From 2ae47ddbc27505652b855449b23d80614c864329 Mon Sep 17 00:00:00 2001
From: "Dr. Stephen Henson" <steve@openssl.org>
Date: Tue, 16 Nov 2010 14:26:18 +0000
Subject: [PATCH] fix CVE-2010-3864

---
 CHANGES      |  5 +++++
 NEWS         |  4 ++++
 ssl/t1_lib.c | 18 ++++++++++++++----
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/CHANGES b/CHANGES
index 23f145ca36..1b5db78d35 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,11 @@
 
  Changes between 0.9.8o and 0.9.8p [xx XXX xxxx]
 
+  *) Fix extension code to avoid race conditions which can result in a buffer
+     overrun vulnerability: resumed sessions must not be modified as they can
+     be shared by multiple threads. CVE-2010-3864
+     [Steve Henson]
+
   *) Fix for double free bug in ssl/s3_clnt.c CVE-2010-2939
      [Steve Henson]
 
diff --git a/NEWS b/NEWS
index 857fb94945..65f4ef2050 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,10 @@
   This file gives a brief overview of the major changes between each OpenSSL
   release. For more details please read the CHANGES file.
 
+  Major changes between OpenSSL 0.9.8o and OpenSSL 0.9.8p:
+
+      o Fix for security issue CVE-2010-3864.
+
   Major changes between OpenSSL 0.9.8n and OpenSSL 0.9.8o:
 
       o Fix for security issue CVE-2010-0742.
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index d61c08c8ef..0cc8320e17 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -432,14 +432,23 @@ int ssl_parse_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char *d, in
 				switch (servname_type)
 					{
 				case TLSEXT_NAMETYPE_host_name:
-					if (s->session->tlsext_hostname == NULL)
+					if (!s->hit)
 						{
-						if (len > TLSEXT_MAXLEN_host_name || 
-							((s->session->tlsext_hostname = OPENSSL_malloc(len+1)) == NULL))
+						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) {
@@ -452,7 +461,8 @@ int ssl_parse_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char *d, in
 
 						}
 					else 
-						s->servername_done = strlen(s->session->tlsext_hostname) == len 
+						s->servername_done = s->session->tlsext_hostname
+							&& strlen(s->session->tlsext_hostname) == len 
 							&& strncmp(s->session->tlsext_hostname, (char *)sdata, len) == 0;
 					
 					break;