Pass MBEDTLS_CONFIG_FILE defines through cmake

CMakeLists.txt

@@ -118,6 +118,10 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
         FORCE)
 endif()
 
+# Make MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE into PATHs
+set(MBEDTLS_CONFIG_FILE "" CACHE FILEPATH "Mbed TLS config file (overrides default).")
+set(MBEDTLS_USER_CONFIG_FILE "" CACHE FILEPATH "Mbed TLS user config file (appended to default).")
+
 # Create a symbolic link from ${base_name} in the binary directory
 # to the corresponding path in the source directory.
 # Note: Copies the file(s) on Windows.
@@ -297,6 +301,20 @@ if(ENABLE_TESTING OR ENABLE_PROGRAMS)
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/library
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/everest/include)
+
+    # Pass-through MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE
+    if(MBEDTLS_CONFIG_FILE)
+        target_compile_definitions(mbedtls_test
+            PUBLIC MBEDTLS_CONFIG_FILE="${MBEDTLS_CONFIG_FILE}")
+        target_compile_definitions(mbedtls_test_helpers
+            PUBLIC MBEDTLS_CONFIG_FILE="${MBEDTLS_CONFIG_FILE}")
+    endif()
+    if(MBEDTLS_USER_CONFIG_FILE)
+        target_compile_definitions(mbedtls_test
+            PUBLIC MBEDTLS_USER_CONFIG_FILE="${MBEDTLS_USER_CONFIG_FILE}")
+        target_compile_definitions(mbedtls_test_helpers
+            PUBLIC MBEDTLS_USER_CONFIG_FILE="${MBEDTLS_USER_CONFIG_FILE}")
+    endif()
 endif()
 
 if(ENABLE_PROGRAMS)

ChangeLog.d/cmake-pass-through-config-defines.txt

@@ -0,0 +1,3 @@
+Features
+   * Allow MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE to be set by
+     setting the CMake variable of the same name at configuration time.

library/CMakeLists.txt

@@ -320,6 +320,15 @@ foreach(target IN LISTS target_libraries)
         PUBLIC $<BUILD_INTERFACE:${MBEDTLS_DIR}/include/>
                $<INSTALL_INTERFACE:include/>
         PRIVATE ${MBEDTLS_DIR}/library/)
+    # Pass-through MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE
+    if(MBEDTLS_CONFIG_FILE)
+        target_compile_definitions(${target}
+            PUBLIC MBEDTLS_CONFIG_FILE="${MBEDTLS_CONFIG_FILE}")
+    endif()
+    if(MBEDTLS_USER_CONFIG_FILE)
+        target_compile_definitions(${target}
+            PUBLIC MBEDTLS_USER_CONFIG_FILE="${MBEDTLS_USER_CONFIG_FILE}")
+    endif()
     install(
         TARGETS ${target}
         EXPORT MbedTLSTargets

tests/scripts/all.sh

@@ -4566,6 +4566,69 @@ support_test_cmake_as_package_install () {
     support_test_cmake_out_of_source
 }
 
+component_build_cmake_custom_config_file () {
+    # Make a copy of config file to use for the in-tree test
+    cp "$CONFIG_H" include/mbedtls_config_in_tree_copy.h
+
+    MBEDTLS_ROOT_DIR="$PWD"
+    mkdir "$OUT_OF_SOURCE_DIR"
+    cd "$OUT_OF_SOURCE_DIR"
+
+    # Build once to get the generated files (which need an intact config file)
+    cmake "$MBEDTLS_ROOT_DIR"
+    make
+
+    msg "build: cmake with -DMBEDTLS_CONFIG_FILE"
+    scripts/config.py -w full_config.h full
+    echo '#error "cmake -DMBEDTLS_CONFIG_FILE is not working."' > "$MBEDTLS_ROOT_DIR/$CONFIG_H"
+    cmake -DGEN_FILES=OFF -DMBEDTLS_CONFIG_FILE=full_config.h "$MBEDTLS_ROOT_DIR"
+    make
+
+    msg "build: cmake with -DMBEDTLS_CONFIG_FILE + -DMBEDTLS_USER_CONFIG_FILE"
+    # In the user config, disable one feature (for simplicity, pick a feature
+    # that nothing else depends on).
+    echo '#undef MBEDTLS_NIST_KW_C' >user_config.h
+
+    cmake -DGEN_FILES=OFF -DMBEDTLS_CONFIG_FILE=full_config.h -DMBEDTLS_USER_CONFIG_FILE=user_config.h "$MBEDTLS_ROOT_DIR"
+    make
+    not programs/test/query_compile_time_config MBEDTLS_NIST_KW_C
+
+    rm -f user_config.h full_config.h
+
+    cd "$MBEDTLS_ROOT_DIR"
+    rm -rf "$OUT_OF_SOURCE_DIR"
+
+    # Now repeat the test for an in-tree build:
+
+    # Restore config for the in-tree test
+    mv include/mbedtls_config_in_tree_copy.h "$CONFIG_H"
+
+    # Build once to get the generated files (which need an intact config)
+    cmake .
+    make
+
+    msg "build: cmake (in-tree) with -DMBEDTLS_CONFIG_FILE"
+    scripts/config.py -w full_config.h full
+    echo '#error "cmake -DMBEDTLS_CONFIG_FILE is not working."' > "$MBEDTLS_ROOT_DIR/$CONFIG_H"
+    cmake -DGEN_FILES=OFF -DMBEDTLS_CONFIG_FILE=full_config.h .
+    make
+
+    msg "build: cmake (in-tree) with -DMBEDTLS_CONFIG_FILE + -DMBEDTLS_USER_CONFIG_FILE"
+    # In the user config, disable one feature (for simplicity, pick a feature
+    # that nothing else depends on).
+    echo '#undef MBEDTLS_NIST_KW_C' >user_config.h
+
+    cmake -DGEN_FILES=OFF -DMBEDTLS_CONFIG_FILE=full_config.h -DMBEDTLS_USER_CONFIG_FILE=user_config.h .
+    make
+    not programs/test/query_compile_time_config MBEDTLS_NIST_KW_C
+
+    rm -f user_config.h full_config.h
+}
+support_build_cmake_custom_config_file () {
+    support_test_cmake_out_of_source
+}
+
+
 component_test_zeroize () {
     # Test that the function mbedtls_platform_zeroize() is not optimized away by
     # different combinations of compilers and optimization flags by using an