configure: Try to use pkg-config to detect mbedTLS

mbedTLS does not seem to have pkg-config support on e.g.
Debian/Ubuntu, so we definitely need to keep the
fallback check as well.

Change-Id: I5d0da76018e874cda5dbab9202a2b817ad5e4692
Signed-off-by: Frank Lichtenheld <[email protected]>
Acked-by: Yuriy Darnobyt <[email protected]>
Message-Id: <[email protected]>
URL: https://www.mail-archive.com/[email protected]/msg29090.html
Signed-off-by: Gert Doering <[email protected]>
Acked-by: Gert Doering <[email protected]>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1422
(cherry picked from commit c829f57)
Message-Id: <[email protected]>
URL: https://www.mail-archive.com/[email protected]/msg34911.html
Signed-off-by: Gert Doering <[email protected]>

Author: flichtenheld

configure.ac

@@ -1010,14 +1010,21 @@ elif test "${with_crypto_library}" = "mbedtls"; then
 
 	if test -z "${MBEDTLS_CFLAGS}" -a -z "${MBEDTLS_LIBS}"; then
 		# if the user did not explicitly specify flags, try to autodetect
-		LIBS="${LIBS} -lmbedtls -lmbedx509 -lmbedcrypto"
-		AC_CHECK_LIB(
-			[mbedtls],
-			[mbedtls_ssl_init],
-			[MBEDTLS_LIBS="-lmbedtls -lmbedx509 -lmbedcrypto"],
-			[AC_MSG_ERROR([Could not find mbed TLS.])],
-			[${PKCS11_HELPER_LIBS}]
+		PKG_CHECK_MODULES([MBEDTLS],
+			[mbedtls >= 2.0.0 mbedx509 >= 2.0.0 mbedcrypto >= 2.0.0],
+			[have_mbedtls="yes"],
+			[LIBS="${LIBS} -lmbedtls -lmbedx509 -lmbedcrypto"]
 		)
+		# mbedtls might not have pkgconfig integration, so try manually
+                if test "${have_mbedtls}" != "yes"; then
+			AC_CHECK_LIB(
+				[mbedtls],
+				[mbedtls_ssl_init],
+				[MBEDTLS_LIBS="-lmbedtls -lmbedx509 -lmbedcrypto"],
+				[AC_MSG_ERROR([Could not find mbed TLS.])],
+				[${PKCS11_HELPER_LIBS}]
+			)
+		fi
 	fi
 
 	CFLAGS="${MBEDTLS_CFLAGS} ${PKCS11_HELPER_CFLAGS} ${CFLAGS}"