Add support for automatic ephemeral EC keys.

This allows an SSL server to enable ECDHE ciphers with a single setting,
which results in an EC key being generated using the first preference
shared curve.

Based on OpenSSL with inspiration from boringssl.

ok miod@

7 files changed, 76 insertions, 13 deletions

diff --git a/lib/libssl/s3_lib.c b/lib/libssl/s3_lib.c
index 246aa6f23df..42f8074f8c3 100644
--- a/lib/libssl/s3_lib.c
+++ b/lib/libssl/s3_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_lib.c,v 1.81 2014/09/30 15:40:09 jsing Exp $ */
+/* $OpenBSD: s3_lib.c,v 1.82 2014/10/03 13:58:17 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -2128,6 +2128,11 @@ ssl3_ctrl(SSL *s, int cmd, long larg, void *parg)
 		ret = 1;
 		break;
 
+	case SSL_CTRL_SET_ECDH_AUTO:
+		s->cert->ecdh_tmp_auto = larg;
+		ret = 1;
+		break;
+
 	default:
 		break;
 	}
@@ -2322,6 +2327,9 @@ ssl3_ctx_ctrl(SSL_CTX *ctx, int cmd, long larg, void *parg)
 		return 1;
 		break;
 
+	case SSL_CTRL_SET_ECDH_AUTO:
+		ctx->cert->ecdh_tmp_auto = larg;
+		return 1;
 
 		/* A Thawte special :-) */
 	case SSL_CTRL_EXTRA_CHAIN_CERT:
diff --git a/lib/libssl/s3_srvr.c b/lib/libssl/s3_srvr.c
index cba875a3e69..c4a8442a3e0 100644
--- a/lib/libssl/s3_srvr.c
+++ b/lib/libssl/s3_srvr.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: s3_srvr.c,v 1.85 2014/09/27 11:03:43 jsing Exp $ */
+/* $OpenBSD: s3_srvr.c,v 1.86 2014/10/03 13:58:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1465,9 +1465,15 @@ ssl3_send_server_key_exchange(SSL *s)
 			const EC_GROUP *group;
 
 			ecdhp = cert->ecdh_tmp;
-			if (ecdhp == NULL && s->cert->ecdh_tmp_cb != NULL)
+			if (s->cert->ecdh_tmp_auto != 0) {
+				int nid = tls1_get_shared_curve(s);
+				if (nid != NID_undef)
+					ecdhp = EC_KEY_new_by_curve_name(nid);
+			} else if (ecdhp == NULL &&
+			    s->cert->ecdh_tmp_cb != NULL) {
 				ecdhp = s->cert->ecdh_tmp_cb(s, 0,
 				    SSL_C_PKEYLENGTH(s->s3->tmp.new_cipher));
+			}
 			if (ecdhp == NULL) {
 				al = SSL_AD_HANDSHAKE_FAILURE;
 				SSLerr(SSL_F_SSL3_SEND_SERVER_KEY_EXCHANGE,
@@ -1482,7 +1488,9 @@ ssl3_send_server_key_exchange(SSL *s)
 			}
 
 			/* Duplicate the ECDH structure. */
-			if ((ecdh = EC_KEY_dup(ecdhp)) == NULL) {
+			if (s->cert->ecdh_tmp_auto != 0) {
+				ecdh = ecdhp;
+			} else if ((ecdh = EC_KEY_dup(ecdhp)) == NULL) {
 				SSLerr(SSL_F_SSL3_SEND_SERVER_KEY_EXCHANGE,
 				    ERR_R_ECDH_LIB);
 				goto err;
diff --git a/lib/libssl/ssl.h b/lib/libssl/ssl.h
index c7dd4259ccb..1e9e8461955 100644
--- a/lib/libssl/ssl.h
+++ b/lib/libssl/ssl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl.h,v 1.66 2014/09/28 14:45:48 reyk Exp $ */
+/* $OpenBSD: ssl.h,v 1.67 2014/10/03 13:58:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1425,6 +1425,8 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 #define SSL_CTRL_GET_EXTRA_CHAIN_CERTS		82
 #define SSL_CTRL_CLEAR_EXTRA_CHAIN_CERTS	83
 
+#define SSL_CTRL_SET_ECDH_AUTO				94
+
 #define DTLSv1_get_timeout(ssl, arg) \
 	SSL_ctrl(ssl,DTLS_CTRL_GET_TIMEOUT,0, (void *)arg)
 #define DTLSv1_handle_timeout(ssl) \
@@ -1449,6 +1451,8 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 	SSL_CTX_ctrl(ctx,SSL_CTRL_SET_TMP_DH,0,(char *)dh)
 #define SSL_CTX_set_tmp_ecdh(ctx,ecdh) \
 	SSL_CTX_ctrl(ctx,SSL_CTRL_SET_TMP_ECDH,0,(char *)ecdh)
+#define SSL_CTX_set_ecdh_auto(ctx, onoff) \
+	SSL_CTX_ctrl(ctx,SSL_CTRL_SET_ECDH_AUTO,onoff,NULL)
 
 #define SSL_need_tmp_RSA(ssl) \
 	SSL_ctrl(ssl,SSL_CTRL_NEED_TMP_RSA,0,NULL)
@@ -1458,6 +1462,8 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 	SSL_ctrl(ssl,SSL_CTRL_SET_TMP_DH,0,(char *)dh)
 #define SSL_set_tmp_ecdh(ssl,ecdh) \
 	SSL_ctrl(ssl,SSL_CTRL_SET_TMP_ECDH,0,(char *)ecdh)
+#define SSL_set_ecdh_auto(s, onoff) \
+	SSL_ctrl(s,SSL_CTRL_SET_ECDH_AUTO,onoff,NULL)
 
 #define SSL_CTX_add_extra_chain_cert(ctx,x509) \
 	SSL_CTX_ctrl(ctx,SSL_CTRL_EXTRA_CHAIN_CERT,0,(char *)x509)
diff --git a/lib/libssl/ssl_cert.c b/lib/libssl/ssl_cert.c
index 6aae59e3106..6f1815067b9 100644
--- a/lib/libssl/ssl_cert.c
+++ b/lib/libssl/ssl_cert.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_cert.c,v 1.41 2014/07/10 08:25:00 guenther Exp $ */
+/* $OpenBSD: ssl_cert.c,v 1.42 2014/10/03 13:58:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -244,6 +244,7 @@ ssl_cert_dup(CERT *cert)
 		}
 	}
 	ret->ecdh_tmp_cb = cert->ecdh_tmp_cb;
+	ret->ecdh_tmp_auto = cert->ecdh_tmp_auto;
 
 	for (i = 0; i < SSL_PKEY_NUM; i++) {
 		if (cert->pkeys[i].x509 != NULL) {
diff --git a/lib/libssl/ssl_lib.c b/lib/libssl/ssl_lib.c
index bd5f9f6da14..f6a21d43514 100644
--- a/lib/libssl/ssl_lib.c
+++ b/lib/libssl/ssl_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_lib.c,v 1.84 2014/09/07 12:16:23 jsing Exp $ */
+/* $OpenBSD: ssl_lib.c,v 1.85 2014/10/03 13:58:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -1943,7 +1943,8 @@ ssl_set_cert_masks(CERT *c, const SSL_CIPHER *cipher)
 	rsa_tmp = (c->rsa_tmp != NULL || c->rsa_tmp_cb != NULL);
 	dh_tmp = (c->dh_tmp != NULL || c->dh_tmp_cb != NULL);
 
-	have_ecdh_tmp = (c->ecdh_tmp != NULL || c->ecdh_tmp_cb != NULL);
+	have_ecdh_tmp = (c->ecdh_tmp != NULL || c->ecdh_tmp_cb != NULL ||
+	    c->ecdh_tmp_auto != 0);
 	cpk = &(c->pkeys[SSL_PKEY_RSA_ENC]);
 	rsa_enc = (cpk->x509 != NULL && cpk->privatekey != NULL);
 	cpk = &(c->pkeys[SSL_PKEY_RSA_SIGN]);
diff --git a/lib/libssl/ssl_locl.h b/lib/libssl/ssl_locl.h
index 8ec4c69d5be..976f835c923 100644
--- a/lib/libssl/ssl_locl.h
+++ b/lib/libssl/ssl_locl.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_locl.h,v 1.70 2014/09/30 15:40:09 jsing Exp $ */
+/* $OpenBSD: ssl_locl.h,v 1.71 2014/10/03 13:58:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -439,13 +439,16 @@ typedef struct cert_st {
 	int valid;
 	unsigned long mask_k;
 	unsigned long mask_a;
+
 	RSA *rsa_tmp;
 	RSA *(*rsa_tmp_cb)(SSL *ssl, int is_export, int keysize);
+
 	DH *dh_tmp;
 	DH *(*dh_tmp_cb)(SSL *ssl, int is_export, int keysize);
+
 	EC_KEY *ecdh_tmp;
-	/* Callback for generating ephemeral ECDH keys */
 	EC_KEY *(*ecdh_tmp_cb)(SSL *ssl, int is_export, int keysize);
+	int ecdh_tmp_auto;
 
 	CERT_PKEY pkeys[SSL_PKEY_NUM];
 
@@ -799,6 +802,7 @@ SSL_COMP *ssl3_comp_find(STACK_OF(SSL_COMP) *sk, int n);
 int tls1_ec_curve_id2nid(int curve_id);
 int tls1_ec_nid2curve_id(int nid);
 int tls1_check_curve(SSL *s, const unsigned char *p, size_t len);
+int tls1_get_shared_curve(SSL *s);
 
 unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *p,
     unsigned char *limit);
diff --git a/lib/libssl/t1_lib.c b/lib/libssl/t1_lib.c
index d40768560cb..678818d51b2 100644
--- a/lib/libssl/t1_lib.c
+++ b/lib/libssl/t1_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: t1_lib.c,v 1.59 2014/09/30 15:40:09 jsing Exp $ */
+/* $OpenBSD: t1_lib.c,v 1.60 2014/10/03 13:58:18 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -408,6 +408,35 @@ tls1_check_curve(SSL *s, const unsigned char *p, size_t len)
 	return (0);
 }
 
+int
+tls1_get_shared_curve(SSL *s)
+{
+	const unsigned char *pref, *supp, *tsupp;
+	size_t preflen, supplen, i, j;
+	unsigned long server_pref;
+	int id;
+
+	/* Cannot do anything on the client side. */
+	if (s->server == 0)
+		return (NID_undef);
+
+	/* Return first preference shared curve. */
+	server_pref = (s->options & SSL_OP_CIPHER_SERVER_PREFERENCE);
+	tls1_get_curvelist(s, (server_pref == 0), &pref, &preflen);
+	tls1_get_curvelist(s, (server_pref != 0), &supp, &supplen);
+
+	for (i = 0; i < preflen; i += 2, pref += 2) {
+		tsupp = supp;
+		for (j = 0; j < supplen; j += 2, tsupp += 2) {
+			if (pref[0] == tsupp[0] && pref[1] == tsupp[1]) {
+				id = (pref[0] << 8) | pref[1];
+				return (tls1_ec_curve_id2nid(id));
+			}
+		}
+	}
+	return (NID_undef);
+}
+
 /* For an EC key set TLS ID and required compression based on parameters. */
 static int
 tls1_set_ec_id(unsigned char *curve_id, unsigned char *comp_id, EC_KEY *ec)
@@ -524,11 +553,17 @@ tls1_check_ec_tmp_key(SSL *s)
 	EC_KEY *ec = s->cert->ecdh_tmp;
 	unsigned char curve_id[2];
 
+	if (s->cert->ecdh_tmp_auto != 0) {
+		/* Need a shared curve. */
+		if (tls1_get_shared_curve(s) != NID_undef)
+			return (1);
+		return (0);
+	}
+
 	if (ec == NULL) {
 		if (s->cert->ecdh_tmp_cb != NULL)
 			return (1);
-		else
-			return (0);
+		return (0);
 	}
 	if (tls1_set_ec_id(curve_id, NULL, ec) != 1)
 		return (0);