PR: 1949

Submitted by: steve@openssl.org

More robust fix and workaround for PR#1949. Don't try to work out if there
is any write pending data as this can be unreliable: always flush.

CHANGES

@@ -884,6 +884,14 @@
 
  Changes between 0.9.8l (?) and 0.9.8m (?)  [xx XXX xxxx]
 
+  *) The code that handled flusing of data in SSL/TLS originally used the
+     BIO_CTRL_INFO ctrl to see if any data was pending first. This caused
+     the problem outlined in PR#1949. The fix suggested there however can
+     trigger problems with buggy BIO_CTRL_WPENDING (e.g. some versions
+     of Apache). So instead simplify the code to flush unconditionally.
+     This should be fine since flushing with no data to flush is a no op.
+     [Steve Henson]
+
   *) Handle TLS versions 2.0 and later properly and correctly use the
      highest version of TLS/SSL supported. Although TLS >= 2.0 is some way
      off ancient servers have a habit of sticking around for a while...

ssl/d1_clnt.c

@@ -148,7 +148,6 @@ int dtls1_connect(SSL *s)
 	{
 	BUF_MEM *buf=NULL;
 	unsigned long Time=(unsigned long)time(NULL);
-	long num1;
 	void (*cb)(const SSL *ssl,int type,int val)=NULL;
 	int ret= -1;
 	int new_state,state,skip=0;;
@@ -511,16 +510,13 @@ int dtls1_connect(SSL *s)
 			break;
 
 		case SSL3_ST_CW_FLUSH:
-			/* number of bytes to be flushed */
-			num1=BIO_ctrl(s->wbio,BIO_CTRL_INFO,0,NULL);
-			if (num1 > 0)
+			s->rwstate=SSL_WRITING;
+			if (BIO_flush(s->wbio) <= 0)
 				{
-				s->rwstate=SSL_WRITING;
-				num1=BIO_flush(s->wbio);
-				if (num1 <= 0) { ret= -1; goto end; }
-				s->rwstate=SSL_NOTHING;
+				ret= -1;
+				goto end;
 				}
-
+			s->rwstate=SSL_NOTHING;
 			s->state=s->s3->tmp.next_state;
 			break;
 

ssl/d1_srvr.c

@@ -147,7 +147,6 @@ int dtls1_accept(SSL *s)
 	BUF_MEM *buf;
 	unsigned long Time=(unsigned long)time(NULL);
 	void (*cb)(const SSL *ssl,int type,int val)=NULL;
-	long num1;
 	unsigned long alg_k;
 	int ret= -1;
 	int new_state,state,skip=0;
@@ -453,17 +452,14 @@ int dtls1_accept(SSL *s)
 			s->init_num=0;
 			break;
 		
-		case SSL3_ST_SW_FLUSH:
-			/* number of bytes to be flushed */
-			num1=BIO_ctrl(s->wbio,BIO_CTRL_INFO,0,NULL);
-			if (num1 > 0)
+		case SSL3_ST_CW_FLUSH:
+			s->rwstate=SSL_WRITING;
+			if (BIO_flush(s->wbio) <= 0)
 				{
-				s->rwstate=SSL_WRITING;
-				num1=BIO_flush(s->wbio);
-				if (num1 <= 0) { ret= -1; goto end; }
-				s->rwstate=SSL_NOTHING;
+				ret= -1;
+				goto end;
 				}
-
+			s->rwstate=SSL_NOTHING;
 			s->state=s->s3->tmp.next_state;
 			break;
 

ssl/s3_clnt.c

@@ -184,7 +184,6 @@ int ssl3_connect(SSL *s)
 	{
 	BUF_MEM *buf=NULL;
 	unsigned long Time=(unsigned long)time(NULL);
-	long num1;
 	void (*cb)(const SSL *ssl,int type,int val)=NULL;
 	int ret= -1;
 	int new_state,state,skip=0;
@@ -520,16 +519,13 @@ int ssl3_connect(SSL *s)
 			break;
 
 		case SSL3_ST_CW_FLUSH:
-			/* number of bytes to be flushed */
-			num1=BIO_ctrl(s->wbio,BIO_CTRL_INFO,0,NULL);
-			if (num1 > 0)
+			s->rwstate=SSL_WRITING;
+			if (BIO_flush(s->wbio) <= 0)
 				{
-				s->rwstate=SSL_WRITING;
-				num1=BIO_flush(s->wbio);
-				if (num1 <= 0) { ret= -1; goto end; }
-				s->rwstate=SSL_NOTHING;
+				ret= -1;
+				goto end;
 				}
-
+			s->rwstate=SSL_NOTHING;
 			s->state=s->s3->tmp.next_state;
 			break;
 

ssl/s3_pkt.c

@@ -330,7 +330,7 @@ again:
 #if 0
 fprintf(stderr, "Record type=%d, Length=%d\n", rr->type, rr->length);
 #endif
-
+fprintf(stderr, "RX version %x, Expecting %x\n", version, s->version);
 		/* Lets check version */
 		if (!s->first_packet)
 			{
@@ -736,7 +736,7 @@ static int do_ssl3_write(SSL *s, int type, const unsigned char *buf,
 
 	*(p++)=(s->version>>8);
 	*(p++)=s->version&0xff;
-
+fprintf(stderr, "Wrote version %x\n", s->version);
 	/* field where we are to write out packet length */
 	plen=p; 
 	p+=2;

ssl/s3_srvr.c

@@ -189,7 +189,6 @@ int ssl3_accept(SSL *s)
 	BUF_MEM *buf;
 	unsigned long alg_k,Time=(unsigned long)time(NULL);
 	void (*cb)(const SSL *ssl,int type,int val)=NULL;
-	long num1;
 	int ret= -1;
 	int new_state,state,skip=0;
 
@@ -483,29 +482,24 @@ int ssl3_accept(SSL *s)
 			break;
 		
 		case SSL3_ST_SW_FLUSH:
-			/* number of bytes to be flushed */
-			/* This originally and incorrectly called BIO_CTRL_INFO
-			 * The reason why this is wrong is mentioned in PR#1949.
-			 * Unfortunately, as suggested in that bug some
-			 * versions of Apache unconditionally return 0
-			 * for BIO_CTRL_WPENDING meaning we don't correctly
-			 * flush data and some operations, like renegotiation,
-			 * don't work. Other software may also be affected so
-			 * call BIO_CTRL_INFO to retain compatibility with
-			 * previous behaviour and BIO_CTRL_WPENDING if we
-			 * get zero to address the PR#1949 case.
+
+			/* This code originally checked to see if
+			 * any data was pending using BIO_CTRL_INFO
+			 * and then flushed. This caused problems
+			 * as documented in PR#1939. The proposed
+			 * fix doesn't completely resolve this issue
+			 * as buggy implementations of BIO_CTRL_PENDING
+			 * still exist. So instead we just flush
+			 * unconditionally.
 			 */
 
-			num1=BIO_ctrl(s->wbio,BIO_CTRL_INFO,0,NULL);
-			if (num1 == 0)
-				num1=BIO_ctrl(s->wbio,BIO_CTRL_WPENDING,0,NULL);
-			if (num1 > 0)
+			s->rwstate=SSL_WRITING;
+			if (BIO_flush(s->wbio) <= 0)
 				{
-				s->rwstate=SSL_WRITING;
-				num1=BIO_flush(s->wbio);
-				if (num1 <= 0) { ret= -1; goto end; }
-				s->rwstate=SSL_NOTHING;
+				ret= -1;
+				goto end;
 				}
+			s->rwstate=SSL_NOTHING;
 
 			s->state=s->s3->tmp.next_state;
 			break;