BlockstreamResearch · jonasnick · Jul 21, 2023 · Feb 4, 2022 · Feb 4, 2022 · Nov 22, 2022
diff --git a/.cirrus.yml b/.cirrus.yml
@@ -1,4 +1,6 @@
 env:
+  ### cirrus config
+  CIRRUS_CLONE_DEPTH: 1
   ### compiler options
   HOST:
   WRAPPER_CMD:
@@ -29,7 +31,7 @@ env:
   SECP256K1_TEST_ITERS:
   BENCH: yes
   SECP256K1_BENCH_ITERS: 2
-  CTIMETEST: yes
+  CTIMETESTS: yes
   # Compile and run the tests
   EXAMPLES: yes
 
@@ -46,8 +48,8 @@ cat_logs_snippet: &CAT_LOGS
       - cat noverify_tests.log || true
     cat_exhaustive_tests_log_script:
       - cat exhaustive_tests.log || true
-    cat_valgrind_ctime_test_log_script:
-      - cat valgrind_ctime_test.log || true
+    cat_ctime_tests_log_script:
+      - cat ctime_tests.log || true
     cat_bench_log_script:
       - cat bench.log || true
     cat_config_log_script:
@@ -60,10 +62,8 @@ cat_logs_snippet: &CAT_LOGS
 merge_base_script_snippet: &MERGE_BASE
   merge_base_script:
     - if [ "$CIRRUS_PR" = "" ]; then exit 0; fi
-    - git fetch $CIRRUS_REPO_CLONE_URL $CIRRUS_BASE_BRANCH
-    - git config --global user.email "ci@ci.ci"
-    - git config --global user.name "ci"
-    - git merge FETCH_HEAD  # Merge base to detect silent merge conflicts
+    - git fetch --depth=1 $CIRRUS_REPO_CLONE_URL "pull/${CIRRUS_PR}/merge"
+    - git checkout FETCH_HEAD  # Use merged changes to detect silent merge conflicts
 
 linux_container_snippet: &LINUX_CONTAINER
   container:
@@ -87,9 +87,10 @@ task:
     - env: {WIDEMUL: int128,                 ECDH: yes, SCHNORRSIG: yes, EXPERIMENTAL: yes, ECDSA_S2C: yes, RANGEPROOF: yes, WHITELIST: yes, GENERATOR: yes, MUSIG: yes, ECDSAADAPTOR: yes, BPPP: yes}
     - env: {WIDEMUL: int128,  ASM: x86_64}
     - env: {                  RECOVERY: yes,            SCHNORRSIG: yes, EXPERIMENTAL: yes, ECDSA_S2C: yes, RANGEPROOF: yes, WHITELIST: yes, GENERATOR: yes, MUSIG: yes, ECDSAADAPTOR: yes, BPPP: yes}
-    - env: {BUILD: distcheck, WITH_VALGRIND: no, CTIMETEST: no, BENCH: no}
+    - env: {CTIMETESTS: no,    RECOVERY: yes, ECDH: yes, SCHNORRSIG: yes, EXPERIMENTAL: yes, ECDSA_S2C: yes, RANGEPROOF: yes, WHITELIST: yes, GENERATOR: yes, MUSIG: yes, ECDSAADAPTOR: yes, BPPP: yes, CPPFLAGS: -DVERIFY}
+    - env: {BUILD: distcheck, WITH_VALGRIND: no, CTIMETESTS: no, BENCH: no}
     - env: {CPPFLAGS: -DDETERMINISTIC}
-    - env: {CFLAGS: -O0, CTIMETEST: no}
+    - env: {CFLAGS: -O0, CTIMETESTS: no}
     - env: { ECMULTGENPRECISION: 2, ECMULTWINDOW: 2 }
     - env: { ECMULTGENPRECISION: 8, ECMULTWINDOW: 4 }
   matrix:
@@ -144,7 +145,7 @@ task:
   env:
     ASM: no
     WITH_VALGRIND: no
-    CTIMETEST: no
+    CTIMETESTS: no
   matrix:
     - env:
         CC: gcc
@@ -177,7 +178,7 @@ task:
     MUSIG: yes
     ECDSAADAPTOR: yes
     BPPP: yes
-    CTIMETEST: no
+    CTIMETESTS: no
   << : *MERGE_BASE
   test_script:
     # https://sourceware.org/bugzilla/show_bug.cgi?id=27008
@@ -196,7 +197,7 @@ task:
     ECDH: yes
     RECOVERY: yes
     SCHNORRSIG: yes
-    CTIMETEST: no
+    CTIMETESTS: no
   matrix:
     - env: {}
     - env: {EXPERIMENTAL: yes, ASM: arm}
@@ -216,7 +217,7 @@ task:
     ECDH: yes
     RECOVERY: yes
     SCHNORRSIG: yes
-    CTIMETEST: no
+    CTIMETESTS: no
   << : *MERGE_BASE
   test_script:
     - ./ci/cirrus.sh
@@ -233,7 +234,7 @@ task:
     ECDH: yes
     RECOVERY: yes
     SCHNORRSIG: yes
-    CTIMETEST: no
+    CTIMETESTS: no
   << : *MERGE_BASE
   test_script:
     - ./ci/cirrus.sh
@@ -247,7 +248,7 @@ task:
     ECDH: yes
     RECOVERY: yes
     SCHNORRSIG: yes
-    CTIMETEST: no
+    CTIMETESTS: no
   matrix:
     - name: "x86_64 (mingw32-w64): Windows (Debian stable, Wine)"
       env:
@@ -277,7 +278,7 @@ task:
     MUSIG: yes
     ECDSAADAPTOR: yes
     BPPP: yes
-    CTIMETEST: no
+    CTIMETESTS: no
     # Use a MinGW-w64 host to tell ./configure we're building for Windows.
     # This will detect some MinGW-w64 tools but then make will need only
     # the MSVC tools CC, AR and NM as specified below.
@@ -288,7 +289,7 @@ task:
     # Set non-essential options that affect the CLI messages here.
     # (They depend on the user's taste, so we don't want to set them automatically in configure.ac.)
     CFLAGS: -nologo -diagnostics:caret
-    LDFLAGS: -XCClinker -nologo -XCClinker -diagnostics:caret
+    LDFLAGS: -Xlinker -Xlinker -Xlinker -nologo
   matrix:
     - name: "x86_64 (MSVC): Windows (Debian stable, Wine)"
     - name: "x86_64 (MSVC): Windows (Debian stable, Wine, int128_struct)"
@@ -325,7 +326,7 @@ task:
     MUSIG: yes
     ECDSAADAPTOR: yes
     BPPP: yes
-    CTIMETEST: no
+    CTIMETESTS: no
   matrix:
     - name: "Valgrind (memcheck)"
       container:
@@ -378,10 +379,11 @@ task:
     MUSIG: yes
     ECDSAADAPTOR: yes
     BPPP: yes
-    CTIMETEST: no
+    CTIMETESTS: yes
     CC: clang
     SECP256K1_TEST_ITERS: 32
     ASM: no
+    WITH_VALGRIND: no
   container:
     memory: 2G
   matrix:

diff --git a/.gitignore b/.gitignore
@@ -5,12 +5,13 @@ bench_generator
 bench_rangeproof
 bench_internal
 bench_whitelist
+noverify_tests
 tests
 example_musig
 exhaustive_tests
 precompute_ecmult_gen
 precompute_ecmult
-valgrind_ctime_test
+ctime_tests
 ecdh_example
 ecdsa_example
 schnorr_example

diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -10,6 +10,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+#### Added
+ - Usage examples: Added a recommended method for securely clearing sensitive data, e.g., secret keys, from memory.
+ - Tests: Added a new test binary `noverify_tests`. This binary runs the tests without some additional checks present in the ordinary `tests` binary and is thereby closer to production binaries. The `noverify_tests` binary is automatically run as part of the `make check` target. 
+
+#### Fixed
+ - Fixed declarations of API variables for MSVC (`__declspec(dllimport)`). This fixes MSVC builds of programs which link against a libsecp256k1 DLL dynamically and use API variables (and not only API functions). Unfortunately, the MSVC linker now will emit warning `LNK4217` when trying to link against libsecp256k1 statically. Pass `/ignore:4217` to the linker to suppress this warning.
+
+#### Changed
+ - Forbade cloning or destroying `secp256k1_context_static`. Create a new context instead of cloning the static context. (If this change breaks your code, your code is probably wrong.)
+ - Forbade randomizing (copies of) `secp256k1_context_static`. Randomizing a copy of `secp256k1_context_static` did not have any effect and did not provide defense-in-depth protection against side-channel attacks. Create a new context if you want to benefit from randomization.
+
+#### Removed
+ - Removed the configuration header `src/libsecp256k1-config.h`. We recommend passing flags to `./configure` to set configuration options (see `./configure --help`). If you cannot or do not want to use `./configure`, pass configuration flags such as `-DSECP256K1_ENABLE_MODULE_SCHNORRSIG` manually to the compiler (see the file `configure.ac` for supported flags). 
+
 ## [0.2.0] - 2022-12-12
 
 #### Added

diff --git a/Makefile.am b/Makefile.am
@@ -49,6 +49,7 @@ noinst_HEADERS += src/modinv64_impl.h
 noinst_HEADERS += src/precomputed_ecmult.h
 noinst_HEADERS += src/precomputed_ecmult_gen.h
 noinst_HEADERS += src/assumptions.h
+noinst_HEADERS += src/checkmem.h
 noinst_HEADERS += src/util.h
 noinst_HEADERS += src/int128.h
 noinst_HEADERS += src/int128_impl.h
@@ -70,12 +71,14 @@ noinst_HEADERS += contrib/lax_der_parsing.h
 noinst_HEADERS += contrib/lax_der_parsing.c
 noinst_HEADERS += contrib/lax_der_privatekey_parsing.h
 noinst_HEADERS += contrib/lax_der_privatekey_parsing.c
-noinst_HEADERS += examples/random.h
+noinst_HEADERS += examples/examples_util.h
 
 PRECOMPUTED_LIB = libsecp256k1_precomputed.la
 noinst_LTLIBRARIES = $(PRECOMPUTED_LIB)
 libsecp256k1_precomputed_la_SOURCES =  src/precomputed_ecmult.c src/precomputed_ecmult_gen.c
-libsecp256k1_precomputed_la_CPPFLAGS = $(SECP_INCLUDES) $(SECP_CONFIG_DEFINES)
+# We need `-I$(top_srcdir)/src` in VPATH builds if libsecp256k1_precomputed_la_SOURCES have been recreated in the build tree.
+# This helps users and packagers who insist on recreating the precomputed files (e.g., Gentoo).
+libsecp256k1_precomputed_la_CPPFLAGS = -I$(top_srcdir)/src $(SECP_CONFIG_DEFINES)
 
 if USE_EXTERNAL_ASM
 COMMON_LIB = libsecp256k1_common.la
@@ -94,42 +97,32 @@ endif
 endif
 
 libsecp256k1_la_SOURCES = src/secp256k1.c
-libsecp256k1_la_CPPFLAGS = $(SECP_INCLUDES) $(SECP_CONFIG_DEFINES)
-libsecp256k1_la_LIBADD = $(SECP_LIBS) $(COMMON_LIB) $(PRECOMPUTED_LIB)
+libsecp256k1_la_CPPFLAGS = $(SECP_CONFIG_DEFINES)
+libsecp256k1_la_LIBADD = $(COMMON_LIB) $(PRECOMPUTED_LIB)
 libsecp256k1_la_LDFLAGS = -no-undefined -version-info $(LIB_VERSION_CURRENT):$(LIB_VERSION_REVISION):$(LIB_VERSION_AGE)
 
-if VALGRIND_ENABLED
-libsecp256k1_la_CPPFLAGS += -DVALGRIND
-endif
-
 noinst_PROGRAMS =
 if USE_BENCHMARK
 noinst_PROGRAMS += bench bench_internal bench_ecmult
 bench_SOURCES = src/bench.c
-bench_LDADD = libsecp256k1.la $(SECP_LIBS) $(SECP_TEST_LIBS) $(COMMON_LIB)
+bench_LDADD = libsecp256k1.la
 bench_CPPFLAGS = $(SECP_CONFIG_DEFINES)
 bench_internal_SOURCES = src/bench_internal.c
-bench_internal_LDADD = $(SECP_LIBS) $(COMMON_LIB) $(PRECOMPUTED_LIB)
-bench_internal_CPPFLAGS = $(SECP_INCLUDES) $(SECP_CONFIG_DEFINES)
+bench_internal_LDADD = $(COMMON_LIB) $(PRECOMPUTED_LIB)
+bench_internal_CPPFLAGS = $(SECP_CONFIG_DEFINES)
 bench_ecmult_SOURCES = src/bench_ecmult.c
-bench_ecmult_LDADD = $(SECP_LIBS) $(COMMON_LIB) $(PRECOMPUTED_LIB)
-bench_ecmult_CPPFLAGS = $(SECP_INCLUDES) $(SECP_CONFIG_DEFINES)
+bench_ecmult_LDADD = $(COMMON_LIB) $(PRECOMPUTED_LIB)
+bench_ecmult_CPPFLAGS = $(SECP_CONFIG_DEFINES)
 endif
 
 TESTS =
 if USE_TESTS
 TESTS += noverify_tests
 noinst_PROGRAMS += noverify_tests
 noverify_tests_SOURCES = src/tests.c
-noverify_tests_CPPFLAGS = $(SECP_INCLUDES) $(SECP_TEST_INCLUDES) $(SECP_CONFIG_DEFINES)
-noverify_tests_LDADD = $(SECP_LIBS) $(SECP_TEST_LIBS) $(COMMON_LIB) $(PRECOMPUTED_LIB)
+noverify_tests_CPPFLAGS = $(SECP_CONFIG_DEFINES)
+noverify_tests_LDADD = $(COMMON_LIB) $(PRECOMPUTED_LIB)
 noverify_tests_LDFLAGS = -static
-if VALGRIND_ENABLED
-noverify_tests_CPPFLAGS += -DVALGRIND
-noinst_PROGRAMS += valgrind_ctime_test
-valgrind_ctime_test_SOURCES = src/valgrind_ctime_test.c
-valgrind_ctime_test_LDADD = libsecp256k1.la $(SECP_LIBS) $(COMMON_LIB)
-endif
 if !ENABLE_COVERAGE
 TESTS += tests
 noinst_PROGRAMS += tests
@@ -140,15 +133,22 @@ tests_LDFLAGS  = $(noverify_tests_LDFLAGS)
 endif
 endif
 
+if USE_CTIME_TESTS
+noinst_PROGRAMS += ctime_tests
+ctime_tests_SOURCES = src/ctime_tests.c
+ctime_tests_LDADD = libsecp256k1.la
+ctime_tests_CPPFLAGS = $(SECP_CONFIG_DEFINES)
+endif
+
 if USE_EXHAUSTIVE_TESTS
 noinst_PROGRAMS += exhaustive_tests
 exhaustive_tests_SOURCES = src/tests_exhaustive.c
-exhaustive_tests_CPPFLAGS = $(SECP_INCLUDES) $(SECP_CONFIG_DEFINES)
+exhaustive_tests_CPPFLAGS = $(SECP_CONFIG_DEFINES)
 if !ENABLE_COVERAGE
 exhaustive_tests_CPPFLAGS += -DVERIFY
 endif
 # Note: do not include $(PRECOMPUTED_LIB) in exhaustive_tests (it uses runtime-generated tables).
-exhaustive_tests_LDADD = $(SECP_LIBS) $(COMMON_LIB)
+exhaustive_tests_LDADD = $(COMMON_LIB)
 exhaustive_tests_LDFLAGS = -static
 TESTS += exhaustive_tests
 endif
@@ -203,12 +203,12 @@ EXTRA_PROGRAMS = precompute_ecmult precompute_ecmult_gen
 CLEANFILES = $(EXTRA_PROGRAMS)
 
 precompute_ecmult_SOURCES = src/precompute_ecmult.c
-precompute_ecmult_CPPFLAGS = $(SECP_INCLUDES) $(SECP_CONFIG_DEFINES)
-precompute_ecmult_LDADD = $(SECP_LIBS) $(COMMON_LIB)
+precompute_ecmult_CPPFLAGS = $(SECP_CONFIG_DEFINES)
+precompute_ecmult_LDADD = $(COMMON_LIB)
 
 precompute_ecmult_gen_SOURCES = src/precompute_ecmult_gen.c
-precompute_ecmult_gen_CPPFLAGS = $(SECP_INCLUDES) $(SECP_CONFIG_DEFINES)
-precompute_ecmult_gen_LDADD = $(SECP_LIBS) $(COMMON_LIB)
+precompute_ecmult_gen_CPPFLAGS = $(SECP_CONFIG_DEFINES)
+precompute_ecmult_gen_LDADD = $(COMMON_LIB)
 
 # See Automake manual, Section "Errors with distclean".
 # We don't list any dependencies for the prebuilt files here because

diff --git a/ci/cirrus.sh b/ci/cirrus.sh
@@ -14,7 +14,7 @@ print_environment() {
             ECMULTWINDOW ECMULTGENPRECISION ASM WIDEMUL WITH_VALGRIND EXTRAFLAGS \
             EXPERIMENTAL ECDH RECOVERY SCHNORRSIG \
             ECDSA_S2C GENERATOR RANGEPROOF WHITELIST MUSIG ECDSAADAPTOR BPPP \
-            SECP256K1_TEST_ITERS BENCH SECP256K1_BENCH_ITERS CTIMETEST\
+            SECP256K1_TEST_ITERS BENCH SECP256K1_BENCH_ITERS CTIMETESTS\
             EXAMPLES \
             HOST WRAPPER_CMD \
             CC CFLAGS CPPFLAGS AR NM
@@ -35,6 +35,8 @@ print_environment
 # This speeds up jobs with many invocations of wine (e.g., ./configure with MSVC) tremendously.
 case "$WRAPPER_CMD" in
     *wine*)
+        # Make sure to shutdown wineserver whenever we exit.
+        trap "wineserver -k || true" EXIT INT HUP
         # This is apparently only reliable when we run a dummy command such as "hh.exe" afterwards.
         wineserver -p && wine hh.exe
         ;;
@@ -67,6 +69,7 @@ fi
     --enable-module-schnorrsig="$SCHNORRSIG"  --enable-module-musig="$MUSIG" --enable-module-ecdsa-adaptor="$ECDSAADAPTOR" \
     --enable-module-schnorrsig="$SCHNORRSIG" \
     --enable-examples="$EXAMPLES" \
+    --enable-ctime-tests="$CTIMETESTS" \
     --with-valgrind="$WITH_VALGRIND" \
     --host="$HOST" $EXTRAFLAGS
 
@@ -83,14 +86,15 @@ export LOG_COMPILER="$WRAPPER_CMD"
 
 make "$BUILD"
 
+# Using the local `libtool` because on macOS the system's libtool has nothing to do with GNU libtool
+EXEC='./libtool --mode=execute'
+if [ -n "$WRAPPER_CMD" ]
+then
+    EXEC="$EXEC $WRAPPER_CMD"
+fi
+
 if [ "$BENCH" = "yes" ]
 then
-    # Using the local `libtool` because on macOS the system's libtool has nothing to do with GNU libtool
-    EXEC='./libtool --mode=execute'
-    if [ -n "$WRAPPER_CMD" ]
-    then
-        EXEC="$EXEC $WRAPPER_CMD"
-    fi
     {
         $EXEC ./bench_ecmult
         $EXEC ./bench_internal
@@ -102,9 +106,13 @@ then
     } >> bench.log 2>&1
 fi
 
-if [ "$CTIMETEST" = "yes" ]
+if [ "$CTIMETESTS" = "yes" ]
 then
-    ./libtool --mode=execute valgrind --error-exitcode=42 ./valgrind_ctime_test > valgrind_ctime_test.log 2>&1
+    if [ "$WITH_VALGRIND" = "yes" ]; then
+        ./libtool --mode=execute valgrind --error-exitcode=42 ./ctime_tests > ctime_tests.log 2>&1
+    else
+        $EXEC ./ctime_tests > ctime_tests.log 2>&1
+    fi
 fi
 
 # Rebuild precomputed files (if not cross-compiling).
@@ -114,9 +122,6 @@ then
     make precomp
 fi
 
-# Shutdown wineserver again
-wineserver -k || true
-
 # Check that no repo files have been modified by the build.
 # (This fails for example if the precomp files need to be updated in the repo.)
 git diff --exit-code