BlockstreamResearch · real-or-random · Jul 24, 2023 · Mar 8, 2023 · Mar 8, 2023 · Mar 10, 2023
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -8,7 +8,20 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
+## [0.3.1] - 2023-04-10
+We strongly recommend updating to 0.3.1 if you use or plan to use Clang >=14 to compile libsecp256k1, e.g., Xcode >=14 on macOS has Clang >=14. When in doubt, check the Clang version using `clang -v`.
+
+#### Security
+ - Fix "constant-timeness" issue with Clang >=14 that could leave applications using libsecp256k1 vulnerable to a timing side-channel attack. The fix avoids secret-dependent control flow and secret-dependent memory accesses in conditional moves of memory objects when libsecp256k1 is compiled with Clang >=14.
+
+#### Added
+  - Added tests against [Project Wycheproof's](https://github.com/google/wycheproof/) set of ECDSA test vectors (Bitcoin "low-S" variant), a fixed set of test cases designed to trigger various edge cases.
+
+#### Changed
+ - Increased minimum required CMake version to 3.13. CMake builds remain experimental.
+
+#### ABI Compatibility
+The ABI is compatible with version 0.3.0.
 
 ## [0.3.0] - 2023-03-08
 
@@ -28,7 +41,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
  - Removed the configuration header `src/libsecp256k1-config.h`. We recommend passing flags to `./configure` or `cmake` to set configuration options (see `./configure --help` or `cmake -LH`). If you cannot or do not want to use one of the supported build systems, pass configuration flags such as `-DSECP256K1_ENABLE_MODULE_SCHNORRSIG` manually to the compiler (see the file `configure.ac` for supported flags).
 
 #### ABI Compatibility
-
 Due to changes in the API regarding `secp256k1_context_static` described above, the ABI is *not* compatible with previous versions.
 
 ## [0.2.0] - 2022-12-12
@@ -48,7 +60,6 @@ Due to changes in the API regarding `secp256k1_context_static` described above,
  - Module `schnorrsig`: renamed `secp256k1_schnorrsig_sign` to `secp256k1_schnorrsig_sign32`.
 
 #### ABI Compatibility
-
 Since this is the first release, we do not compare application binary interfaces.
 However, there are earlier unreleased versions of libsecp256k1 that are *not* ABI compatible with this version.
 
@@ -59,6 +70,7 @@ The number was given by the build system since the introduction of autotools in
 Therefore, this version number does not uniquely identify a set of source files.
 
 [unreleased]: https://github.com/bitcoin-core/secp256k1/compare/v0.3.0...HEAD
+[0.3.1]: https://github.com/bitcoin-core/secp256k1/compare/v0.3.0...v0.3.1
 [0.3.0]: https://github.com/bitcoin-core/secp256k1/compare/v0.2.0...v0.3.0
 [0.2.0]: https://github.com/bitcoin-core/secp256k1/compare/423b6d19d373f1224fd671a982584d7e7900bc93..v0.2.0
 [0.1.0]: https://github.com/bitcoin-core/secp256k1/commit/423b6d19d373f1224fd671a982584d7e7900bc93
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.1)
+cmake_minimum_required(VERSION 3.13)
 
 if(CMAKE_VERSION VERSION_GREATER 3.14)
   # MSVC runtime library flags are selected by the CMAKE_MSVC_RUNTIME_LIBRARY abstraction.
@@ -10,15 +10,15 @@ endif()
 # The package (a.k.a. release) version is based on semantic versioning 2.0.0 of
 # the API. All changes in experimental modules are treated as
 # backwards-compatible and therefore at most increase the minor version.
-project(libsecp256k1 VERSION 0.3.0 LANGUAGES C)
+project(libsecp256k1 VERSION 0.3.1 LANGUAGES C)
 
 # The library version is based on libtool versioning of the ABI. The set of
 # rules for updating the version can be found here:
 # https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html
 # All changes in experimental modules are treated as if they don't affect the
 # interface and therefore only increase the revision.
 set(${PROJECT_NAME}_LIB_VERSION_CURRENT 2)
-set(${PROJECT_NAME}_LIB_VERSION_REVISION 0)
+set(${PROJECT_NAME}_LIB_VERSION_REVISION 1)
 set(${PROJECT_NAME}_LIB_VERSION_AGE 0)
 
 set(CMAKE_C_STANDARD 90)
@@ -147,7 +147,7 @@ else()
 endif()
 
 # Define custom "Coverage" build type.
-set(CMAKE_C_FLAGS_COVERAGE "${CMAKE_C_FLAGS_RELWITHDEBINFO} -O0 -DCOVERAGE=1 --coverage -Wno-unused-parameter" CACHE STRING
+set(CMAKE_C_FLAGS_COVERAGE "${CMAKE_C_FLAGS_RELWITHDEBINFO} -O0 -DCOVERAGE=1 --coverage" CACHE STRING
   "Flags used by the C compiler during \"Coverage\" builds."
   FORCE
 )
@@ -203,11 +203,6 @@ else()
   try_add_compile_option(-Wundef)
 endif()
 
-if(CMAKE_VERSION VERSION_GREATER 3.2)
-  # Honor visibility properties for all target types.
-  # See: https://cmake.org/cmake/help/latest/policy/CMP0063.html
-  cmake_policy(SET CMP0063 NEW)
-endif()
 set(CMAKE_C_VISIBILITY_PRESET hidden)
 
 # Ask CTest to create a "check" target (e.g., make check) as alias for the "test" target.

diff --git a/Makefile.am b/Makefile.am
@@ -292,3 +292,20 @@ endif
 if ENABLE_MODULE_ECDSA_ADAPTOR
 include src/modules/ecdsa_adaptor/Makefile.am.include
 endif
+
+EXTRA_DIST += src/wycheproof/WYCHEPROOF_COPYING
+EXTRA_DIST += src/wycheproof/ecdsa_secp256k1_sha256_bitcoin_test.h
+EXTRA_DIST += src/wycheproof/ecdsa_secp256k1_sha256_bitcoin_test.json
+EXTRA_DIST += tools/tests_wycheproof_generate.py
+
+TESTVECTORS = src/wycheproof/ecdsa_secp256k1_sha256_bitcoin_test.h
+
+src/wycheproof/ecdsa_secp256k1_sha256_bitcoin_test.h: src/wycheproof/ecdsa_secp256k1_sha256_bitcoin_test.json
+	python3 tools/tests_wycheproof_generate.py $< > $@
+
+testvectors: $(TESTVECTORS)
+
+maintainer-clean-testvectors: clean-testvectors
+
+clean-testvectors:
+	rm -f $(TESTVECTORS)
diff --git a/ci/cirrus.sh b/ci/cirrus.sh
@@ -118,8 +118,8 @@ fi
 # Rebuild precomputed files (if not cross-compiling).
 if [ -z "$HOST" ]
 then
-    make clean-precomp
-    make precomp
+    make clean-precomp clean-testvectors
+    make precomp testvectors
 fi
 
 # Check that no repo files have been modified by the build.

diff --git a/configure.ac b/configure.ac
@@ -29,6 +29,11 @@ AM_INIT_AUTOMAKE([1.11.2 foreign subdir-objects])
 # Make the compilation flags quiet unless V=1 is used.
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 
+if test "${CFLAGS+set}" = "set"; then
+  CFLAGS_overridden=yes
+else
+  CFLAGS_overridden=no
+fi
 AC_PROG_CC
 AM_PROG_AS
 AM_PROG_AR
@@ -88,11 +93,14 @@ esac
 AC_DEFUN([SECP_TRY_APPEND_DEFAULT_CFLAGS], [
     # GCC and compatible (incl. clang)
     if test "x$GCC" = "xyes"; then
-      # Try to append -Werror=unknown-warning-option to CFLAGS temporarily. Otherwise clang will
-      # not error out if it gets unknown warning flags and the checks here will always succeed
-      # no matter if clang knows the flag or not.
+      # Try to append -Werror to CFLAGS temporarily. Otherwise checks for some unsupported
+      # flags will succeed.
+      # Note that failure to append -Werror does not necessarily mean that -Werror is not
+      # supported. The compiler may already be warning about something unrelated, for example
+      # about some path issue. If that is the case, -Werror cannot be used because all
+      # of those warnings would be turned into errors.
       SECP_TRY_APPEND_DEFAULT_CFLAGS_saved_CFLAGS="$CFLAGS"
-      SECP_TRY_APPEND_CFLAGS([-Werror=unknown-warning-option], CFLAGS)
+      SECP_TRY_APPEND_CFLAGS([-Werror], CFLAGS)
 
       SECP_TRY_APPEND_CFLAGS([-std=c89 -pedantic -Wno-long-long -Wnested-externs -Wshadow -Wstrict-prototypes -Wundef], $1) # GCC >= 3.0, -Wlong-long is implied by -pedantic.
       SECP_TRY_APPEND_CFLAGS([-Wno-overlength-strings], $1) # GCC >= 4.2, -Woverlength-strings is implied by -pedantic.
@@ -286,6 +294,12 @@ fi
 if test x"$enable_coverage" = x"yes"; then
     SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DCOVERAGE=1"
     SECP_CFLAGS="-O0 --coverage $SECP_CFLAGS"
+    # If coverage is enabled, and the user has not overridden CFLAGS,
+    # override Autoconf's value "-g -O2" with "-g". Otherwise we'd end up
+    # with "-O0 --coverage -g -O2".
+    if test "$CFLAGS_overridden" = "no"; then
+      CFLAGS="-g"
+    fi
     LDFLAGS="--coverage $LDFLAGS"
 else
     # Most likely the CFLAGS already contain -O2 because that is autoconf's default.

diff --git a/doc/release-process.md b/doc/release-process.md
@@ -15,15 +15,20 @@ This process also assumes that there will be no minor releases for old major rel
 ## Regular release
 
 1. Open a PR to the master branch with a commit (using message `"release: prepare for $MAJOR.$MINOR.$PATCH"`, for example) that
-   * finalizes the release notes in [CHANGELOG.md](../CHANGELOG.md) (make sure to include an entry for `### ABI Compatibility`) and
-   * updates `_PKG_VERSION_*`, `_LIB_VERSION_*`, and sets `_PKG_VERSION_IS_RELEASE` to `true` in `configure.ac`.
+   * finalizes the release notes in [CHANGELOG.md](../CHANGELOG.md) (make sure to include an entry for `### ABI Compatibility`),
+   * updates `_PKG_VERSION_*` and `_LIB_VERSION_*` and sets `_PKG_VERSION_IS_RELEASE` to `true` in `configure.ac`, and
+   * updates `project(libsecp256k1 VERSION ...)` and `${PROJECT_NAME}_LIB_VERSION_*` in `CMakeLists.txt`.
 2. After the PR is merged, tag the commit and push it:
    ```
    RELEASE_COMMIT=<merge commit of step 1>
    git tag -s v$MAJOR.$MINOR.$PATCH -m "libsecp256k1 $MAJOR.$MINOR.$PATCH" $RELEASE_COMMIT
    git push [email protected]:bitcoin-core/secp256k1.git v$MAJOR.$MINOR.$PATCH
    ```
-3. Open a PR to the master branch with a commit (using message `"release cleanup: bump version after $MAJOR.$MINOR.$PATCH"`, for example) that sets `_PKG_VERSION_IS_RELEASE` to `false` and `_PKG_VERSION_PATCH` to `$PATCH + 1` and increases `_LIB_VERSION_REVISION`. If other maintainers are not present to approve the PR, it can be merged without ACKs.
+3. Open a PR to the master branch with a commit (using message `"release cleanup: bump version after $MAJOR.$MINOR.$PATCH"`, for example) that
+   * sets `_PKG_VERSION_IS_RELEASE` to `false` and increments `_PKG_VERSION_PATCH` and `_LIB_VERSION_REVISION` in `configure.ac`, and
+   * increments the `$PATCH` component of `project(libsecp256k1 VERSION ...)` and `${PROJECT_NAME}_LIB_VERSION_REVISION` in `CMakeLists.txt`.
+
+   If other maintainers are not present to approve the PR, it can be merged without ACKs.
 4. Create a new GitHub release with a link to the corresponding entry in [CHANGELOG.md](../CHANGELOG.md).
 
 ## Maintenance release
@@ -38,7 +43,9 @@ Note that bugfixes only need to be backported to releases for which no compatibl
 2. Open a pull request to the `$MAJOR.$MINOR` branch that
    * includes the bugfixes,
    * finalizes the release notes,
-   * bumps `_PKG_VERSION_PATCH` and `_LIB_VERSION_REVISION` in `configure.ac` (with commit message `"release: update PKG_ and LIB_VERSION for $MAJOR.$MINOR.$PATCH"`, for example).
+   * increments `_PKG_VERSION_PATCH` and `_LIB_VERSION_REVISION` in `configure.ac`
+     and the `$PATCH` component of `project(libsecp256k1 VERSION ...)` and `${PROJECT_NAME}_LIB_VERSION_REVISION` in `CMakeLists.txt`
+     (with commit message `"release: bump versions for $MAJOR.$MINOR.$PATCH"`, for example).
 3. After the PRs are merged, update the release branch and tag the commit:
    ```
    git checkout $MAJOR.$MINOR && git pull