Enable LIBOQS_DIR as cache entry and environment variable.

Fix #273

`liboqs_DIR` is a CMake cache entry to hint CMake about the location of liboqs
CMake package.

However, being able to use `LIBOQS_DIR` (full capitalized) would be more
convenient.

This PR adds the ability to use either `liboqs_DIR` as a cache entry, `liboqs_DIR`
as an environment variable, `LIBOQS_DIR` as a cache entry and `LIBOQS_DIR`
as an env variable.

Tests were also added to make sure that these variables are well taken
by CMake during the configuration stage.

.github/workflows/linux.yml

@@ -224,3 +224,85 @@ jobs:
         with:
           name: oqsprovider-aarch64
           path: build/*.deb
+
+  test_cmake_liboqs_dir_value:
+    name: "Test CMake `liboqs_DIR` and `LIBOQS_DIR` values"
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+    container:
+      image: openquantumsafe/ci-ubuntu-jammy:latest
+    env:
+      OPENSSL_BRANCH: "master"
+      INSTALL_DIR: "/opt/install"
+      LIBOQS_CMAKE_PACKAGE_DIR: "/usr/lib/cmake/liboqs"
+      LIBOQS_CMAKE_PACKAGE_ALT_DIR: "/opt/install/lib/cmake/liboqs"
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Prepare install directory
+        run: mkdir -p "${INSTALL_DIR}"
+
+      - name: Clone and build liboqs for linux-aarch64
+        working-directory: /opt/
+        run: |
+          git clone --depth=1 --branch main https://github.com/open-quantum-safe/liboqs.git liboqs
+          cd liboqs
+          mkdir build install
+          cmake -GNinja -B build \
+                -DCMAKE_INSTALL_PREFIX="${INSTALL_DIR}" \
+                -DOQS_USE_OPENSSL=OFF
+          cmake --build build -j$(nproc)
+          cmake --install build
+
+      - name: Test oqs-provider CMake script against `liboqs_DIR`, `LIBOQS_DIR`
+        run: |
+          get_liboqs_dir() {
+              cmake -L build/ | grep '^liboqs_DIR' | cut -d'=' -f2
+          }
+
+          cmake -B build -Dliboqs_DIR="${LIBOQS_CMAKE_PACKAGE_ALT_DIR}"
+          cmake -L build/
+          value="$(get_liboqs_dir)"
+          if [ "${value}" != "${LIBOQS_CMAKE_PACKAGE_ALT_DIR}" ]; then
+              echo "liboqs_DIR cache entry did not work: got ${value}, expected ${LIBOQS_CMAKE_PACKAGE_ALT_DIR}"
+              exit 1
+          fi
+
+          rm -rf build
+          cmake -B build -DLIBOQS_DIR="${LIBOQS_CMAKE_PACKAGE_ALT_DIR}"
+          value="$(get_liboqs_dir)"
+          if [ "${value}" != "${LIBOQS_CMAKE_PACKAGE_ALT_DIR}" ]; then
+              echo "LIBOQS_DIR cache entry did not work: got ${value}, expected ${LIBOQS_CMAKE_PACKAGE_ALT_DIR}"
+              exit 1
+          fi
+
+          rm -rf build
+          if cmake -B build -Dliboqs_DIR="${LIBOQS_CMAKE_PACKAGE_DIR}" -DLIBOQS_DIR="${LIBOQS_CMAKE_PACKAGE_ALT_DIR}"; then
+              echo "cmake succeed when it should have failed: liboqs_DIR and LIBOQS_DIR cache entries mismatched"
+              exit 1
+          fi
+
+          rm -rf build
+          env LIBOQS_DIR="${LIBOQS_CMAKE_PACKAGE_ALT_DIR}" cmake -B build
+          value="$(get_liboqs_dir)"
+          if [ "${value}" != "${LIBOQS_CMAKE_PACKAGE_ALT_DIR}" ]; then
+              echo "LIBOQS_DIR environment variable did not work: got ${value}, expected ${LIBOQS_CMAKE_PACKAGE_ALT_DIR}"
+              exit 1
+          fi
+
+          rm -rf build
+          if env LIBOQS_DIR="${LIBOQS_CMAKE_PACKAGE_ALT_DIR}" cmake -B build -Dliboqs_DIR="${LIBOQS_CMAKE_PACKAGE_DIR}"; then
+              echo "cmake succeed when it should have failed: LIBOQS_DIR cache entry and LIBOQS_DIR environment variable mismatched"
+              exit 1
+          fi
+
+          rm -rf build
+          env liboqs_DIR="${LIBOQS_CMAKE_PACKAGE_ALT_DIR}" cmake -B build
+          value="$(get_liboqs_dir)"
+          if [ "${value}" != "${LIBOQS_CMAKE_PACKAGE_ALT_DIR}" ]; then
+              echo "liboqs_DIR environment variable did not work: got ${value}, expected ${LIBOQS_CMAKE_PACKAGE_ALT_DIR}"
+              exit 1
+          fi

CMakeLists.txt

@@ -67,6 +67,46 @@ get_filename_component(OPENSSL_LIB_DIR ${OPENSSL_CRYPTO_LIBRARY} DIRECTORY)
 set(OPENSSL_MODULES_PATH ${OPENSSL_LIB_DIR}/ossl-modules)
 endif()
 
+if(DEFINED liboqs_DIR)
+    get_filename_component(value "${liboqs_DIR}" REALPATH)
+    set(liboqs_DIR "${value}" CACHE PATH "Path to liboqs CMake configuration directory" FORCE)
+endif()
+
+set(liboqs_search_path "")
+if (DEFINED LIBOQS_DIR)
+    get_filename_component(LIBOQS_DIR "${LIBOQS_DIR}" REALPATH)
+    if (DEFINED liboqs_DIR AND NOT "${liboqs_DIR}" STREQUAL "${LIBOQS_DIR}")
+        message(FATAL_ERROR "`liboqs_DIR` and `LIBOQS_DIR` cache entries mismatch ('${liboqs_DIR}' != '${LIBOQS_DIR}').")
+    endif()
+    set(liboqs_search_path "${LIBOQS_DIR}")
+endif()
+
+if (DEFINED ENV{LIBOQS_DIR})
+    get_filename_component(value "$ENV{LIBOQS_DIR}" REALPATH)
+    if (DEFINED liboqs_DIR AND NOT "${liboqs_DIR}" STREQUAL "${value}")
+        message(FATAL_ERROR "`liboqs_DIR` cache entry and `LIBOQS_DIR` environment variable mismatch ('${liboqs_DIR}' != '${value}').")
+    endif()
+    if (liboqs_search_path AND NOT "${liboqs_search_path}" STREQUAL "${value}")
+        message(FATAL_ERROR "`LIBOQS_DIR` cache entry and `LIBOQS_DIR` environment variable mismatch ('${LIBOQS_DIR}' != '$ENV{LIBOQS_DIR}').")
+    endif()
+    set(liboqs_search_path "${value}")
+endif()
+
+if (DEFINED ENV{liboqs_DIR})
+    get_filename_component(value "$ENV{liboqs_DIR}" REALPATH)
+    if (DEFINED liboqs_DIR AND NOT "${liboqs_DIR}" STREQUAL "${value}")
+        message(FATAL_ERROR "`liboqs_DIR` cache entry and `liboqs_DIR` environment variable mismatch ('${liboqs_DIR}' != '${value}'.")
+    endif()
+    if (liboqs_search_path AND NOT "${liboqs_search_path}" STREQUAL "${value}")
+        message(FATAL_ERROR "`libos_DIR` environment variable does not match the value previously set ('${value}' != '${liboqs_search_path}').")
+    endif()
+    set(liboqs_search_path "${value}")
+endif()
+
+if (liboqs_search_path)
+    set(liboqs_DIR "${liboqs_search_path}" CACHE PATH "Path to liboqs configuration directory" FORCE)
+endif()
+
 # Add required include for liboqs
 find_package(liboqs REQUIRED)
 get_target_property(LIBOQS_INCLUDE_DIR OQS::oqs INTERFACE_INCLUDE_DIRECTORIES)