From: Dr. Stephen Henson <steve@openssl.org>
Date: Tue, 22 Mar 2005 14:11:06 +0000 (+0000)
Subject: Ensure (SSL_RANDOM_BYTES - 4) of pseudo random data is used for server and
X-Git-Tag: OpenSSL_0_9_7g~17^2~20
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=59b6836ab2cff27c9d7062699abcbf805350b8ad

Ensure (SSL_RANDOM_BYTES - 4) of pseudo random data is used for server and
client random values.
---

diff --git a/CHANGES b/CHANGES
index f6b293d3a1..7c3722ee28 100644
--- a/CHANGES
+++ b/CHANGES
@@ -763,6 +763,28 @@
 
  Changes between 0.9.7e and 0.9.7f  [XX xxx XXXX]
 
+  *) Use (SSL_RANDOM_VALUE - 4) bytes of pseudo random data when generating
+     server and client random values. Previously
+     (SSL_RANDOM_VALUE - sizeof(time_t)) would be used which would result in
+     less random data when sizeof(time_t) > 4 (some 64 bit platforms).
+
+     This change has negligible security impact because:
+
+     1. Server and client random values still have 24 bytes of pseudo random
+        data.
+
+     2. Server and client random values are sent in the clear in the initial
+        handshake.
+
+     3. The master secret is derived using the premaster secret (48 bytes in
+        size for static RSA ciphersuites) as well as client server and random
+        values.
+
+     The OpenSSL team would like to thank the UK NISCC for bringing this issue
+     to our attention. 
+
+     [Stephen Henson, reported by UK NISCC]
+
   *) Use Windows randomness collection on Cygwin.
      [Ulf Möller]
 
diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 56dbf75fe3..54598f0f8b 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -562,7 +562,7 @@ static int ssl3_client_hello(SSL *s)
 		p=s->s3->client_random;
 		Time=time(NULL);			/* Time */
 		l2n(Time,p);
-		RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE-sizeof(Time));
+		RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE-4);
 
 		/* Do the message type and length last */
 		d=p= &(buf[4]);
diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c
index 898f49810c..28b30fec23 100644
--- a/ssl/s3_srvr.c
+++ b/ssl/s3_srvr.c
@@ -996,7 +996,7 @@ static int ssl3_send_server_hello(SSL *s)
 		p=s->s3->server_random;
 		Time=time(NULL);			/* Time */
 		l2n(Time,p);
-		RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE-sizeof(Time));
+		RAND_pseudo_bytes(p,SSL3_RANDOM_SIZE-4);
 		/* Do the message type and length last */
 		d=p= &(buf[4]);