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Attack Tree Analysis for jedisct1/libsodium

Objective: Gain Unauthorized Access to Sensitive Data OR Cause Denial of Service (DoS) via Libsodium

Attack Tree Visualization

Goal: Gain Unauthorized Access to Sensitive Data OR Cause Denial of Service (DoS) via Libsodium ├── 1. Exploit Implementation Errors in Application's Use of Libsodium [HIGH-RISK] │ ├── 1.1 Incorrect API Usage [HIGH-RISK] │ │ ├── 1.1.1 Key Reuse (e.g., same nonce with secretbox) [HIGH-RISK] │ │ │ ├── 1.1.1.1 Attacker observes multiple ciphertexts with same key/nonce. │ │ │ │ └── 1.1.1.1.1 Attacker performs cryptanalysis to recover plaintext or key. [CRITICAL] │ │ │ └── 1.1.1.2 Application code explicitly reuses nonces. [CRITICAL] │ │ │ └── 1.1.1.2.1 Attacker exploits predictable nonce generation. │ │ ├── 1.1.3 Ignoring Return Values/Error Codes │ │ │ ├── 1.1.3.1 Application doesn't check for crypto_secretbox_open() failure. [CRITICAL] │ │ │ │ └── 1.1.3.1.1 Attacker provides manipulated ciphertext, leading to incorrect decryption or memory corruption. │ │ ├── 1.1.4 Buffer Overflow/Underflow in Handling Libsodium Outputs [HIGH-RISK] │ │ │ ├── 1.1.4.1 Application allocates insufficient buffer for ciphertext. [CRITICAL] │ │ │ │ └── 1.1.4.1.1 Libsodium writes past buffer boundary, leading to memory corruption or crash (DoS). │ └── 1.2 Data Leakage Through Unprotected Memory [HIGH-RISK] │ └── 1.2.2 Application doesn't use sodium_memzero to clear sensitive data. [CRITICAL] │ └── 1.2.2.1 Attacker gains access to memory and retrieves keys/plaintext. └── 2. Exploit Vulnerabilities in Libsodium Itself (Highly Unlikely, but Included for Completeness) └── 2.3 Supply Chain Attack └── 2.3.2 Compromised distribution channel. └── 2.3.2.1 Attacker replaces legitimate libsodium library with a backdoored version. [CRITICAL]

Attack Tree Path: 1. Exploit Implementation Errors in Application's Use of Libsodium [HIGH-RISK]

  • 1.1 Incorrect API Usage [HIGH-RISK] This is the most likely area for vulnerabilities due to developer error.

  • 1.1.1 Key Reuse (e.g., same nonce with secretbox) [HIGH-RISK] Nonce reuse with the same key in symmetric encryption (like crypto_secretbox) completely breaks confidentiality.

    • 1.1.1.1.1 Attacker performs cryptanalysis to recover plaintext or key. [CRITICAL]
      • Description: If the attacker observes multiple ciphertexts encrypted with the same key and nonce, they can use well-known cryptanalytic techniques (e.g., "two-time pad" attack) to recover the plaintext.
      • Mitigation: Never reuse a nonce with the same key. Use randombytes_buf() to generate a unique nonce for every encryption operation. This is paramount.
    • 1.1.1.2 Application code explicitly reuses nonces. [CRITICAL]
      • Description: The application code might have a flaw where the same nonce value is used repeatedly, either due to a hardcoded value, a counter that resets, or a predictable pattern.
      • Mitigation: Code review and static analysis to ensure nonces are generated uniquely for each encryption. Dynamic analysis (testing) can also help reveal this.

  • 1.1.3 Ignoring Return Values/Error Codes

    • 1.1.3.1 Application doesn't check for crypto_secretbox_open() failure. [CRITICAL]
      • Description: If the application doesn't check the return value of crypto_secretbox_open() (or other decryption functions), it might proceed to use potentially unauthenticated or corrupted data. An attacker could provide a manipulated ciphertext that, while failing authentication, still leads to undesirable behavior (e.g., memory corruption, incorrect logic).
      • Mitigation: Always check the return value of every libsodium function, especially decryption functions. If the function indicates failure, do not use the output data. Handle the error appropriately (e.g., log the error, return an error to the user, terminate the operation).

  • 1.1.4 Buffer Overflow/Underflow in Handling Libsodium Outputs [HIGH-RISK] These are classic memory safety vulnerabilities.

    • 1.1.4.1 Application allocates insufficient buffer for ciphertext. [CRITICAL]
      • Description: When encrypting data, the ciphertext is often larger than the plaintext (due to padding and authentication tags). If the application doesn't allocate enough space for the ciphertext, libsodium might write past the end of the allocated buffer, leading to memory corruption. This can potentially lead to arbitrary code execution or a denial-of-service (crash).
      • Mitigation: Carefully calculate the required buffer size for the ciphertext. Libsodium provides functions (e.g., crypto_secretbox_MACBYTES, crypto_secretbox_NONCEBYTES) to help determine the necessary size. Use static analysis tools and fuzzing to detect potential buffer overflows.

  • 1.2 Data Leakage Through Unprotected Memory [HIGH-RISK] Sensitive data (keys, plaintexts) should never remain in memory longer than necessary.

  • 1.2.2 Application doesn't use sodium_memzero to clear sensitive data. [CRITICAL]

    • Description: After using sensitive data (keys, plaintexts, intermediate buffers), the application should securely erase it from memory. Simply deallocating the memory is not sufficient, as the data might still be present in memory and could be recovered by an attacker.
    • Mitigation: Use sodium_memzero() to securely wipe the contents of memory buffers containing sensitive data immediately after they are no longer needed. This overwrites the memory with zeros, preventing data leakage.

Attack Tree Path: 2. Exploit Vulnerabilities in Libsodium Itself (Highly Unlikely)

  • 2.3 Supply Chain Attack
    • 2.3.2.1 Attacker replaces legitimate libsodium library with a backdoored version. [CRITICAL]
      • Description: If an attacker can compromise the distribution channel for libsodium (e.g., the package manager, the download server), they could replace the legitimate library with a modified version containing malicious code. This would give the attacker control over any application using the compromised library.
      • Mitigation: Verify the integrity of the downloaded libsodium library using checksums (e.g., SHA256) and digital signatures (if available). Obtain libsodium from trusted sources, such as the official GitHub repository or a reputable package manager that verifies package integrity.