Merge pull request #75 from vparla/feature/post-quantum-crypto-guidance

Cryptographic Security Guidelines: add PQC readiness; consolidate into core rule

Author: santosomar

skills/software-security/rules/codeguard-1-crypto-algorithms.md

@@ -1,115 +1,126 @@
 ---
-description: Cryptographic Security Guidelines
+description: Cryptographic Security Guidelines & Post-Quantum Readiness
 alwaysApply: true
 ---
 
 rule_id: codeguard-1-crypto-algorithms
 
-# Cryptographic Security Guidelines
+# Cryptographic Security Guidelines & Post-Quantum Readiness
 
-## Banned (Insecure) Algorithms
+## 1. Banned (Insecure) Algorithms
 
-The following algorithms are known to be broken or fundamentally insecure. **NEVER** generate or use code with these algorithms.
-Examples:
+The following algorithms are known to be broken or fundamentally insecure. NEVER generate or use code with these algorithms.
 
-* Hash: `MD2`, `MD4`, `MD5`, `SHA-0`
-* Symmetric: `RC2`, `RC4`, `Blowfish`, `DES`, `3DES`
-* Key Exchange: Static RSA, Anonymous Diffie-Hellman
-* Classical: `Vigenère`
+*   Hash: `MD2`, `MD4`, `MD5`, `SHA-0`
+*   Symmetric: `RC2`, `RC4`, `Blowfish`, `DES`, `3DES`
+*   Key Exchange: Static RSA, Anonymous Diffie-Hellman
+*   Classical: `Vigenère`
 
-## Deprecated (Legacy/Weak) Algorithms
+Reason: These are cryptographically broken and vulnerable to collision or man-in-the-middle attacks.
 
-The following algorithms are not outright broken, but have known weaknesses, or are considered obsolete. **NEVER** generate or use code with these algorithms.
-Examples:
+## 2. Deprecated (Legacy/Weak) Algorithms
 
-* Hash: `SHA-1`
-* Symmetric: `AES-CBC`, `AES-ECB`
-* Signature: RSA with `PKCS#1 v1.5` padding
-* Key Exchange: DHE with weak/common primes
+The following algorithms have known weaknesses or are considered obsolete. Avoid in new designs and prioritize migration.
 
+*   Hash: `SHA-1`
+*   Symmetric: `AES-CBC`, `AES-ECB`
+*   Signature: RSA with `PKCS#1 v1.5` padding
+*   Key Exchange: DHE with weak/common primes
 
-## Deprecated SSL/Crypto APIs - FORBIDDEN
-NEVER use these deprecated functions. Use the replacement APIs listed below:
+## 3. Recommended & Post-Quantum Ready Algorithms
 
-### Symmetric Encryption (AES)
+Implement these modern, secure algorithms to ensure resistance against both classical and quantum threats.
+
+### Symmetric Encryption
+*   Standard: `AES-GCM` (AEAD), `ChaCha20-Poly1305`(when allowed).
+*   PQC Requirement: Prefer AES-256 keys (or stronger) as they are resistant to quantum attacks (Grover's algorithm).
+*   Avoid: Custom crypto or unauthenticated modes.
+
+### Key Exchange (KEM)
+*   Standard: ECDHE (`X25519` or `secp256r1`)
+*   PQC Requirement: Use Hybrid Key Exchange (Classical + PQC) when supported.
+    *   Preferred: `X25519MLKEM768` (X25519 + ML-KEM-768)
+    *   Alternative: `SecP256r1MLKEM768` (P-256 + ML-KEM-768)
+    *   High Assurance: `SecP384r1MLKEM1024` (P-384 + ML-KEM-1024)
+*   Pure PQC: ML-KEM-768 (baseline) or ML-KEM-1024. Avoid ML-KEM-512 unless explicitly risk-accepted.
+*   Constraints:
+    *   Use vendor-documented identifiers (RFC 9242/9370).
+    *   Remove legacy/draft "Hybrid-Kyber" groups (e.g., `X25519Kyber`) and draft or hardcoded OIDs.
+
+### Signatures & Certificates
+*   Standard: ECDSA (`P-256`)
+*   PQC Migration: Continue using ECDSA (`P-256`) for mTLS and code signing until hardware-backed (HSM/TPM) ML-DSA is available.
+*   Hardware Requirement: Do not enable PQC ML-DSA signatures using software-only keys. Require HSM/TPM storage.
+
+### Protocol Versions
+*   (D)TLS: Enforce (D)TLS 1.3 only (or later).
+*   IPsec: Enforce IKEv2 only.
+    *   Use ESP with AEAD (AES-256-GCM).
+    *   Require PFS via ECDHE.
+    *   Implement RFC 9242 and RFC 9370 for Hybrid PQC (ML-KEM + ECDHE).
+    *   Ensure re-keys (CREATE_CHILD_SA) maintain hybrid algorithms.
+*   SSH: Enable only vendor-supported PQC/hybrid KEX (e.g., `sntrup761x25519`).
+
+## 4. Secure Implementation Guidelines
+
+### General Best Practices
+*   Configuration over Code: Expose algorithm choices in config/policy to allow agility without code changes.
+*   Key Management:
+    *   Use KMS/HSM for key storage.
+    *   Generate keys with a CSPRNG.
+    *   Separate encryption keys from signature keys.
+    *   Rotate keys per policy.
+    *   NEVER hardcode keys, secrets, or experimental OIDs.
+*   Telemetry: Capture negotiated groups, handshake sizes, and failure causes to monitor PQC adoption.
+
+### Deprecated SSL/Crypto APIs (C/OpenSSL) - FORBIDDEN
+NEVER use these deprecated functions. Use the replacement EVP high-level APIs.
+
+#### Symmetric Encryption (AES)
 - Deprecated: `AES_encrypt()`, `AES_decrypt()`
-- Replacement: Use EVP high-level APIs:
-  ```c
-  EVP_EncryptInit_ex()
+- Replacement:
+
+  EVP_EncryptInit_ex()   // Use EVP_aes_256_gcm() for PQC readiness
   EVP_EncryptUpdate()
   EVP_EncryptFinal_ex()
-  EVP_DecryptInit_ex()
-  EVP_DecryptUpdate()
-  EVP_DecryptFinal_ex()
-  ```
-
-### RSA Operations
-- Deprecated: `RSA_new()`, `RSA_up_ref()`, `RSA_free()`, `RSA_set0_crt_params()`, `RSA_get0_n()`
-- Replacement: Use EVP key management APIs:
-  ```c
+
+
+#### RSA/PKEY Operations
+- Deprecated: `RSA_new()`, `RSA_free()`, `RSA_get0_n()`
+- Replacement:
+
   EVP_PKEY_new()
   EVP_PKEY_up_ref()
   EVP_PKEY_free()
-  ```
-
-### Hash Functions
-- Deprecated: `SHA1_Init()`, `SHA1_Update()`, `SHA1_Final()`
-- Replacement: Use EVP digest APIs:
-  ```c
-  EVP_DigestInit_ex()
-  EVP_DigestUpdate()
-  EVP_DigestFinal_ex()
-  EVP_Q_digest()  // For simple one-shot hashing
-  ```
-
-### MAC Operations
-- Deprecated: `CMAC_Init()`, `HMAC()` (especially with SHA1)
-- Replacement: Use EVP MAC APIs:
-  ```c
-  EVP_Q_MAC()  // For simple MAC operations
-  ```
-
-### Key Wrapping
-- Deprecated: `AES_wrap_key()`, `AES_unwrap_key()`
-- Replacement: Use EVP key wrapping APIs or implement using EVP encryption
-
-### Other Deprecated Functions
-- Deprecated: `DSA_sign()`, `DH_check()`
-- Replacement: Use corresponding EVP APIs for DSA and DH operations
-
-## Banned Insecure Algorithms - STRICTLY FORBIDDEN
-These algorithms MUST NOT be used in any form:
-
-### Hash Algorithms (Banned)
-- MD2, MD4, MD5, SHA-0
-- Reason: Cryptographically broken, vulnerable to collision attacks
-- Use Instead: SHA-256, SHA-384, SHA-512
-
-### Symmetric Ciphers (Banned)
-- RC2, RC4, Blowfish, DES, 3DES
-- Reason: Weak key sizes, known vulnerabilities
-- Use Instead: AES-128, AES-256, ChaCha20
-
-### Key Exchange (Banned)
-- Static RSA key exchange
-- Anonymous Diffie-Hellman
-- Reason: No forward secrecy, vulnerable to man-in-the-middle attacks
-- Use Instead: ECDHE, DHE with proper validation
-
-## Broccoli Project Specific Requirements
-- HMAC() with SHA1: Deprecated per Broccoli project requirements
+ 
+
+#### Hash & MAC Functions
+- Deprecated: `SHA1_Init()`, `HMAC()` (especially with SHA1)
+- Replacement:
+
+  EVP_DigestInit_ex() // Use SHA-256 or stronger
+  EVP_Q_MAC()         // For one-shot MAC
+
+
+## 5. Broccoli Project Specific Requirements
+- HMAC() with SHA1: Deprecated.
 - Replacement: Use HMAC with SHA-256 or stronger:
-  ```c
-  // Instead of HMAC() with SHA1
-  EVP_Q_MAC(NULL, "HMAC", NULL, "SHA256", NULL, key, key_len, data, data_len, out, out_size, &out_len);
-  ```
 
-## Secure Crypto Implementation Pattern
+
+// Example: Secure replacement for HMAC-SHA1
+```c
+EVP_Q_MAC(NULL, "HMAC", NULL, "SHA256", NULL, key, key_len, data, data_len, out, out_size, &out_len);
+```
+
+## 6. Secure Crypto Implementation Pattern
+
+
+// Example: Secure AES-256-GCM encryption (PQC-Ready Symmetric Strength)
 ```c
-// Example: Secure AES encryption
 EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
 if (!ctx) handle_error();
 
+// Use AES-256-GCM
 if (EVP_EncryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, key, iv) != 1)
     handle_error();
 
@@ -124,11 +135,3 @@ ciphertext_len += len;
 
 EVP_CIPHER_CTX_free(ctx);
 ```
-
-## Code Review Checklist
-- [ ] No deprecated SSL/crypto APIs used
-- [ ] No banned algorithms (MD5, DES, RC4, etc.)
-- [ ] HMAC uses SHA-256 or stronger (not SHA1)
-- [ ] All crypto operations use EVP high-level APIs
-- [ ] Proper error handling for all crypto operations
-- [ ] Key material properly zeroed after use