Port multi-buffer tests

Make maximum fragment length configurable and add various fragmentation
tests, in addition to the existing multi-buffer tests.
Reviewed-by: NRich Salz <rsalz@openssl.org>

test/README.ssltest.md

@@ -60,6 +60,19 @@ When HandshakeMode is Resume or Renegotiate, the original handshake is expected
 to succeed. All configured test expectations are verified against the second
 handshake.
 
+* ApplicationData - amount of application data bytes to send (integer, defaults
+  to 256 bytes). Applies to both client and server. Application data is sent in
+  64kB chunks (but limited by MaxFragmentSize and available parallelization, see
+  below).
+
+* MaxFragmentSize - maximum send fragment size (integer, defaults to 512 in
+  tests - see `SSL_CTX_set_max_send_fragment` for documentation). Applies to
+  both client and server. Lowering the fragment size will split handshake and
+  application data up between more `SSL_write` calls, thus allowing to exercise
+  different code paths. In particular, if the buffer size (64kB) is at least
+  four times as large as the maximum fragment, interleaved multi-buffer crypto
+  implementations may be used on some platforms.
+
 ### Test expectations
 
 * ExpectedResult - expected handshake outcome. One of

test/handshake_helper.c

@@ -270,6 +270,7 @@ static int server_alpn_cb(SSL *s, const unsigned char **out,
  */
 static void configure_handshake_ctx(SSL_CTX *server_ctx, SSL_CTX *server2_ctx,
                                     SSL_CTX *client_ctx,
+                                    const SSL_TEST_CTX *test,
                                     const SSL_TEST_EXTRA_CONF *extra,
                                     CTX_DATA *server_ctx_data,
                                     CTX_DATA *server2_ctx_data,
@@ -278,6 +279,15 @@ static void configure_handshake_ctx(SSL_CTX *server_ctx, SSL_CTX *server2_ctx,
     unsigned char *ticket_keys;
     size_t ticket_key_len;
 
+    TEST_check(SSL_CTX_set_max_send_fragment(server_ctx,
+                                             test->max_fragment_size) == 1);
+    if (server2_ctx != NULL) {
+        TEST_check(SSL_CTX_set_max_send_fragment(server2_ctx,
+                                                 test->max_fragment_size) == 1);
+    }
+    TEST_check(SSL_CTX_set_max_send_fragment(client_ctx,
+                                             test->max_fragment_size) == 1);
+
     switch (extra->client.verify_callback) {
     case SSL_TEST_VERIFY_ACCEPT_ALL:
         SSL_CTX_set_cert_verify_callback(client_ctx, &verify_accept_cb,
@@ -686,9 +696,22 @@ static char *dup_str(const unsigned char *in, size_t len)
     return ret;
 }
 
+/*
+ * Note that |extra| points to the correct client/server configuration
+ * within |test_ctx|. When configuring the handshake, general mode settings
+ * are taken from |test_ctx|, and client/server-specific settings should be
+ * taken from |extra|.
+ *
+ * The configuration code should never reach into |test_ctx->extra| or
+ * |test_ctx->resume_extra| directly.
+ *
+ * (We could refactor test mode settings into a substructure. This would result
+ * in cleaner argument passing but would complicate the test configuration
+ * parsing.)
+ */
 static HANDSHAKE_RESULT *do_handshake_internal(
     SSL_CTX *server_ctx, SSL_CTX *server2_ctx, SSL_CTX *client_ctx,
-    const SSL_TEST_EXTRA_CONF *extra, int app_data_size,
+    const SSL_TEST_CTX *test_ctx, const SSL_TEST_EXTRA_CONF *extra,
     SSL_SESSION *session_in, SSL_SESSION **session_out)
 {
     PEER server, client;
@@ -712,15 +735,15 @@ static HANDSHAKE_RESULT *do_handshake_internal(
     memset(&server, 0, sizeof(server));
     memset(&client, 0, sizeof(client));
 
-    configure_handshake_ctx(server_ctx, server2_ctx, client_ctx, extra,
+    configure_handshake_ctx(server_ctx, server2_ctx, client_ctx, test_ctx, extra,
                             &server_ctx_data, &server2_ctx_data, &client_ctx_data);
 
     /* Setup SSL and buffers; additional configuration happens below. */
     create_peer(&server, server_ctx);
     create_peer(&client, client_ctx);
 
-    server.bytes_to_write = client.bytes_to_read = app_data_size;
-    client.bytes_to_write = server.bytes_to_read = app_data_size;
+    server.bytes_to_write = client.bytes_to_read = test_ctx->app_data_size;
+    client.bytes_to_write = server.bytes_to_read = test_ctx->app_data_size;
 
     configure_handshake_ssl(server.ssl, client.ssl, extra);
     if (session_in != NULL) {
@@ -869,7 +892,7 @@ HANDSHAKE_RESULT *do_handshake(SSL_CTX *server_ctx, SSL_CTX *server2_ctx,
     SSL_SESSION *session = NULL;
 
     result = do_handshake_internal(server_ctx, server2_ctx, client_ctx,
-                                   &test_ctx->extra, test_ctx->app_data_size,
+                                   test_ctx, &test_ctx->extra,
                                    NULL, &session);
     if (test_ctx->handshake_mode == SSL_TEST_HANDSHAKE_SIMPLE)
         goto end;
@@ -884,7 +907,7 @@ HANDSHAKE_RESULT *do_handshake(SSL_CTX *server_ctx, SSL_CTX *server2_ctx,
     HANDSHAKE_RESULT_free(result);
     /* We don't support SNI on second handshake yet, so server2_ctx is NULL. */
     result = do_handshake_internal(resume_server_ctx, NULL, resume_client_ctx,
-                                   &test_ctx->resume_extra, test_ctx->app_data_size,
+                                   test_ctx, &test_ctx->resume_extra,
                                    session, NULL);
  end:
     SSL_SESSION_free(session);

test/recipes/80-test_ssl_new.t

@@ -29,7 +29,7 @@ map { s/\.in// } @conf_files;
 
 # We hard-code the number of tests to double-check that the globbing above
 # finds all files as expected.
-plan tests => 12;  # = scalar @conf_srcs
+plan tests => 13;  # = scalar @conf_srcs
 
 # Some test results depend on the configuration of enabled protocols. We only
 # verify generated sources in the default configuration.
@@ -59,6 +59,11 @@ my %skip = (
   "10-resumption.conf" => disabled("tls1_1") || disabled("tls1_2"),
   "11-dtls_resumption.conf" => disabled("dtls1") || disabled("dtls1_2"),
   "12-ct.conf" => $no_tls || $no_ct || $no_ec,
+  # We could run some of these tests without TLS 1.2 if we had a per-test
+  # disable instruction but that's a bizarre configuration not worth
+  # special-casing for.
+  # We should review this once we have TLS 1.3.
+  "13-fragmentation.conf" => disabled("tls1_2")
 );
 
 foreach my $conf (@conf_files) {

test/recipes/80-test_ssl_old.t

@@ -79,7 +79,7 @@ my $client_sess="client.ss";
 # new format in ssl_test.c and add recipes to 80-test_ssl_new.t instead.
 plan tests =>
     1				# For testss
-    +7  			# For the first testssl
+    +6  			# For the first testssl
     ;
 
 subtest 'test_ss' => sub {
@@ -579,28 +579,6 @@ sub testssl {
 	     'test tls1 with SRP auth via BIO pair');
 	}
     };
-
-    subtest 'Multi-buffer tests' => sub {
-	######################################################################
-
-	plan tests => 2;
-
-      SKIP: {
-	  skip "Neither SSLv3 nor any TLS version are supported by this OpenSSL build", 2
-	      if $no_anytls;
-
-	  skip "skipping multi-buffer tests", 2
-	      if (POSIX::uname())[4] ne "x86_64";
-
-	  ok(run(test([@ssltest, "-cipher", "AES128-SHA",    "-bytes", "8m"])));
-
-	  # We happen to know that AES128-SHA256 is TLSv1.2 only... for now.
-	  skip "TLSv1.2 is not supported by this OpenSSL configuration", 1
-	      if $no_tls1_2;
-
-	  ok(run(test([@ssltest, "-cipher", "AES128-SHA256", "-bytes", "8m"])));
-	}
-    };
 }
 
 unlink $CAkey;

test/ssl-tests/13-fragmentation.conf

+# Generated with generate_ssl_tests.pl
+
+num_tests = 16
+
+test-0 = 0-one-fragment-minus-app-data
+test-1 = 1-one-fragment-app-data
+test-2 = 2-one-fragment-plus-app-data
+test-3 = 3-small-app-data
+test-4 = 4-small-app-data-large-fragment-size
+test-5 = 5-medium-app-data
+test-6 = 6-medium-plus-app-data
+test-7 = 7-large-app-data
+test-8 = 8-large-app-data-large-fragment-size
+test-9 = 9-large-app-data-odd-fragment-size
+test-10 = 10-large-app-data-aes-sha1-multibuffer
+test-11 = 11-large-app-data-aes-sha2-multibuffer
+test-12 = 12-large-app-data-aes-sha1-multibuffer-odd-fragment
+test-13 = 13-large-app-data-aes-sha2-multibuffer-odd-fragment
+test-14 = 14-small-app-data-aes-sha1-multibuffer
+test-15 = 15-small-app-data-aes-sha2-multibuffer
+# ===========================================================
+
+[0-one-fragment-minus-app-data]
+ssl_conf = 0-one-fragment-minus-app-data-ssl
+
+[0-one-fragment-minus-app-data-ssl]
+server = 0-one-fragment-minus-app-data-server
+client = 0-one-fragment-minus-app-data-client
+
+[0-one-fragment-minus-app-data-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[0-one-fragment-minus-app-data-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-0]
+ApplicationData = 511
+
+
+# ===========================================================
+
+[1-one-fragment-app-data]
+ssl_conf = 1-one-fragment-app-data-ssl
+
+[1-one-fragment-app-data-ssl]
+server = 1-one-fragment-app-data-server
+client = 1-one-fragment-app-data-client
+
+[1-one-fragment-app-data-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[1-one-fragment-app-data-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-1]
+ApplicationData = 512
+
+
+# ===========================================================
+
+[2-one-fragment-plus-app-data]
+ssl_conf = 2-one-fragment-plus-app-data-ssl
+
+[2-one-fragment-plus-app-data-ssl]
+server = 2-one-fragment-plus-app-data-server
+client = 2-one-fragment-plus-app-data-client
+
+[2-one-fragment-plus-app-data-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[2-one-fragment-plus-app-data-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-2]
+ApplicationData = 513
+
+
+# ===========================================================
+
+[3-small-app-data]
+ssl_conf = 3-small-app-data-ssl
+
+[3-small-app-data-ssl]
+server = 3-small-app-data-server
+client = 3-small-app-data-client
+
+[3-small-app-data-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[3-small-app-data-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-3]
+ApplicationData = 4097
+
+
+# ===========================================================
+
+[4-small-app-data-large-fragment-size]
+ssl_conf = 4-small-app-data-large-fragment-size-ssl
+
+[4-small-app-data-large-fragment-size-ssl]
+server = 4-small-app-data-large-fragment-size-server
+client = 4-small-app-data-large-fragment-size-client
+
+[4-small-app-data-large-fragment-size-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[4-small-app-data-large-fragment-size-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-4]
+ApplicationData = 4097
+MaxFragmentSize = 16384
+
+
+# ===========================================================
+
+[5-medium-app-data]
+ssl_conf = 5-medium-app-data-ssl
+
+[5-medium-app-data-ssl]
+server = 5-medium-app-data-server
+client = 5-medium-app-data-client
+
+[5-medium-app-data-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[5-medium-app-data-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-5]
+ApplicationData = 32775
+
+
+# ===========================================================
+
+[6-medium-plus-app-data]
+ssl_conf = 6-medium-plus-app-data-ssl
+
+[6-medium-plus-app-data-ssl]
+server = 6-medium-plus-app-data-server
+client = 6-medium-plus-app-data-client
+
+[6-medium-plus-app-data-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[6-medium-plus-app-data-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-6]
+ApplicationData = 131069
+
+
+# ===========================================================
+
+[7-large-app-data]
+ssl_conf = 7-large-app-data-ssl
+
+[7-large-app-data-ssl]
+server = 7-large-app-data-server
+client = 7-large-app-data-client
+
+[7-large-app-data-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[7-large-app-data-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-7]
+ApplicationData = 1048576
+
+
+# ===========================================================
+
+[8-large-app-data-large-fragment-size]
+ssl_conf = 8-large-app-data-large-fragment-size-ssl
+
+[8-large-app-data-large-fragment-size-ssl]
+server = 8-large-app-data-large-fragment-size-server
+client = 8-large-app-data-large-fragment-size-client
+
+[8-large-app-data-large-fragment-size-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[8-large-app-data-large-fragment-size-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-8]
+ApplicationData = 1048576
+MaxFragmentSize = 16384
+
+
+# ===========================================================
+
+[9-large-app-data-odd-fragment-size]
+ssl_conf = 9-large-app-data-odd-fragment-size-ssl
+
+[9-large-app-data-odd-fragment-size-ssl]
+server = 9-large-app-data-odd-fragment-size-server
+client = 9-large-app-data-odd-fragment-size-client
+
+[9-large-app-data-odd-fragment-size-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[9-large-app-data-odd-fragment-size-client]
+CipherString = DEFAULT
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-9]
+ApplicationData = 1048576
+MaxFragmentSize = 5115
+
+
+# ===========================================================
+
+[10-large-app-data-aes-sha1-multibuffer]
+ssl_conf = 10-large-app-data-aes-sha1-multibuffer-ssl
+
+[10-large-app-data-aes-sha1-multibuffer-ssl]
+server = 10-large-app-data-aes-sha1-multibuffer-server
+client = 10-large-app-data-aes-sha1-multibuffer-client
+
+[10-large-app-data-aes-sha1-multibuffer-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[10-large-app-data-aes-sha1-multibuffer-client]
+CipherString = AES128-SHA
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-10]
+ApplicationData = 1048576
+MaxFragmentSize = 4096
+
+
+# ===========================================================
+
+[11-large-app-data-aes-sha2-multibuffer]
+ssl_conf = 11-large-app-data-aes-sha2-multibuffer-ssl
+
+[11-large-app-data-aes-sha2-multibuffer-ssl]
+server = 11-large-app-data-aes-sha2-multibuffer-server
+client = 11-large-app-data-aes-sha2-multibuffer-client
+
+[11-large-app-data-aes-sha2-multibuffer-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[11-large-app-data-aes-sha2-multibuffer-client]
+CipherString = AES128-SHA256
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-11]
+ApplicationData = 1048576
+MaxFragmentSize = 4096
+
+
+# ===========================================================
+
+[12-large-app-data-aes-sha1-multibuffer-odd-fragment]
+ssl_conf = 12-large-app-data-aes-sha1-multibuffer-odd-fragment-ssl
+
+[12-large-app-data-aes-sha1-multibuffer-odd-fragment-ssl]
+server = 12-large-app-data-aes-sha1-multibuffer-odd-fragment-server
+client = 12-large-app-data-aes-sha1-multibuffer-odd-fragment-client
+
+[12-large-app-data-aes-sha1-multibuffer-odd-fragment-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[12-large-app-data-aes-sha1-multibuffer-odd-fragment-client]
+CipherString = AES128-SHA
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-12]
+ApplicationData = 1048579
+MaxFragmentSize = 5115
+
+
+# ===========================================================
+
+[13-large-app-data-aes-sha2-multibuffer-odd-fragment]
+ssl_conf = 13-large-app-data-aes-sha2-multibuffer-odd-fragment-ssl
+
+[13-large-app-data-aes-sha2-multibuffer-odd-fragment-ssl]
+server = 13-large-app-data-aes-sha2-multibuffer-odd-fragment-server
+client = 13-large-app-data-aes-sha2-multibuffer-odd-fragment-client
+
+[13-large-app-data-aes-sha2-multibuffer-odd-fragment-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[13-large-app-data-aes-sha2-multibuffer-odd-fragment-client]
+CipherString = AES128-SHA256
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-13]
+ApplicationData = 1048573
+MaxFragmentSize = 5125
+
+
+# ===========================================================
+
+[14-small-app-data-aes-sha1-multibuffer]
+ssl_conf = 14-small-app-data-aes-sha1-multibuffer-ssl
+
+[14-small-app-data-aes-sha1-multibuffer-ssl]
+server = 14-small-app-data-aes-sha1-multibuffer-server
+client = 14-small-app-data-aes-sha1-multibuffer-client
+
+[14-small-app-data-aes-sha1-multibuffer-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[14-small-app-data-aes-sha1-multibuffer-client]
+CipherString = AES128-SHA
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-14]
+ApplicationData = 4096
+MaxFragmentSize = 4096
+
+
+# ===========================================================
+
+[15-small-app-data-aes-sha2-multibuffer]
+ssl_conf = 15-small-app-data-aes-sha2-multibuffer-ssl
+
+[15-small-app-data-aes-sha2-multibuffer-ssl]
+server = 15-small-app-data-aes-sha2-multibuffer-server
+client = 15-small-app-data-aes-sha2-multibuffer-client
+
+[15-small-app-data-aes-sha2-multibuffer-server]
+Certificate = ${ENV::TEST_CERTS_DIR}/servercert.pem
+CipherString = DEFAULT
+PrivateKey = ${ENV::TEST_CERTS_DIR}/serverkey.pem
+
+[15-small-app-data-aes-sha2-multibuffer-client]
+CipherString = AES128-SHA256
+VerifyCAFile = ${ENV::TEST_CERTS_DIR}/rootcert.pem
+VerifyMode = Peer
+
+[test-15]
+ApplicationData = 4096
+MaxFragmentSize = 4096
+
+

test/ssl-tests/13-fragmentation.conf.in

+# -*- mode: perl; -*-
+# Copyright 2016-2016 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the OpenSSL license (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+
+## Test version negotiation
+
+use strict;
+use warnings;
+
+package ssltests;
+
+
+our @tests = (
+    # Default fragment size is 512.
+    {
+        name => "one-fragment-minus-app-data",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 511,
+        }
+    },
+    {
+        name => "one-fragment-app-data",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 512,
+        }
+    },
+    {
+        name => "one-fragment-plus-app-data",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 513,
+        }
+    },
+    {
+        name => "small-app-data",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 4 * 1024 + 1,
+        }
+    },
+    {
+        name => "small-app-data-large-fragment-size",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 4 * 1024 + 1,
+            MaxFragmentSize => 16384,
+        }
+    },
+    {
+        name => "medium-app-data",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 32 * 1024 + 7,
+        }
+    },
+    # Exceeds the 64kB write buffer size.
+    {
+        name => "medium-plus-app-data",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 128 * 1024 - 3,
+        }
+    },
+    {
+        name => "large-app-data",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 1024 * 1024,
+        }
+    },
+    {
+        name => "large-app-data-large-fragment-size",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 1024 * 1024,
+            MaxFragmentSize => 16384,
+        }
+    },
+    {
+        name => "large-app-data-odd-fragment-size",
+        server => { },
+        client => { },
+        test => {
+            ApplicationData => 1024 * 1024,
+            MaxFragmentSize => 5 * 1024 - 5,
+        }
+    },
+    # When the buffer / fragment size ratio is sufficiently large,
+    # multi-buffer code kicks in on some platforms for AES-SHA.  The
+    # exact minimum ratio depends on the platform, and is usually
+    # around 4. Since the the test buffer is 64kB, a 4kB fragment is
+    # easily sufficient.
+    #
+    # (We run this test on all platforms though it's only true multibuffer
+    #  on some of them.)
+    {
+        name => "large-app-data-aes-sha1-multibuffer",
+        server => { },
+        client => {
+            CipherString => "AES128-SHA",
+        },
+        test => {
+            ApplicationData => 1024 * 1024,
+            MaxFragmentSize => 4 * 1024,
+        }
+    },
+    {
+        name => "large-app-data-aes-sha2-multibuffer",
+        server => { },
+        client => {
+            CipherString => "AES128-SHA256",
+        },
+        test => {
+            ApplicationData => 1024 * 1024,
+            MaxFragmentSize => 4 * 1024,
+        }
+    },
+        {
+        name => "large-app-data-aes-sha1-multibuffer-odd-fragment",
+        server => { },
+        client => {
+            CipherString => "AES128-SHA",
+        },
+        test => {
+            ApplicationData => 1024 * 1024 + 3,
+            MaxFragmentSize => 5 * 1024 - 5,
+        }
+    },
+    {
+        name => "large-app-data-aes-sha2-multibuffer-odd-fragment",
+        server => { },
+        client => {
+            CipherString => "AES128-SHA256",
+        },
+        test => {
+            ApplicationData => 1024 * 1024 - 3,
+            MaxFragmentSize => 5 * 1024 + 5,
+        }
+    },
+    # Test that multibuffer-capable code also handles small data correctly.
+    # Here fragment size == app data size < buffer size,
+    # so no multibuffering should happen.
+    {
+        name => "small-app-data-aes-sha1-multibuffer",
+        server => { },
+        client => {
+            CipherString => "AES128-SHA",
+        },
+        test => {
+            ApplicationData => 4 * 1024,
+            MaxFragmentSize => 4 * 1024,
+        }
+    },
+    {
+        name => "small-app-data-aes-sha2-multibuffer",
+        server => { },
+        client => {
+            CipherString => "AES128-SHA256",
+        },
+        test => {
+            ApplicationData => 4 * 1024,
+            MaxFragmentSize => 4 * 1024,
+        }
+    },
+);

test/ssl_test_ctx.c

@@ -17,6 +17,8 @@
 #include "testutil.h"
 
 static const int default_app_data_size = 256;
+/* Default set to be as small as possible to exercise fragmentation. */
+static const int default_max_fragment_size = 512;
 
 static int parse_boolean(const char *value, int *result)
 {
@@ -389,11 +391,17 @@ IMPLEMENT_SSL_TEST_BOOL_OPTION(SSL_TEST_CTX, test, resumption_expected)
 IMPLEMENT_SSL_TEST_BOOL_OPTION(SSL_TEST_SERVER_CONF, server, broken_session_ticket)
 
 /***********************/
-/* Applicationdata     */
+/* ApplicationData     */
 /***********************/
 
 IMPLEMENT_SSL_TEST_INT_OPTION(SSL_TEST_CTX, test, app_data_size)
 
+/***********************/
+/* MaxFragmentSize     */
+/***********************/
+
+IMPLEMENT_SSL_TEST_INT_OPTION(SSL_TEST_CTX, test, max_fragment_size)
+
 /*************************************************************/
 /* Known test options and their corresponding parse methods. */
 /*************************************************************/
@@ -417,6 +425,7 @@ static const ssl_test_ctx_option ssl_test_ctx_options[] = {
     { "HandshakeMode", &parse_handshake_mode },
     { "ResumptionExpected", &parse_test_resumption_expected },
     { "ApplicationData", &parse_test_app_data_size },
+    { "MaxFragmentSize", &parse_test_max_fragment_size },
 };
 
 /* Nested client options. */
@@ -456,6 +465,7 @@ SSL_TEST_CTX *SSL_TEST_CTX_new()
     ret = OPENSSL_zalloc(sizeof(*ret));
     TEST_check(ret != NULL);
     ret->app_data_size = default_app_data_size;
+    ret->max_fragment_size = default_max_fragment_size;
     return ret;
 }
 

test/ssl_test_ctx.h

@@ -109,6 +109,8 @@ typedef struct {
      * Both peers will send |app_data_size| bytes interleaved.
      */
     int app_data_size;
+    /* Maximum send fragment size. */
+    int max_fragment_size;
 
     /*
      * Extra server/client configurations. Per-handshake.

test/ssl_test_ctx_test.c

@@ -115,6 +115,12 @@ static int SSL_TEST_CTX_equal(SSL_TEST_CTX *ctx, SSL_TEST_CTX *ctx2)
         return 0;
     }
 
+    if (ctx->max_fragment_size != ctx2->max_fragment_size) {
+        fprintf(stderr, "MaxFragmentSize mismatch: %d vs %d.\n",
+                ctx->max_fragment_size, ctx2->max_fragment_size);
+        return 0;
+    }
+
     if (!SSL_TEST_EXTRA_CONF_equal(&ctx->extra, &ctx2->extra)) {
         fprintf(stderr, "Extra conf mismatch.\n");
         return 0;
@@ -246,6 +252,7 @@ static int test_good_configuration()
     fixture.expected_ctx->method = SSL_TEST_METHOD_DTLS;
     fixture.expected_ctx->handshake_mode = SSL_TEST_HANDSHAKE_RESUME;
     fixture.expected_ctx->app_data_size = 1024;
+    fixture.expected_ctx->max_fragment_size = 2048;
 
     fixture.expected_ctx->expected_result = SSL_TEST_SERVER_FAIL;
     fixture.expected_ctx->expected_client_alert = SSL_AD_UNKNOWN_CA;

test/ssl_test_ctx_test.conf

@@ -9,6 +9,7 @@ resume-client = ssltest_good_resume_client_extra
 Method = DTLS
 HandshakeMode = Resume
 ApplicationData = 1024
+MaxFragmentSize = 2048
 
 ExpectedResult = ServerFail
 ExpectedClientAlert = UnknownCA