CAPEC-68 - Subvert Code-signing Facilities

Because languages use code signing facilities to vouch for code's identity and to thus tie code to its assigned privileges within an environment, subverting this mechanism can be instrumental in an attacker escalating privilege.

Any means of subverting the way that a virtual machine enforces code signing classifies for this style of attack. This pattern does not include circumstances through which a signing key has been stolen.

Severity

Likelihood

Confidentiality

Integrity

Availability

  • Attack Methods 2
  • Spoofing
  • API Abuse
  • Purposes 1
  • Exploitation
  • Scopes 1
  • Gain privileges / assume identity
  • Authorization
  • Access_Control
  • Confidentiality

High level: Subverting code signing is not a trivial activity. Most code signing and verification schemes are based on use of cryptography and the attacker needs to have an understand of these cryptographic operations in good detail. Additionally the attacker also needs to be aware of the way memory is assigned and accessed by the container since, often, the only way to subvert code signing would be to patch the code in memory.

A framework-based language that supports code signing (such as, and most commonly, Java or .NET)

Deployed code that has been signed by its authoring vendor, or a partner.

The attacker will, for most circumstances, also need to be able to place code in the victim container. This does not necessarily mean that they will have to subvert host-level security, except when explicitly indicated.

The Attacker needs no special resources beyond the listed prerequisites in order to conduct this style of attack.

Understanding, and possibly exploiting, the effect of certain flags or environment variables on code signing.

Introducing unmanaged code into a container-managed environment

Use Well-Known Cryptography Appropriately and Correctly

A given code signing scheme may be fallible due to improper use of cryptography. Developers must never roll out their own cryptography, nor should existing primitives be modified or ignored.

If an attacker cannot attack the scheme directly, he might try to alter the environment that affects the signing and verification processes. A possible mitigation is to avoid reliance on flags or environment variables that are user-controllable.