Mirage Crypto OCaml AES-GCM Plaintext Leak Before 2.2.0

Executive Summary

This vulnerability affects the mirage-crypto package before version 2.2.0 for OCaml. The issue is in the AES.GCM.authenticate_decrypt_into and Chacha20.authenticate_decrypt_into functions. These functions decrypt data into a buffer provided by the caller and then verify the authentication tag. If the tag is forged, the functions return false but the decrypted plaintext remains in the buffer, potentially exposing sensitive data.

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Detection Guidance

This vulnerability is specific to the mirage-crypto OCaml package and does not have direct network or system detection methods. You should check if your system uses the vulnerable version of mirage-crypto (before 2.2.0) by inspecting installed packages. For OCaml projects, use commands like 'opam list mirage-crypto' to verify the version.

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Impact Analysis

An attacker could exploit this to decrypt ciphertext without knowing the correct key by providing a forged tag. This could lead to unauthorized access to decrypted data, even though the system reports decryption failure. The impact includes potential exposure of sensitive information stored or transmitted using these cryptographic functions.

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Compliance Impact

This vulnerability could violate compliance requirements that mandate secure encryption and protection of sensitive data. For example, GDPR requires appropriate technical measures to ensure data security, and HIPAA mandates encryption for protected health information. Failure to properly decrypt data could result in unauthorized access, leading to potential regulatory penalties.

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Mitigation Strategies

Immediately upgrade the mirage-crypto package to version 2.2.0 or later. If you are using OCaml with opam, run 'opam update' followed by 'opam upgrade mirage-crypto'. Review any applications using this library to ensure they are recompiled with the updated version.

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