3 Commits

Author	SHA1	Message	Date
Kgothatso Ngako	7afee05de8	tools: add the iceberg test vector generator ... src/modules/iceberg/vectors.h opens with regeneration instructions that name ./tools/test_vectors_iceberg_generate.py, and that script was never committed. The same header calls the file "the one thing in this repository that cannot be rebuilt from what the repository contains", which the missing generator made true twice over: neither the reference nor the tool that reads it was reachable from a clone. Recovered from the tree the Iceberg C is vendored in, at sources/secp256k1-kmp/native/secp256k1 of the benchmark repository (bitcoin-core/secp256k1 branch iceberg-module, commit 96201552, per that repository's PINS.txt). Confirmed to be the generator that produced the checked-in vectors before committing it: - its HEADER template reproduces the header of vectors.h exactly, including the ICEBERG_VECTOR_MAX_PARTICIPANTS 9 and ICEBERG_VECTOR_MAX_SEEDS 126 it computes from the configuration list; - its seed rule, sha256("iceberg test vectors|<label>|<rank>"), reproduces the checked-in 2of3 seeds byte for byte; - the whole of that tree's src/modules/iceberg/ matches this one byte for byte except tests_impl.h, which differs only because the tests here are ported to the unit_test.h test-module framework. The script cannot be re-run from a clone alone, by design: it takes the nkohen/Iceberg Python reference as its argument and that reference is deliberately not vendored, since it is not ours and pinning a copy would hide it drifting. Its docstring gives the clone and the pinned commit (7b55ef6d), which is now the whole of what regenerating requires. Also restore the executable bit on the frost and chilldkg generators. Both carry a usage line telling the reader to run them directly, and every other generator in tools/ is 0755. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-09-01 23:37:52 +02:00
Kgothatso Ngako	7e73badcbd	frost: fix constant-time violations and C90 conformance ... The module's BIP 445 logic itself is unchanged and was independently validated against the pinned spec commit bb5396f (BIP v0.10.0), both via the checked-in test vectors and via differential testing against the Python reference over 360 randomised configurations (n up to 128, shuffled non-contiguous signer ids, mixed xonly/plain tweak chains, variable-length messages, pubshares present and absent). Every change below is structural: the differential harness produces byte-identical pubnonces, aggnonces, partial signatures and final signatures before and after. Two classes of problem prevented the module from passing CI. 1. Constant-time violations (ctime_tests) ----------------------------------------- The CI matrix enables FROST in rows that also run "valgrind --error-exitcode=42 ./ctime_tests" -- WITH_VALGRIND and CTIMETESTS both default to 'yes'. With the module enabled that job reported 639 "conditional jump depends on uninitialised value" errors, all originating from two sites: - secp256k1_frost_derive_coefficient returned !overflow && !secp256k1_scalar_is_zero(out) where the short-circuiting && branches on `overflow`, which is derived from the threshold secret key. The caller declassifies the return value, but the branch has already happened inside the callee. Replaced with a bitwise &, matching the existing idiom in secp256k1_scalar_set_b32_seckey (src/scalar_impl.h). - secp256k1_frost_sign_internal performs the self-verification recommended by BIP 445, which runs the *variable-time* secp256k1_ecmult over the partial signature s. nonce_pts and pk were already declassified ahead of that call; s was not. Since s is the public output of the function, declassifying it before the self-verification is both correct and sufficient. secp256k1_frost_deterministic_sign carried three more instances of the same class, invisible until now because ctime_tests did not exercise that path at all: - the `if (!valid)` check on secp256k1_scalar_set_b32_seckey lacked the declassify that the identical checks in secp256k1_frost_nonce_gen and secp256k1_frost_sign_internal already have; - secp256k1_frost_det_nonce_function used the same short-circuiting &&, here over the secret nonces; - the branch on that function's result was not declassified. The && in det_nonce_function is rewritten via two int locals rather than a bare bitwise &: clang's -Wbitwise-instead-of-logical fires when both operands are `!f(...)` expressions, which would break the -Werror clang builds. ctime_tests now also covers secp256k1_frost_deterministic_sign, so that path stays checked from here on. None of these leak anything of value in practice -- they reveal only negligible-probability events (a hash overflowing the curve order, a zero nonce) or whether a secret share is a valid secret key -- but they violate the project's declassification discipline and fail the ctime test. 2. C90 conformance (-Werror -pedantic-errors) --------------------------------------------- The project targets C90 (CMAKE_C_STANDARD 90, -std=c89 -pedantic) and CI passes WERROR_CFLAGS='-Werror -pedantic-errors'. Compiling src/tests.c with those flags produced 62 errors in three groups: - 40x "ISO C forbids empty initializer braces before C2X" in the generated vectors.h; empty {} initializers are C23-only. Fixed in tools/test_vectors_frost_generate.py so it survives regeneration: hexstr_to_intarray now emits "0" for an empty byte string (all six of its call sites wrap the result in braces), and init_group's `counted` helper emits "{ 0 }" for an empty group. In every affected slot the paired count/length field is 0, so the padding element is never read. - 1x "comma at end of enumerator list" (C99+), also in the generator. - 21x "initializer element is not computable at load time" across 11 lines of tests_impl.h. C90 requires constant expressions in initializers for automatic aggregates, so const secp256k1_frost_pubnonce *ptrs[2] = { &a, &b }; is invalid. Rewritten as a declaration plus assignments, the style the musig tests already use, which is why the pre-existing tree was green. vectors.h is regenerated from the spec's JSON vectors. Its hex payload is byte-identical (verified by hashing every 0xNN token) and the file still reproduces exactly from tools/test_vectors_frost_generate.py. Verification ------------ - gcc and clang, -std=c89 -pedantic-errors -Werror, with and without -DVERIFY: clean (was 62 errors) - ctime_tests under MemorySanitizer: 0 reports (was 639); exits 0 with halt_on_error=1 - tests, noverify_tests and frost_example: pass - vectors.h regenerates identically from the pinned spec vectors - 240 signing + 120 deterministic-signing differential cases against the BIP 445 Python reference: byte-identical to the pre-fix build Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-08-31 00:57:43 +02:00
Kgothatso Ngako	2d97cc2242	Frost Module logic.	2026-08-31 00:05:16 +02:00