cmake: auto detection of CURL_CA_BUNDLE/CURL_CA_PATH

set(CURL_CA_PATH "auto" CACHE STRING

    "Location of default CA path. Set 'none' to disable or 'auto' for auto-detection. Defaults to 'auto'.")

if("${CURL_CA_BUNDLE}" STREQUAL "none")

if("${CURL_CA_BUNDLE}" STREQUAL "")

    message(FATAL_ERROR "Invalid value of CURL_CA_BUNDLE. Use 'none', 'auto' or file path.")

elseif("${CURL_CA_BUNDLE}" STREQUAL "none")

    unset(CURL_CA_BUNDLE CACHE)

elseif("${CURL_CA_BUNDLE}" STREQUAL "auto")

    # TODO: implement

    message(SEND_ERROR "Auto mode not implemented for CURL_CA_BUNDLE")

elseif("${CURL_CA_BUNDLE}" STREQUAL "")

    message(SEND_ERROR "Invalid value of CURL_CA_BUNDLE. Use 'none', 'auto' or path.")

    unset(CURL_CA_BUNDLE CACHE)

    set(CURL_CA_BUNDLE_AUTODETECT TRUE)

else()

    set(CURL_CA_BUNDLE_SET TRUE)

endif()

if("${CURL_CA_PATH}" STREQUAL "none")

if("${CURL_CA_PATH}" STREQUAL "")

    message(FATAL_ERROR "Invalid value of CURL_CA_PATH. Use 'none', 'auto' or directory path.")

elseif("${CURL_CA_PATH}" STREQUAL "none")

    unset(CURL_CA_PATH CACHE)

elseif("${CURL_CA_PATH}" STREQUAL "auto")

    # TODO: implement

    message(SEND_ERROR "Auto mode not implemented for CURL_CA_PATH")

elseif("${CURL_CA_PATH}" STREQUAL "")

    message(SEND_ERROR "Invalid value of CURL_CA_PATH. Use 'none', 'auto' or path.")

    unset(CURL_CA_PATH CACHE)

    set(CURL_CA_PATH_AUTODETECT TRUE)

else()

    set(CURL_CA_PATH_SET TRUE)

endif()

if(CURL_CA_BUNDLE_SET AND CURL_CA_PATH_AUTODETECT)

    # Skip autodetection of unset CA path because CA bundle is set explicitly

elseif(CURL_CA_PATH_SET AND CURL_CA_BUNDLE_AUTODETECT)

    # Skip autodetection of unset CA bundle because CA path is set explicitly

elseif(CURL_CA_PATH_AUTODETECT OR CURL_CA_BUNDLE_AUTODETECT)

    # first try autodetecting a CA bundle, then a CA path

    if(CURL_CA_BUNDLE_AUTODETECT)

        set(SEARCH_CA_BUNDLE_PATHS

            /etc/ssl/certs/ca-certificates.crt

            /etc/pki/tls/certs/ca-bundle.crt

            /usr/share/ssl/certs/ca-bundle.crt

            /usr/local/share/certs/ca-root-nss.crt

            /etc/ssl/cert.pem)

        foreach(SEARCH_CA_BUNDLE_PATH ${SEARCH_CA_BUNDLE_PATHS})

            if(EXISTS "${SEARCH_CA_BUNDLE_PATH}")

                message(STATUS "Found CA bundle: ${SEARCH_CA_BUNDLE_PATH}")

                set(CURL_CA_BUNDLE "${SEARCH_CA_BUNDLE_PATH}")

                set(CURL_CA_BUNDLE_SET TRUE CACHE)

                break()

            endif()

        endforeach()

    endif()

    if(CURL_CA_PATH_AUTODETECT AND (NOT CURL_CA_PATH_SET))

        if(EXISTS "/etc/ssl/certs")

            set(CURL_CA_PATH "/etc/ssl/certs")

            set(CURL_CA_PATH_SET TRUE CACHE)

        endif()

    endif()

endif()

if(CURL_CA_PATH_SET AND NOT (USE_OPENSSL OR GNUTLS_ENABLED))

    message(FATAL_ERROR

            "CA path only supported by OpenSSL, GnuTLS or PolarSSL. "

            "Set CURL_CA_PATH=none or enable one of those TLS backends.")

endif()