Support ALPN.

This change adds support for ALPN[1] in OpenSSL. ALPN is the IETF
blessed version of NPN and we'll be supporting both ALPN and NPN for
some time yet.

Cherry-picked from 6f017a8f9db3a79f3a3406cf8d493ccd346db691.

[1] https://tools.ietf.org/html/draft-ietf-tls-applayerprotoneg-00

6 files changed, 326 insertions, 3 deletions

diff --git a/ssl/s3_lib.c b/ssl/s3_lib.c
index f3acb8a96a..601168126b 100644
--- a/ssl/s3_lib.c
+++ b/ssl/s3_lib.c
@@ -3002,6 +3002,11 @@ void ssl3_free(SSL *s)
 		BIO_free(s->s3->handshake_buffer);
 	}
 	if (s->s3->handshake_dgst) ssl3_free_digest_list(s);
+#ifndef OPENSSL_NO_TLSEXT
+	if (s->s3->alpn_selected)
+		OPENSSL_free(s->s3->alpn_selected);
+#endif
+
 #ifndef OPENSSL_NO_SRP
 	SSL_SRP_CTX_free(s);
 #endif
@@ -3080,6 +3085,14 @@ void ssl3_clear(SSL *s)
 	if (s->s3->handshake_dgst) {
 		ssl3_free_digest_list(s);
 	}	
+
+#if !defined(OPENSSL_NO_TLSEXT)
+	if (s->s3->alpn_selected)
+		{
+		free(s->s3->alpn_selected);
+		s->s3->alpn_selected = NULL;
+		}
+#endif
 	memset(s->s3,0,sizeof *s->s3);
 	s->s3->rbuf.buf = rp;
 	s->s3->wbuf.buf = wp;
diff --git a/ssl/ssl.h b/ssl/ssl.h
index bd2b576308..700e2c3e02 100644
--- a/ssl/ssl.h
+++ b/ssl/ssl.h
@@ -1097,6 +1097,31 @@ struct ssl_ctx_st
 				    void *arg);
 	void *next_proto_select_cb_arg;
 # endif
+
+	/* ALPN information
+	 * (we are in the process of transitioning from NPN to ALPN.) */
+
+	/* For a server, this contains a callback function that allows the
+	 * server to select the protocol for the connection.
+	 *   out: on successful return, this must point to the raw protocol
+	 *        name (without the length prefix).
+	 *   outlen: on successful return, this contains the length of |*out|.
+	 *   in: points to the client's list of supported protocols in
+	 *       wire-format.
+	 *   inlen: the length of |in|. */
+	int (*alpn_select_cb)(SSL *s,
+			      const unsigned char **out,
+			      unsigned char *outlen,
+			      const unsigned char* in,
+			      unsigned int inlen,
+			      void *arg);
+	void *alpn_select_cb_arg;
+
+	/* For a client, this contains the list of supported protocols in wire
+	 * format. */
+	unsigned char* alpn_client_proto_list;
+	unsigned alpn_client_proto_list_len;
+
         /* SRTP profiles we are willing to do from RFC 5764 */
 	STACK_OF(SRTP_PROTECTION_PROFILE) *srtp_profiles;
 # ifndef OPENSSL_NO_EC
@@ -1195,6 +1220,21 @@ void SSL_get0_next_proto_negotiated(const SSL *s,
 #define OPENSSL_NPN_NO_OVERLAP	2
 #endif
 
+int SSL_CTX_set_alpn_protos(SSL_CTX *ctx, const unsigned char* protos,
+			    unsigned protos_len);
+int SSL_set_alpn_protos(SSL *ssl, const unsigned char* protos,
+			unsigned protos_len);
+void SSL_CTX_set_alpn_select_cb(SSL_CTX* ctx,
+				int (*cb) (SSL *ssl,
+					   const unsigned char **out,
+					   unsigned char *outlen,
+					   const unsigned char *in,
+					   unsigned int inlen,
+					   void *arg),
+				void *arg);
+void SSL_get0_alpn_selected(const SSL *ssl, const unsigned char **data,
+			    unsigned *len);
+
 #ifndef OPENSSL_NO_PSK
 /* the maximum length of the buffer given to callbacks containing the
  * resulting identity/psk */
@@ -1501,6 +1541,11 @@ struct ssl_st
 	                                 */
 	unsigned int tlsext_hb_pending; /* Indicates if a HeartbeatRequest is in flight */
 	unsigned int tlsext_hb_seq;     /* HeartbeatRequest sequence number */
+
+	/* For a client, this contains the list of supported protocols in wire
+	 * format. */
+	unsigned char* alpn_client_proto_list;
+	unsigned alpn_client_proto_list_len;
 #else
 #define session_ctx ctx
 #endif /* OPENSSL_NO_TLSEXT */
diff --git a/ssl/ssl3.h b/ssl/ssl3.h
index 171c76a73c..05317005de 100644
--- a/ssl/ssl3.h
+++ b/ssl/ssl3.h
@@ -580,7 +580,17 @@ typedef struct ssl3_state_st
 	 * as the types were received in the client hello. */
 	unsigned short *tlsext_custom_types;
 	size_t tlsext_custom_types_count; /* how many tlsext_custom_types */
-#endif
+
+	/* ALPN information
+	 * (we are in the process of transitioning from NPN to ALPN.) */
+
+	/* In a server these point to the selected ALPN protocol after the
+	 * ClientHello has been processed. In a client these contain the
+	 * protocol that the server selected once the ServerHello has been
+	 * processed. */
+	unsigned char *alpn_selected;
+	unsigned alpn_selected_len;
+#endif	/* OPENSSL_NO_TLSEXT */
 	} SSL3_STATE;
 
 #endif
diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index dad33fa14b..aaf6a4cdfd 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -381,6 +381,17 @@ SSL *SSL_new(SSL_CTX *ctx)
 # ifndef OPENSSL_NO_NEXTPROTONEG
 	s->next_proto_negotiated = NULL;
 # endif
+
+	if (s->ctx->alpn_client_proto_list)
+		{
+		s->alpn_client_proto_list =
+			OPENSSL_malloc(s->ctx->alpn_client_proto_list_len);
+		if (s->alpn_client_proto_list == NULL)
+			goto err;
+		memcpy(s->alpn_client_proto_list, s->ctx->alpn_client_proto_list,
+		       s->ctx->alpn_client_proto_list_len);
+		s->alpn_client_proto_list_len = s->ctx->alpn_client_proto_list_len;
+		}
 #endif
 
 	s->verify_result=X509_V_OK;
@@ -605,6 +616,8 @@ void SSL_free(SSL *s)
 		sk_OCSP_RESPID_pop_free(s->tlsext_ocsp_ids, OCSP_RESPID_free);
 	if (s->tlsext_ocsp_resp)
 		OPENSSL_free(s->tlsext_ocsp_resp);
+	if (s->alpn_client_proto_list)
+		OPENSSL_free(s->alpn_client_proto_list);
 #endif
 
 	if (s->client_CA != NULL)
@@ -1769,7 +1782,78 @@ int SSL_CTX_set_custom_srv_ext(SSL_CTX *ctx, unsigned short ext_type,
 	return 1;
 	}
 
-#endif
+/* SSL_CTX_set_alpn_protos sets the ALPN protocol list on |ctx| to |protos|.
+ * |protos| must be in wire-format (i.e. a series of non-empty, 8-bit
+ * length-prefixed strings).
+ *
+ * Returns 0 on success. */
+int SSL_CTX_set_alpn_protos(SSL_CTX *ctx, const unsigned char* protos,
+			    unsigned protos_len)
+	{
+	if (ctx->alpn_client_proto_list)
+		OPENSSL_free(ctx->alpn_client_proto_list);
+
+	ctx->alpn_client_proto_list = OPENSSL_malloc(protos_len);
+	if (!ctx->alpn_client_proto_list)
+		return 1;
+	memcpy(ctx->alpn_client_proto_list, protos, protos_len);
+	ctx->alpn_client_proto_list_len = protos_len;
+
+	return 0;
+	}
+
+/* SSL_set_alpn_protos sets the ALPN protocol list on |ssl| to |protos|.
+ * |protos| must be in wire-format (i.e. a series of non-empty, 8-bit
+ * length-prefixed strings).
+ *
+ * Returns 0 on success. */
+int SSL_set_alpn_protos(SSL *ssl, const unsigned char* protos,
+			unsigned protos_len)
+	{
+	if (ssl->alpn_client_proto_list)
+		OPENSSL_free(ssl->alpn_client_proto_list);
+
+	ssl->alpn_client_proto_list = OPENSSL_malloc(protos_len);
+	if (!ssl->alpn_client_proto_list)
+		return 1;
+	memcpy(ssl->alpn_client_proto_list, protos, protos_len);
+	ssl->alpn_client_proto_list_len = protos_len;
+
+	return 0;
+	}
+
+/* SSL_CTX_set_alpn_select_cb sets a callback function on |ctx| that is called
+ * during ClientHello processing in order to select an ALPN protocol from the
+ * client's list of offered protocols. */
+void SSL_CTX_set_alpn_select_cb(SSL_CTX* ctx,
+				int (*cb) (SSL *ssl,
+					   const unsigned char **out,
+					   unsigned char *outlen,
+					   const unsigned char *in,
+					   unsigned int inlen,
+					   void *arg),
+				void *arg)
+	{
+	ctx->alpn_select_cb = cb;
+	ctx->alpn_select_cb_arg = arg;
+	}
+
+/* SSL_get0_alpn_selected gets the selected ALPN protocol (if any) from |ssl|.
+ * On return it sets |*data| to point to |*len| bytes of protocol name (not
+ * including the leading length-prefix byte). If the server didn't respond with
+ * a negotiated protocol then |*len| will be zero. */
+void SSL_get0_alpn_selected(const SSL *ssl, const unsigned char **data,
+			    unsigned *len)
+	{
+	*data = NULL;
+	if (ssl->s3)
+		*data = ssl->s3->alpn_selected;
+	if (*data == NULL)
+		*len = 0;
+	else
+		*len = ssl->s3->alpn_selected_len;
+	}
+#endif /* !OPENSSL_NO_TLSEXT */
 
 int SSL_export_keying_material(SSL *s, unsigned char *out, size_t olen,
 	const char *label, size_t llen, const unsigned char *p, size_t plen,
@@ -2132,6 +2216,8 @@ void SSL_CTX_free(SSL_CTX *a)
 	if (a->tlsext_ellipticcurvelist)
 		OPENSSL_free(a->tlsext_ellipticcurvelist);
 # endif /* OPENSSL_NO_EC */
+	if (a->alpn_client_proto_list != NULL)
+		OPENSSL_free(a->alpn_client_proto_list);
 #endif
 
 	OPENSSL_free(a);
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index ea10a52f91..41010ee647 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -1371,6 +1371,18 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *p, unsigned cha
 		}
 #endif
 
+	if (s->alpn_client_proto_list && !s->s3->tmp.finish_md_len)
+		{
+		if ((size_t)(limit - ret) < 6 + s->alpn_client_proto_list_len)
+			return NULL;
+		s2n(TLSEXT_TYPE_application_layer_protocol_negotiation,ret);
+		s2n(2 + s->alpn_client_proto_list_len,ret);
+		s2n(s->alpn_client_proto_list_len,ret);
+		memcpy(ret, s->alpn_client_proto_list,
+		       s->alpn_client_proto_list_len);
+		ret += s->alpn_client_proto_list_len;
+		}
+
         if(SSL_get_srtp_profiles(s))
                 {
                 int el;
@@ -1753,6 +1765,21 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *p, unsigned cha
 			}
 		}
 
+	if (s->s3->alpn_selected)
+		{
+		const unsigned char *selected = s->s3->alpn_selected;
+		unsigned len = s->s3->alpn_selected_len;
+
+		if ((long)(limit - ret - 4 - 2 - 1 - len) < 0)
+			return NULL;
+		s2n(TLSEXT_TYPE_application_layer_protocol_negotiation,ret);
+		s2n(3 + len,ret);
+		s2n(1 + len,ret);
+		*ret++ = len;
+		memcpy(ret, selected, len);
+		ret += len;
+		}
+
 	if ((extdatalen = ret-p-2)== 0) 
 		return p;
 
@@ -1760,6 +1787,76 @@ unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *p, unsigned cha
 	return ret;
 	}
 
+/* tls1_alpn_handle_client_hello is called to process the ALPN extension in a
+ * ClientHello.
+ *   data: the contents of the extension, not including the type and length.
+ *   data_len: the number of bytes in |data|
+ *   al: a pointer to the alert value to send in the event of a non-zero
+ *       return.
+ *
+ *   returns: 0 on success. */
+static int tls1_alpn_handle_client_hello(SSL *s, const unsigned char *data,
+					 unsigned data_len, int *al)
+	{
+	unsigned i;
+	unsigned proto_len;
+	const unsigned char *selected;
+	unsigned char selected_len;
+	int r;
+
+	if (s->ctx->alpn_select_cb == NULL)
+		return 0;
+
+	if (data_len < 2)
+		goto parse_error;
+
+	/* data should contain a uint16 length followed by a series of 8-bit,
+	 * length-prefixed strings. */
+	i = ((unsigned) data[0]) << 8 |
+	    ((unsigned) data[1]);
+	data_len -= 2;
+	data += 2;
+	if (data_len != i)
+		goto parse_error;
+
+	if (data_len < 2)
+		goto parse_error;
+
+	for (i = 0; i < data_len;)
+		{
+		proto_len = data[i];
+		i++;
+
+		if (proto_len == 0)
+			goto parse_error;
+
+		if (i + proto_len < i || i + proto_len > data_len)
+			goto parse_error;
+
+		i += proto_len;
+		}
+
+	r = s->ctx->alpn_select_cb(s, &selected, &selected_len, data, data_len,
+				   s->ctx->alpn_select_cb_arg);
+	if (r == SSL_TLSEXT_ERR_OK) {
+		if (s->s3->alpn_selected)
+			OPENSSL_free(s->s3->alpn_selected);
+		s->s3->alpn_selected = OPENSSL_malloc(selected_len);
+		if (!s->s3->alpn_selected)
+			{
+			*al = SSL_AD_INTERNAL_ERROR;
+			return -1;
+			}
+		memcpy(s->s3->alpn_selected, selected, selected_len);
+		s->s3->alpn_selected_len = selected_len;
+	}
+	return 0;
+
+parse_error:
+	*al = SSL_AD_DECODE_ERROR;
+	return -1;
+	}
+
 static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char *d, int n, int *al) 
 	{	
 	unsigned short type;
@@ -1775,6 +1872,12 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char
 	s->s3->next_proto_neg_seen = 0;
 #endif
 
+	if (s->s3->alpn_selected)
+		{
+		OPENSSL_free(s->s3->alpn_selected);
+		s->s3->alpn_selected = NULL;
+		}
+
 #ifndef OPENSSL_NO_HEARTBEATS
 	s->tlsext_heartbeat &= ~(SSL_TLSEXT_HB_ENABLED |
 	                       SSL_TLSEXT_HB_DONT_SEND_REQUESTS);
@@ -2233,7 +2336,8 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char
 #endif
 #ifndef OPENSSL_NO_NEXTPROTONEG
 		else if (type == TLSEXT_TYPE_next_proto_neg &&
-			 s->s3->tmp.finish_md_len == 0)
+			 s->s3->tmp.finish_md_len == 0 &&
+			 s->s3->alpn_selected == NULL)
 			{
 			/* We shouldn't accept this extension on a
 			 * renegotiation.
@@ -2254,6 +2358,16 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char
 			}
 #endif
 
+		else if (type == TLSEXT_TYPE_application_layer_protocol_negotiation &&
+			 s->ctx->alpn_select_cb &&
+			 s->s3->tmp.finish_md_len == 0)
+			{
+			if (tls1_alpn_handle_client_hello(s, data, size, al) != 0)
+				return 0;
+			/* ALPN takes precedence over NPN. */
+			s->s3->next_proto_neg_seen = 0;
+			}
+
 		/* session ticket processed earlier */
 		else if (type == TLSEXT_TYPE_use_srtp)
                         {
@@ -2443,6 +2557,12 @@ static int ssl_scan_serverhello_tlsext(SSL *s, unsigned char **p, unsigned char
 	s->s3->next_proto_neg_seen = 0;
 #endif
 
+	if (s->s3->alpn_selected)
+		{
+		OPENSSL_free(s->s3->alpn_selected);
+		s->s3->alpn_selected = NULL;
+		}
+
 #ifndef OPENSSL_NO_HEARTBEATS
 	s->tlsext_heartbeat &= ~(SSL_TLSEXT_HB_ENABLED |
 	                       SSL_TLSEXT_HB_DONT_SEND_REQUESTS);
@@ -2608,6 +2728,52 @@ static int ssl_scan_serverhello_tlsext(SSL *s, unsigned char **p, unsigned char
 			s->s3->next_proto_neg_seen = 1;
 			}
 #endif
+
+		else if (type == TLSEXT_TYPE_application_layer_protocol_negotiation)
+			{
+			unsigned len;
+
+			/* We must have requested it. */
+			if (s->alpn_client_proto_list == NULL)
+				{
+				*al = TLS1_AD_UNSUPPORTED_EXTENSION;
+				return 0;
+				}
+			if (size < 4)
+				{
+				*al = TLS1_AD_DECODE_ERROR;
+				return 0;
+				}
+			/* The extension data consists of:
+			 *   uint16 list_length
+			 *   uint8 proto_length;
+			 *   uint8 proto[proto_length]; */
+			len = data[0];
+			len <<= 8;
+			len |= data[1];
+			if (len != (unsigned) size - 2)
+				{
+				*al = TLS1_AD_DECODE_ERROR;
+				return 0;
+				}
+			len = data[2];
+			if (len != (unsigned) size - 3)
+				{
+				*al = TLS1_AD_DECODE_ERROR;
+				return 0;
+				}
+			if (s->s3->alpn_selected)
+				OPENSSL_free(s->s3->alpn_selected);
+			s->s3->alpn_selected = OPENSSL_malloc(len);
+			if (!s->s3->alpn_selected)
+				{
+				*al = TLS1_AD_INTERNAL_ERROR;
+				return 0;
+				}
+			memcpy(s->s3->alpn_selected, data + 3, len);
+			s->s3->alpn_selected_len = len;
+			}
+
 		else if (type == TLSEXT_TYPE_renegotiate)
 			{
 			if(!ssl_parse_serverhello_renegotiate_ext(s, data, size, al))
diff --git a/ssl/tls1.h b/ssl/tls1.h
index c59a02fee3..b1b85bf632 100644
--- a/ssl/tls1.h
+++ b/ssl/tls1.h
@@ -230,6 +230,9 @@ extern "C" {
 /* ExtensionType value from RFC5620 */
 #define TLSEXT_TYPE_heartbeat	15
 
+/* ExtensionType value from draft-ietf-tls-applayerprotoneg-00 */
+#define TLSEXT_TYPE_application_layer_protocol_negotiation 16
+
 /* ExtensionType value from RFC4507 */
 #define TLSEXT_TYPE_session_ticket		35