int ssl_parse_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char *d, int n, int *al)
	{
	unsigned short type;
	unsigned short size;
	unsigned short len;
	unsigned char *data = *p;
	int renegotiate_seen = 0;
	int sigalg_seen = 0;

	s->servername_done = 0;
	s->tlsext_status_type = -1;
#ifndef OPENSSL_NO_NEXTPROTONEG
	s->s3->next_proto_neg_seen = 0;
#endif

#ifndef OPENSSL_NO_HEARTBEATS
	s->tlsext_heartbeat &= ~(SSL_TLSEXT_HB_ENABLED |
	                       SSL_TLSEXT_HB_DONT_SEND_REQUESTS);
#endif

#ifndef OPENSSL_NO_EC
	if (s->options & SSL_OP_SAFARI_ECDHE_ECDSA_BUG)
		ssl_check_for_safari(s, data, d, n);
#endif /* !OPENSSL_NO_EC */

	if (data >= (d+n-2))
		goto ri_check;
	n2s(data,len);

	if (data > (d+n-len)) 
		goto ri_check;

	while (data <= (d+n-4))
		{
		n2s(data,type);
		n2s(data,size);

		if (data+size > (d+n))
	   		goto ri_check;
#if 0
		fprintf(stderr,"Received extension type %d size %d\n",type,size);
#endif
		if (s->tlsext_debug_cb)
			s->tlsext_debug_cb(s, 0, type, data, size,
						s->tlsext_debug_arg);
/* The servername extension is treated as follows:

   - Only the hostname type is supported with a maximum length of 255.
   - The servername is rejected if too long or if it contains zeros,
     in which case an fatal alert is generated.
   - The servername field is maintained together with the session cache.
   - When a session is resumed, the servername call back invoked in order
     to allow the application to position itself to the right context. 
   - The servername is acknowledged if it is new for a session or when 
     it is identical to a previously used for the same session. 
     Applications can control the behaviour.  They can at any time
     set a 'desirable' servername for a new SSL object. This can be the
     case for example with HTTPS when a Host: header field is received and
     a renegotiation is requested. In this case, a possible servername
     presented in the new client hello is only acknowledged if it matches
     the value of the Host: field. 
   - Applications must  use SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION
     if they provide for changing an explicit servername context for the session,
     i.e. when the session has been established with a servername extension. 
   - On session reconnect, the servername extension may be absent. 

*/      

		if (type == TLSEXT_TYPE_server_name)
			{
			unsigned char *sdata;
			int servname_type;
			int dsize; 
		
			if (size < 2) 
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			n2s(data,dsize);  
			size -= 2;
			if (dsize > size  ) 
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				} 

			sdata = data;
			while (dsize > 3) 
				{
	 			servname_type = *(sdata++); 
				n2s(sdata,len);
				dsize -= 3;

				if (len > dsize) 
					{
					*al = SSL_AD_DECODE_ERROR;
					return 0;
					}
				if (s->servername_done == 0)
				switch (servname_type)
					{
				case TLSEXT_NAMETYPE_host_name:
					if (!s->hit)
						{
						if(s->session->tlsext_hostname)
							{
							*al = SSL_AD_DECODE_ERROR;
							return 0;
							}
						if (len > TLSEXT_MAXLEN_host_name)
							{
							*al = TLS1_AD_UNRECOGNIZED_NAME;
							return 0;
							}
						if ((s->session->tlsext_hostname = OPENSSL_malloc(len+1)) == NULL)
							{
							*al = TLS1_AD_INTERNAL_ERROR;
							return 0;
							}
						memcpy(s->session->tlsext_hostname, sdata, len);
						s->session->tlsext_hostname[len]='\0';
						if (strlen(s->session->tlsext_hostname) != len) {
							OPENSSL_free(s->session->tlsext_hostname);
							s->session->tlsext_hostname = NULL;
							*al = TLS1_AD_UNRECOGNIZED_NAME;
							return 0;
						}
						s->servername_done = 1; 

						}
					else 
						s->servername_done = s->session->tlsext_hostname
							&& strlen(s->session->tlsext_hostname) == len 
							&& strncmp(s->session->tlsext_hostname, (char *)sdata, len) == 0;
					
					break;

				default:
					break;
					}
				 
				dsize -= len;
				}
			if (dsize != 0) 
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}

			}
#ifndef OPENSSL_NO_SRP
		else if (type == TLSEXT_TYPE_srp)
			{
			if (size <= 0 || ((len = data[0])) != (size -1))
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			if (s->srp_ctx.login != NULL)
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			if ((s->srp_ctx.login = OPENSSL_malloc(len+1)) == NULL)
				return -1;
			memcpy(s->srp_ctx.login, &data[1], len);
			s->srp_ctx.login[len]='\0';
  
			if (strlen(s->srp_ctx.login) != len) 
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			}
#endif

#ifndef OPENSSL_NO_EC
		else if (type == TLSEXT_TYPE_ec_point_formats)
			{
			unsigned char *sdata = data;
			int ecpointformatlist_length = *(sdata++);

			if (ecpointformatlist_length != size - 1)
				{
				*al = TLS1_AD_DECODE_ERROR;
				return 0;
				}
			if (!s->hit)
				{
				if(s->session->tlsext_ecpointformatlist)
					{
					OPENSSL_free(s->session->tlsext_ecpointformatlist);
					s->session->tlsext_ecpointformatlist = NULL;
					}
				s->session->tlsext_ecpointformatlist_length = 0;
				if ((s->session->tlsext_ecpointformatlist = OPENSSL_malloc(ecpointformatlist_length)) == NULL)
					{
					*al = TLS1_AD_INTERNAL_ERROR;
					return 0;
					}
				s->session->tlsext_ecpointformatlist_length = ecpointformatlist_length;
				memcpy(s->session->tlsext_ecpointformatlist, sdata, ecpointformatlist_length);
				}
#if 0
			fprintf(stderr,"ssl_parse_clienthello_tlsext s->session->tlsext_ecpointformatlist (length=%i) ", s->session->tlsext_ecpointformatlist_length);
			sdata = s->session->tlsext_ecpointformatlist;
			for (i = 0; i < s->session->tlsext_ecpointformatlist_length; i++)
				fprintf(stderr,"%i ",*(sdata++));
			fprintf(stderr,"\n");
#endif
			}
		else if (type == TLSEXT_TYPE_elliptic_curves)
			{
			unsigned char *sdata = data;
			int ellipticcurvelist_length = (*(sdata++) << 8);
			ellipticcurvelist_length += (*(sdata++));

			if (ellipticcurvelist_length != size - 2 ||
				ellipticcurvelist_length < 1)
				{
				*al = TLS1_AD_DECODE_ERROR;
				return 0;
				}
			if (!s->hit)
				{
				if(s->session->tlsext_ellipticcurvelist)
					{
					*al = TLS1_AD_DECODE_ERROR;
					return 0;
					}
				s->session->tlsext_ellipticcurvelist_length = 0;
				if ((s->session->tlsext_ellipticcurvelist = OPENSSL_malloc(ellipticcurvelist_length)) == NULL)
					{
					*al = TLS1_AD_INTERNAL_ERROR;
					return 0;
					}
				s->session->tlsext_ellipticcurvelist_length = ellipticcurvelist_length;
				memcpy(s->session->tlsext_ellipticcurvelist, sdata, ellipticcurvelist_length);
				}
#if 0
			fprintf(stderr,"ssl_parse_clienthello_tlsext s->session->tlsext_ellipticcurvelist (length=%i) ", s->session->tlsext_ellipticcurvelist_length);
			sdata = s->session->tlsext_ellipticcurvelist;
			for (i = 0; i < s->session->tlsext_ellipticcurvelist_length; i++)
				fprintf(stderr,"%i ",*(sdata++));
			fprintf(stderr,"\n");
#endif
			}
#endif /* OPENSSL_NO_EC */
#ifdef TLSEXT_TYPE_opaque_prf_input
		else if (type == TLSEXT_TYPE_opaque_prf_input &&
	             s->version != DTLS1_VERSION)
			{
			unsigned char *sdata = data;

			if (size < 2)
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			n2s(sdata, s->s3->client_opaque_prf_input_len);
			if (s->s3->client_opaque_prf_input_len != size - 2)
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}

			if (s->s3->client_opaque_prf_input != NULL) /* shouldn't really happen */
				OPENSSL_free(s->s3->client_opaque_prf_input);
			if (s->s3->client_opaque_prf_input_len == 0)
				s->s3->client_opaque_prf_input = OPENSSL_malloc(1); /* dummy byte just to get non-NULL */
			else
				s->s3->client_opaque_prf_input = BUF_memdup(sdata, s->s3->client_opaque_prf_input_len);
			if (s->s3->client_opaque_prf_input == NULL)
				{
				*al = TLS1_AD_INTERNAL_ERROR;
				return 0;
				}
			}
#endif
		else if (type == TLSEXT_TYPE_session_ticket)
			{
			if (s->tls_session_ticket_ext_cb &&
			    !s->tls_session_ticket_ext_cb(s, data, size, s->tls_session_ticket_ext_cb_arg))
				{
				*al = TLS1_AD_INTERNAL_ERROR;
				return 0;
				}
			}
		else if (type == TLSEXT_TYPE_renegotiate)
			{
			if(!ssl_parse_clienthello_renegotiate_ext(s, data, size, al))
				return 0;
			renegotiate_seen = 1;
			}
		else if (type == TLSEXT_TYPE_signature_algorithms)
			{
			int dsize;
			if (sigalg_seen || size < 2) 
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			sigalg_seen = 1;
			n2s(data,dsize);
			size -= 2;
			if (dsize != size || dsize & 1) 
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			if (!tls1_process_sigalgs(s, data, dsize))
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}
			}
		else if (type == TLSEXT_TYPE_status_request &&
		         s->version != DTLS1_VERSION)
			{
		
			if (size < 5) 
				{
				*al = SSL_AD_DECODE_ERROR;
				return 0;
				}

			s->tlsext_status_type = *data++;
			size--;
			if (s->tlsext_status_type == TLSEXT_STATUSTYPE_ocsp)
				{
				const unsigned char *sdata;
				int dsize;
				/* Read in responder_id_list */
				n2s(data,dsize);
				size -= 2;
				if (dsize > size  ) 
					{
					*al = SSL_AD_DECODE_ERROR;
					return 0;
					}
				while (dsize > 0)
					{
					OCSP_RESPID *id;
					int idsize;
					if (dsize < 4)
						{
						*al = SSL_AD_DECODE_ERROR;
						return 0;
						}
					n2s(data, idsize);
					dsize -= 2 + idsize;
					size -= 2 + idsize;
					if (dsize < 0)
						{
						*al = SSL_AD_DECODE_ERROR;
						return 0;
						}
					sdata = data;
					data += idsize;
					id = d2i_OCSP_RESPID(NULL,
								&sdata, idsize);
					if (!id)
						{
						*al = SSL_AD_DECODE_ERROR;
						return 0;
						}
					if (data != sdata)
						{
						OCSP_RESPID_free(id);
						*al = SSL_AD_DECODE_ERROR;
						return 0;
						}
					if (!s->tlsext_ocsp_ids
						&& !(s->tlsext_ocsp_ids =
						sk_OCSP_RESPID_new_null()))
						{
						OCSP_RESPID_free(id);
						*al = SSL_AD_INTERNAL_ERROR;
						return 0;
						}
					if (!sk_OCSP_RESPID_push(
							s->tlsext_ocsp_ids, id))
						{
						OCSP_RESPID_free(id);
						*al = SSL_AD_INTERNAL_ERROR;
						return 0;
						}
					}

				/* Read in request_extensions */
				if (size < 2)
					{
					*al = SSL_AD_DECODE_ERROR;
					return 0;
					}
				n2s(data,dsize);
				size -= 2;
				if (dsize != size)
					{
					*al = SSL_AD_DECODE_ERROR;
					return 0;
					}
				sdata = data;
				if (dsize > 0)
					{
					if (s->tlsext_ocsp_exts)
						{
						sk_X509_EXTENSION_pop_free(s->tlsext_ocsp_exts,
									   X509_EXTENSION_free);
						}

					s->tlsext_ocsp_exts =
						d2i_X509_EXTENSIONS(NULL,
							&sdata, dsize);
					if (!s->tlsext_ocsp_exts
						|| (data + dsize != sdata))
						{
						*al = SSL_AD_DECODE_ERROR;
						return 0;
						}
					}
				}
				/* We don't know what to do with any other type
 			 	* so ignore it.
 			 	*/
				else
					s->tlsext_status_type = -1;
			}
#ifndef OPENSSL_NO_HEARTBEATS
		else if (type == TLSEXT_TYPE_heartbeat)
			{
			switch(data[0])
				{
				case 0x01:	/* Client allows us to send HB requests */
							s->tlsext_heartbeat |= SSL_TLSEXT_HB_ENABLED;
							break;
				case 0x02:	/* Client doesn't accept HB requests */
							s->tlsext_heartbeat |= SSL_TLSEXT_HB_ENABLED;
							s->tlsext_heartbeat |= SSL_TLSEXT_HB_DONT_SEND_REQUESTS;
							break;
				default:	*al = SSL_AD_ILLEGAL_PARAMETER;
							return 0;
				}
			}
#endif
#ifndef OPENSSL_NO_NEXTPROTONEG
		else if (type == TLSEXT_TYPE_next_proto_neg &&
			 s->s3->tmp.finish_md_len == 0)
			{
			/* We shouldn't accept this extension on a
			 * renegotiation.
			 *
			 * s->new_session will be set on renegotiation, but we
			 * probably shouldn't rely that it couldn't be set on
			 * the initial renegotation too in certain cases (when
			 * there's some other reason to disallow resuming an
			 * earlier session -- the current code won't be doing
			 * anything like that, but this might change).

			 * A valid sign that there's been a previous handshake
			 * in this connection is if s->s3->tmp.finish_md_len >
			 * 0.  (We are talking about a check that will happen
			 * in the Hello protocol round, well before a new
			 * Finished message could have been computed.) */
			s->s3->next_proto_neg_seen = 1;
			}
#endif

		/* session ticket processed earlier */
#ifndef OPENSSL_NO_SRTP
		else if (SSL_IS_DTLS(s) && SSL_get_srtp_profiles(s)
			 && type == TLSEXT_TYPE_use_srtp)
			{
			if(ssl_parse_clienthello_use_srtp_ext(s, data, size,
							      al))
				return 0;
			}
#endif

		data+=size;
		}
				
	*p = data;

	ri_check:

	/* Need RI if renegotiating */

	if (!renegotiate_seen && s->renegotiate &&
		!(s->options & SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION))
		{
		*al = SSL_AD_HANDSHAKE_FAILURE;
	 	SSLerr(SSL_F_SSL_PARSE_CLIENTHELLO_TLSEXT,
				SSL_R_UNSAFE_LEGACY_RENEGOTIATION_DISABLED);
		return 0;
		}

	return 1;
	}