d1_pkt.c

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		int alert_level = s->d1->alert_fragment[0];
		int alert_descr = s->d1->alert_fragment[1];

		s->d1->alert_fragment_len = 0;

		if (s->msg_callback)
			s->msg_callback(0, s->version, SSL3_RT_ALERT, 
				s->d1->alert_fragment, 2, s, s->msg_callback_arg);

		if (s->info_callback != NULL)
			cb=s->info_callback;
		else if (s->ctx->info_callback != NULL)
			cb=s->ctx->info_callback;

		if (cb != NULL)
			{
			j = (alert_level << 8) | alert_descr;
			cb(s, SSL_CB_READ_ALERT, j);
			}

		if (alert_level == 1) /* warning */
			{
			s->s3->warn_alert = alert_descr;
			if (alert_descr == SSL_AD_CLOSE_NOTIFY)
				{
				s->shutdown |= SSL_RECEIVED_SHUTDOWN;
				return(0);
				}
#if 0
            /* XXX: this is a possible improvement in the future */
			/* now check if it's a missing record */
			if (alert_descr == DTLS1_AD_MISSING_HANDSHAKE_MESSAGE)
				{
				unsigned short seq;
				unsigned int frag_off;
				unsigned char *p = &(s->d1->alert_fragment[2]);

				n2s(p, seq);
				n2l3(p, frag_off);

				dtls1_retransmit_message(s, seq, frag_off, &found);
				if ( ! found  && SSL_in_init(s))
					{
					/* fprintf( stderr,"in init = %d\n", SSL_in_init(s)); */
					/* requested a message not yet sent, 
					   send an alert ourselves */
					ssl3_send_alert(s,SSL3_AL_WARNING,
						DTLS1_AD_MISSING_HANDSHAKE_MESSAGE);
					}
				}
#endif
			}
		else if (alert_level == 2) /* fatal */
			{
			char tmp[16];

			s->rwstate=SSL_NOTHING;
			s->s3->fatal_alert = alert_descr;
			SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_AD_REASON_OFFSET + alert_descr);
			BIO_snprintf(tmp,sizeof tmp,"%d",alert_descr);
			ERR_add_error_data(2,"SSL alert number ",tmp);
			s->shutdown|=SSL_RECEIVED_SHUTDOWN;
			SSL_CTX_remove_session(s->ctx,s->session);
			return(0);
			}
		else
			{
			al=SSL_AD_ILLEGAL_PARAMETER;
			SSLerr(SSL_F_DTLS1_READ_BYTES,SSL_R_UNKNOWN_ALERT_TYPE);
			goto f_err;
			}

		goto start;
		}

	if (s->shutdown & SSL_SENT_SHUTDOWN) /* but we have not received a shutdown */
		{
		s->rwstate=SSL_NOTHING;
		rr->length=0;
		return(0);
		}

	if (rr->type == SSL3_RT_CHANGE_CIPHER_SPEC)
        {
        struct ccs_header_st ccs_hdr;

		dtls1_get_ccs_header(rr->data, &ccs_hdr);

		if ( ccs_hdr.seq == s->d1->handshake_read_seq)
			{
			/* 'Change Cipher Spec' is just a single byte, so we know
			 * exactly what the record payload has to look like */
			/* XDTLS: check that epoch is consistent */
			if (	(rr->length != DTLS1_CCS_HEADER_LENGTH) || 
				(rr->off != 0) || (rr->data[0] != SSL3_MT_CCS))
				{
				i=SSL_AD_ILLEGAL_PARAMETER;
				SSLerr(SSL_F_DTLS1_READ_BYTES,SSL_R_BAD_CHANGE_CIPHER_SPEC);
				goto err;
				}
			
			rr->length=0;
			
			if (s->msg_callback)
				s->msg_callback(0, s->version, SSL3_RT_CHANGE_CIPHER_SPEC, 
					rr->data, 1, s, s->msg_callback_arg);
			
			s->s3->change_cipher_spec=1;
			if (!ssl3_do_change_cipher_spec(s))
				goto err;
			
			/* do this whenever CCS is processed */
			dtls1_reset_seq_numbers(s, SSL3_CC_READ);
			
			/* handshake read seq is reset upon handshake completion */
			s->d1->handshake_read_seq++;
			
			goto start;
			}
		else
			{
			rr->length = 0;
			goto start;
			}
		}

	/* Unexpected handshake message (Client Hello, or protocol violation) */
	if ((s->d1->handshake_fragment_len >= DTLS1_HM_HEADER_LENGTH) && 
		!s->in_handshake)
		{
		struct hm_header_st msg_hdr;
		
		/* this may just be a stale retransmit */
		dtls1_get_message_header(rr->data, &msg_hdr);
		if( rr->epoch != s->d1->r_epoch)
			{
			rr->length = 0;
			goto start;
			}

		if (((s->state&SSL_ST_MASK) == SSL_ST_OK) &&
			!(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS))
			{
#if 0 /* worked only because C operator preferences are not as expected (and
       * because this is not really needed for clients except for detecting
       * protocol violations): */
			s->state=SSL_ST_BEFORE|(s->server)
				?SSL_ST_ACCEPT
				:SSL_ST_CONNECT;
#else
			s->state = s->server ? SSL_ST_ACCEPT : SSL_ST_CONNECT;
#endif
			s->new_session=1;
			}
		i=s->handshake_func(s);
		if (i < 0) return(i);
		if (i == 0)
			{
			SSLerr(SSL_F_DTLS1_READ_BYTES,SSL_R_SSL_HANDSHAKE_FAILURE);
			return(-1);
			}

		if (!(s->mode & SSL_MODE_AUTO_RETRY))
			{
			if (s->s3->rbuf.left == 0) /* no read-ahead left? */
				{
				BIO *bio;
				/* In the case where we try to read application data,
				 * but we trigger an SSL handshake, we return -1 with
				 * the retry option set.  Otherwise renegotiation may
				 * cause nasty problems in the blocking world */
				s->rwstate=SSL_READING;
				bio=SSL_get_rbio(s);
				BIO_clear_retry_flags(bio);
				BIO_set_retry_read(bio);
				return(-1);
				}
			}
		goto start;
		}

	switch (rr->type)
		{
	default:
#ifndef OPENSSL_NO_TLS
		/* TLS just ignores unknown message types */
		if (s->version == TLS1_VERSION)
			{
			rr->length = 0;
			goto start;
			}
#endif
		al=SSL_AD_UNEXPECTED_MESSAGE;
		SSLerr(SSL_F_DTLS1_READ_BYTES,SSL_R_UNEXPECTED_RECORD);
		goto f_err;
	case SSL3_RT_CHANGE_CIPHER_SPEC:
	case SSL3_RT_ALERT:
	case SSL3_RT_HANDSHAKE:
		/* we already handled all of these, with the possible exception
		 * of SSL3_RT_HANDSHAKE when s->in_handshake is set, but that
		 * should not happen when type != rr->type */
		al=SSL_AD_UNEXPECTED_MESSAGE;
		SSLerr(SSL_F_DTLS1_READ_BYTES,ERR_R_INTERNAL_ERROR);
		goto f_err;
	case SSL3_RT_APPLICATION_DATA:
		/* At this point, we were expecting handshake data,
		 * but have application data.  If the library was
		 * running inside ssl3_read() (i.e. in_read_app_data
		 * is set) and it makes sense to read application data
		 * at this point (session renegotiation not yet started),
		 * we will indulge it.
		 */
		if (s->s3->in_read_app_data &&
			(s->s3->total_renegotiations != 0) &&
			((
				(s->state & SSL_ST_CONNECT) &&
				(s->state >= SSL3_ST_CW_CLNT_HELLO_A) &&
				(s->state <= SSL3_ST_CR_SRVR_HELLO_A)
				) || (
					(s->state & SSL_ST_ACCEPT) &&
					(s->state <= SSL3_ST_SW_HELLO_REQ_A) &&
					(s->state >= SSL3_ST_SR_CLNT_HELLO_A)
					)
				))
			{
			s->s3->in_read_app_data=2;
			return(-1);
			}
		else
			{
			al=SSL_AD_UNEXPECTED_MESSAGE;
			SSLerr(SSL_F_DTLS1_READ_BYTES,SSL_R_UNEXPECTED_RECORD);
			goto f_err;
			}
		}
	/* not reached */

f_err:
	ssl3_send_alert(s,SSL3_AL_FATAL,al);
err:
	return(-1);
	}

int
dtls1_write_app_data_bytes(SSL *s, int type, const void *buf_, int len)
	{
	unsigned int n,tot;
	int i;

	if (SSL_in_init(s) && !s->in_handshake)
		{
		i=s->handshake_func(s);
		if (i < 0) return(i);
		if (i == 0)
			{
			SSLerr(SSL_F_DTLS1_WRITE_APP_DATA_BYTES,SSL_R_SSL_HANDSHAKE_FAILURE);
			return -1;
			}
		}

	tot = s->s3->wnum;
	n = len - tot;

	while( n)
		{
		/* dtls1_write_bytes sends one record at a time, sized according to 
		 * the currently known MTU */
		i = dtls1_write_bytes(s, type, buf_, len);
		if (i <= 0) return i;
		
		if ((i == (int)n) ||
			(type == SSL3_RT_APPLICATION_DATA &&
				(s->mode & SSL_MODE_ENABLE_PARTIAL_WRITE)))
			{
			/* next chunk of data should get another prepended empty fragment
			 * in ciphersuites with known-IV weakness: */
			s->s3->empty_fragment_done = 0;
			return tot+i;
			}

		tot += i;
		n-=i;
		}

	return tot;
	}


	/* this only happens when a client hello is received and a handshake 
	 * is started. */
static int
have_handshake_fragment(SSL *s, int type, unsigned char *buf, 
	int len, int peek)
	{
	
	if ((type == SSL3_RT_HANDSHAKE) && (s->d1->handshake_fragment_len > 0))
		/* (partially) satisfy request from storage */
		{
		unsigned char *src = s->d1->handshake_fragment;
		unsigned char *dst = buf;
		unsigned int k,n;
		
		/* peek == 0 */
		n = 0;
		while ((len > 0) && (s->d1->handshake_fragment_len > 0))
			{
			*dst++ = *src++;
			len--; s->d1->handshake_fragment_len--;
			n++;
			}
		/* move any remaining fragment bytes: */
		for (k = 0; k < s->d1->handshake_fragment_len; k++)
			s->d1->handshake_fragment[k] = *src++;
		return n;
		}
	
	return 0;
	}




/* Call this to write data in records of type 'type'
 * It will return <= 0 if not all data has been sent or non-blocking IO.
 */
int dtls1_write_bytes(SSL *s, int type, const void *buf_, int len)
	{
	const unsigned char *buf=buf_;
	unsigned int tot,n,nw;
	int i;
	unsigned int mtu;

	s->rwstate=SSL_NOTHING;
	tot=s->s3->wnum;

	n=(len-tot);

	/* handshake layer figures out MTU for itself, but data records
	 * are also sent through this interface, so need to figure out MTU */
#if 0
	mtu = BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_GET_MTU, 0, NULL);
	mtu += DTLS1_HM_HEADER_LENGTH;  /* HM already inserted */
#endif
	mtu = s->d1->mtu;

	if (mtu > SSL3_RT_MAX_PLAIN_LENGTH)
		mtu = SSL3_RT_MAX_PLAIN_LENGTH;

	if (n > mtu)
		nw=mtu;
	else
		nw=n;
	
	i=do_dtls1_write(s, type, &(buf[tot]), nw, 0);
	if (i <= 0)
		{
		s->s3->wnum=tot;
		return i;
		}

	if ( (int)s->s3->wnum + i == len)
		s->s3->wnum = 0;
	else 
		s->s3->wnum += i;

	return tot + i;
	}

int do_dtls1_write(SSL *s, int type, const unsigned char *buf, unsigned int len, int create_empty_fragment)
	{
	unsigned char *p,*pseq;
	int i,mac_size,clear=0;
	int prefix_len = 0;
	SSL3_RECORD *wr;
	SSL3_BUFFER *wb;
	SSL_SESSION *sess;
	int bs;

	/* first check if there is a SSL3_BUFFER still being written
	 * out.  This will happen with non blocking IO */
	if (s->s3->wbuf.left != 0)
		{
		OPENSSL_assert(0); /* XDTLS:  want to see if we ever get here */
		return(ssl3_write_pending(s,type,buf,len));
		}

	/* If we have an alert to send, lets send it */
	if (s->s3->alert_dispatch)
		{
		i=s->method->ssl_dispatch_alert(s);
		if (i <= 0)
			return(i);
		/* if it went, fall through and send more stuff */
		}

	if (len == 0 && !create_empty_fragment)
		return 0;

	wr= &(s->s3->wrec);
	wb= &(s->s3->wbuf);
	sess=s->session;

	if (	(sess == NULL) ||
		(s->enc_write_ctx == NULL) ||
		(s->write_hash == NULL))
		clear=1;

	if (clear)
		mac_size=0;
	else
		mac_size=EVP_MD_size(s->write_hash);

	/* DTLS implements explicit IV, so no need for empty fragments */
#if 0
	/* 'create_empty_fragment' is true only when this function calls itself */
	if (!clear && !create_empty_fragment && !s->s3->empty_fragment_done
		&& SSL_version(s) != DTLS1_VERSION)
		{
		/* countermeasure against known-IV weakness in CBC ciphersuites
		 * (see http://www.openssl.org/~bodo/tls-cbc.txt) 
		 */

		if (s->s3->need_empty_fragments && type == SSL3_RT_APPLICATION_DATA)
			{
			/* recursive function call with 'create_empty_fragment' set;
			 * this prepares and buffers the data for an empty fragment
			 * (these 'prefix_len' bytes are sent out later
			 * together with the actual payload) */
			prefix_len = s->method->do_ssl_write(s, type, buf, 0, 1);
			if (prefix_len <= 0)
				goto err;

			if (s->s3->wbuf.len < (size_t)prefix_len + SSL3_RT_MAX_PACKET_SIZE)
				{
				/* insufficient space */
				SSLerr(SSL_F_DO_DTLS1_WRITE, ERR_R_INTERNAL_ERROR);
				goto err;
				}
			}
		
		s->s3->empty_fragment_done = 1;
		}