Commit 4af79303 authored by Nick Mathewson's avatar Nick Mathewson
Browse files

Do not include a timestamp in the ClientHello Random field. 

Instead, send random bytes.

While the gmt_unix_time record was added in an ostensible attempt to
mitigate the dangers of a bad RNG, its presence leaks the host's view
of the current time in the clear.  This minor leak can help
fingerprint TLS instances across networks and protocols... and what's
worse, it's doubtful thet the gmt_unix_time record does any good at
all for its intended purpose, since:

    * It's quite possible to open two TLS connections in one second.
    * If the PRNG output is prone to repeat itself, ephemeral
    * handshakes (and who knows what else besides) are broken.
parent 46ebd9e3

ssl/d1_clnt.c

+2 −4
Original line number Diff line number Diff line
@@ -773,7 +773,7 @@ int dtls1_client_hello(SSL *s) 
	unsigned char *buf;

	unsigned char *p,*d;

	unsigned int i,j;

	unsigned long Time,l;

	unsigned long l;

	SSL_COMP *comp;



	buf=(unsigned char *)s->init_buf->data;
@@ -801,9 +801,7 @@ int dtls1_client_hello(SSL *s) 
		for (i=0;p[i]=='\0' && i<sizeof(s->s3->client_random);i++) ;

		if (i==sizeof(s->s3->client_random))

			{

			Time=(unsigned long)time(NULL);	/* Time */

			l2n(Time,p);

			RAND_pseudo_bytes(p,sizeof(s->s3->client_random)-4);

			RAND_pseudo_bytes(p,sizeof(s->s3->client_random));

			}



		/* Do the message type and length last */

ssl/s23_clnt.c

+2 −4
Original line number Diff line number Diff line
@@ -274,7 +274,7 @@ static int ssl23_client_hello(SSL *s) 
	unsigned char *buf;

	unsigned char *p,*d;

	int i,ch_len;

	unsigned long Time,l;

	unsigned long l;

	int ssl2_compat;

	int version = 0, version_major, version_minor;

#ifndef OPENSSL_NO_COMP
@@ -355,9 +355,7 @@ static int ssl23_client_hello(SSL *s) 
#endif



		p=s->s3->client_random;

		Time=(unsigned long)time(NULL);		/* Time */

		l2n(Time,p);

		if (RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE-4) <= 0)

		if (RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE) <= 0)

			return -1;



		if (version == TLS1_2_VERSION)

ssl/s3_clnt.c

+2 −4
Original line number Diff line number Diff line
@@ -655,7 +655,7 @@ int ssl3_client_hello(SSL *s) 
	unsigned char *buf;

	unsigned char *p,*d;

	int i;

	unsigned long Time,l;

	unsigned long l;

#ifndef OPENSSL_NO_COMP

	int j;

	SSL_COMP *comp;
@@ -680,9 +680,7 @@ int ssl3_client_hello(SSL *s) 
		/* else use the pre-loaded session */



		p=s->s3->client_random;

		Time=(unsigned long)time(NULL);			/* Time */

		l2n(Time,p);

		if (RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE-4) <= 0)

		if (RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE) <= 0)

			goto err;



		/* Do the message type and length last */