Merge branch 'TLS-1.3'

1 files changed, 585 insertions, 124 deletions

diff --git a/security/nss/lib/ssl/ssl3ext.c b/security/nss/lib/ssl/ssl3ext.c
index 271084cf7..ade280903 100644
--- a/security/nss/lib/ssl/ssl3ext.c
+++ b/security/nss/lib/ssl/ssl3ext.c
@@ -14,8 +14,20 @@
 #include "sslimpl.h"
 #include "sslproto.h"
 #include "ssl3exthandle.h"
+#include "tls13err.h"
 #include "tls13exthandle.h"
 
+/* Callback function that handles a received extension. */
+typedef SECStatus (*ssl3ExtensionHandlerFunc)(const sslSocket *ss,
+                                              TLSExtensionData *xtnData,
+                                              SECItem *data);
+
+/* Row in a table of hello extension handlers. */
+typedef struct {
+    SSLExtensionType ex_type;
+    ssl3ExtensionHandlerFunc ex_handler;
+} ssl3ExtensionHandler;
+
 /* Table of handlers for received TLS hello extensions, one per extension.
  * In the second generation, this table will be dynamic, and functions
  * will be registered here.
@@ -31,16 +43,15 @@ static const ssl3ExtensionHandler clientHelloHandlers[] = {
     { ssl_app_layer_protocol_xtn, &ssl3_ServerHandleAppProtoXtn },
     { ssl_use_srtp_xtn, &ssl3_ServerHandleUseSRTPXtn },
     { ssl_cert_status_xtn, &ssl3_ServerHandleStatusRequestXtn },
-    { ssl_signature_algorithms_xtn, &ssl3_ServerHandleSigAlgsXtn },
+    { ssl_signature_algorithms_xtn, &ssl3_HandleSigAlgsXtn },
     { ssl_extended_master_secret_xtn, &ssl3_HandleExtendedMasterSecretXtn },
     { ssl_signed_cert_timestamp_xtn, &ssl3_ServerHandleSignedCertTimestampXtn },
     { ssl_tls13_key_share_xtn, &tls13_ServerHandleKeyShareXtn },
     { ssl_tls13_pre_shared_key_xtn, &tls13_ServerHandlePreSharedKeyXtn },
     { ssl_tls13_early_data_xtn, &tls13_ServerHandleEarlyDataXtn },
-    { ssl_tls13_psk_key_exchange_modes_xtn,
-      &tls13_ServerHandlePskKeyExchangeModesXtn },
-    { ssl_tls13_short_header_xtn, &tls13_HandleShortHeaderXtn },
-    { -1, NULL }
+    { ssl_tls13_psk_key_exchange_modes_xtn, &tls13_ServerHandlePskModesXtn },
+    { ssl_tls13_cookie_xtn, &tls13_ServerHandleCookieXtn },
+    { 0, NULL }
 };
 
 /* These two tables are used by the client, to handle server hello
@@ -59,36 +70,38 @@ static const ssl3ExtensionHandler serverHelloHandlersTLS[] = {
     { ssl_tls13_key_share_xtn, &tls13_ClientHandleKeyShareXtn },
     { ssl_tls13_pre_shared_key_xtn, &tls13_ClientHandlePreSharedKeyXtn },
     { ssl_tls13_early_data_xtn, &tls13_ClientHandleEarlyDataXtn },
-    { ssl_tls13_short_header_xtn, &tls13_HandleShortHeaderXtn },
-    { -1, NULL }
+    { 0, NULL }
 };
 
 static const ssl3ExtensionHandler helloRetryRequestHandlers[] = {
     { ssl_tls13_key_share_xtn, tls13_ClientHandleKeyShareXtnHrr },
     { ssl_tls13_cookie_xtn, tls13_ClientHandleHrrCookie },
-    { -1, NULL }
+    { 0, NULL }
 };
 
 static const ssl3ExtensionHandler serverHelloHandlersSSL3[] = {
     { ssl_renegotiation_info_xtn, &ssl3_HandleRenegotiationInfoXtn },
-    { -1, NULL }
+    { 0, NULL }
 };
 
 static const ssl3ExtensionHandler newSessionTicketHandlers[] = {
-    { ssl_tls13_ticket_early_data_info_xtn,
-      &tls13_ClientHandleTicketEarlyDataInfoXtn },
-    { -1, NULL }
+    { ssl_tls13_early_data_xtn,
+      &tls13_ClientHandleTicketEarlyDataXtn },
+    { 0, NULL }
 };
 
 /* This table is used by the client to handle server certificates in TLS 1.3 */
 static const ssl3ExtensionHandler serverCertificateHandlers[] = {
     { ssl_signed_cert_timestamp_xtn, &ssl3_ClientHandleSignedCertTimestampXtn },
     { ssl_cert_status_xtn, &ssl3_ClientHandleStatusRequestXtn },
-    { -1, NULL }
+    { 0, NULL }
 };
 
 static const ssl3ExtensionHandler certificateRequestHandlers[] = {
-    { -1, NULL }
+    { ssl_signature_algorithms_xtn, &ssl3_HandleSigAlgsXtn },
+    { ssl_tls13_certificate_authorities_xtn,
+      &tls13_ClientHandleCertAuthoritiesXtn },
+    { 0, NULL }
 };
 
 /* Tables of functions to format TLS hello extensions, one function per
@@ -101,14 +114,14 @@ static const ssl3ExtensionHandler certificateRequestHandlers[] = {
  * the client hello is empty (for example, the extended master secret
  * extension, if it were listed last). See bug 1243641.
  */
-static const ssl3HelloExtensionSender clientHelloSendersTLS[SSL_MAX_EXTENSIONS] =
+static const sslExtensionBuilder clientHelloSendersTLS[] =
     {
-      { ssl_server_name_xtn, &ssl3_SendServerNameXtn },
+      { ssl_server_name_xtn, &ssl3_ClientSendServerNameXtn },
       { ssl_extended_master_secret_xtn, &ssl3_SendExtendedMasterSecretXtn },
       { ssl_renegotiation_info_xtn, &ssl3_SendRenegotiationInfoXtn },
       { ssl_supported_groups_xtn, &ssl_SendSupportedGroupsXtn },
       { ssl_ec_point_formats_xtn, &ssl3_SendSupportedPointFormatsXtn },
-      { ssl_session_ticket_xtn, &ssl3_SendSessionTicketXtn },
+      { ssl_session_ticket_xtn, &ssl3_ClientSendSessionTicketXtn },
       { ssl_next_proto_nego_xtn, &ssl3_ClientSendNextProtoNegoXtn },
       { ssl_app_layer_protocol_xtn, &ssl3_ClientSendAppProtoXtn },
       { ssl_use_srtp_xtn, &ssl3_ClientSendUseSRTPXtn },
@@ -121,22 +134,155 @@ static const ssl3HelloExtensionSender clientHelloSendersTLS[SSL_MAX_EXTENSIONS]
        * client hello is empty. They are not intolerant of TLS 1.2, so list
        * signature_algorithms at the end. See bug 1243641. */
       { ssl_tls13_supported_versions_xtn, &tls13_ClientSendSupportedVersionsXtn },
-      { ssl_tls13_short_header_xtn, &tls13_SendShortHeaderXtn },
-      { ssl_signature_algorithms_xtn, &ssl3_ClientSendSigAlgsXtn },
+      { ssl_signature_algorithms_xtn, &ssl3_SendSigAlgsXtn },
       { ssl_tls13_cookie_xtn, &tls13_ClientSendHrrCookieXtn },
-      { ssl_tls13_psk_key_exchange_modes_xtn,
-        &tls13_ClientSendPskKeyExchangeModesXtn },
-      { ssl_padding_xtn, &ssl3_ClientSendPaddingExtension },
+      { ssl_tls13_psk_key_exchange_modes_xtn, &tls13_ClientSendPskModesXtn },
       /* The pre_shared_key extension MUST be last. */
       { ssl_tls13_pre_shared_key_xtn, &tls13_ClientSendPreSharedKeyXtn },
-      /* any extra entries will appear as { 0, NULL }    */
+      { 0, NULL }
     };
 
-static const ssl3HelloExtensionSender clientHelloSendersSSL3[SSL_MAX_EXTENSIONS] = {
-    { ssl_renegotiation_info_xtn, &ssl3_SendRenegotiationInfoXtn }
-    /* any extra entries will appear as { 0, NULL }    */
+static const sslExtensionBuilder clientHelloSendersSSL3[] = {
+    { ssl_renegotiation_info_xtn, &ssl3_SendRenegotiationInfoXtn },
+    { 0, NULL }
+};
+
+static const sslExtensionBuilder tls13_cert_req_senders[] = {
+    { ssl_signature_algorithms_xtn, &ssl3_SendSigAlgsXtn },
+    { ssl_tls13_certificate_authorities_xtn, &tls13_SendCertAuthoritiesXtn },
+    { 0, NULL }
+};
+
+static const sslExtensionBuilder tls13_hrr_senders[] = {
+    { ssl_tls13_key_share_xtn, &tls13_ServerSendHrrKeyShareXtn },
+    { ssl_tls13_cookie_xtn, &tls13_ServerSendHrrCookieXtn },
+    { ssl_tls13_supported_versions_xtn, &tls13_ServerSendSupportedVersionsXtn },
+    { 0, NULL }
+};
+
+static const struct {
+    SSLExtensionType type;
+    SSLExtensionSupport support;
+} ssl_supported_extensions[] = {
+    { ssl_server_name_xtn, ssl_ext_native_only },
+    { ssl_cert_status_xtn, ssl_ext_native },
+    { ssl_supported_groups_xtn, ssl_ext_native_only },
+    { ssl_ec_point_formats_xtn, ssl_ext_native },
+    { ssl_signature_algorithms_xtn, ssl_ext_native_only },
+    { ssl_use_srtp_xtn, ssl_ext_native },
+    { ssl_app_layer_protocol_xtn, ssl_ext_native_only },
+    { ssl_signed_cert_timestamp_xtn, ssl_ext_native },
+    { ssl_padding_xtn, ssl_ext_native },
+    { ssl_extended_master_secret_xtn, ssl_ext_native_only },
+    { ssl_session_ticket_xtn, ssl_ext_native_only },
+    { ssl_tls13_key_share_xtn, ssl_ext_native_only },
+    { ssl_tls13_pre_shared_key_xtn, ssl_ext_native_only },
+    { ssl_tls13_early_data_xtn, ssl_ext_native_only },
+    { ssl_tls13_supported_versions_xtn, ssl_ext_native_only },
+    { ssl_tls13_cookie_xtn, ssl_ext_native_only },
+    { ssl_tls13_psk_key_exchange_modes_xtn, ssl_ext_native_only },
+    { ssl_tls13_ticket_early_data_info_xtn, ssl_ext_native_only },
+    { ssl_tls13_certificate_authorities_xtn, ssl_ext_native },
+    { ssl_next_proto_nego_xtn, ssl_ext_none },
+    { ssl_renegotiation_info_xtn, ssl_ext_native }
 };
 
+static SSLExtensionSupport
+ssl_GetExtensionSupport(PRUint16 type)
+{
+    unsigned int i;
+    for (i = 0; i < PR_ARRAY_SIZE(ssl_supported_extensions); ++i) {
+        if (type == ssl_supported_extensions[i].type) {
+            return ssl_supported_extensions[i].support;
+        }
+    }
+    return ssl_ext_none;
+}
+
+SECStatus
+SSLExp_GetExtensionSupport(PRUint16 type, SSLExtensionSupport *support)
+{
+    *support = ssl_GetExtensionSupport(type);
+    return SECSuccess;
+}
+
+SECStatus
+SSLExp_InstallExtensionHooks(PRFileDesc *fd, PRUint16 extension,
+                             SSLExtensionWriter writer, void *writerArg,
+                             SSLExtensionHandler handler, void *handlerArg)
+{
+    sslSocket *ss = ssl_FindSocket(fd);
+    PRCList *cursor;
+    sslCustomExtensionHooks *hook;
+
+    if (!ss) {
+        return SECFailure; /* Code already set. */
+    }
+
+    /* Need to specify both or neither, but not just one. */
+    if ((writer && !handler) || (!writer && handler)) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+
+    if (ssl_GetExtensionSupport(extension) == ssl_ext_native_only) {
+        PORT_SetError(SEC_ERROR_INVALID_ARGS);
+        return SECFailure;
+    }
+
+    if (ss->firstHsDone || ((ss->ssl3.hs.ws != idle_handshake) &&
+                            (ss->ssl3.hs.ws != wait_client_hello))) {
+        PORT_SetError(PR_INVALID_STATE_ERROR);
+        return SECFailure;
+    }
+
+    /* Remove any old handler. */
+    for (cursor = PR_NEXT_LINK(&ss->extensionHooks);
+         cursor != &ss->extensionHooks;
+         cursor = PR_NEXT_LINK(cursor)) {
+        hook = (sslCustomExtensionHooks *)cursor;
+        if (hook->type == extension) {
+            PR_REMOVE_LINK(&hook->link);
+            PORT_Free(hook);
+            break;
+        }
+    }
+
+    if (!writer && !handler) {
+        return SECSuccess;
+    }
+
+    hook = PORT_ZNew(sslCustomExtensionHooks);
+    if (!hook) {
+        return SECFailure; /* This removed the old one, oh well. */
+    }
+
+    hook->type = extension;
+    hook->writer = writer;
+    hook->writerArg = writerArg;
+    hook->handler = handler;
+    hook->handlerArg = handlerArg;
+    PR_APPEND_LINK(&hook->link, &ss->extensionHooks);
+    return SECSuccess;
+}
+
+static sslCustomExtensionHooks *
+ssl_FindCustomExtensionHooks(sslSocket *ss, PRUint16 extension)
+{
+    PRCList *cursor;
+
+    for (cursor = PR_NEXT_LINK(&ss->extensionHooks);
+         cursor != &ss->extensionHooks;
+         cursor = PR_NEXT_LINK(cursor)) {
+        sslCustomExtensionHooks *hook = (sslCustomExtensionHooks *)cursor;
+        if (hook->type == extension) {
+            return hook;
+        }
+    }
+
+    return NULL;
+}
+
 static PRBool
 arrayContainsExtension(const PRUint16 *array, PRUint32 len, PRUint16 ex_type)
 {
@@ -156,8 +302,11 @@ ssl3_ExtensionNegotiated(const sslSocket *ss, PRUint16 ex_type)
                                   xtnData->numNegotiated, ex_type);
 }
 
+/* This checks for whether an extension was advertised.  On the client, this
+ * covers extensions that are sent in ClientHello; on the server, extensions
+ * sent in CertificateRequest (TLS 1.3 only). */
 PRBool
-ssl3_ClientExtensionAdvertised(const sslSocket *ss, PRUint16 ex_type)
+ssl3_ExtensionAdvertised(const sslSocket *ss, PRUint16 ex_type)
 {
     const TLSExtensionData *xtnData = &ss->xtnData;
     return arrayContainsExtension(xtnData->advertised,
@@ -240,6 +389,44 @@ ssl3_FindExtension(sslSocket *ss, SSLExtensionType extension_type)
     return NULL;
 }
 
+static SECStatus
+ssl_CallExtensionHandler(sslSocket *ss, SSLHandshakeType handshakeMessage,
+                         TLSExtension *extension,
+                         const ssl3ExtensionHandler *handler)
+{
+    SECStatus rv = SECSuccess;
+    SSLAlertDescription alert = handshake_failure;
+    sslCustomExtensionHooks *customHooks;
+
+    customHooks = ssl_FindCustomExtensionHooks(ss, extension->type);
+    if (customHooks) {
+        if (customHooks->handler) {
+            rv = customHooks->handler(ss->fd, handshakeMessage,
+                                      extension->data.data,
+                                      extension->data.len,
+                                      &alert, customHooks->handlerArg);
+        }
+    } else {
+        /* Find extension_type in table of Hello Extension Handlers. */
+        for (; handler->ex_handler != NULL; ++handler) {
+            if (handler->ex_type == extension->type) {
+                rv = (*handler->ex_handler)(ss, &ss->xtnData, &extension->data);
+                break;
+            }
+        }
+    }
+
+    if (rv != SECSuccess) {
+        if (!ss->ssl3.fatalAlertSent) {
+            /* Send an alert if the handler didn't already. */
+            (void)SSL3_SendAlert(ss, alert_fatal, alert);
+        }
+        return SECFailure;
+    }
+
+    return SECSuccess;
+}
+
 /* Go through the hello extensions in |ss->ssl3.hs.remoteExtensions|.
  * For each one, find the extension handler in the table, and
  * if present, invoke that handler.
@@ -250,42 +437,46 @@ ssl3_FindExtension(sslSocket *ss, SSLExtensionType extension_type)
  * right phase.
  */
 SECStatus
-ssl3_HandleParsedExtensions(sslSocket *ss,
-                            SSL3HandshakeType handshakeMessage)
+ssl3_HandleParsedExtensions(sslSocket *ss, SSLHandshakeType message)
 {
     const ssl3ExtensionHandler *handlers;
     /* HelloRetryRequest doesn't set ss->version. It might be safe to
      * do so, but we weren't entirely sure. TODO(ekr@rtfm.com). */
     PRBool isTLS13 = (ss->version >= SSL_LIBRARY_VERSION_TLS_1_3) ||
-                     (handshakeMessage == hello_retry_request);
+                     (message == ssl_hs_hello_retry_request);
+    /* The following messages can include extensions that were not included in
+     * the original ClientHello. */
+    PRBool allowNotOffered = (message == ssl_hs_client_hello) ||
+                             (message == ssl_hs_certificate_request) ||
+                             (message == ssl_hs_new_session_ticket);
     PRCList *cursor;
 
-    switch (handshakeMessage) {
-        case client_hello:
+    switch (message) {
+        case ssl_hs_client_hello:
             handlers = clientHelloHandlers;
             break;
-        case new_session_ticket:
+        case ssl_hs_new_session_ticket:
             PORT_Assert(ss->version >= SSL_LIBRARY_VERSION_TLS_1_3);
             handlers = newSessionTicketHandlers;
             break;
-        case hello_retry_request:
+        case ssl_hs_hello_retry_request:
             handlers = helloRetryRequestHandlers;
             break;
-        case encrypted_extensions:
+        case ssl_hs_encrypted_extensions:
             PORT_Assert(ss->version >= SSL_LIBRARY_VERSION_TLS_1_3);
         /* fall through */
-        case server_hello:
+        case ssl_hs_server_hello:
             if (ss->version > SSL_LIBRARY_VERSION_3_0) {
                 handlers = serverHelloHandlersTLS;
             } else {
                 handlers = serverHelloHandlersSSL3;
             }
             break;
-        case certificate:
+        case ssl_hs_certificate:
             PORT_Assert(!ss->sec.isServer);
             handlers = serverCertificateHandlers;
             break;
-        case certificate_request:
+        case ssl_hs_certificate_request:
             PORT_Assert(!ss->sec.isServer);
             handlers = certificateRequestHandlers;
             break;
@@ -299,28 +490,39 @@ ssl3_HandleParsedExtensions(sslSocket *ss,
          cursor != &ss->ssl3.hs.remoteExtensions;
          cursor = PR_NEXT_LINK(cursor)) {
         TLSExtension *extension = (TLSExtension *)cursor;
-        const ssl3ExtensionHandler *handler;
+        SECStatus rv;
 
         /* Check whether the server sent an extension which was not advertised
-         * in the ClientHello */
-        if (!ss->sec.isServer &&
-            !ssl3_ClientExtensionAdvertised(ss, extension->type) &&
-            (handshakeMessage != new_session_ticket) &&
-            (extension->type != ssl_tls13_cookie_xtn)) {
+         * in the ClientHello.
+         *
+         * Note that a TLS 1.3 server should check if CertificateRequest
+         * extensions were sent.  But the extensions used for CertificateRequest
+         * do not have any response, so we rely on
+         * ssl3_ExtensionAdvertised to return false on the server.  That
+         * results in the server only rejecting any extension. */
+        if (!allowNotOffered && (extension->type != ssl_tls13_cookie_xtn) &&
+            !ssl3_ExtensionAdvertised(ss, extension->type)) {
             (void)SSL3_SendAlert(ss, alert_fatal, unsupported_extension);
             PORT_SetError(SSL_ERROR_RX_UNEXPECTED_EXTENSION);
             return SECFailure;
         }
 
         /* Check that this is a legal extension in TLS 1.3 */
-        if (isTLS13 && !tls13_ExtensionAllowed(extension->type, handshakeMessage)) {
-            if (handshakeMessage == client_hello) {
-                /* Skip extensions not used in TLS 1.3 */
-                continue;
+        if (isTLS13 &&
+            !ssl_FindCustomExtensionHooks(ss, extension->type)) {
+            switch (tls13_ExtensionStatus(extension->type, message)) {
+                case tls13_extension_allowed:
+                    break;
+                case tls13_extension_unknown:
+                    if (allowNotOffered) {
+                        continue; /* Skip over unknown extensions. */
+                    }
+                /* Fall through. */
+                case tls13_extension_disallowed:
+                    tls13_FatalError(ss, SSL_ERROR_EXTENSION_DISALLOWED_FOR_VERSION,
+                                     unsupported_extension);
+                    return SECFailure;
             }
-            tls13_FatalError(ss, SSL_ERROR_EXTENSION_DISALLOWED_FOR_VERSION,
-                             unsupported_extension);
-            return SECFailure;
         }
 
         /* Special check for this being the last extension if it's
@@ -334,23 +536,9 @@ ssl3_HandleParsedExtensions(sslSocket *ss,
             return SECFailure;
         }
 
-        /* find extension_type in table of Hello Extension Handlers */
-        for (handler = handlers; handler->ex_type >= 0; handler++) {
-            /* if found, call this handler */
-            if (handler->ex_type == extension->type) {
-                SECStatus rv;
-
-                rv = (*handler->ex_handler)(ss, &ss->xtnData,
-                                            (PRUint16)extension->type,
-                                            &extension->data);
-                if (rv != SECSuccess) {
-                    if (!ss->ssl3.fatalAlertSent) {
-                        /* send a generic alert if the handler didn't already */
-                        (void)SSL3_SendAlert(ss, alert_fatal, handshake_failure);
-                    }
-                    return SECFailure;
-                }
-            }
+        rv = ssl_CallExtensionHandler(ss, message, extension, handlers);
+        if (rv != SECSuccess) {
+            return SECFailure;
         }
     }
     return SECSuccess;
@@ -361,7 +549,7 @@ ssl3_HandleParsedExtensions(sslSocket *ss,
 SECStatus
 ssl3_HandleExtensions(sslSocket *ss,
                       PRUint8 **b, PRUint32 *length,
-                      SSL3HandshakeType handshakeMessage)
+                      SSLHandshakeType handshakeMessage)
 {
     SECStatus rv;
 
@@ -383,21 +571,30 @@ SECStatus
 ssl3_RegisterExtensionSender(const sslSocket *ss,
                              TLSExtensionData *xtnData,
                              PRUint16 ex_type,
-                             ssl3HelloExtensionSenderFunc cb)
+                             sslExtensionBuilderFunc cb)
 {
     int i;
-    ssl3HelloExtensionSender *sender;
+    sslExtensionBuilder *sender;
     if (ss->version < SSL_LIBRARY_VERSION_TLS_1_3) {
         sender = &xtnData->serverHelloSenders[0];
     } else {
-        if (tls13_ExtensionAllowed(ex_type, server_hello)) {
-            PORT_Assert(!tls13_ExtensionAllowed(ex_type, encrypted_extensions));
+        if (tls13_ExtensionStatus(ex_type, ssl_hs_server_hello) ==
+            tls13_extension_allowed) {
+            PORT_Assert(tls13_ExtensionStatus(ex_type,
+                                              ssl_hs_encrypted_extensions) ==
+                        tls13_extension_disallowed);
             sender = &xtnData->serverHelloSenders[0];
-        } else if (tls13_ExtensionAllowed(ex_type, certificate)) {
+        } else if (tls13_ExtensionStatus(ex_type,
+                                         ssl_hs_encrypted_extensions) ==
+                   tls13_extension_allowed) {
+            sender = &xtnData->encryptedExtensionsSenders[0];
+        } else if (tls13_ExtensionStatus(ex_type, ssl_hs_certificate) ==
+                   tls13_extension_allowed) {
             sender = &xtnData->certificateSenders[0];
         } else {
-            PORT_Assert(tls13_ExtensionAllowed(ex_type, encrypted_extensions));
-            sender = &xtnData->encryptedExtensionsSenders[0];
+            PORT_Assert(0);
+            PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
+            return SECFailure;
         }
     }
     for (i = 0; i < SSL_MAX_EXTENSIONS; ++i, ++sender) {
@@ -418,32 +615,289 @@ ssl3_RegisterExtensionSender(const sslSocket *ss,
     return SECFailure;
 }
 
-/* call each of the extension senders and return the accumulated length */
-PRInt32
-ssl3_CallHelloExtensionSenders(sslSocket *ss, PRBool append, PRUint32 maxBytes,
-                               const ssl3HelloExtensionSender *sender)
+static SECStatus
+ssl_CallCustomExtensionSenders(sslSocket *ss, sslBuffer *buf,
+                               SSLHandshakeType message)
 {
-    PRInt32 total_exten_len = 0;
-    int i;
+    sslBuffer tail = SSL_BUFFER_EMPTY;
+    SECStatus rv;
+    PRCList *cursor;
 
-    if (!sender) {
-        if (ss->vrange.max > SSL_LIBRARY_VERSION_3_0) {
-            sender = &clientHelloSendersTLS[0];
-        } else {
-            sender = &clientHelloSendersSSL3[0];
+    /* Save any extensions that want to be last. */
+    if (ss->xtnData.lastXtnOffset) {
+        rv = sslBuffer_Append(&tail, buf->buf + ss->xtnData.lastXtnOffset,
+                              buf->len - ss->xtnData.lastXtnOffset);
+        if (rv != SECSuccess) {
+            return SECFailure;
         }
+        buf->len = ss->xtnData.lastXtnOffset;
     }
 
-    for (i = 0; i < SSL_MAX_EXTENSIONS; ++i, ++sender) {
-        if (sender->ex_sender) {
-            PRInt32 extLen = (*sender->ex_sender)(ss, &ss->xtnData, append, maxBytes);
-            if (extLen < 0)
-                return -1;
-            maxBytes -= extLen;
-            total_exten_len += extLen;
+    /* Reserve the maximum amount of space possible. */
+    rv = sslBuffer_Grow(buf, 65535);
+    if (rv != SECSuccess) {
+        return SECFailure;
+    }
+
+    for (cursor = PR_NEXT_LINK(&ss->extensionHooks);
+         cursor != &ss->extensionHooks;
+         cursor = PR_NEXT_LINK(cursor)) {
+        sslCustomExtensionHooks *hook =
+            (sslCustomExtensionHooks *)cursor;
+        PRBool append = PR_FALSE;
+        unsigned int len = 0;
+
+        if (hook->writer) {
+            /* The writer writes directly into |buf|.  Provide space that allows
+             * for the existing extensions, any tail, plus type and length. */
+            unsigned int space = buf->space - (buf->len + tail.len + 4);
+            append = (*hook->writer)(ss->fd, message,
+                                     buf->buf + buf->len + 4, &len, space,
+                                     hook->writerArg);
+            if (len > space) {
+                PORT_SetError(SEC_ERROR_APPLICATION_CALLBACK_ERROR);
+                goto loser;
+            }
+        }
+        if (!append) {
+            continue;
+        }
+
+        rv = sslBuffer_AppendNumber(buf, hook->type, 2);
+        if (rv != SECSuccess) {
+            goto loser; /* Code already set. */
+        }
+        rv = sslBuffer_AppendNumber(buf, len, 2);
+        if (rv != SECSuccess) {
+            goto loser; /* Code already set. */
+        }
+        buf->len += len;
+
+        if (message == ssl_hs_client_hello ||
+            message == ssl_hs_certificate_request) {
+            ss->xtnData.advertised[ss->xtnData.numAdvertised++] = hook->type;
         }
     }
-    return total_exten_len;
+
+    sslBuffer_Append(buf, tail.buf, tail.len);
+    sslBuffer_Clear(&tail);
+    return SECSuccess;
+
+loser:
+    sslBuffer_Clear(&tail);
+    return SECFailure;
+}
+
+/* Call extension handlers for the given message. */
+SECStatus
+ssl_ConstructExtensions(sslSocket *ss, sslBuffer *buf, SSLHandshakeType message)
+{
+    const sslExtensionBuilder *sender;
+    SECStatus rv;
+
+    PORT_Assert(buf->len == 0);
+
+    switch (message) {
+        case ssl_hs_client_hello:
+            if (ss->vrange.max > SSL_LIBRARY_VERSION_3_0) {
+                sender = clientHelloSendersTLS;
+            } else {
+                sender = clientHelloSendersSSL3;
+            }
+            break;
+
+        case ssl_hs_server_hello:
+            sender = ss->xtnData.serverHelloSenders;
+            break;
+
+        case ssl_hs_certificate_request:
+            PORT_Assert(ss->version >= SSL_LIBRARY_VERSION_TLS_1_3);
+            sender = tls13_cert_req_senders;
+            break;
+
+        case ssl_hs_certificate:
+            PORT_Assert(ss->version >= SSL_LIBRARY_VERSION_TLS_1_3);
+            sender = ss->xtnData.certificateSenders;
+            break;
+
+        case ssl_hs_encrypted_extensions:
+            PORT_Assert(ss->version >= SSL_LIBRARY_VERSION_TLS_1_3);
+            sender = ss->xtnData.encryptedExtensionsSenders;
+            break;
+
+        case ssl_hs_hello_retry_request:
+            PORT_Assert(ss->version >= SSL_LIBRARY_VERSION_TLS_1_3);
+            sender = tls13_hrr_senders;
+            break;
+
+        default:
+            PORT_Assert(0);
+            PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
+            return SECFailure;
+    }
+
+    for (; sender->ex_sender != NULL; ++sender) {
+        PRBool append = PR_FALSE;
+        unsigned int start = buf->len;
+        unsigned int length;
+
+        if (ssl_FindCustomExtensionHooks(ss, sender->ex_type)) {
+            continue;
+        }
+
+        /* Save space for the extension type and length. Note that we don't grow
+         * the buffer now; rely on sslBuffer_Append* to do that. */
+        buf->len += 4;
+        rv = (*sender->ex_sender)(ss, &ss->xtnData, buf, &append);
+        if (rv != SECSuccess) {
+            goto loser;
+        }
+
+        /* Save the length and go back to the start. */
+        length = buf->len - start - 4;
+        buf->len = start;
+        if (!append) {
+            continue;
+        }
+
+        buf->len = start;
+        rv = sslBuffer_AppendNumber(buf, sender->ex_type, 2);
+        if (rv != SECSuccess) {
+            goto loser; /* Code already set. */
+        }
+        rv = sslBuffer_AppendNumber(buf, length, 2);
+        if (rv != SECSuccess) {
+            goto loser; /* Code already set. */
+        }
+        /* Skip over the extension body. */
+        buf->len += length;
+
+        if (message == ssl_hs_client_hello ||
+            message == ssl_hs_certificate_request) {
+            ss->xtnData.advertised[ss->xtnData.numAdvertised++] =
+                sender->ex_type;
+        }
+    }
+
+    if (!PR_CLIST_IS_EMPTY(&ss->extensionHooks)) {
+        rv = ssl_CallCustomExtensionSenders(ss, buf, message);
+        if (rv != SECSuccess) {
+            goto loser;
+        }
+    }
+
+    if (buf->len > 0xffff) {
+        PORT_SetError(SSL_ERROR_TX_RECORD_TOO_LONG);
+        goto loser;
+    }
+
+    return SECSuccess;
+
+loser:
+    sslBuffer_Clear(buf);
+    return SECFailure;
+}
+
+/* This extension sender can be used anywhere that an always empty extension is
+ * needed. Mostly that is for ServerHello where sender registration is dynamic;
+ * ClientHello senders are usually conditional in some way. */
+SECStatus
+ssl_SendEmptyExtension(const sslSocket *ss, TLSExtensionData *xtnData,
+                       sslBuffer *buf, PRBool *append)
+{
+    *append = PR_TRUE;
+    return SECSuccess;
+}
+
+/* Takes the size of the ClientHello, less the record header, and determines how
+ * much padding is required. */
+static unsigned int
+ssl_CalculatePaddingExtLen(const sslSocket *ss, unsigned int clientHelloLength)
+{
+    unsigned int recordLength = 1 /* handshake message type */ +
+                                3 /* handshake message length */ +
+                                clientHelloLength;
+    unsigned int extensionLen;
+
+    /* Don't pad for DTLS, for SSLv3, or for renegotiation. */
+    if (IS_DTLS(ss) ||
+        ss->vrange.max < SSL_LIBRARY_VERSION_TLS_1_0 ||
+        ss->firstHsDone) {
+        return 0;
+    }
+
+    /* A padding extension may be included to ensure that the record containing
+     * the ClientHello doesn't have a length between 256 and 511 bytes
+     * (inclusive). Initial ClientHello records with such lengths trigger bugs
+     * in F5 devices. */
+    if (recordLength < 256 || recordLength >= 512) {
+        return 0;
+    }
+
+    extensionLen = 512 - recordLength;
+    /* Extensions take at least four bytes to encode. Always include at least
+     * one byte of data if we are padding. Some servers will time out or
+     * terminate the connection if the last ClientHello extension is empty. */
+    if (extensionLen < 5) {
+        extensionLen = 5;
+    }
+
+    return extensionLen - 4;
+}
+
+/* ssl3_SendPaddingExtension possibly adds an extension which ensures that a
+ * ClientHello record is either < 256 bytes or is >= 512 bytes. This ensures
+ * that we don't trigger bugs in F5 products.
+ *
+ * This takes an existing extension buffer, |buf|, and the length of the
+ * remainder of the ClientHello, |prefixLen|.  It modifies the extension buffer
+ * to insert padding at the right place.
+ */
+SECStatus
+ssl_InsertPaddingExtension(const sslSocket *ss, unsigned int prefixLen,
+                           sslBuffer *buf)
+{
+    static unsigned char padding[252] = { 0 };
+    unsigned int paddingLen;
+    unsigned int tailLen;
+    SECStatus rv;
+
+    /* Account for the size of the header, the length field of the extensions
+     * block and the size of the existing extensions. */
+    paddingLen = ssl_CalculatePaddingExtLen(ss, prefixLen + 2 + buf->len);
+    if (!paddingLen) {
+        return SECSuccess;
+    }
+
+    /* Move the tail if there is one. This only happens if we are sending the
+     * TLS 1.3 PSK extension, which needs to be at the end. */
+    if (ss->xtnData.lastXtnOffset) {
+        PORT_Assert(buf->len > ss->xtnData.lastXtnOffset);
+        tailLen = buf->len - ss->xtnData.lastXtnOffset;
+        rv = sslBuffer_Grow(buf, buf->len + 4 + paddingLen);
+        if (rv != SECSuccess) {
+            return SECFailure;
+        }
+        PORT_Memmove(buf->buf + ss->xtnData.lastXtnOffset + 4 + paddingLen,
+                     buf->buf + ss->xtnData.lastXtnOffset,
+                     tailLen);
+        buf->len = ss->xtnData.lastXtnOffset;
+    } else {
+        tailLen = 0;
+    }
+
+    rv = sslBuffer_AppendNumber(buf, ssl_padding_xtn, 2);
+    if (rv != SECSuccess) {
+        return SECFailure; /* Code already set. */
+    }
+    rv = sslBuffer_AppendVariable(buf, padding, paddingLen, 2);
+    if (rv != SECSuccess) {
+        return SECFailure; /* Code already set. */
+    }
+
+    buf->len += tailLen;
+
+    return SECSuccess;
 }
 
 void
@@ -460,52 +914,59 @@ ssl3_DestroyRemoteExtensions(PRCList *list)
 
 /* Initialize the extension data block. */
 void
-ssl3_InitExtensionData(TLSExtensionData *xtnData)
+ssl3_InitExtensionData(TLSExtensionData *xtnData, const sslSocket *ss)
 {
+    unsigned int advertisedMax;
+    PRCList *cursor;
+
     /* Set things up to the right starting state. */
     PORT_Memset(xtnData, 0, sizeof(*xtnData));
     xtnData->peerSupportsFfdheGroups = PR_FALSE;
     PR_INIT_CLIST(&xtnData->remoteKeyShares);
+
+    /* Allocate enough to allow for native extensions, plus any custom ones. */
+    if (ss->sec.isServer) {
+        advertisedMax = PR_MAX(PR_ARRAY_SIZE(certificateRequestHandlers),
+                               PR_ARRAY_SIZE(tls13_cert_req_senders));
+    } else {
+        advertisedMax = PR_MAX(PR_ARRAY_SIZE(clientHelloHandlers),
+                               PR_ARRAY_SIZE(clientHelloSendersTLS));
+        ++advertisedMax; /* For the RI SCSV, which we also track. */
+    }
+    for (cursor = PR_NEXT_LINK(&ss->extensionHooks);
+         cursor != &ss->extensionHooks;
+         cursor = PR_NEXT_LINK(cursor)) {
+        ++advertisedMax;
+    }
+    xtnData->advertised = PORT_ZNewArray(PRUint16, advertisedMax);
 }
 
-/* Free everything that has been allocated and then reset back to
- * the starting state. */
 void
-ssl3_ResetExtensionData(TLSExtensionData *xtnData)
+ssl3_DestroyExtensionData(TLSExtensionData *xtnData)
 {
-    /* Clean up. */
     ssl3_FreeSniNameArray(xtnData);
-    PORT_Free(xtnData->clientSigSchemes);
+    PORT_Free(xtnData->sigSchemes);
     SECITEM_FreeItem(&xtnData->nextProto, PR_FALSE);
     tls13_DestroyKeyShares(&xtnData->remoteKeyShares);
-
-    /* Now reinit. */
-    ssl3_InitExtensionData(xtnData);
-}
-
-/* Thunks to let extension handlers operate on const sslSocket* objects. */
-SECStatus
-ssl3_ExtAppendHandshake(const sslSocket *ss, const void *void_src,
-                        PRInt32 bytes)
-{
-    return ssl3_AppendHandshake((sslSocket *)ss, void_src, bytes);
-}
-
-SECStatus
-ssl3_ExtAppendHandshakeNumber(const sslSocket *ss, PRInt32 num,
-                              PRInt32 lenSize)
-{
-    return ssl3_AppendHandshakeNumber((sslSocket *)ss, num, lenSize);
+    SECITEM_FreeItem(&xtnData->certReqContext, PR_FALSE);
+    SECITEM_FreeItem(&xtnData->applicationToken, PR_FALSE);
+    if (xtnData->certReqAuthorities.arena) {
+        PORT_FreeArena(xtnData->certReqAuthorities.arena, PR_FALSE);
+        xtnData->certReqAuthorities.arena = NULL;
+    }
+    PORT_Free(xtnData->advertised);
 }
 
-SECStatus
-ssl3_ExtAppendHandshakeVariable(const sslSocket *ss,
-                                const PRUint8 *src, PRInt32 bytes,
-                                PRInt32 lenSize)
+/* Free everything that has been allocated and then reset back to
+ * the starting state. */
+void
+ssl3_ResetExtensionData(TLSExtensionData *xtnData, const sslSocket *ss)
 {
-    return ssl3_AppendHandshakeVariable((sslSocket *)ss, src, bytes, lenSize);
+    ssl3_DestroyExtensionData(xtnData);
+    ssl3_InitExtensionData(xtnData, ss);
 }
 
+/* Thunks to let extension handlers operate on const sslSocket* objects. */
 void
 ssl3_ExtSendAlert(const sslSocket *ss, SSL3AlertLevel level,
                   SSL3AlertDescription desc)