifiers that are protected in transit and at rest.
Implementation: Utilize a session timeout for all sessions, for example 20 minutes. If the user does not explicitly logout, the server terminates their session after this period of inactivity. If the user logs back in then a new session key is generated.
Implementation: Verify authenticity of all identifiers at runtime.

Related Weaknesses

References

REF-1

Exploiting Software: How to Break Code
G. Hoglund, G. McGraw.

Submission

Modifications