Check SNI/ALPN in TLS 1.2 stateful session ID resumption

Author: holtrop-wolfssl

src/internal.c

@@ -38086,6 +38086,30 @@ static int AddPSKtoPreMasterSecret(WOLFSSL* ssl)
             ssl->options.resuming = 0;
             return ret;
         }
+#if defined(HAVE_SESSION_TICKET) && \
+    (defined(HAVE_SNI) || defined(HAVE_ALPN))
+        /* Do not resume session if sniHash/alpnHash do not match. */
+        if (!ssl->options.useTicket) {
+            byte curHash[TICKET_BINDING_HASH_SZ];
+#ifdef HAVE_SNI
+            if (TicketSniHash(ssl, curHash) != 0 ||
+                    XMEMCMP(curHash, session->sniHash,
+                            TICKET_BINDING_HASH_SZ) != 0) {
+                WOLFSSL_MSG("Resumed session SNI mismatch, full handshake");
+                ssl->options.resuming = 0;
+            }
+#endif
+#ifdef HAVE_ALPN
+            if (ssl->options.resuming &&
+                    (TicketAlpnHash(ssl, curHash) != 0 ||
+                     XMEMCMP(curHash, session->alpnHash,
+                             TICKET_BINDING_HASH_SZ) != 0)) {
+                WOLFSSL_MSG("Resumed session ALPN mismatch, full handshake");
+                ssl->options.resuming = 0;
+            }
+#endif
+        }
+#endif /* HAVE_SESSION_TICKET && (HAVE_SNI || HAVE_ALPN) */
 #if !defined(WOLFSSL_NO_TICKET_EXPIRE) && !defined(NO_ASN_TIME)
         /* check if the ticket is valid */
         if (LowResTimer() > session->bornOn + ssl->timeout) {
@@ -39450,7 +39474,7 @@ static int AddPSKtoPreMasterSecret(WOLFSSL* ssl)
 
 #ifdef HAVE_SNI
     /* Hash server-selected SNI; zeros dst when none. */
-    static int TicketSniHash(WOLFSSL* ssl, byte* dst)
+    int TicketSniHash(WOLFSSL* ssl, byte* dst)
     {
         char* name = NULL;
         word16 nameLen;
@@ -39470,16 +39494,23 @@ static int AddPSKtoPreMasterSecret(WOLFSSL* ssl)
 
 #ifdef HAVE_ALPN
     /* Hash negotiated ALPN; zeros dst when none. */
-    static int TicketAlpnHash(WOLFSSL* ssl, byte* dst)
+    int TicketAlpnHash(WOLFSSL* ssl, byte* dst)
     {
-        char* proto = NULL;
-        word16 protoLen = 0;
-
-        if (TLSX_ALPN_GetRequest(ssl->extensions, (void**)&proto,
-                                 &protoLen) == WOLFSSL_SUCCESS &&
-                proto != NULL && protoLen > 0) {
-            return wc_Hash(TICKET_BINDING_HASH_TYPE, (const byte*)proto,
-                           protoLen, dst, TICKET_BINDING_HASH_SZ);
+        TLSX* extension;
+        ALPN* alpn;
+
+        extension = TLSX_Find(ssl->extensions, TLSX_APPLICATION_LAYER_PROTOCOL);
+        if (extension != NULL) {
+            alpn = (ALPN*)extension->data;
+            if (alpn != NULL && alpn->negotiated == 1 &&
+                    alpn->protocol_name != NULL) {
+                word32 protoLen = (word32)XSTRLEN(alpn->protocol_name);
+                if (protoLen > 0) {
+                    return wc_Hash(TICKET_BINDING_HASH_TYPE,
+                                   (const byte*)alpn->protocol_name,
+                                   protoLen, dst, TICKET_BINDING_HASH_SZ);
+                }
+            }
         }
 
         XMEMSET(dst, 0, TICKET_BINDING_HASH_SZ);

src/ssl_sess.c

@@ -2715,6 +2715,16 @@ int wolfSSL_i2d_SSL_SESSION(WOLFSSL_SESSION* sess, unsigned char** p)
 #ifdef HAVE_SESSION_TICKET
     /* ticket len | ticket */
     size += OPAQUE16_LEN + sess->ticketLen;
+#if !defined(NO_WOLFSSL_SERVER) && !defined(NO_TLS)
+#ifdef HAVE_SNI
+    /* sniHash */
+    size += TICKET_BINDING_HASH_SZ;
+#endif
+#ifdef HAVE_ALPN
+    /* alpnHash */
+    size += TICKET_BINDING_HASH_SZ;
+#endif
+#endif /* !NO_WOLFSSL_SERVER && !NO_TLS */
 #endif
 
     if (p != NULL) {
@@ -2800,6 +2810,16 @@ int wolfSSL_i2d_SSL_SESSION(WOLFSSL_SESSION* sess, unsigned char** p)
         c16toa(sess->ticketLen, data + idx); idx += OPAQUE16_LEN;
         XMEMCPY(data + idx, sess->ticket, sess->ticketLen);
         idx += sess->ticketLen;
+#if !defined(NO_WOLFSSL_SERVER) && !defined(NO_TLS)
+#ifdef HAVE_SNI
+        XMEMCPY(data + idx, sess->sniHash, TICKET_BINDING_HASH_SZ);
+        idx += TICKET_BINDING_HASH_SZ;
+#endif
+#ifdef HAVE_ALPN
+        XMEMCPY(data + idx, sess->alpnHash, TICKET_BINDING_HASH_SZ);
+        idx += TICKET_BINDING_HASH_SZ;
+#endif
+#endif /* !NO_WOLFSSL_SERVER && !NO_TLS */
 #endif
     }
 #endif
@@ -3086,6 +3106,26 @@ WOLFSSL_SESSION* wolfSSL_d2i_SSL_SESSION(WOLFSSL_SESSION** sess,
         goto end;
     }
     XMEMCPY(s->ticket, data + idx, s->ticketLen); idx += s->ticketLen;
+#if !defined(NO_WOLFSSL_SERVER) && !defined(NO_TLS)
+#ifdef HAVE_SNI
+    /* sniHash - SNI binding for stateful resumption (RFC 6066 section 3) */
+    if (i - idx < TICKET_BINDING_HASH_SZ) {
+        ret = BUFFER_ERROR;
+        goto end;
+    }
+    XMEMCPY(s->sniHash, data + idx, TICKET_BINDING_HASH_SZ);
+    idx += TICKET_BINDING_HASH_SZ;
+#endif
+#ifdef HAVE_ALPN
+    /* alpnHash - ALPN binding for stateful resumption */
+    if (i - idx < TICKET_BINDING_HASH_SZ) {
+        ret = BUFFER_ERROR;
+        goto end;
+    }
+    XMEMCPY(s->alpnHash, data + idx, TICKET_BINDING_HASH_SZ);
+    idx += TICKET_BINDING_HASH_SZ;
+#endif
+#endif /* !NO_WOLFSSL_SERVER && !NO_TLS */
 #endif
     (void)idx;
 
@@ -3664,6 +3704,16 @@ void SetupSession(WOLFSSL* ssl)
         session->sessionCtxSz = ssl->sessionCtxSz;
     }
 #endif
+#if defined(HAVE_SESSION_TICKET) && \
+    !defined(NO_WOLFSSL_SERVER) && !defined(NO_TLS)
+    /* Bind the current SNI/ALPN to the session to verify on later resumption */
+#ifdef HAVE_SNI
+    (void)TicketSniHash(ssl, session->sniHash);
+#endif
+#ifdef HAVE_ALPN
+    (void)TicketAlpnHash(ssl, session->alpnHash);
+#endif
+#endif /* HAVE_SESSION_TICKET && !NO_WOLFSSL_SERVER && !NO_TLS */
     session->timeout = ssl->timeout;
 #ifndef NO_ASN_TIME
     session->bornOn  = LowResTimer();

tests/api/test_tls.c

@@ -906,6 +906,88 @@ int test_tls_set_session_min_downgrade(void)
     return EXPECT_RESULT();
 }
 
+#if defined(HAVE_MANUAL_MEMIO_TESTS_DEPENDENCIES) && \
+    !defined(WOLFSSL_NO_TLS12) && defined(HAVE_SNI) && \
+    defined(HAVE_SESSION_TICKET) && !defined(NO_SESSION_CACHE)
+/* Accept-all SNI callback. */
+static int accept_any_sni_cb(WOLFSSL* ssl, int* ret, void* arg)
+{
+    (void)ssl; (void)ret; (void)arg;
+    return 0; /* accept */
+}
+#endif
+
+/* TLS resumption must proceed with full handshake to establish new session if
+ * SNI/ALPN does not match previously established session. */
+int test_tls12_session_id_resumption_sni_mismatch(void)
+{
+    EXPECT_DECLS;
+#if defined(HAVE_MANUAL_MEMIO_TESTS_DEPENDENCIES) && \
+    !defined(WOLFSSL_NO_TLS12) && defined(HAVE_SNI) && \
+    defined(HAVE_SESSION_TICKET) && !defined(NO_SESSION_CACHE)
+    WOLFSSL_CTX *ctx_c = NULL, *ctx_s = NULL;
+    WOLFSSL *ssl_c = NULL, *ssl_s = NULL;
+    WOLFSSL_SESSION *sess = NULL;
+    struct test_memio_ctx test_ctx;
+    const char* sniA = "public.example";
+    const char* sniB = "admin.example";
+
+    /* Step 1: full TLS 1.2 handshake under SNI=public.example, with the
+     * session ticket path disabled so resumption can only happen via the
+     * server's session-ID cache. The server-side SNI callback ensures
+     * ssl->extensions retains the client's SNI in builds that don't
+     * compile in WOLFSSL_ALWAYS_KEEP_SNI. */
+    XMEMSET(&test_ctx, 0, sizeof(test_ctx));
+    ExpectIntEQ(test_memio_setup(&test_ctx, &ctx_c, &ctx_s, &ssl_c, &ssl_s,
+                    wolfTLSv1_2_client_method, wolfTLSv1_2_server_method), 0);
+    wolfSSL_CTX_set_servername_callback(ctx_s, accept_any_sni_cb);
+    ExpectIntEQ(wolfSSL_NoTicketTLSv12(ssl_c), WOLFSSL_SUCCESS);
+    ExpectIntEQ(wolfSSL_NoTicketTLSv12(ssl_s), WOLFSSL_SUCCESS);
+    ExpectIntEQ(wolfSSL_UseSNI(ssl_c, WOLFSSL_SNI_HOST_NAME,
+                    sniA, (word16)XSTRLEN(sniA)), WOLFSSL_SUCCESS);
+    ExpectIntEQ(test_memio_do_handshake(ssl_c, ssl_s, 10, NULL), 0);
+    /* Sanity: the first handshake was not a resumption. */
+    ExpectIntEQ(wolfSSL_session_reused(ssl_s), 0);
+    ExpectNotNull(sess = wolfSSL_get1_session(ssl_c));
+
+    wolfSSL_free(ssl_c); ssl_c = NULL;
+    wolfSSL_free(ssl_s); ssl_s = NULL;
+
+    /* Step 2: new SSL objects on the SAME WOLFSSL_CTX (so the server's
+     * session cache still holds the entry from step 1). The client offers
+     * the saved session but advertises a *different* SNI. The server's
+     * cache lookup will match by session ID, but per RFC 6066 Section 3 the
+     * server MUST NOT resume because the SNI differs from the original. */
+    XMEMSET(&test_ctx, 0, sizeof(test_ctx));
+    ExpectNotNull(ssl_c = wolfSSL_new(ctx_c));
+    wolfSSL_SetIOReadCtx(ssl_c, &test_ctx);
+    wolfSSL_SetIOWriteCtx(ssl_c, &test_ctx);
+    ExpectNotNull(ssl_s = wolfSSL_new(ctx_s));
+    wolfSSL_SetIOReadCtx(ssl_s, &test_ctx);
+    wolfSSL_SetIOWriteCtx(ssl_s, &test_ctx);
+    ExpectIntEQ(wolfSSL_NoTicketTLSv12(ssl_c), WOLFSSL_SUCCESS);
+    ExpectIntEQ(wolfSSL_NoTicketTLSv12(ssl_s), WOLFSSL_SUCCESS);
+    ExpectIntEQ(wolfSSL_UseSNI(ssl_c, WOLFSSL_SNI_HOST_NAME,
+                    sniB, (word16)XSTRLEN(sniB)), WOLFSSL_SUCCESS);
+    ExpectIntEQ(wolfSSL_set_session(ssl_c, sess), WOLFSSL_SUCCESS);
+    ExpectIntEQ(test_memio_do_handshake(ssl_c, ssl_s, 10, NULL), 0);
+
+    /* Post-fix expected behavior: server falls back to a full handshake
+     * because the SNI in the ClientHello does not match the SNI bound to
+     * the cached session. Pre-fix, the server silently resumes - which is
+     * the bug. Both sides should report no resumption. */
+    ExpectIntEQ(wolfSSL_session_reused(ssl_s), 0);
+    ExpectIntEQ(wolfSSL_session_reused(ssl_c), 0);
+
+    wolfSSL_SESSION_free(sess);
+    wolfSSL_free(ssl_c);
+    wolfSSL_free(ssl_s);
+    wolfSSL_CTX_free(ctx_c);
+    wolfSSL_CTX_free(ctx_s);
+#endif
+    return EXPECT_RESULT();
+}
+
 int test_tls_set_curves_list_ecc_fallback(void)
 {
     EXPECT_DECLS;

tests/api/test_tls.h

@@ -33,6 +33,7 @@ int test_tls12_bad_cv_sig_alg(void);
 int test_tls12_no_null_compression(void);
 int test_tls12_etm_failed_resumption(void);
 int test_tls_set_session_min_downgrade(void);
+int test_tls12_session_id_resumption_sni_mismatch(void);
 int test_tls_set_curves_list_ecc_fallback(void);
 int test_tls12_corrupted_finished(void);
 int test_tls12_peerauth_failsafe(void);
@@ -51,6 +52,7 @@ int test_wolfSSL_alert_desc_string(void);
         TEST_DECL_GROUP("tls", test_tls12_no_null_compression),                \
         TEST_DECL_GROUP("tls", test_tls12_etm_failed_resumption),              \
         TEST_DECL_GROUP("tls", test_tls_set_session_min_downgrade),            \
+        TEST_DECL_GROUP("tls", test_tls12_session_id_resumption_sni_mismatch), \
         TEST_DECL_GROUP("tls", test_tls_set_curves_list_ecc_fallback),         \
         TEST_DECL_GROUP("tls", test_tls12_corrupted_finished),                 \
         TEST_DECL_GROUP("tls", test_tls12_peerauth_failsafe),                  \

wolfssl/internal.h

@@ -6824,9 +6824,21 @@ WOLFSSL_LOCAL int DoClientTicket_ex(const WOLFSSL* ssl, PreSharedKey* psk,
 #endif
 
 WOLFSSL_LOCAL int DoClientTicket(WOLFSSL* ssl, const byte* input, word32 len);
+/* TicketSniHash, TicketAlpnHash, and VerifyTicketBinding are defined in
+ * internal.c only when !NO_WOLFSSL_SERVER && !NO_TLS - gate the
+ * declarations to match so client-only or no-TLS builds don't compile in
+ * call sites that would fail to link. */
+#if !defined(NO_WOLFSSL_SERVER) && !defined(NO_TLS)
+#ifdef HAVE_SNI
+WOLFSSL_LOCAL int TicketSniHash(WOLFSSL* ssl, byte* dst);
+#endif
+#ifdef HAVE_ALPN
+WOLFSSL_LOCAL int TicketAlpnHash(WOLFSSL* ssl, byte* dst);
+#endif
 #if defined(HAVE_SNI) || defined(HAVE_ALPN)
 WOLFSSL_LOCAL int VerifyTicketBinding(WOLFSSL* ssl);
 #endif
+#endif /* !NO_WOLFSSL_SERVER && !NO_TLS */
 #endif /* HAVE_SESSION_TICKET */
 WOLFSSL_LOCAL int SendData(WOLFSSL* ssl, const void* data, size_t sz);
 #ifdef WOLFSSL_THREADED_CRYPT