diff --git a/mozilla/security/nss/lib/ssl/ssl3con.c b/mozilla/security/nss/lib/ssl/ssl3con.c
index 246c2d80a87..3951be4b9c4 100644
--- a/mozilla/security/nss/lib/ssl/ssl3con.c
+++ b/mozilla/security/nss/lib/ssl/ssl3con.c
@@ -32,7 +32,7 @@
  * may use your version of this file under either the MPL or the
  * GPL.
  *
- * $Id: ssl3con.c,v 1.5 2000-05-18 15:32:18 mcgreer%netscape.com Exp $
+ * $Id: ssl3con.c,v 1.6 2000-05-24 03:35:23 nelsonb%netscape.com Exp $
  */
 
 #include "cert.h"
@@ -1813,6 +1813,7 @@ ssl3_GenerateSessionKeys(sslSocket *ss, const PK11SymKey *pms)
     SECItem           params;
     int               keySize;
     CK_FLAGS          keyFlags;
+    CK_VERSION        pms_version;
     CK_SSL3_KEY_MAT_PARAMS key_material_params;
     CK_SSL3_KEY_MAT_OUT    returnedKeys;
     CK_SSL3_MASTER_KEY_DERIVE_PARAMS master_params;
@@ -1832,7 +1833,7 @@ ssl3_GenerateSessionKeys(sslSocket *ss, const PK11SymKey *pms)
     }
 
     if (pms || !pwSpec->master_secret) {
-	master_params.pVersion                     = NULL;
+	master_params.pVersion                     = &pms_version;
 	master_params.RandomInfo.pClientRandom     = cr;
 	master_params.RandomInfo.ulClientRandomLen = SSL3_RANDOM_LENGTH;
 	master_params.RandomInfo.pServerRandom     = sr;
@@ -1846,6 +1847,15 @@ ssl3_GenerateSessionKeys(sslSocket *ss, const PK11SymKey *pms)
 	pwSpec->master_secret = PK11_DeriveWithFlags((PK11SymKey *)pms, 
 					master_derive, &params, key_derive, 
 					CKA_DERIVE, 0, keyFlags);
+	if (pwSpec->master_secret != NULL && ss->detectRollBack) {
+	    SSL3ProtocolVersion client_version;
+	    client_version = pms_version.major << 8 | pms_version.minor;
+	    if (client_version != ss->clientHelloVersion) {
+		/* Destroy it.  Version roll-back detected. */
+		PK11_FreeSymKey(pwSpec->master_secret);
+	    	pwSpec->master_secret = NULL;
+	    }
+	}
 	if (pwSpec->master_secret == NULL) {
 	    /* Generate a faux master secret in the same slot as the old one. */
 	    PK11SlotInfo * slot = PK11_GetSlotFromKey((PK11SymKey *)pms);
@@ -2556,7 +2566,8 @@ ssl3_SendClientHello(sslSocket *ss)
 	return rv;	/* err set by ssl3_AppendHandshake* */
     }
 
-    rv = ssl3_AppendHandshakeNumber(ss, ss->version, 2);
+    ss->clientHelloVersion = ss->version;
+    rv = ssl3_AppendHandshakeNumber(ss, ss->clientHelloVersion, 2);
     if (rv != SECSuccess) {
 	return rv;	/* err set by ssl3_AppendHandshake* */
     }
@@ -4545,7 +4556,7 @@ ssl3_HandleClientHello(sslSocket *ss, SSL3Opaque *b, PRUint32 length)
     tmp = ssl3_ConsumeHandshakeNumber(ss, 2, &b, &length);
     if (tmp < 0)
 	goto loser;		/* malformed, alert already sent */
-    version = (SSL3ProtocolVersion)tmp;
+    ss->clientHelloVersion = version = (SSL3ProtocolVersion)tmp;
     rv = ssl3_NegotiateVersion(ss, version);
     if (rv != SECSuccess) {
 	/* We can't do the usual isTLS test here, because the negotiated
@@ -4968,6 +4979,7 @@ ssl3_HandleV2ClientHello(sslSocket *ss, unsigned char *buffer, int length)
     suite_length = (buffer[3] << 8) | buffer[4];
     sid_length   = (buffer[5] << 8) | buffer[6];
     rand_length  = (buffer[7] << 8) | buffer[8];
+    ss->clientHelloVersion = version;
 
     rv = ssl3_NegotiateVersion(ss, version);
     if (rv != SECSuccess) {
@@ -5722,8 +5734,8 @@ ssl3_GenerateRSAPMS(sslSocket *ss, ssl3CipherSpec *spec,
     }
 
     /* Generate the pre-master secret ...  */
-    version.major = MSB(ss->version);
-    version.minor = LSB(ss->version);
+    version.major = MSB(ss->clientHelloVersion);
+    version.minor = LSB(ss->clientHelloVersion);
 
     param.data = (unsigned char *)&version;
     param.len  = sizeof version;
@@ -5777,7 +5789,10 @@ ssl3_HandleRSAClientKeyExchange(sslSocket *ss,
 	}
     }
     /*
-     * decrypt out of the incoming buffer
+     * decrypt pms out of the incoming buffer
+     * Note: CKM_SSL3_PRE_MASTER_KEY_GEN is NOT the mechanism used to do 
+     *	the unwrap.  Rather, it is the mechanism with which the unwrapped
+     *	pms will be used.
      */
     pms = PK11_PubUnwrapSymKey(serverKey, &enc_pms,
 			       CKM_SSL3_PRE_MASTER_KEY_GEN, CKA_DERIVE, 0);
diff --git a/mozilla/security/nss/lib/ssl/sslcon.c b/mozilla/security/nss/lib/ssl/sslcon.c
index 6a9cc564fff..4cc859e62c5 100644
--- a/mozilla/security/nss/lib/ssl/sslcon.c
+++ b/mozilla/security/nss/lib/ssl/sslcon.c
@@ -32,7 +32,7 @@
  * may use your version of this file under either the MPL or the
  * GPL.
  *
- * $Id: sslcon.c,v 1.1 2000-03-31 19:33:44 relyea%netscape.com Exp $
+ * $Id: sslcon.c,v 1.2 2000-05-24 03:35:23 nelsonb%netscape.com Exp $
  */
 
 #include "cert.h"
@@ -3075,16 +3075,15 @@ invalid:
     cp = msg = ci->sendBuf.buf;
     msg[0] = SSL_MT_CLIENT_HELLO;
     if ( ss->enableTLS ) {
-	msg[1] = MSB(SSL_LIBRARY_VERSION_3_1_TLS);
-	msg[2] = LSB(SSL_LIBRARY_VERSION_3_1_TLS);
+	ss->clientHelloVersion = SSL_LIBRARY_VERSION_3_1_TLS;
     } else if ( ss->enableSSL3 ) {
-	msg[1] = MSB(SSL_LIBRARY_VERSION_3_0);
-	msg[2] = LSB(SSL_LIBRARY_VERSION_3_0);
+	ss->clientHelloVersion = SSL_LIBRARY_VERSION_3_0;
     } else {
-	msg[1] = MSB(SSL_LIBRARY_VERSION_2);
-	msg[2] = LSB(SSL_LIBRARY_VERSION_2);
+	ss->clientHelloVersion = SSL_LIBRARY_VERSION_2;
     }
     
+    msg[1] = MSB(ss->clientHelloVersion);
+    msg[2] = LSB(ss->clientHelloVersion);
     msg[3] = MSB(localCipherSize);
     msg[4] = LSB(localCipherSize);
     msg[5] = MSB(sidLen);
diff --git a/mozilla/security/nss/lib/ssl/sslimpl.h b/mozilla/security/nss/lib/ssl/sslimpl.h
index 77f56616aa7..4454ed0a602 100644
--- a/mozilla/security/nss/lib/ssl/sslimpl.h
+++ b/mozilla/security/nss/lib/ssl/sslimpl.h
@@ -33,7 +33,7 @@
  * may use your version of this file under either the MPL or the
  * GPL.
  *
- * $Id: sslimpl.h,v 1.2 2000-05-12 18:43:28 dougt%netscape.com Exp $
+ * $Id: sslimpl.h,v 1.3 2000-05-24 03:35:23 nelsonb%netscape.com Exp $
  */
 
 #ifndef __sslimpl_h_
@@ -222,6 +222,22 @@ typedef struct {
 
 #define ssl_V3_SUITES_IMPLEMENTED 13
 
+typedef struct sslOptionsStr {
+    unsigned int useSecurity		: 1;  /*  1 */
+    unsigned int useSocks		: 1;  /*  2 */
+    unsigned int requestCertificate	: 1;  /*  3 */
+    unsigned int requireCertificate	: 2;  /*  4-5 */
+    unsigned int handshakeAsClient	: 1;  /*  6 */
+    unsigned int handshakeAsServer	: 1;  /*  7 */
+    unsigned int enableSSL2		: 1;  /*  8 */
+    unsigned int enableSSL3		: 1;  /*  9 */
+    unsigned int enableTLS		: 1;  /* 10 */
+    unsigned int noCache		: 1;  /* 11 */
+    unsigned int fdx			: 1;  /* 12 */
+    unsigned int v2CompatibleHello	: 1;  /* 13 */
+    unsigned int detectRollBack  	: 1;  /* 14 */
+} sslOptions;
+
 /*
 ** SSL Socket struct
 **
@@ -249,11 +265,13 @@ struct sslSocketStr {
     unsigned int     noCache		: 1;
     unsigned int     fdx		: 1; /* simultaneous read/write threads */
     unsigned int     v2CompatibleHello	: 1; /* Send v3+ client hello in v2 format */
+    unsigned int     detectRollBack   	: 1; /* Detect rollback to SSL v3 */
     unsigned int     connected		: 1; /* initial handshake is complete. */
     unsigned int     recvdCloseNotify	: 1; /* received SSL EOF. */
 
     /* version of the protocol to use */
     SSL3ProtocolVersion version;
+    SSL3ProtocolVersion clientHelloVersion; /* version sent in client hello. */
 
     /* Non-zero if socks is enabled */
     sslSocksInfo *   socks;
diff --git a/mozilla/security/nss/lib/ssl/sslsock.c b/mozilla/security/nss/lib/ssl/sslsock.c
index c9c27958f91..8cd4d9ebb59 100644
--- a/mozilla/security/nss/lib/ssl/sslsock.c
+++ b/mozilla/security/nss/lib/ssl/sslsock.c
@@ -34,7 +34,7 @@
  * may use your version of this file under either the MPL or the
  * GPL.
  *
- * $Id: sslsock.c,v 1.1 2000-03-31 19:37:07 relyea%netscape.com Exp $
+ * $Id: sslsock.c,v 1.2 2000-05-24 03:35:23 nelsonb%netscape.com Exp $
  */
 #include "seccomon.h"
 #include "cert.h"
@@ -145,20 +145,7 @@ sslSocketOps ssl_secure_socks_ops = {	/* Both SSL and Socks. */
 /*
 ** default settings for socket enables
 */
-static struct {
-    unsigned int useSecurity		: 1;
-    unsigned int useSocks		: 1;
-    unsigned int requestCertificate	: 1;
-    unsigned int requireCertificate	: 2;
-    unsigned int handshakeAsClient	: 1;
-    unsigned int handshakeAsServer	: 1;
-    unsigned int enableSSL2		: 1;
-    unsigned int enableSSL3		: 1;
-    unsigned int enableTLS		: 1;
-    unsigned int noCache		: 1;
-    unsigned int fdx			: 1;
-    unsigned int v2CompatibleHello	: 1;
-} ssl_defaults = {
+static sslOptions ssl_defaults = {
     PR_TRUE, 	/* useSecurity        */
     PR_FALSE,	/* useSocks           */
     PR_FALSE,	/* requestCertificate */
@@ -167,10 +154,11 @@ static struct {
     PR_FALSE,	/* handshakeAsServer  */
     PR_TRUE,	/* enableSSL2         */
     PR_TRUE,	/* enableSSL3         */
-    PR_FALSE,	/* enableTLS          */
+    PR_TRUE, 	/* enableTLS          */ /* now defaults to on in NSS 3.0 */
     PR_FALSE,	/* noCache            */
     PR_FALSE,	/* fdx                */
     PR_TRUE,	/* v2CompatibleHello  */
+    PR_TRUE,	/* detectRollBack     */
 };
 
 sslSessionIDLookupFunc  ssl_sid_lookup;
@@ -260,6 +248,7 @@ ssl_DupSocket(sslSocket *os)
 	ss->noCache            = os->noCache;
 	ss->fdx                = os->fdx;
 	ss->v2CompatibleHello  = os->v2CompatibleHello;
+	ss->detectRollBack     = os->detectRollBack;
 	ss->peerID             = !os->peerID ? NULL : PORT_Strdup(os->peerID);
 	ss->url                = !os->url    ? NULL : PORT_Strdup(os->url);
 
@@ -596,6 +585,10 @@ SSL_OptionSet(PRFileDesc *fd, PRInt32 which, PRBool on)
 	}
 	break;
 
+      case SSL_ROLLBACK_DETECTION:  
+	ss->detectRollBack = on;
+        break;
+
       default:
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
 	rv = SECFailure;
@@ -641,6 +634,7 @@ SSL_OptionGet(PRFileDesc *fd, PRInt32 which, PRBool *pOn)
     case SSL_NO_CACHE:            on = ss->noCache;            break;
     case SSL_ENABLE_FDX:          on = ss->fdx;                break;
     case SSL_V2_COMPATIBLE_HELLO: on = ss->v2CompatibleHello;  break;
+    case SSL_ROLLBACK_DETECTION:  on = ss->detectRollBack;     break;
 
     default:
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
@@ -678,6 +672,7 @@ SSL_OptionGetDefault(PRInt32 which, PRBool *pOn)
     case SSL_NO_CACHE:            on = ssl_defaults.noCache;		break;
     case SSL_ENABLE_FDX:          on = ssl_defaults.fdx;                break;
     case SSL_V2_COMPATIBLE_HELLO: on = ssl_defaults.v2CompatibleHello;  break;
+    case SSL_ROLLBACK_DETECTION:  on = ssl_defaults.detectRollBack;     break;
 
     default:
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
@@ -760,6 +755,10 @@ SSL_OptionSetDefault(PRInt32 which, PRBool on)
 	}
 	break;
 
+      case SSL_ROLLBACK_DETECTION:  
+	ssl_defaults.detectRollBack = on;
+	break;
+
       default:
 	PORT_SetError(SEC_ERROR_INVALID_ARGS);
 	return SECFailure;
@@ -1769,6 +1768,7 @@ ssl_NewSocket(void)
 	ss->enableTLS          = ssl_defaults.enableTLS ;
 	ss->fdx                = ssl_defaults.fdx;
 	ss->v2CompatibleHello  = ssl_defaults.v2CompatibleHello;
+	ss->detectRollBack     = ssl_defaults.detectRollBack;
 	ss->peer               = 0;
 	ss->port               = 0;
 	ss->noCache            = ssl_defaults.noCache;