res/res_rtp_asterisk: Add ECDH support

This will add ECDH support to Asterisk. It will
detect auto ECDH support in OpenSSL
(1.0.2b and above) during ./configure. If this is
available, it will use it,
otherwise it will fall back to prime256v1 (this
behavior is consistent with
other projects such as Apache and nginx).

This fixes WebRTC being broken in Firefox 38+ due
to Firefox now only supporting
ciphers with perfect forward secrecy.

ASTERISK-25265 #close

Change-Id: I8c13b33a2a79c0bde2e69e4ba6afa5ab9351465b

4 files changed, 79 insertions, 0 deletions

diff --git a/configure b/configure
index e2cf9c94f..a0468b9e5 100755
--- a/configure
+++ b/configure
@@ -1089,6 +1089,10 @@ PBX_DAHDI
 DAHDI_DIR
 DAHDI_INCLUDE
 DAHDI_LIB
+PBX_OPENSSL_ECDH_AUTO
+OPENSSL_ECDH_AUTO_DIR
+OPENSSL_ECDH_AUTO_INCLUDE
+OPENSSL_ECDH_AUTO_LIB
 PBX_OPENSSL_EC
 OPENSSL_EC_DIR
 OPENSSL_EC_INCLUDE
@@ -8696,6 +8700,18 @@ PBX_OPENSSL_EC=0
 
 
 
+OPENSSL_ECDH_AUTO_DESCRIP="OpenSSL Auto ECDH Support"
+OPENSSL_ECDH_AUTO_OPTION=crypto
+OPENSSL_ECDH_AUTO_DIR=${CRYPTO_DIR}
+
+PBX_OPENSSL_ECDH_AUTO=0
+
+
+
+
+
+
+
     DAHDI_DESCRIP="DAHDI"
     DAHDI_OPTION="dahdi"
     PBX_DAHDI=0
@@ -30266,6 +30282,53 @@ fi
 
 fi
 
+if test "$PBX_OPENSSL" = "1";
+then
+
+    if test "x${PBX_OPENSSL_ECDH_AUTO}" != "x1" -a "${USE_OPENSSL_ECDH_AUTO}" != "no"; then
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for SSL_CTX_set_ecdh_auto declared in openssl/ssl.h" >&5
+$as_echo_n "checking for SSL_CTX_set_ecdh_auto declared in openssl/ssl.h... " >&6; }
+        saved_cppflags="${CPPFLAGS}"
+        if test "x${OPENSSL_ECDH_AUTO_DIR}" != "x"; then
+            OPENSSL_ECDH_AUTO_INCLUDE="-I${OPENSSL_ECDH_AUTO_DIR}/include"
+        fi
+        CPPFLAGS="${CPPFLAGS} ${OPENSSL_ECDH_AUTO_INCLUDE}"
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+ #include <openssl/ssl.h>
+int
+main ()
+{
+#if !defined(SSL_CTX_set_ecdh_auto)
+                                    (void) SSL_CTX_set_ecdh_auto;
+                                #endif
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+     { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+                PBX_OPENSSL_ECDH_AUTO=1
+
+$as_echo "#define HAVE_OPENSSL_ECDH_AUTO 1" >>confdefs.h
+
+
+
+else
+     { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
+        CPPFLAGS="${saved_cppflags}"
+    fi
+
+fi
+
 
 if test "x${PBX_SRTP}" != "x1" -a "${USE_SRTP}" != "no"; then
    pbxlibdir=""
diff --git a/configure.ac b/configure.ac
index 971f9bf8a..329280924 100644
--- a/configure.ac
+++ b/configure.ac
@@ -414,6 +414,7 @@ AST_EXT_LIB_SETUP([CRYPT], [password and data encryption], [crypt])
 AST_EXT_LIB_SETUP([CRYPTO], [OpenSSL Cryptography], [crypto])
 AST_EXT_LIB_SETUP_OPTIONAL([OPENSSL_SRTP], [OpenSSL SRTP Extension Support], [CRYPTO], [crypto])
 AST_EXT_LIB_SETUP_OPTIONAL([OPENSSL_EC], [OpenSSL Elliptic Curve Support], [CRYPTO], [crypto])
+AST_EXT_LIB_SETUP_OPTIONAL([OPENSSL_ECDH_AUTO], [OpenSSL Auto ECDH Support], [CRYPTO], [crypto])
 AST_EXT_LIB_SETUP([DAHDI], [DAHDI], [dahdi])
 AST_EXT_LIB_SETUP([FFMPEG], [Ffmpeg and avcodec], [avcodec])
 AST_EXT_LIB_SETUP([GSM], [External GSM], [gsm], [, use 'internal' GSM otherwise])
@@ -2283,6 +2284,11 @@ then
 	AST_EXT_LIB_CHECK([OPENSSL_EC], [ssl], [EC_KEY_new_by_curve_name], [openssl/ec.h], [-lcrypto])
 fi
 
+if test "$PBX_OPENSSL" = "1";
+then
+        AST_C_DECLARE_CHECK([OPENSSL_ECDH_AUTO], [SSL_CTX_set_ecdh_auto], [openssl/ssl.h])
+fi
+
 AST_EXT_LIB_CHECK([SRTP], [srtp], [srtp_init], [srtp/srtp.h])
 
 if test "$PBX_SRTP" = "1";
diff --git a/include/asterisk/autoconfig.h.in b/include/asterisk/autoconfig.h.in
index 4efff1f21..542f5d2a0 100644
--- a/include/asterisk/autoconfig.h.in
+++ b/include/asterisk/autoconfig.h.in
@@ -548,6 +548,9 @@
 /* Define to 1 if CRYPTO has the OpenSSL Elliptic Curve Support feature. */
 #undef HAVE_OPENSSL_EC
 
+/* Define if your system has SSL_CTX_set_ecdh_auto declared. */
+#undef HAVE_OPENSSL_ECDH_AUTO
+
 /* Define to 1 if CRYPTO has the OpenSSL SRTP Extension Support feature. */
 #undef HAVE_OPENSSL_SRTP
 
diff --git a/res/res_rtp_asterisk.c b/res/res_rtp_asterisk.c
index 5d206c1a0..0c47e1e25 100644
--- a/res/res_rtp_asterisk.c
+++ b/res/res_rtp_asterisk.c
@@ -1288,6 +1288,13 @@ static int ast_rtp_dtls_set_configuration(struct ast_rtp_instance *instance, con
 
 	SSL_CTX_set_read_ahead(rtp->ssl_ctx, 1);
 
+#ifdef HAVE_OPENSSL_ECDH_AUTO
+	SSL_CTX_set_ecdh_auto(rtp->ssl_ctx, 1);
+#else
+	SSL_CTX_set_tmp_ecdh(rtp->ssl_ctx,
+		EC_KEY_new_by_curve_name(NID_X9_62_prime256v1));
+#endif
+
 	rtp->dtls_verify = dtls_cfg->verify;
 
 	SSL_CTX_set_verify(rtp->ssl_ctx, (rtp->dtls_verify & AST_RTP_DTLS_VERIFY_FINGERPRINT) || (rtp->dtls_verify & AST_RTP_DTLS_VERIFY_CERTIFICATE) ?