5bb280eb25
- Integrated `zupt_mac_verify_ct` in `zupt_decrypt_buffer()` to replace C XOR loop for HMAC-SHA256 - Integrated `zupt_ct_select_32` in `zupt_mlkem768_decaps()` to replace C `cmov()` for FO transformation - Added `include/zupt_jasmin.h` with extern declarations and ABI docs - Added `#ifdef ZUPT_USE_JASMIN` guards with clean C fallbacks in `zupt_crypto.c` and `zupt_mlkem.c` - Makefile now auto-detects `jasmin/*.s`, assembles and links with `-DZUPT_USE_JASMIN` Closes #3
178 lines
7.7 KiB
Markdown
178 lines
7.7 KiB
Markdown
# Security Audit — Zupt v1.5.0
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**Date:** March 28, 2026
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**Author:** Cristian Cezar Moisés
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**Audit type:** Self-audit with formal verification (Jasmin) and NIST/RFC test vectors
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**Status:** No independent third-party audit performed
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---
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## 1. Cryptographic Test Vector Verification
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All primitives tested against published reference vectors:
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| Primitive | Standard | Vectors | Status |
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|-----------|----------|---------|--------|
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| SHA-256 | FIPS 180-4 | 3 (empty, "abc", 448-bit) | **PASS** |
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| HMAC-SHA256 | RFC 4231 | 2 (TC2: "Jefe", TC3: 20×0xAA) | **PASS** |
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| SHA3-256 | FIPS 202 | 2 (empty, "abc") | **PASS** |
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| SHAKE-128 | FIPS 202 | 1 (empty, 128-bit output) | **PASS** |
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| X25519 | RFC 7748 §5.2 | 2 (both test vectors) | **PASS** |
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| ML-KEM-768 | FIPS 203 | 2 (5-trial roundtrip + implicit rejection) | **PASS** |
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| XXH64 | xxHash spec | 1 (empty string, seed=0) | **PASS** |
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| **Total** | | **13** | **13/13 PASS** |
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Reproduction: `make test-vectors && ./test_vectors`
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---
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## 2. Functional Test Results
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| Suite | Tests | Result | What It Covers |
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|-------|-------|--------|----------------|
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| Regression | 16 | **16/16 PASS** | All codecs, modes, encryption, edge cases, corruption detection |
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| Multi-threaded | 14 | **14/14 PASS** | N=1/2/4/8 threads, large files, 1000 files, MT+encryption |
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| Post-quantum | 10 | **10/10 PASS** | Keygen, PQ encrypt/decrypt, wrong key, password compat, PQ+MT, 2MB |
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| Quick smoke | 9 | **9/9 PASS** | Normal, solid, encrypted, wrong pw, MT, fast, store, PQ, integrity |
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| NIST vectors | 13 | **13/13 PASS** | See table above |
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| **Total** | **62** | **62/62 PASS** | |
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Reproduction: `make test-all`
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---
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## 3. Memory Safety
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| Tool | Command | Result |
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|------|---------|--------|
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| AddressSanitizer | `make test-asan` | **Zero errors** |
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| UndefinedBehaviorSanitizer | Built with `-fsanitize=address,undefined` | **Zero errors** |
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| All code paths tested | Normal + solid + encrypted + PQ + MT | **Clean** |
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Reproduction:
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```bash
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make test-asan
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./zupt_asan compress /tmp/t.zupt /path/to/data/
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./zupt_asan extract -o /tmp/out/ /tmp/t.zupt
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./zupt_asan keygen -o /tmp/k.key
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./zupt_asan compress --pq /tmp/pub.key /tmp/pq.zupt /path/to/data/
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./zupt_asan extract --pq /tmp/k.key -o /tmp/pqout/ /tmp/pq.zupt
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```
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---
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## 4. Compiler Warning Audit
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| Compiler | Flags | Warnings |
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|----------|-------|----------|
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| GCC 13.x | `-Wall -Wextra -Wpedantic -O2 -std=c11` | **Zero** |
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| Clang 18.x | `-Wall -Wextra -Wpedantic -O2 -std=c11` | **Zero** |
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---
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## 5. Constant-Time Analysis
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| Function | Location | CT Method | Jasmin Verified? | Risk Level |
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|----------|----------|-----------|-----------------|------------|
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| HMAC comparison | `zupt_crypto.c:252` | 4×u64 XOR accumulation | **Yes** — `zupt_mac_verify_ct` linked | **None** (Jasmin proven) |
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| ML-KEM FO select | `zupt_mlkem.c:593` | 4×u64 masked select | **Yes** — `zupt_ct_select_32` linked | **None** (Jasmin proven) |
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| ML-KEM NTT butterfly | `zupt_mlkem.c` | Montgomery reduction (branchless) | No | Low |
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| ML-KEM CBD sampling | `zupt_mlkem.c` | Bitwise operations only | No | Low |
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| X25519 fe_cswap | `zupt_x25519.c:95` | Masked XOR swap | No (limb mismatch) | Low (C is branchless) |
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| X25519 Montgomery ladder | `zupt_x25519.c:243` | Fixed 255 iterations | No | Low |
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| AES-256 encrypt | `zupt_aes256.c:59` | **Table-based S-box** | **No** | **HIGH on shared HW** |
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| SHA-256 | `zupt_sha256.c` | Table-based constants | No | Low (not secret-indexed) |
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| Keccak-f[1600] | `zupt_keccak.c` | Bitwise XOR/ROT only | No | None |
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| Key wipe | `zupt_crypto.c` | `explicit_bzero` / volatile | No | Low |
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### Jasmin Assembly Verification
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Two functions confirmed active in binary via `nm`:
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```
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0000000000014ae0 T zupt_mac_verify_ct ← Jasmin assembly, CT proven
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0000000000014b20 T zupt_ct_select_32 ← Jasmin assembly, CT proven
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```
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Assembly generated by `jasminc 2026.03.0`. Constant-time enforced by Jasmin type system: secret-typed variables cannot flow into branch conditions or memory indices.
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### Not Wired (with reason)
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| Function | Issue | Fallback |
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|----------|-------|----------|
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| `zupt_fe_cswap` | Jasmin: 4×u64 limbs, C: 5×u51 — incompatible | C masked XOR (branchless) |
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| `zupt_aes256_blk` | Stack offset bug: `rk.[1]` → `[rsp+1]` not `[rsp+16]` | C table-based AES |
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---
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## 6. Key Material Lifecycle
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| Phase | Method | Verified |
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|-------|--------|----------|
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| Generation | OS CSPRNG: `getrandom(2)` / `/dev/urandom` / `RtlGenRandom` | Hard fail if unavailable |
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| Storage | Stack-local arrays (no heap allocation for keys) | ASAN verified |
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| Usage | Passed by const pointer to AES-CTR / HMAC | No copies to heap |
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| Wipe | `zupt_secure_wipe()`: `explicit_bzero` (glibc 2.25+), `SecureZeroMemory` (Win), volatile fallback | Compiler cannot optimize out |
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| Scope exit | Stack frame destroyed | Keys were on stack |
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All intermediate buffers in PBKDF2, hybrid KEM, ML-KEM encaps/decaps, and X25519 wiped before return.
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---
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## 7. Nonce Security
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**Scheme:** `per_block_nonce = base_nonce XOR pad_le(block_seq, 8)`
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- `base_nonce`: 128-bit random from CSPRNG, generated once per archive.
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- `block_seq`: monotonically increasing 0, 1, 2, ... per archive.
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- **Uniqueness within archive:** Guaranteed (distinct seq → distinct nonce).
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- **Uniqueness across archives:** 2^-128 collision probability per pair (birthday bound on random base).
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---
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## 8. Encrypt-then-MAC Ordering
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| Step | Action | Verified |
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|------|--------|----------|
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| 1 | Compute HMAC over `nonce ‖ ciphertext` | HMAC input is nonce+ct, not plaintext |
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| 2 | Verify HMAC before any decryption | Code path: MAC check → early return if fail → decrypt only on success |
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| 3 | Decrypt only authenticated data | No plaintext produced from unauthenticated ciphertext |
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**Prevents:** Chosen-ciphertext attacks, padding oracles, ciphertext tampering.
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---
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## 9. Bugs Found and Fixed (v0.5.1 → v1.5.0)
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| Bug | Severity | Version Fixed | Impact |
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|-----|----------|---------------|--------|
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| Huffman Kraft-inequality violation | Critical | v0.5.1 | Data corruption on specific inputs |
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| Heap-buffer-overflow in LZ match finder | Critical | v0.5.1 | Potential code execution |
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| `rand()` CSPRNG fallback | Critical | v0.5.1 | Predictable encryption keys |
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| ML-KEM `poly_basemul` OOB | Critical | v1.0.0 | Buffer overread in NTT |
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| ML-KEM missing `poly_tomont` | Critical | v1.0.0 | Public key in wrong domain |
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| ML-KEM inverted FO `cmov` | Critical | v1.0.0 | Always selected rejection key |
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| ML-KEM `inv_ntt` wrong table | High | v1.0.0 | NTT roundtrip failure |
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| PQ nonce mismatch | High | v1.0.0 | Encrypt/decrypt used different nonces |
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| X25519 `AA + a24*E` formula | High | v1.1.0 | Wrong curve, not interoperable |
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| Dead `match_cost()` | Low | v1.1.0 | Clang warning |
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| `const polyvec` qualifier | Low | v1.1.0 | Pedantic warnings |
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| `__int128` pedantic | Low | v1.1.0 | Pedantic warning |
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---
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## 10. Known Limitations
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| Limitation | Impact | Mitigation | Status |
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|------------|--------|------------|--------|
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| Table-based AES (C fallback) | Cache-timing on shared hardware | Jasmin AES-NI path exists but has offset bug | **Open** — fix `.jazz` source |
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| Table-based SHA-256 | Theoretical cache-timing | Not used on secret-indexed data | **Accepted** |
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| PBKDF2 not quantum-safe | Quantum password brute-force | Use `--pq` mode | **Documented** |
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| No `mlock()` | Keys swappable to disk | Short key lifetime + `zupt_secure_wipe` | **Planned** |
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| No fuzzing performed | Undiscovered bugs | AFL++ setup in FUZZING.md | **Planned** |
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| No independent audit | Self-assessed only | Open source + Jasmin proofs | **Planned** |
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| X25519 Jasmin not linked | C fallback for fe_cswap | C is branchless but compiler-dependent | **Open** — limb mismatch |
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---
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© 2026 Cristian Cezar Moisés — MIT License
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