Introduce secp256k1_sha256_initialize_midstate() in the hash layer and use it at all tagged-hash midstate call sites across schnorrsig, musig, and ellswift.
Document the byte-counter contract at the declaration site in hash.h and add run_sha256_initialize_midstate_tests() to directly verify helper behavior against initialize_tagged.
Also switch the helper to take const uint32_t state[8] to reduce argument-order risk at call sites.
ae00c552df Add VERIFY_CHECKs that flags are 0 or 1 (John Moffett)
Pull request description:
Flags for constant-time masking rely on the values being exactly `0` or `1` rather than `0` or true (any nonzero). One function, `secp256k1_fe_cmov` [documents](e7f7083b53/src/field.h (L315)) and [`VERIFY_CHECK`s](e7f7083b53/src/field_impl.h (L365)) this, but most don't.
This updates the documentation and adds `VERIFY_CHECK`s enforcing `flag == 0 || flag == 1` for:
`secp256k1_fe_storage_cmov`
`secp256k1_gej_cmov`
`secp256k1_ge_storage_cmov`
`secp256k1_scalar_cadd_bit`
`secp256k1_scalar_cond_negate`
`secp256k1_scalar_cmov`
`secp256k1_int_cmov`
ACKs for top commit:
furszy:
ACK ae00c55
hebasto:
re-ACK ae00c552df.
Tree-SHA512: c9d358929d39d93b0aea602d318429f7e82af96bf601f048a1cdeb0621b8adc6d1204648d352aa2060cb0f63db6dcf0da863854375ed313cea44dfad61c19a18
Flags for constant-time masking rely
on the values being exactly 0 or 1 rather
than 0 or true. Add VERIFY_CHECKs to enforce
in VERIFY builds as a preventative
measure and add documentation where relevant.
2f4546ce56 test: add --log option to display tests execution (furszy)
95b9953ea4 test: Add option to display all available tests (furszy)
953f7b0088 test: support running specific tests/modules targets (furszy)
0302c1a3d7 test: add --help for command-line options (furszy)
9ec3bfe22d test: adapt modules to the new test infrastructure (furszy)
48789dafc2 test: introduce (mini) unit test framework (furszy)
9cce703863 refactor: move 'gettime_i64()' to tests_common.h (furszy)
Pull request description:
Early Note:
Don’t be scared by the PR’s line changes count — most of it’s just doc or part of the test framework API.
Context:
Currently, all tests run single-threaded sequentially and the library lacks the ability to specify which test (or group of tests) you would like to run. This is not only inconvenient as more tests are added but also time consuming during development and affects downstream projects that may want to parallelize the workload (such as Bitcoin-Core CI).
PR Goal:
Introduce a lightweight, extensible C89 unit test framework with no dynamic memory allocations, providing a structured way to register, execute, and report tests. The framework supports named command-line arguments in `-key=value` form, parallel test execution across multiple worker processes, granular test selection (selecting tests either by name or by module name), and time accumulation reports.
The introduced framework supports:
* `-help` or `-h`: display list of available commands along with their descriptions.
* `-jobs=<num>`: distribute tests across multiple worker processes (default: sequential if 0).
* `-target=<name>` or `-t=<name>`: run only specific tests by name; can be repeated to select multiple tests.
* `-target=<module name>`, `-t=<module>` Run all tests within a specific module (can be provided multiple times)
* `-seed=<hex>`: set a specific RNG seed (defaults to random if unspecified).
* `-iterations=<n>`: specify the number of iterations.
* `-list_tests`: display list of available tests and modules you can run.
* `-log=<0|1>`: enable or disable test execution logging (default: 0 = disabled).
Beyond these features, the idea is to also make future developments smoother, as adding new tests require only a single entry in the central test registry, and new command-line options can be introduced easily by extending the framework’s `parse_arg()` function.
Compatibility Note:
The framework continues accepting the two positional arguments previously supported (iterations and seed), ensuring existing workflows remain intact.
Testing Notes:
Have fun. You can quickly try it through `./tests -j=<workers_num>` for parallel execution or `./tests -t=<test_name>` to run a specific test (call `./tests -print_tests` to display all available tests and modules).
Extra Note:
I haven't checked the exhaustive tests file so far, but I will soon. For now, this only runs all tests declared in the `tests` binary.
Testing Results: (Current master branch vs PR in seconds)
* Raspberry Pi 5: master \~100 s → PR \~38 s (5 jobs)
* MacBook Pro M1: master \~30 s → PR \~10 s (6 jobs)
ACKs for top commit:
theStack:
re-ACK 2f4546ce56
real-or-random:
ACK 2f4546ce56
hebasto:
ACK 2f4546ce56.
Tree-SHA512: 85ca2cbb620b84b35b353d5d4cf093c388fc3851ca405eeb0e458f8fa72b60534bccd357c7edabf8fc9aa93d9ad0a6fbac3dd5c4d5f9dfdf4d8701a9834755b9
secp256k1_memclear has the side effect of undefining bytes for
valgrind checks. In some cases, we may want to zero bytes
but allow subsequent reads. So we split memclear into
memclear_explicit, which makes no guarantees about the content
of the buffer on return, and memzero_explicit, which guarantees
zero value on return.
Change the memset in partial_sign to use memzero_explicit.
Move the sha256_tag_test_internal function out of the musig module
into tests.c. This makes it available to other modules wishing to verify tagged
hashes without needing to duplicate the function.
Change the function signature to expect a const unsigned char and update
the tagged hash tests to use static const unsigned char character
arrays (where necessary).
Add a comment for each tag. This is done as a convenience for checking
the strings against the protocol specifications, where the tags are
normally specified as strings.
Update tests in the ellswift and schnorrsig modules to use the
sha256_tag_test_internal helper function.
765ef53335 Clear _gej instances after point multiplication to avoid potential leaks (Sebastian Falbesoner)
349e6ab916 Introduce separate _clear functions for hash module (Tim Ruffing)
99cc9fd6d0 Don't rely on memset to set signed integers to 0 (Tim Ruffing)
97c57f42ba Implement various _clear() functions with secp256k1_memclear() (Tim Ruffing)
9bb368d146 Use secp256k1_memclear() to clear stack memory instead of memset() (Tim Ruffing)
e3497bbf00 Separate between clearing memory and setting to zero in tests (Tim Ruffing)
d79a6ccd43 Separate secp256k1_fe_set_int( . , 0 ) from secp256k1_fe_clear() (Tim Ruffing)
1c08126222 Add secp256k1_memclear() for clearing secret data (Tim Ruffing)
e7d384488e Don't clear secrets in pippenger implementation (Tim Ruffing)
Pull request description:
This PR picks up #636 (which in turn picked up #448, so this is take number three) and is essentially a rebase on master.
Some changes to the original PR:
* the clearing function now has the `secp256k1_` prefix again, since the related helper `_memczero` got it as well (see PR #835 / commit e89278f211)
* the original commit b17a7df8145a6a86d49c354c7e7b59a432ea5346 ("Make _set_fe_int( . , 0 ) set magnitude to 0") is not needed anymore, since it was already applied in PR #943 (commit d49011f54c)
* clearing of stack memory with `secp256k1_memclear` is now also done on modules that have been newly introduced since then, i.e. schnorr and ellswift (of course, there is still no guarantee that all places where clearing is necessary are covered)
So far I haven't looked at any disassembly and possible performance implications yet (there were some concerns expressed in https://github.com/bitcoin-core/secp256k1/pull/636#issuecomment-620118629), happy to go deeper there if this gets Concept ACKed.
The proposed method of using a memory barrier to prevent optimizating away the memset is still used in BoringSSL (where it was originally picked up from) and in the Linux Kernel, see e.g. 5af122c3df/crypto/mem.c (L335) and d456068672/include/linux/string.h (L348) / d456068672/include/linux/compiler.h (L102)Fixes#185.
ACKs for top commit:
sipa:
reACK 765ef53335
real-or-random:
ACK 765ef53335
Tree-SHA512: 5a034d5ad14178c06928022459f3d4f0877d06f576b24ab07b86b3608b0b3e9273217b8309a1db606f024f3032731f13013114b1e0828964b578814d1efb2959
Quoting sipa (see https://github.com/bitcoin-core/secp256k1/pull/1479#discussion_r1790079414):
"When performing an EC multiplication A = aG for secret a, the resulting
_affine_ coordinates of A are presumed to not leak information about a (ECDLP),
but the same is not necessarily true for the Jacobian coordinates that come
out of our multiplication algorithm."
For the ECDH point multiplication result, the result in Jacobi coordinates should be
cleared not only to avoid leaking the scalar, but even more so as it's a representation
of the resulting shared secret.
This gives the caller more control about whether the state should
be cleaned (= should be considered secret). Moreover, it gives the
caller the possibility to clean a hash struct without finalizing it.
All of the invocations of secp256k1_memclear() operate on stack
memory and happen after the function is done with the memory object.
This commit replaces existing memset() invocations and also adds
secp256k1_memclear() to code locations where clearing was missing;
there is no guarantee that this commit covers all code locations
where clearing is necessary.
Co-Authored-By: isle2983 <isle2983@yahoo.com>
The area marked as non-secret exceeds the nonce_pts array in the
second iteration of the for loop. Fix that by passing the correct
size to the _declassify call.
