Tobias Frauenschläger
0fb2d2ec11
wc_ecc_import_x963_ex2 only checked whether an imported public point lies on the intended curve when both USE_ECC_B_PARAM was compiled in and the caller passed untrusted=1. In a default ./configure build, USE_ECC_B_PARAM is not defined, so the check was compiled out entirely. Additionally, the legacy wrapper wc_ecc_import_x963_ex unconditionally passed untrusted=0, meaning ECIES (wc_ecc_decrypt), PKCS#7 KARI, and the EVP ECDH layer never triggered the check even when the macro was present. In the OpenSSL compatibility layer, wolfSSL_ECPoint_d2i guarded its on-curve check behind !wolfSSL_BN_is_one(point->Z), but wc_ecc_import_point_der_ex always sets Z=1 for uncompressed points, making the check dead code. An attacker who can supply an EC public key (e.g. via an ECIES ciphertext, PKCS#7 enveloped-data, EVP_PKEY_derive, or EC_POINT_oct2point + ECDH_compute_key) can choose a point on a twist of the target curve with a smooth-order subgroup. Each ECDH query leaks the victim's static private scalar modulo a small prime; CRT reconstruction across enough queries recovers the full key (Biehl-Meyer-Müller invalid-curve attack). Static-key ECIES and PKCS#7 KARI are directly affected; TLS is affected in default builds because the USE_ECC_B_PARAM gate defeated the untrusted=1 flag that the handshake does pass. Four changes close the attack: 1. Remove the USE_ECC_B_PARAM gate completely in the code base so that wc_ecc_point_is_on_curve() is compiled in all builds, not only those with HAVE_COMP_KEY or OPENSSL_EXTRA (only set for legacy FIPS builds in settings.h). 2. wc_ecc_import_x963_ex: pass untrusted=1 to wc_ecc_import_x963_ex2 so that ECIES, PKCS#7 KARI, and EVP callers that go through the four-argument wrapper always validate the imported point. 3. wc_ecc_import_x963_ex2: use the lightweight sp_ecc_is_point_NNN helpers (curve-equation check only) instead of sp_ecc_check_key_NNN (which additionally performs a full point*order scalar multiply). For prime-order curves (P-256, P-384, P-521, SM2) the on-curve equation check y^2 = x^3 + ax + b is sufficient to defeat invalid-curve attacks — every non-identity point on a prime-order curve has the full group order, so the expensive order-multiply check is unnecessary. This avoids the ~50% ECDH performance regression caused by the redundant scalar multiplication. 4. wolfSSL_ECPoint_d2i (pk_ec.c): add unconditional on-curve validation via wolfSSL_EC_POINT_is_on_curve after import. The existing check was gated on !wolfSSL_BN_is_one(point->Z) and therefore dead code for all uncompressed-point imports. This closes the OpenSSL compat layer attack path (EC_POINT_oct2point followed by ECDH_compute_key). Non-SP curves fall back to wc_ecc_point_is_on_curve which performs the same equation check using mp_int arithmetic. Reported by: Nicholas Carlini (Anthropic) & Thai Duong (Calif.io)
wolfCrypt Test
Tool for performing cryptographic algorithm testing.
Example Output
Run on Intel(R) Core(TM) i7-7920HQ CPU @ 3.10GHz.
./configure --enable-intelasm --enable-aesni --enable-sp --enable-sp-asm && make
./wolfcrypt/test/testwolfcrypt
------------------------------------------------------------------------------
wolfSSL version 4.0.0
------------------------------------------------------------------------------
error test passed!
MEMORY test passed!
base64 test passed!
asn test passed!
MD5 test passed!
SHA test passed!
SHA-224 test passed!
SHA-256 test passed!
SHA-384 test passed!
SHA-512 test passed!
SHA-3 test passed!
Hash test passed!
HMAC-MD5 test passed!
HMAC-SHA test passed!
HMAC-SHA224 test passed!
HMAC-SHA256 test passed!
HMAC-SHA384 test passed!
HMAC-SHA512 test passed!
HMAC-SHA3 test passed!
GMAC test passed!
Chacha test passed!
POLY1305 test passed!
ChaCha20-Poly1305 AEAD test passed!
AES test passed!
AES192 test passed!
AES256 test passed!
AES-GCM test passed!
RANDOM test passed!
RSA test passed!
DH test passed!
ECC test passed!
logging test passed!
mutex test passed!
memcb test passed!
Test complete
Windows Visual Studio
For building wolfCrypt test project in Visual Studio open the test.sln. For newer Visual Studio version it may prompt for a one-way upgrade. Then you may have to right-click on the solution and choose Retarget solution to update the project files for your Visual Studio version.
If you see an error about rc.exe then you'll need to update the "Target Platform Version". You can do this by right-clicking on the test project -> General -> "Target Platform Version" and changing to 8.1 (needs to match the wolfssl library project).
This solution includes the wolfSSL library project at <wolfssl-root>wolfssl.vcxproj and will compile the library, then the test project.
Jan 2026 - Reviewing the older FIPS compliant CRNGT test specified in FIPS 140-2 ss 4.9.2 vs the newer replacement tests RCT/ADP that are allowed to replace the CRNGT under the new FIPS 140-3 / ISO 19790 standard.
================================================================================ DRBG Continuous Health Test Statistical Analysis & Diagnostic Report
OVERVIEW
This document describes the statistical false positive behavior of the DRBG continuous health test in wc_RNG_TestSeed() and provides diagnostic tools to distinguish between:
- Statistical false positives (expected behavior)
- Entropy source depletion (under heavy concurrent load)
- Actual stuck entropy source (hardware failure)
BACKGROUND: THE ISSUE
The DRBG was experiencing high volumes of (DRBG_CONT_FIPS_E) on wc_InitRng() calls.
Example error: ERROR: wc_InitRng failed at iteration 330788 with code -209
This raises the question: Is this a bug in wc_RNG_TestSeed() or expected statistical behavior?
STATISTICAL ANALYSIS
The wc_RNG_TestSeed() Function Behavior:
- Compares ALL consecutive SEED_BLOCK_SZ chunks in the seed buffer
- With FIPS mode (typical configuration): SEED_SZ = 256 * 4 / 8 = 128 bytes (1024-bits) SEED_BLOCK_SZ = 4 bytes (default) (32-bits) seedSz passed to test = 132 bytes (SEED_SZ + SEED_BLOCK_SZ) Number of comparisons = ~32 consecutive block pairs
False Positive Probability Calculation:
- Probability one 4-byte block equals another random 4-byte block: 1/2^32
- With 32 comparisons per seed: 32/2^32 ≈ 1 in 134 million per wc_InitRng()
Test Configuration (Default):
- 40 threads × 100M iterations = 4 BILLION total wc_InitRng() calls
- Expected false positives: 4,000,000,000 × (32/2^32) ≈ 30 failures
Conclusion: Seeing failures around 1 in 30-140 million is EXPECTED STATISTICAL BEHAVIOR. Under heavy concurrent load (40 threads), entropy source depletion can also cause legitimate failures.
TESTING IT
Non-FIPS:
./configure CFLAGS="-DWC_RNG_SEED_DEBUG -DREALLY_LONG_DRBG_CONTINUOUS_TEST"
make
./wolfcrypt/test/testwolfcrypt
FIPS:
./configure --enable-fips=<flavor> CFLAGS="-DWC_RNG_SEED_DEBUG -DREALLY_LONG_DRBG_CONTINUOUS_TEST"
make
./fips-hash.sh
make
./wolfcrypt/test/testwolfcrypt
OUTPUTS EXPECTED
Non-FIPS:
Math: Multi-Precision: Wolf(SP) word-size=64 bits=4096 sp_int.c
------------------------------------------------------------------------------
wolfSSL version 5.8.4
------------------------------------------------------------------------------
macro test passed!
error test passed!
MEMORY test passed!
base64 test passed!
asn test passed!
MD5 test passed!
SHA test passed!
SHA-224 test passed!
SHA-256 test passed!
SHA-384 test passed!
SHA-512 test passed!
SHA-512/224 test passed!
SHA-512/256 test passed!
SHA-3 test passed!
RNG Entropy Source: getrandom() syscall
===============================================
DRBG Continuous Test Validation Suite
===============================================
FIPS Build: NO
--- Test 1: Basic RNG Functionality ---
Generated 32 random bytes successfully
[PASS] Basic RNG Functionality
--- Test 2: Multiple RNG Instances ---
Successfully operated 100 RNG instances concurrently
[PASS] Multiple RNG Instances
--- Test 3: FIPS Status Check ---
SKIPPED: FIPS not enabled
[PASS] FIPS Status Check
--- Test 4: RNG ReInit Test (multi-threaded) ---
Configuration: 40 threads × 100000000 iterations = 4000000000 total
Test Profile: Default (Aggressive multi-threaded)
Expected statistical false positive rate: ~29.80 failures
Duplicate block at offset 4:
Block 1: E6 E9 D1 7B
Block 2: E6 E9 D1 7B
Full seed buffer (52 bytes):
DA 93 B7 88 E6 E9 D1 7B E6 E9 D1 7B A5 4C C9 E9
13 EE D8 4C B3 C1 71 DE 32 37 17 F2 E7 A4 29 7D
9B 02 B0 0C EC 8D AC F5 DA B1 71 05 84 C0 61 75
59 6D 87 B5
ERROR: wc_InitRng failed at iteration 778551 with code -209
ERROR: wc_RNG_GenerateBlock failed at iteration 778551 with code -199
... (18 other failures truncated here for brevity) ... Duplicate block at offset 16: Block 1: C1 19 37 B1 Block 2: C1 19 37 B1 Full seed buffer (52 bytes): 62 66 5B D2 F5 54 47 9B 59 DD 0A 55 4B 52 8C 39 C1 19 37 B1 C1 19 37 B1 3F 62 CB 2E FE 56 65 4D 4F 0C A7 7D 1C 09 48 51 30 1B CA 00 56 9F 29 A7 E3 93 EF 8E ERROR: wc_InitRng failed at iteration 90467867 with code -209 ERROR: wc_RNG_GenerateBlock failed at iteration 90467867 with code -199 Thread 0 Succeeded ... 38 other thread results truncated here for brevity (all threads succeeded even though they experienced 1 or 2 failures in several of the threads) ... Thread 39 Succeeded Reinitialized RNG 4000000000 times across 40 threads Experienced 0 thread failures and 40 thread successes 20/4000000000 API calls failed <--- This is the bread and the butter of the test, we unfortunately expect to see ~29.80 failures, prior to the newer FIPS 140-3 RCT and ADP tests the CRNGT was required. Now the CRNGT is replaceable by the more mathematically robust RCT/ADP. [PASS] RNG Reinitialization
TESTING RESULTS with the CRNGT test:
Old implementation non-FIPS: Run 1 - 6 failures in 4 billion runs (100M per thread, 40 threads) Run 2 - 11 failures in 4 billion (100M per thread, 40 threads) Run 3 - 13 failures in 4 billion (100M per thread, 40 threads)
Old implementation with FIPS: (keeping in mind just a single failure means catastrophic failure for the entire module until power cycled): Run 1 - 3990118689 failures in 4 billion API calls (yikes)
TESTING RESULTS with the RCT/ADP tests in place of the CRNGT test:
New implementation non-FIPS: 4 billion successes New implementation FIPS: 4 billion successes