openssl: Require min version 3.0.0 for HKDF to support larger MODP groups and nonces

Also enables the `kdf` plugin automatically if building against an older
version of OpenSSL.

Closes strongswan/strongswan#2602

Co-authored-by: Tobias Brunner <tobias@strongswan.org>

diff --git a/configure.ac b/configure.ac
index 37c47bccb22c594fb56aa63d520bb628e07e36ef..6a294bc77e08ea3fa9287d6171fb6e75b703ed55 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -525,15 +525,28 @@ if test x$cert_enroll = xtrue; then
 fi
 
 if test x$kdf = xfalse; then
+       openssl_hkdf=false
+       if test x$openssl = xtrue; then
+               AC_MSG_CHECKING(for OpenSSL >= 3.0 for HKDF)
+               AC_COMPILE_IFELSE(
+                       [AC_LANG_PROGRAM(
+                               [[#include <openssl/opensslv.h>]],
+                               [[#if OPENSSL_VERSION_NUMBER < 0x30000000L && !defined(OPENSSL_IS_AWSLC)
+                                       #error OpenSSL version unusable
+                                 #endif]])],
+                       [AC_MSG_RESULT([yes]); openssl_hkdf=true],
+                       [AC_MSG_RESULT([no])]
+               )
+       fi
        if test x$aesni = xtrue -o x$cmac = xtrue -o x$xcbc = xtrue; then
                AC_MSG_WARN(m4_normalize([
                        kdf plugin is required for possible use of PRF_AES128_XCBC/CMAC
                        by one of these plugins: aesni, cmac, xcbc]))
                kdf=true
-       elif test x$botan = xfalse -a x$openssl = xfalse -a x$wolfssl = xfalse; then
+       elif test x$botan = xfalse -a x$openssl_hkdf = xfalse -a x$wolfssl = xfalse; then
                AC_MSG_WARN(m4_normalize([
                        kdf plugin is required because none of the following plugins is
-                       enabled: botan, openssl, wolfssl]))
+                       enabled or usable: botan, openssl, wolfssl]))
                kdf=true
        fi
 fi

diff --git a/scripts/test.sh b/scripts/test.sh
index d8fde062eedcdaaa59059bcda3428cb95aabdf86..fe7a2f412e203c584dcb52b8b032b7af962b1c29 100755 (executable)
--- a/scripts/test.sh
+++ b/scripts/test.sh
@@ -240,6 +240,9 @@ openssl*)
                use_custom_openssl $1
        elif system_uses_openssl3; then
                prepare_system_openssl $1
+       else
+               # the kdf plugin is necessary to build against older OpenSSL versions
+               TESTS_PLUGINS="$TESTS_PLUGINS kdf"
        fi
        ;;
 gcrypt)
@@ -352,13 +355,6 @@ win*)
                TARGET=
        else
                CONFIG="$CONFIG --enable-openssl"
-               case "$IMG" in
-               2015|2017)
-                       # old OpenSSL versions don't provide HKDF
-                       CONFIG="$CONFIG --enable-kdf"
-                       ;;
-               esac
-
                CFLAGS="$CFLAGS -I$OPENSSL_DIR/include"
                LDFLAGS="-L$OPENSSL_DIR/lib"
                case "$IMG" in

diff --git a/src/libstrongswan/plugins/openssl/openssl_plugin.c b/src/libstrongswan/plugins/openssl/openssl_plugin.c
index 0068e7572f488be2d444ac7ed919f4406adac8ba..f567a8d6e560c827cda45192ef37b7e2ba6725a1 100644 (file)
--- a/src/libstrongswan/plugins/openssl/openssl_plugin.c
+++ b/src/libstrongswan/plugins/openssl/openssl_plugin.c
@@ -496,8 +496,11 @@ METHOD(plugin_t, get_features, int,
                        PLUGIN_PROVIDE(SIGNER, AUTH_HMAC_SHA2_512_256),
                        PLUGIN_PROVIDE(SIGNER, AUTH_HMAC_SHA2_512_512),
 #endif
-#if OPENSSL_VERSION_NUMBER >= 0x10101000L
-               /* HKDF is available since 1.1.0, expand-only mode only since 1.1.1 */
+#if OPENSSL_VERSION_NUMBER >= 0x30000000L || \
+       defined (OPENSSL_IS_AWSLC)
+               /* HKDF is available since 1.1.0, expand-only mode only since 1.1.1,
+                * but 3.0.0 is required to support larger MODP groups and nonces
+                * with its 2048 byte buffer size */
                PLUGIN_REGISTER(KDF, openssl_kdf_create),
                        PLUGIN_PROVIDE(KDF, KDF_PRF),
                        PLUGIN_PROVIDE(KDF, KDF_PRF_PLUS),