Add test cases for DTLS_get_data_mtu()

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>

1 files changed, 190 insertions, 0 deletions

diff --git a/test/dtls_mtu_test.c b/test/dtls_mtu_test.c
new file mode 100644
index 0000000000..df1013ac51
--- /dev/null
+++ b/test/dtls_mtu_test.c
@@ -0,0 +1,190 @@
+/*
+ * Copyright 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
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include <openssl/dtls1.h>
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+
+#include "ssltestlib.h"
+
+/* for SSL_USE_ETM() */
+#include "../ssl/ssl_locl.h"
+
+static int debug = 0;
+
+static unsigned int clnt_psk_callback(SSL *ssl, const char *hint,
+                                      char *ident, unsigned int max_ident_len,
+                                      unsigned char *psk,
+                                      unsigned int max_psk_len)
+{
+    snprintf(ident, max_ident_len, "psk");
+
+    if (max_psk_len > 20)
+        max_psk_len = 20;
+    memset(psk, 0x5a, max_psk_len);
+
+    return max_psk_len;
+}
+
+static unsigned int srvr_psk_callback(SSL *ssl, const char *identity,
+                                      unsigned char *psk,
+                                      unsigned int max_psk_len)
+{
+    if (max_psk_len > 20)
+        max_psk_len = 20;
+    memset(psk, 0x5a, max_psk_len);
+    return max_psk_len;
+}
+
+static int mtu_test(SSL_CTX *ctx, const char *cs, int no_etm)
+{
+    SSL *srvr_ssl = NULL, *clnt_ssl = NULL;
+    BIO *sc_bio = NULL;
+    int i;
+    size_t s;
+    size_t mtus[30];
+    unsigned char buf[600];
+    int rv = 0;
+
+    memset(buf, 0x5a, sizeof(buf));
+
+    if (create_ssl_objects(ctx, ctx, &srvr_ssl, &clnt_ssl, NULL, NULL) != 1)
+        goto out;
+
+    if (no_etm)
+        SSL_set_options(srvr_ssl, SSL_OP_NO_ENCRYPT_THEN_MAC);
+
+    if (SSL_set_cipher_list(srvr_ssl, cs) != 1 ||
+        SSL_set_cipher_list(clnt_ssl, cs) != 1) {
+        ERR_print_errors_fp(stdout);
+        goto out;
+    }
+    sc_bio = SSL_get_rbio(srvr_ssl);
+
+    if (create_ssl_connection(clnt_ssl, srvr_ssl) != 1)
+        goto out;
+
+    if (debug)
+        printf("Channel established\n");
+
+    /* For record MTU values between 500 and 539, call DTLS_get_data_mtu()
+     * to query the payload MTU which will fit. */
+    for (i = 0; i < 30; i++) {
+        SSL_set_mtu(clnt_ssl, 500 + i);
+        mtus[i] = DTLS_get_data_mtu(clnt_ssl);
+        if (debug)
+            printf("%s%s payload MTU for record mtu %d = %"OSSLzu"\n",
+                   cs, no_etm ? "-noEtM":"", 500 + i, mtus[i]);
+        if (mtus[i] == 0) {
+            fprintf(stderr,
+                    "payload MTU failed with record MTU %d for %s\n",
+                    500 + i, cs);
+            goto out;
+        }
+    }
+
+    /* Now get out of the way */
+    SSL_set_mtu(clnt_ssl, 1000);
+
+    /* Now for all values in the range of payload MTUs, send
+     * a payload of that size and see what actual record size
+     * we end up with. */
+    for (s = mtus[0]; s <= mtus[29]; s++) {
+        size_t reclen;
+        if (SSL_write(clnt_ssl, buf, s) != (int)s) {
+            ERR_print_errors_fp(stdout);
+            goto out;
+        }
+        reclen = BIO_read(sc_bio, buf, sizeof(buf));
+        if (debug)
+            printf("record %"OSSLzu" for payload %"OSSLzu"\n", reclen, s);
+
+        for (i = 0; i < 30; i++) {
+            /* DTLS_get_data_mtu() with record MTU 500+i returned mtus[i] ... */
+
+            if (s <= mtus[i] && reclen > (size_t)(500 + i)) {
+                /* We sent a packet smaller than or equal to mtus[j] and
+                 * that made a record *larger* than the record MTU 500+j! */
+                fprintf(stderr,
+                        "%s: Payload MTU %"OSSLzu" reported for record MTU %d\n"
+                        "but sending a payload of %"OSSLzu" made a record of %"OSSLzu"(too large)\n",
+                        cs, mtus[i], 500 + i, s, reclen);
+                goto out;
+            }
+            if (s > mtus[i] && reclen <= (size_t)(500 + i)) {
+                /* We sent a *larger* packet than mtus[i] and that *still*
+                 * fits within the record MTU 500+i, so DTLS_get_data_mtu()
+                 * was overly pessimistic. */
+                fprintf(stderr,
+                        "%s: Payload MTU %"OSSLzu" reported for record MTU %d\n"
+                        "but sending a payload of %"OSSLzu" made a record of %"OSSLzu" (too small)\n",
+                        cs, mtus[i], 500 + i, s, reclen);
+                goto out;
+            }
+        }
+    }
+    rv = 1;
+    if (SSL_USE_ETM(clnt_ssl))
+        rv = 2;
+ out:
+    SSL_free(clnt_ssl);
+    SSL_free(srvr_ssl);
+    return rv;
+}
+
+int main(void)
+{
+    SSL_CTX *ctx = SSL_CTX_new(DTLS_method());
+    STACK_OF(SSL_CIPHER) *ciphers;
+    int i, rv = 0;
+
+    SSL_CTX_set_psk_server_callback(ctx, srvr_psk_callback);
+    SSL_CTX_set_psk_client_callback(ctx, clnt_psk_callback);
+    SSL_CTX_set_security_level(ctx, 0);
+
+    /* We only care about iterating over each enc/mac; we don't
+     * want to repeat the test for each auth/kx variant.
+     * So keep life simple and only do (non-DH) PSK. */
+    if (!SSL_CTX_set_cipher_list(ctx, "PSK")) {
+        fprintf(stderr, "Failed to set PSK cipher list\n");
+        goto out;
+    }
+
+    ciphers = SSL_CTX_get_ciphers(ctx);
+    for (i = 0; i < sk_SSL_CIPHER_num(ciphers); i++) {
+        const SSL_CIPHER *cipher = sk_SSL_CIPHER_value(ciphers, i);
+        const char *cipher_name = SSL_CIPHER_get_name(cipher);
+
+        /* As noted above, only one test for each enc/mac variant. */
+        if (strncmp(cipher_name, "PSK-", 4))
+            continue;
+
+        rv = mtu_test(ctx, cipher_name, 0);
+        if (!rv)
+            break;
+
+        printf("DTLS MTU test OK for %s\n", cipher_name);
+        if (rv == 1)
+            continue;
+
+        /* mtu_test() returns 2 if it used Encrypt-then-MAC */
+        rv = mtu_test(ctx, cipher_name, 1);
+        if (!rv)
+            break;
+
+        printf("DTLS MTU test OK for %s without Encrypt-then-MAC\n", cipher_name);
+    }
+ out:
+    SSL_CTX_free(ctx);
+
+    return !rv;
+}