Mbed TLS CMake improvements.

Try to use the Mbed TLS cmake configuration data if present, and
refactor our FindModule to adhere to the same basic API.

cmake/FindMbedTLS.cmake

@@ -0,0 +1,122 @@
+#
+# Copyright 2024 Staysail Systems, Inc. <info@staysail.tech>
+# Copyright 2017 Capitar IT Group BV <info@capitar.com>
+#
+# This software is supplied under the terms of the MIT License, a
+# copy of which should be located in the distribution where this
+# file was obtained (LICENSE.txt).  A copy of the license may also be
+# found online at https://opensource.org/licenses/MIT.
+#
+
+#
+# Try to find the Mbed TLS libraries.
+# This tries to emulate the same expectations that the stock Mbed TLS
+# module uses in Mbed TLS v3.x.
+#
+# Sets the following:
+#
+#  MbedTLS_FOUND          - True if we found Mbed TLS.
+#  MbedTLS_TARGET         - Target of the mbedtls library.
+#  MbedX509_TARGET        - Target of the mbedx509 library.
+#  MbedCrypto_TARGET      - Target of the mbedcrypto library.
+#  MbedTLS_VERSION        - $major.$minor.$revision (e.g. ``2.6.0``).
+#
+#  MBEDTLS_CRYPTO_LIBRARY - The mbedcrypto library.
+#  MBEDTLS_X509_LIBRARY   - The mbedx509 library.
+#  MBEDTLS_TLS_LIBRARY    - The mbedtls library.
+#  MBEDTLS_LIBRARIES      - List of all three Mbed TLS libraries.
+#
+# Hints:
+#
+# Set ``MBEDTLS_ROOT_DIR`` to the root directory of Mbed TLS installation.
+#
+
+set(_MBEDTLS_ROOT_HINTS ${MBEDTLS_ROOT_DIR} ENV MBEDTLS_ROOT_DIR)
+
+set(_MBED_REQUIRED_VARS MbedTLS_TARGET MbedX509_TARGET MbedCrypto_TARGET MbedTLS_VERSION)
+
+include(FindPackageHandleStandardArgs)
+include(CMakePushCheckState)
+
+find_path(_MBEDTLS_INCLUDE_DIR
+        NAMES mbedtls/ssl.h
+        HINTS ${_MBEDTLS_ROOT_HINTS}
+        # PATHS /usr/local
+        PATH_SUFFIXES include)
+
+find_library(_MBEDCRYPTO_LIBRARY
+        NAMES mbedcrypto
+        HINTS ${_MBEDTLS_ROOT_HINTS}
+        # PATHS /usr/local
+        # PATH_SUFFIXES lib
+        )
+
+find_library(_MBEDX509_LIBRARY
+        NAMES mbedx509
+        HINTS ${_MBEDTLS_ROOT_HINTS}
+        #PATHS /usr/local
+        # PATH_SUFFIXES lib
+        )
+
+find_library(_MBEDTLS_LIBRARY
+        NAMES mbedtls
+        HINTS ${_MBEDTLS_ROOT_HINTS}
+        #PATHS /usr/local
+        #PATH_SUFFIXES lib
+        )
+
+if ("${_MBEDTLS_TLS_LIBRARY}" STREQUAL "_MBEDTLS_TLS_LIBRARY-NOTFOUND")
+    message("Failed to find Mbed TLS library")
+else()
+
+    cmake_push_check_state(RESET)
+    set(CMAKE_REQUIRED_INCLUDES ${_MBEDTLS_INCLUDE_DIR} ${CMAKE_REQUIRED_INCLUDES_${BUILD_TYPE}})
+    list(APPEND CMAKE_REQUIRED_LIBRARIES ${_MBEDTLS_LIBRARY} ${_MBEDX509_LIBRARY} ${_MBEDCRYPTO_LIBRARY})
+    check_symbol_exists(mbedtls_ssl_init "mbedtls/ssl.h" _MBEDTLS_V2_OR_NEWER)
+    cmake_pop_check_state()
+
+    if (NOT _MBEDTLS_V2_OR_NEWER)
+        message("Mbed TLS too old (must be version 2 or newer) ${_MBEDTLS_V2_OR_NEWER} UP ${_MbedTLS_V2}")
+
+    else()
+        # Extract the version from the header... hopefully it matches the library.
+        if (EXISTS ${_MBEDTLS_INCLUDE_DIR}/mbedtls/build_info.h)
+            file(STRINGS ${_MBEDTLS_INCLUDE_DIR}/mbedtls/build_info.h _MBEDTLS_VERLINE
+                    REGEX "^#define[ \t]+MBEDTLS_VERSION_STRING[\t ].*")
+        else ()
+            file(STRINGS ${_MBEDTLS_INCLUDE_DIR}/mbedtls/version.h _MBEDTLS_VERLINE
+                    REGEX "^#define[ \t]+MBEDTLS_VERSION_STRING[\t ].*")
+        endif ()
+
+        string(REGEX REPLACE ".*MBEDTLS_VERSION_STRING[\t ]+\"(.*)\"" "\\1" MbedTLS_VERSION ${_MBEDTLS_VERLINE})
+        message("Mbed TLS version: ${MbedTLS_VERSION}")
+    endif()
+endif()
+
+
+add_library(MbedTLS::mbedtls UNKNOWN IMPORTED)
+add_library(MbedTLS::mbedx509 UNKNOWN IMPORTED)
+add_library(MbedTLS::mbedcrypto UNKNOWN IMPORTED)
+
+
+set_target_properties(MbedTLS::mbedtls PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${_MBEDTLS_INCLUDE_DIR}")
+set_target_properties(MbedTLS::mbedx509 PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${_MBEDTLS_INCLUDE_DIR}")
+set_target_properties(MbedTLS::mbedcrypto PROPERTIES INTERFACE_INCLUDE_DIRECTORIES "${_MBEDTLS_INCLUDE_DIR}")
+
+if (WIN32)
+    set_target_properties(MbedTLS::mbedtls PROPERTIES IMPORTED_IMPLIB "${_MBEDTLS_LIBRARY}")
+    set_target_properties(MbedTLS::mbedx509 PROPERTIES IMPORTED_IMPLIB "${_MBEDX509_LIBRARY}")
+    set_target_properties(MbedTLS::mbedcrypto PROPERTIES IMPORTED_IMPLIB "${_MBEDCRYPTO_LIBRARY}")
+else()
+    set_target_properties(MbedTLS::mbedtls PROPERTIES IMPORTED_LOCATION "${_MBEDTLS_LIBRARY}")
+    set_target_properties(MbedTLS::mbedx509 PROPERTIES IMPORTED_LOCATION "${_MBEDX509_LIBRARY}")
+    set_target_properties(MbedTLS::mbedcrypto PROPERTIES IMPORTED_LOCATION "${_MBEDCRYPTO_LIBRARY}")
+endif()
+
+set(MbedTLS_TARGET MbedTLS::mbedtls)
+set(MbedX509_TARGET MbedTLS::mbedx509)
+set(MbedCrypto_TARGET MbedTLS::mbedcrypto)
+
+find_package_handle_standard_args(MbedTLS REQUIRED_VARS ${_MBED_REQUIRED_VARS})
+mark_as_advanced(${_MBED_REQUIRED_VARS})
+

cmake/NNGHelpers.cmake

@@ -1,5 +1,5 @@
 #
-# Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+# Copyright 2024 Staysail Systems, Inc. <info@staysail.tech>
 #
 # This software is supplied under the terms of the MIT License, a
 # copy of which should be located in the distribution where this
@@ -55,6 +55,12 @@ function(nng_link_libraries)
     target_link_libraries(nng_testing PRIVATE ${ARGN})
 endfunction()
 
+function(nng_link_libraries_public)
+    target_link_libraries(nng PRIVATE ${ARGN})
+    target_link_libraries(nng_testing PRIVATE ${ARGN})
+endfunction()
+
+
 # nng_include_directories adds include directories.
 function(nng_include_directories)
     target_include_directories(nng PRIVATE ${ARGN})

src/supplemental/tls/mbedtls/CMakeLists.txt

@@ -1,5 +1,5 @@
 #
-# Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+# Copyright 2024 Staysail Systems, Inc. <info@staysail.tech>
 #
 # This software is supplied under the terms of the MIT License, a
 # copy of which should be located in the distribution where this
@@ -10,7 +10,7 @@
 if (NNG_TLS_ENGINE STREQUAL "mbed")
     message(WARNING "
         ************************************************************
-        Linking against Mbed TLS changes license terms (Apache 2.0).
+        Linking against Mbed TLS may change license terms.
         Consult a lawyer and the license files for details.
         ************************************************************")
     nng_sources(tls.c)
@@ -23,8 +23,17 @@ if (NNG_TLS_ENGINE STREQUAL "mbed")
     if (TARGET mbedtls)
         nng_link_libraries(mbedtls)
     else()
-        nng_find_package(mbedTLS)
-        nng_link_libraries(${MBEDTLS_LIBRARIES})
-        nng_include_directories(${MBEDTLS_INCLUDE_DIR})
+        # We want to prefer config mode over our local find package.
+        # mbedTLS v3 has a config file, which should work better than
+        # what we do here.  We do restore the setting though because
+        # user applications might not expect this.
+        if (NOT CMAKE_FIND_PAKCAGE_PREFER_CONFIG)
+            set(CMAKE_FIND_PACKAGE_PREFER_CONFIG TRUE)
+            find_package(MbedTLS REQUIRED)
+            set(CMAKE_FIND_PACKAGE_PREFER_CONFIG FALSE)
+        else()
+            find_package(MbedTLS REQUIRED)
+        endif()
+        nng_link_libraries_public(MbedTLS::mbedtls MbedTLS::mbedcrypto MbedTLS::mbedx509)
     endif()
 endif()