Rewrite session ticket TLS extension handling using CBB/CBS and the new

extension framework.

ok jsing@ beck@

4 files changed, 447 insertions, 66 deletions

diff --git a/src/lib/libssl/ssl_tlsext.c b/src/lib/libssl/ssl_tlsext.c
index c050224c70..1813d46f41 100644
--- a/src/lib/libssl/ssl_tlsext.c
+++ b/src/lib/libssl/ssl_tlsext.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_tlsext.c,v 1.6 2017/08/11 20:14:13 doug Exp $ */
+/* $OpenBSD: ssl_tlsext.c,v 1.7 2017/08/12 21:17:03 doug Exp $ */
 /*
  * Copyright (c) 2016, 2017 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -492,6 +492,131 @@ tlsext_sni_serverhello_parse(SSL *s, CBS *cbs, int *alert)
         return 1;
 }
 
+/*
+ * SessionTicket extension - RFC 5077 section 3.2
+ */
+int
+tlsext_sessionticket_clienthello_needs(SSL *s)
+{
+        /*
+         * Send session ticket extension when enabled and not overridden.
+         *
+         * When renegotiating, send an empty session ticket to indicate support.
+         */
+        if ((SSL_get_options(s) & SSL_OP_NO_TICKET) != 0)
+                return 0;
+
+        if (s->internal->new_session)
+                return 1;
+
+        if (s->internal->tlsext_session_ticket != NULL &&
+            s->internal->tlsext_session_ticket->data == NULL)
+                return 0;
+
+        return 1;
+}
+
+int
+tlsext_sessionticket_clienthello_build(SSL *s, CBB *cbb)
+{
+        /*
+         * Signal that we support session tickets by sending an empty
+         * extension when renegotiating or no session found.
+         */
+        if (s->internal->new_session || s->session == NULL)
+                return 1;
+
+        if (s->session->tlsext_tick != NULL) {
+                /* Attempt to resume with an existing session ticket */
+                if (!CBB_add_bytes(cbb, s->session->tlsext_tick,
+                    s->session->tlsext_ticklen))
+                        return 0;
+
+        } else if (s->internal->tlsext_session_ticket != NULL) {
+                /*
+                 * Attempt to resume with a custom provided session ticket set
+                 * by SSL_set_session_ticket_ext().
+                 */
+                if (s->internal->tlsext_session_ticket->length > 0) {
+                        size_t ticklen = s->internal->tlsext_session_ticket->length;
+
+                        if ((s->session->tlsext_tick = malloc(ticklen)) == NULL)
+                                return 0;
+                        memcpy(s->session->tlsext_tick,
+                            s->internal->tlsext_session_ticket->data,
+                            ticklen);
+                        s->session->tlsext_ticklen = ticklen;
+
+                        if (!CBB_add_bytes(cbb, s->session->tlsext_tick,
+                            s->session->tlsext_ticklen))
+                                return 0;
+                }
+        }
+
+        if (!CBB_flush(cbb))
+                return 0;
+
+        return 1;
+}
+
+int
+tlsext_sessionticket_clienthello_parse(SSL *s, CBS *cbs, int *alert)
+{
+        if (s->internal->tls_session_ticket_ext_cb) {
+                if (!s->internal->tls_session_ticket_ext_cb(s, CBS_data(cbs),
+                    (int)CBS_len(cbs),
+                    s->internal->tls_session_ticket_ext_cb_arg)) {
+                        *alert = TLS1_AD_INTERNAL_ERROR;
+                        return 0;
+                }
+        }
+
+        /* We need to signal that this was processed fully */
+        if (!CBS_skip(cbs, CBS_len(cbs))) {
+                *alert = TLS1_AD_INTERNAL_ERROR;
+                return 0;
+        }
+
+        return 1;
+}
+
+int
+tlsext_sessionticket_serverhello_needs(SSL *s)
+{
+        return (s->internal->tlsext_ticket_expected &&
+            !(SSL_get_options(s) & SSL_OP_NO_TICKET));
+}
+
+int
+tlsext_sessionticket_serverhello_build(SSL *s, CBB *cbb)
+{
+        /* Empty ticket */
+
+        return 1;
+}
+
+int
+tlsext_sessionticket_serverhello_parse(SSL *s, CBS *cbs, int *alert)
+{
+        if (s->internal->tls_session_ticket_ext_cb) {
+                if (!s->internal->tls_session_ticket_ext_cb(s, CBS_data(cbs),
+                    (int)CBS_len(cbs),
+                    s->internal->tls_session_ticket_ext_cb_arg)) {
+                        *alert = TLS1_AD_INTERNAL_ERROR;
+                        return 0;
+                }
+        }
+
+        if ((SSL_get_options(s) & SSL_OP_NO_TICKET) != 0 || CBS_len(cbs) > 0) {
+                *alert = TLS1_AD_UNSUPPORTED_EXTENSION;
+                return 0;
+        }
+
+        s->internal->tlsext_ticket_expected = 1;
+
+        return 1;
+}
+
 struct tls_extension {
         uint16_t type;
         int (*clienthello_needs)(SSL *s);
@@ -539,6 +664,15 @@ static struct tls_extension tls_extensions[] = {
                 .serverhello_build = tlsext_ec_serverhello_build,
                 .serverhello_parse = tlsext_ec_serverhello_parse,
         },
+        {
+                .type = TLSEXT_TYPE_session_ticket,
+                .clienthello_needs = tlsext_sessionticket_clienthello_needs,
+                .clienthello_build = tlsext_sessionticket_clienthello_build,
+                .clienthello_parse = tlsext_sessionticket_clienthello_parse,
+                .serverhello_needs = tlsext_sessionticket_serverhello_needs,
+                .serverhello_build = tlsext_sessionticket_serverhello_build,
+                .serverhello_parse = tlsext_sessionticket_serverhello_parse,
+        },
 };
 
 #define N_TLS_EXTENSIONS (sizeof(tls_extensions) / sizeof(*tls_extensions))
diff --git a/src/lib/libssl/ssl_tlsext.h b/src/lib/libssl/ssl_tlsext.h
index 38f8ffaa65..1e701e941a 100644
--- a/src/lib/libssl/ssl_tlsext.h
+++ b/src/lib/libssl/ssl_tlsext.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_tlsext.h,v 1.5 2017/08/11 20:14:13 doug Exp $ */
+/* $OpenBSD: ssl_tlsext.h,v 1.6 2017/08/12 21:17:03 doug Exp $ */
 /*
  * Copyright (c) 2016, 2017 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -44,6 +44,12 @@ int tlsext_ecpf_serverhello_needs(SSL *s);
 int tlsext_ecpf_serverhello_build(SSL *s, CBB *cbb);
 int tlsext_ecpf_serverhello_parse(SSL *s, CBS *cbs, int *alert);
 
+int tlsext_sessionticket_clienthello_needs(SSL *s);
+int tlsext_sessionticket_clienthello_build(SSL *s, CBB *cbb);
+int tlsext_sessionticket_clienthello_parse(SSL *s, CBS *cbs, int *alert);
+int tlsext_sessionticket_serverhello_needs(SSL *s);
+int tlsext_sessionticket_serverhello_build(SSL *s, CBB *cbb);
+int tlsext_sessionticket_serverhello_parse(SSL *s, CBS *cbs, int *alert);
 
 int tlsext_clienthello_build(SSL *s, CBB *cbb);
 int tlsext_clienthello_parse_one(SSL *s, CBS *cbs, uint16_t tlsext_type,
diff --git a/src/lib/libssl/t1_lib.c b/src/lib/libssl/t1_lib.c
index 911e8d3f4e..63d401c337 100644
--- a/src/lib/libssl/t1_lib.c
+++ b/src/lib/libssl/t1_lib.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: t1_lib.c,v 1.128 2017/08/12 21:03:08 jsing Exp $ */
+/* $OpenBSD: t1_lib.c,v 1.129 2017/08/12 21:17:03 doug Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -690,39 +690,6 @@ ssl_add_clienthello_tlsext(SSL *s, unsigned char *p, unsigned char *limit)
                 return NULL;
         ret += len;
 
-        if (!(SSL_get_options(s) & SSL_OP_NO_TICKET)) {
-                int ticklen;
-                if (!s->internal->new_session && s->session && s->session->tlsext_tick)
-                        ticklen = s->session->tlsext_ticklen;
-                else if (s->session && s->internal->tlsext_session_ticket &&
-                    s->internal->tlsext_session_ticket->data) {
-                        ticklen = s->internal->tlsext_session_ticket->length;
-                        s->session->tlsext_tick = malloc(ticklen);
-                        if (!s->session->tlsext_tick)
-                                return NULL;
-                        memcpy(s->session->tlsext_tick,
-                            s->internal->tlsext_session_ticket->data, ticklen);
-                        s->session->tlsext_ticklen = ticklen;
-                } else
-                        ticklen = 0;
-                if (ticklen == 0 && s->internal->tlsext_session_ticket &&
-                    s->internal->tlsext_session_ticket->data == NULL)
-                        goto skip_ext;
-                /* Check for enough room 2 for extension type, 2 for len
-                 * rest for ticket
-                 */
-                if ((size_t)(limit - ret) < 4 + ticklen)
-                        return NULL;
-                s2n(TLSEXT_TYPE_session_ticket, ret);
-
-                s2n(ticklen, ret);
-                if (ticklen) {
-                        memcpy(ret, s->session->tlsext_tick, ticklen);
-                        ret += ticklen;
-                }
-        }
-skip_ext:
-
         if (TLS1_get_client_version(s) >= TLS1_2_VERSION) {
                 if ((size_t)(limit - ret) < sizeof(tls12_sigalgs) + 6)
                         return NULL;
@@ -884,15 +851,6 @@ ssl_add_serverhello_tlsext(SSL *s, unsigned char *p, unsigned char *limit)
          * extension.
          */
 
-        if (s->internal->tlsext_ticket_expected &&
-            !(SSL_get_options(s) & SSL_OP_NO_TICKET)) {
-                if ((size_t)(limit - ret) < 4)
-                        return NULL;
-
-                s2n(TLSEXT_TYPE_session_ticket, ret);
-                s2n(0, ret);
-        }
-
         if (s->internal->tlsext_status_expected) {
                 if ((size_t)(limit - ret) < 4)
                         return NULL;
@@ -1068,13 +1026,7 @@ ssl_parse_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char *d,
                 if (!tlsext_clienthello_parse_one(s, &cbs, type, al))
                         return 0;
 
-                if (type == TLSEXT_TYPE_session_ticket) {
-                        if (s->internal->tls_session_ticket_ext_cb &&
-                            !s->internal->tls_session_ticket_ext_cb(s, data, size, s->internal->tls_session_ticket_ext_cb_arg)) {
-                                *al = TLS1_AD_INTERNAL_ERROR;
-                                return 0;
-                        }
-                } else if (type == TLSEXT_TYPE_signature_algorithms) {
+                if (type == TLSEXT_TYPE_signature_algorithms) {
                         int dsize;
                         if (sigalg_seen || size < 2) {
                                 *al = SSL_AD_DECODE_ERROR;
@@ -1277,19 +1229,7 @@ ssl_parse_serverhello_tlsext(SSL *s, unsigned char **p, size_t n, int *al)
                 if (!tlsext_serverhello_parse_one(s, &cbs, type, al))
                         return 0;
 
-                if (type == TLSEXT_TYPE_session_ticket) {
-                        if (s->internal->tls_session_ticket_ext_cb &&
-                            !s->internal->tls_session_ticket_ext_cb(s, data, size, s->internal->tls_session_ticket_ext_cb_arg)) {
-                                *al = TLS1_AD_INTERNAL_ERROR;
-                                return 0;
-                        }
-                        if ((SSL_get_options(s) & SSL_OP_NO_TICKET) || (size > 0)) {
-                                *al = TLS1_AD_UNSUPPORTED_EXTENSION;
-                                return 0;
-                        }
-                        s->internal->tlsext_ticket_expected = 1;
-                }
-                else if (type == TLSEXT_TYPE_status_request &&
+                if (type == TLSEXT_TYPE_status_request &&
                     s->version != DTLS1_VERSION) {
                         /* MUST be empty and only sent if we've requested
                          * a status request message.
diff --git a/src/regress/lib/libssl/tlsext/tlsexttest.c b/src/regress/lib/libssl/tlsext/tlsexttest.c
index 880142202e..1267f50a49 100644
--- a/src/regress/lib/libssl/tlsext/tlsexttest.c
+++ b/src/regress/lib/libssl/tlsext/tlsexttest.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tlsexttest.c,v 1.9 2017/08/12 19:09:37 beck Exp $ */
+/* $OpenBSD: tlsexttest.c,v 1.10 2017/08/12 21:17:03 doug Exp $ */
 /*
  * Copyright (c) 2017 Joel Sing <jsing@openbsd.org>
  * Copyright (c) 2017 Doug Hogan <doug@openbsd.org>
@@ -1298,6 +1298,304 @@ test_tlsext_sni_serverhello(void)
         return (failure);
 }
 
+/*
+ * Session ticket - RFC 5077 since no known implementations use 4507.
+ *
+ * Session tickets can be length 0 (special case) to 2^16-1.
+ *
+ * The state is encrypted by the server so it is opaque to the client.
+ */
+static uint8_t tlsext_sessionticket_hello_min[1];
+static uint8_t tlsext_sessionticket_hello_max[65535];
+
+static int
+test_tlsext_sessionticket_clienthello(void)
+{
+        unsigned char *data = NULL;
+        SSL_CTX *ssl_ctx = NULL;
+        SSL *ssl = NULL;
+        int failure;
+        CBB cbb;
+        size_t dlen;
+        uint8_t dummy[1234];
+
+        failure = 1;
+
+        CBB_init(&cbb, 0);
+
+        /* Create fake session tickets with random data. */
+        arc4random_buf(tlsext_sessionticket_hello_min,
+            sizeof(tlsext_sessionticket_hello_min));
+        arc4random_buf(tlsext_sessionticket_hello_max,
+            sizeof(tlsext_sessionticket_hello_max));
+
+        if ((ssl_ctx = SSL_CTX_new(TLS_client_method())) == NULL)
+                errx(1, "failed to create SSL_CTX");
+        if ((ssl = SSL_new(ssl_ctx)) == NULL)
+                errx(1, "failed to create SSL");
+
+        /* Should need a ticket by default. */
+        if (!tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("clienthello should need Sessionticket for default "
+                    "ciphers\n");
+                goto err;
+        }
+
+        /* Test disabling tickets. */
+        if ((SSL_set_options(ssl, SSL_OP_NO_TICKET) & SSL_OP_NO_TICKET) == 0) {
+                FAIL("Cannot disable tickets in the TLS connection");
+                return 0;
+        }
+        if (tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("clienthello should not need SessionTicket if it was disabled");
+                goto err;
+        }
+
+        /* Test re-enabling tickets. */
+        if ((SSL_clear_options(ssl, SSL_OP_NO_TICKET) & SSL_OP_NO_TICKET) != 0) {
+                FAIL("Cannot re-enable tickets in the TLS connection");
+                return 0;
+        }
+        if (!tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("clienthello should need SessionTicket if it was disabled");
+                goto err;
+        }
+
+        /* Since we don't have a session, we should build an empty ticket. */
+        if (!tlsext_sessionticket_clienthello_build(ssl, &cbb)) {
+                FAIL("Cannot build a ticket");
+                goto err;
+        }
+        if (!CBB_finish(&cbb, &data, &dlen)) {
+                FAIL("Cannot finish CBB");
+                goto err;
+        }
+        if (dlen != 0) {
+                FAIL("Expected 0 length but found %zu\n", dlen);
+                goto err;
+        }
+
+        CBB_cleanup(&cbb);
+        CBB_init(&cbb, 0);
+        free(data);
+        data = NULL;
+
+        /* With a new session (but no ticket), we should still have 0 length */
+        if ((ssl->session = SSL_SESSION_new()) == NULL)
+                errx(1, "failed to create session");
+        if (!tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("Should still want a session ticket with a new session");
+                goto err;
+        }
+        if (!tlsext_sessionticket_clienthello_build(ssl, &cbb)) {
+                FAIL("Cannot build a ticket");
+                goto err;
+        }
+        if (!CBB_finish(&cbb, &data, &dlen)) {
+                FAIL("Cannot finish CBB");
+                goto err;
+        }
+        if (dlen != 0) {
+                FAIL("Expected 0 length but found %zu\n", dlen);
+                goto err;
+        }
+
+        CBB_cleanup(&cbb);
+        CBB_init(&cbb, 0);
+        free(data);
+        data = NULL;
+
+        /* With a new session (and ticket), we should use that ticket */
+        SSL_SESSION_free(ssl->session);
+        if ((ssl->session = SSL_SESSION_new()) == NULL)
+                errx(1, "failed to create session");
+
+        arc4random_buf(&dummy, sizeof(dummy));
+        if ((ssl->session->tlsext_tick = malloc(sizeof(dummy))) == NULL) {
+                errx(1, "failed to malloc");
+        }
+        memcpy(ssl->session->tlsext_tick, dummy, sizeof(dummy));
+        ssl->session->tlsext_ticklen = sizeof(dummy);
+
+        if (!tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("Should still want a session ticket with a new session");
+                goto err;
+        }
+        if (!tlsext_sessionticket_clienthello_build(ssl, &cbb)) {
+                FAIL("Cannot build a ticket");
+                goto err;
+        }
+        if (!CBB_finish(&cbb, &data, &dlen)) {
+                FAIL("Cannot finish CBB");
+                goto err;
+        }
+        if (dlen != sizeof(dummy)) {
+                FAIL("Expected %zu length but found %zu\n", sizeof(dummy), dlen);
+                goto err;
+        }
+        if (memcmp(data, dummy, dlen) != 0) {
+                FAIL("serverhello SNI differs:\n");
+                compare_data(data, dlen,
+                    dummy, sizeof(dummy));
+                goto err;
+        }
+
+        CBB_cleanup(&cbb);
+        CBB_init(&cbb, 0);
+        free(data);
+        data = NULL;
+        free(ssl->session->tlsext_tick);
+        ssl->session->tlsext_tick = NULL;
+        ssl->session->tlsext_ticklen = 0;
+
+        /*
+         * Send in NULL to disable session tickets at runtime without going
+         * through SSL_set_options().
+         */
+        if (!SSL_set_session_ticket_ext(ssl, NULL, 0)) {
+                FAIL("Could not set a NULL custom ticket");
+                goto err;
+        }
+        /* Should not need a ticket in this case */
+        if (tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("Should not want to use session tickets with a NULL custom");
+                goto err;
+        }
+
+        /*
+         * If you want to remove the tlsext_session_ticket behavior, you have
+         * to do it manually.
+         */
+        free(ssl->internal->tlsext_session_ticket);
+        ssl->internal->tlsext_session_ticket = NULL;
+
+        if (!tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("Should need a session ticket again when the custom one is removed");
+                goto err;
+        }
+
+        /* Test a custom session ticket (not recommended in practice) */
+        if (!SSL_set_session_ticket_ext(ssl, tlsext_sessionticket_hello_max,
+            sizeof(tlsext_sessionticket_hello_max))) {
+                FAIL("Should be able to set a custom ticket");
+                goto err;
+        }
+        if (!tlsext_sessionticket_clienthello_needs(ssl)) {
+                FAIL("Should need a session ticket again when the custom one is not empty");
+                goto err;
+        }
+        if (!tlsext_sessionticket_clienthello_build(ssl, &cbb)) {
+                FAIL("Cannot build a ticket with a max length random payload");
+                goto err;
+        }
+        if (!CBB_finish(&cbb, &data, &dlen)) {
+                FAIL("Cannot finish CBB");
+                goto err;
+        }
+        if (dlen != sizeof(tlsext_sessionticket_hello_max)) {
+                FAIL("Expected %zu length but found %zu\n",
+                    sizeof(tlsext_sessionticket_hello_max), dlen);
+                goto err;
+        }
+        if (memcmp(data, tlsext_sessionticket_hello_max,
+            sizeof(tlsext_sessionticket_hello_max)) != 0) {
+                FAIL("Expected to get what we passed in");
+                compare_data(data, dlen,
+                    tlsext_sessionticket_hello_max,
+                    sizeof(tlsext_sessionticket_hello_max));
+                goto err;
+        }
+
+        failure = 0;
+
+ err:
+        CBB_cleanup(&cbb);
+        SSL_CTX_free(ssl_ctx);
+        SSL_free(ssl);
+        free(data);
+
+        return (failure);
+}
+
+
+static int
+test_tlsext_sessionticket_serverhello(void)
+{
+        SSL_CTX *ssl_ctx = NULL;
+        SSL *ssl = NULL;
+        int failure;
+        uint8_t *data;
+        size_t dlen;
+        CBB cbb;
+
+        CBB_init(&cbb, 0);
+
+        failure = 1;
+
+        if ((ssl_ctx = SSL_CTX_new(TLS_server_method())) == NULL)
+                errx(1, "failed to create SSL_CTX");
+        if ((ssl = SSL_new(ssl_ctx)) == NULL)
+                errx(1, "failed to create SSL");
+
+        /*
+         * By default, should not need a session ticket since the ticket
+         * is not yet expected.
+         */
+        if (tlsext_sessionticket_serverhello_needs(ssl)) {
+                FAIL("serverhello should not need SessionTicket by default\n");
+                goto err;
+        }
+
+        /* Test disabling tickets. */
+        if ((SSL_set_options(ssl, SSL_OP_NO_TICKET) & SSL_OP_NO_TICKET) == 0) {
+                FAIL("Cannot disable tickets in the TLS connection");
+                return 0;
+        }
+        if (tlsext_sessionticket_serverhello_needs(ssl)) {
+                FAIL("serverhello should not need SessionTicket if it was disabled");
+                goto err;
+        }
+
+        /* Test re-enabling tickets. */
+        if ((SSL_clear_options(ssl, SSL_OP_NO_TICKET) & SSL_OP_NO_TICKET) != 0) {
+                FAIL("Cannot re-enable tickets in the TLS connection");
+                return 0;
+        }
+        if (tlsext_sessionticket_serverhello_needs(ssl)) {
+                FAIL("serverhello should not need SessionTicket yet");
+                goto err;
+        }
+
+        /* Set expected to require it. */
+        ssl->internal->tlsext_ticket_expected = 1;
+        if (!tlsext_sessionticket_serverhello_needs(ssl)) {
+                FAIL("serverhello should now be required for SessionTicket");
+                goto err;
+        }
+
+        /* server hello's session ticket should always be 0 length payload. */
+        if (!tlsext_sessionticket_serverhello_build(ssl, &cbb)) {
+                FAIL("Cannot build a ticket with a max length random payload");
+                goto err;
+        }
+        if (!CBB_finish(&cbb, &data, &dlen)) {
+                FAIL("Cannot finish CBB");
+                goto err;
+        }
+        if (dlen != 0) {
+                FAIL("Expected 0 length but found %zu\n", dlen);
+                goto err;
+        }
+
+        failure = 0;
+
+ err:
+        SSL_CTX_free(ssl_ctx);
+        SSL_free(ssl);
+
+        return (failure);
+}
+
 int
 main(int argc, char **argv)
 {
@@ -1317,5 +1615,8 @@ main(int argc, char **argv)
         failed |= test_tlsext_sni_clienthello();
         failed |= test_tlsext_sni_serverhello();
 
+        failed |= test_tlsext_sessionticket_clienthello();
+        failed |= test_tlsext_sessionticket_serverhello();
+
         return (failed);
 }