Revision f5c7f5dfbaf0d2f7d946d0fe86f08e6bcb36ed0d authored by Matt Caswell on 30 June 2016, 12:17:08 UTC, committed by Matt Caswell on 22 August 2016, 09:53:55 UTC
DTLS can handle out of order record delivery. Additionally since handshake messages can be bigger than will fit into a single packet, the messages can be fragmented across multiple records (as with normal TLS). That means that the messages can arrive mixed up, and we have to reassemble them. We keep a queue of buffered messages that are "from the future", i.e. messages we're not ready to deal with yet but have arrived early. The messages held there may not be full yet - they could be one or more fragments that are still in the process of being reassembled. The code assumes that we will eventually complete the reassembly and when that occurs the complete message is removed from the queue at the point that we need to use it. However, DTLS is also tolerant of packet loss. To get around that DTLS messages can be retransmitted. If we receive a full (non-fragmented) message from the peer after previously having received a fragment of that message, then we ignore the message in the queue and just use the non-fragmented version. At that point the queued message will never get removed. Additionally the peer could send "future" messages that we never get to in order to complete the handshake. Each message has a sequence number (starting from 0). We will accept a message fragment for the current message sequence number, or for any sequence up to 10 into the future. However if the Finished message has a sequence number of 2, anything greater than that in the queue is just left there. So, in those two ways we can end up with "orphaned" data in the queue that will never get removed - except when the connection is closed. At that point all the queues are flushed. An attacker could seek to exploit this by filling up the queues with lots of large messages that are never going to be used in order to attempt a DoS by memory exhaustion. I will assume that we are only concerned with servers here. It does not seem reasonable to be concerned about a memory exhaustion attack on a client. They are unlikely to process enough connections for this to be an issue. A "long" handshake with many messages might be 5 messages long (in the incoming direction), e.g. ClientHello, Certificate, ClientKeyExchange, CertificateVerify, Finished. So this would be message sequence numbers 0 to 4. Additionally we can buffer up to 10 messages in the future. Therefore the maximum number of messages that an attacker could send that could get orphaned would typically be 15. The maximum size that a DTLS message is allowed to be is defined by max_cert_list, which by default is 100k. Therefore the maximum amount of "orphaned" memory per connection is 1500k. Message sequence numbers get reset after the Finished message, so renegotiation will not extend the maximum number of messages that can be orphaned per connection. As noted above, the queues do get cleared when the connection is closed. Therefore in order to mount an effective attack, an attacker would have to open many simultaneous connections. Issue reported by Quan Luo. CVE-2016-2179 Reviewed-by: Richard Levitte <levitte@openssl.org>
1 parent 5dfd038
ssl_test_ctx.c
/*
* 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 <string.h>
#include <openssl/e_os2.h>
#include <openssl/crypto.h>
#include "e_os.h"
#include "ssl_test_ctx.h"
#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)
{
if (strcasecmp(value, "Yes") == 0) {
*result = 1;
return 1;
}
else if (strcasecmp(value, "No") == 0) {
*result = 0;
return 1;
}
return 0;
}
#define IMPLEMENT_SSL_TEST_BOOL_OPTION(struct_type, name, field) \
static int parse_##name##_##field(struct_type *ctx, const char *value) \
{ \
return parse_boolean(value, &ctx->field); \
}
#define IMPLEMENT_SSL_TEST_STRING_OPTION(struct_type, name, field) \
static int parse_##name##_##field(struct_type *ctx, const char *value) \
{ \
OPENSSL_free(ctx->field); \
ctx->field = OPENSSL_strdup(value); \
TEST_check(ctx->field != NULL); \
return 1; \
}
#define IMPLEMENT_SSL_TEST_INT_OPTION(struct_type, name, field) \
static int parse_##name##_##field(struct_type *ctx, const char *value) \
{ \
ctx->field = atoi(value); \
return 1; \
}
/* True enums and other test configuration values that map to an int. */
typedef struct {
const char *name;
int value;
} test_enum;
__owur static int parse_enum(const test_enum *enums, size_t num_enums,
int *value, const char *name)
{
size_t i;
for (i = 0; i < num_enums; i++) {
if (strcmp(enums[i].name, name) == 0) {
*value = enums[i].value;
return 1;
}
}
return 0;
}
static const char *enum_name(const test_enum *enums, size_t num_enums,
int value)
{
size_t i;
for (i = 0; i < num_enums; i++) {
if (enums[i].value == value) {
return enums[i].name;
}
}
return "InvalidValue";
}
/*******************/
/* ExpectedResult. */
/*******************/
static const test_enum ssl_test_results[] = {
{"Success", SSL_TEST_SUCCESS},
{"ServerFail", SSL_TEST_SERVER_FAIL},
{"ClientFail", SSL_TEST_CLIENT_FAIL},
{"InternalError", SSL_TEST_INTERNAL_ERROR},
};
__owur static int parse_expected_result(SSL_TEST_CTX *test_ctx, const char *value)
{
int ret_value;
if (!parse_enum(ssl_test_results, OSSL_NELEM(ssl_test_results),
&ret_value, value)) {
return 0;
}
test_ctx->expected_result = ret_value;
return 1;
}
const char *ssl_test_result_name(ssl_test_result_t result)
{
return enum_name(ssl_test_results, OSSL_NELEM(ssl_test_results), result);
}
/**********************************************/
/* ExpectedClientAlert / ExpectedServerAlert. */
/**********************************************/
static const test_enum ssl_alerts[] = {
{"UnknownCA", SSL_AD_UNKNOWN_CA},
{"HandshakeFailure", SSL_AD_HANDSHAKE_FAILURE},
{"UnrecognizedName", SSL_AD_UNRECOGNIZED_NAME},
{"BadCertificate", SSL_AD_BAD_CERTIFICATE},
{"NoApplicationProtocol", SSL_AD_NO_APPLICATION_PROTOCOL},
};
__owur static int parse_alert(int *alert, const char *value)
{
return parse_enum(ssl_alerts, OSSL_NELEM(ssl_alerts), alert, value);
}
__owur static int parse_client_alert(SSL_TEST_CTX *test_ctx, const char *value)
{
return parse_alert(&test_ctx->expected_client_alert, value);
}
__owur static int parse_server_alert(SSL_TEST_CTX *test_ctx, const char *value)
{
return parse_alert(&test_ctx->expected_server_alert, value);
}
const char *ssl_alert_name(int alert)
{
return enum_name(ssl_alerts, OSSL_NELEM(ssl_alerts), alert);
}
/********************/
/* ExpectedProtocol */
/********************/
static const test_enum ssl_protocols[] = {
{"TLSv1.2", TLS1_2_VERSION},
{"TLSv1.1", TLS1_1_VERSION},
{"TLSv1", TLS1_VERSION},
{"SSLv3", SSL3_VERSION},
{"DTLSv1", DTLS1_VERSION},
{"DTLSv1.2", DTLS1_2_VERSION},
};
__owur static int parse_protocol(SSL_TEST_CTX *test_ctx, const char *value)
{
return parse_enum(ssl_protocols, OSSL_NELEM(ssl_protocols),
&test_ctx->expected_protocol, value);
}
const char *ssl_protocol_name(int protocol)
{
return enum_name(ssl_protocols, OSSL_NELEM(ssl_protocols), protocol);
}
/***********************/
/* VerifyCallback. */
/***********************/
static const test_enum ssl_verify_callbacks[] = {
{"None", SSL_TEST_VERIFY_NONE},
{"AcceptAll", SSL_TEST_VERIFY_ACCEPT_ALL},
{"RejectAll", SSL_TEST_VERIFY_REJECT_ALL},
};
__owur static int parse_client_verify_callback(SSL_TEST_CLIENT_CONF *client_conf,
const char *value)
{
int ret_value;
if (!parse_enum(ssl_verify_callbacks, OSSL_NELEM(ssl_verify_callbacks),
&ret_value, value)) {
return 0;
}
client_conf->verify_callback = ret_value;
return 1;
}
const char *ssl_verify_callback_name(ssl_verify_callback_t callback)
{
return enum_name(ssl_verify_callbacks, OSSL_NELEM(ssl_verify_callbacks),
callback);
}
/**************/
/* ServerName */
/**************/
static const test_enum ssl_servername[] = {
{"None", SSL_TEST_SERVERNAME_NONE},
{"server1", SSL_TEST_SERVERNAME_SERVER1},
{"server2", SSL_TEST_SERVERNAME_SERVER2},
{"invalid", SSL_TEST_SERVERNAME_INVALID},
};
__owur static int parse_servername(SSL_TEST_CLIENT_CONF *client_conf,
const char *value)
{
int ret_value;
if (!parse_enum(ssl_servername, OSSL_NELEM(ssl_servername),
&ret_value, value)) {
return 0;
}
client_conf->servername = ret_value;
return 1;
}
__owur static int parse_expected_servername(SSL_TEST_CTX *test_ctx,
const char *value)
{
int ret_value;
if (!parse_enum(ssl_servername, OSSL_NELEM(ssl_servername),
&ret_value, value)) {
return 0;
}
test_ctx->expected_servername = ret_value;
return 1;
}
const char *ssl_servername_name(ssl_servername_t server)
{
return enum_name(ssl_servername, OSSL_NELEM(ssl_servername),
server);
}
/**********************/
/* ServerNameCallback */
/**********************/
static const test_enum ssl_servername_callbacks[] = {
{"None", SSL_TEST_SERVERNAME_CB_NONE},
{"IgnoreMismatch", SSL_TEST_SERVERNAME_IGNORE_MISMATCH},
{"RejectMismatch", SSL_TEST_SERVERNAME_REJECT_MISMATCH},
};
__owur static int parse_servername_callback(SSL_TEST_SERVER_CONF *server_conf,
const char *value)
{
int ret_value;
if (!parse_enum(ssl_servername_callbacks,
OSSL_NELEM(ssl_servername_callbacks), &ret_value, value)) {
return 0;
}
server_conf->servername_callback = ret_value;
return 1;
}
const char *ssl_servername_callback_name(ssl_servername_callback_t callback)
{
return enum_name(ssl_servername_callbacks,
OSSL_NELEM(ssl_servername_callbacks), callback);
}
/*************************/
/* SessionTicketExpected */
/*************************/
static const test_enum ssl_session_ticket[] = {
{"Ignore", SSL_TEST_SESSION_TICKET_IGNORE},
{"Yes", SSL_TEST_SESSION_TICKET_YES},
{"No", SSL_TEST_SESSION_TICKET_NO},
};
__owur static int parse_session_ticket(SSL_TEST_CTX *test_ctx, const char *value)
{
int ret_value;
if (!parse_enum(ssl_session_ticket, OSSL_NELEM(ssl_session_ticket),
&ret_value, value)) {
return 0;
}
test_ctx->session_ticket_expected = ret_value;
return 1;
}
const char *ssl_session_ticket_name(ssl_session_ticket_t server)
{
return enum_name(ssl_session_ticket,
OSSL_NELEM(ssl_session_ticket),
server);
}
/***********************/
/* Method */
/***********************/
static const test_enum ssl_test_methods[] = {
{"TLS", SSL_TEST_METHOD_TLS},
{"DTLS", SSL_TEST_METHOD_DTLS},
};
__owur static int parse_test_method(SSL_TEST_CTX *test_ctx, const char *value)
{
int ret_value;
if (!parse_enum(ssl_test_methods, OSSL_NELEM(ssl_test_methods),
&ret_value, value)) {
return 0;
}
test_ctx->method = ret_value;
return 1;
}
const char *ssl_test_method_name(ssl_test_method_t method)
{
return enum_name(ssl_test_methods, OSSL_NELEM(ssl_test_methods), method);
}
/************************************/
/* NPN and ALPN options */
/************************************/
IMPLEMENT_SSL_TEST_STRING_OPTION(SSL_TEST_CLIENT_CONF, client, npn_protocols)
IMPLEMENT_SSL_TEST_STRING_OPTION(SSL_TEST_SERVER_CONF, server, npn_protocols)
IMPLEMENT_SSL_TEST_STRING_OPTION(SSL_TEST_CTX, test, expected_npn_protocol)
IMPLEMENT_SSL_TEST_STRING_OPTION(SSL_TEST_CLIENT_CONF, client, alpn_protocols)
IMPLEMENT_SSL_TEST_STRING_OPTION(SSL_TEST_SERVER_CONF, server, alpn_protocols)
IMPLEMENT_SSL_TEST_STRING_OPTION(SSL_TEST_CTX, test, expected_alpn_protocol)
/***********************/
/* Handshake mode */
/***********************/
static const test_enum ssl_handshake_modes[] = {
{"Simple", SSL_TEST_HANDSHAKE_SIMPLE},
{"Resume", SSL_TEST_HANDSHAKE_RESUME},
{"Renegotiate", SSL_TEST_HANDSHAKE_RENEGOTIATE},
};
__owur static int parse_handshake_mode(SSL_TEST_CTX *test_ctx, const char *value)
{
int ret_value;
if (!parse_enum(ssl_handshake_modes, OSSL_NELEM(ssl_handshake_modes),
&ret_value, value)) {
return 0;
}
test_ctx->handshake_mode = ret_value;
return 1;
}
const char *ssl_handshake_mode_name(ssl_handshake_mode_t mode)
{
return enum_name(ssl_handshake_modes, OSSL_NELEM(ssl_handshake_modes),
mode);
}
/***********************/
/* CT Validation */
/***********************/
static const test_enum ssl_ct_validation_modes[] = {
{"None", SSL_TEST_CT_VALIDATION_NONE},
{"Permissive", SSL_TEST_CT_VALIDATION_PERMISSIVE},
{"Strict", SSL_TEST_CT_VALIDATION_STRICT},
};
__owur static int parse_ct_validation(SSL_TEST_CLIENT_CONF *client_conf,
const char *value)
{
int ret_value;
if (!parse_enum(ssl_ct_validation_modes, OSSL_NELEM(ssl_ct_validation_modes),
&ret_value, value)) {
return 0;
}
client_conf->ct_validation = ret_value;
return 1;
}
const char *ssl_ct_validation_name(ssl_ct_validation_t mode)
{
return enum_name(ssl_ct_validation_modes, OSSL_NELEM(ssl_ct_validation_modes),
mode);
}
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 */
/***********************/
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. */
/*************************************************************/
/* Top-level options. */
typedef struct {
const char *name;
int (*parse)(SSL_TEST_CTX *test_ctx, const char *value);
} ssl_test_ctx_option;
static const ssl_test_ctx_option ssl_test_ctx_options[] = {
{ "ExpectedResult", &parse_expected_result },
{ "ExpectedClientAlert", &parse_client_alert },
{ "ExpectedServerAlert", &parse_server_alert },
{ "ExpectedProtocol", &parse_protocol },
{ "ExpectedServerName", &parse_expected_servername },
{ "SessionTicketExpected", &parse_session_ticket },
{ "Method", &parse_test_method },
{ "ExpectedNPNProtocol", &parse_test_expected_npn_protocol },
{ "ExpectedALPNProtocol", &parse_test_expected_alpn_protocol },
{ "HandshakeMode", &parse_handshake_mode },
{ "ResumptionExpected", &parse_test_resumption_expected },
{ "ApplicationData", &parse_test_app_data_size },
{ "MaxFragmentSize", &parse_test_max_fragment_size },
};
/* Nested client options. */
typedef struct {
const char *name;
int (*parse)(SSL_TEST_CLIENT_CONF *conf, const char *value);
} ssl_test_client_option;
static const ssl_test_client_option ssl_test_client_options[] = {
{ "VerifyCallback", &parse_client_verify_callback },
{ "ServerName", &parse_servername },
{ "NPNProtocols", &parse_client_npn_protocols },
{ "ALPNProtocols", &parse_client_alpn_protocols },
{ "CTValidation", &parse_ct_validation },
};
/* Nested server options. */
typedef struct {
const char *name;
int (*parse)(SSL_TEST_SERVER_CONF *conf, const char *value);
} ssl_test_server_option;
static const ssl_test_server_option ssl_test_server_options[] = {
{ "ServerNameCallback", &parse_servername_callback },
{ "NPNProtocols", &parse_server_npn_protocols },
{ "ALPNProtocols", &parse_server_alpn_protocols },
{ "BrokenSessionTicket", &parse_server_broken_session_ticket },
};
/*
* Since these methods are used to create tests, we use TEST_check liberally
* for malloc failures and other internal errors.
*/
SSL_TEST_CTX *SSL_TEST_CTX_new()
{
SSL_TEST_CTX *ret;
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;
}
static void ssl_test_extra_conf_free_data(SSL_TEST_EXTRA_CONF *conf)
{
OPENSSL_free(conf->client.npn_protocols);
OPENSSL_free(conf->server.npn_protocols);
OPENSSL_free(conf->server2.npn_protocols);
OPENSSL_free(conf->client.alpn_protocols);
OPENSSL_free(conf->server.alpn_protocols);
OPENSSL_free(conf->server2.alpn_protocols);
}
static void ssl_test_ctx_free_extra_data(SSL_TEST_CTX *ctx)
{
ssl_test_extra_conf_free_data(&ctx->extra);
ssl_test_extra_conf_free_data(&ctx->resume_extra);
}
void SSL_TEST_CTX_free(SSL_TEST_CTX *ctx)
{
ssl_test_ctx_free_extra_data(ctx);
OPENSSL_free(ctx->expected_npn_protocol);
OPENSSL_free(ctx->expected_alpn_protocol);
OPENSSL_free(ctx);
}
static int parse_client_options(SSL_TEST_CLIENT_CONF *client, const CONF *conf,
const char *client_section)
{
STACK_OF(CONF_VALUE) *sk_conf;
int i;
size_t j;
sk_conf = NCONF_get_section(conf, client_section);
TEST_check(sk_conf != NULL);
for (i = 0; i < sk_CONF_VALUE_num(sk_conf); i++) {
int found = 0;
const CONF_VALUE *option = sk_CONF_VALUE_value(sk_conf, i);
for (j = 0; j < OSSL_NELEM(ssl_test_client_options); j++) {
if (strcmp(option->name, ssl_test_client_options[j].name) == 0) {
if (!ssl_test_client_options[j].parse(client, option->value)) {
fprintf(stderr, "Bad value %s for option %s\n",
option->value, option->name);
return 0;
}
found = 1;
break;
}
}
if (!found) {
fprintf(stderr, "Unknown test option: %s\n", option->name);
return 0;
}
}
return 1;
}
static int parse_server_options(SSL_TEST_SERVER_CONF *server, const CONF *conf,
const char *server_section)
{
STACK_OF(CONF_VALUE) *sk_conf;
int i;
size_t j;
sk_conf = NCONF_get_section(conf, server_section);
TEST_check(sk_conf != NULL);
for (i = 0; i < sk_CONF_VALUE_num(sk_conf); i++) {
int found = 0;
const CONF_VALUE *option = sk_CONF_VALUE_value(sk_conf, i);
for (j = 0; j < OSSL_NELEM(ssl_test_server_options); j++) {
if (strcmp(option->name, ssl_test_server_options[j].name) == 0) {
if (!ssl_test_server_options[j].parse(server, option->value)) {
fprintf(stderr, "Bad value %s for option %s\n",
option->value, option->name);
return 0;
}
found = 1;
break;
}
}
if (!found) {
fprintf(stderr, "Unknown test option: %s\n", option->name);
return 0;
}
}
return 1;
}
SSL_TEST_CTX *SSL_TEST_CTX_create(const CONF *conf, const char *test_section)
{
STACK_OF(CONF_VALUE) *sk_conf;
SSL_TEST_CTX *ctx;
int i;
size_t j;
sk_conf = NCONF_get_section(conf, test_section);
TEST_check(sk_conf != NULL);
ctx = SSL_TEST_CTX_new();
TEST_check(ctx != NULL);
for (i = 0; i < sk_CONF_VALUE_num(sk_conf); i++) {
int found = 0;
const CONF_VALUE *option = sk_CONF_VALUE_value(sk_conf, i);
/* Subsections */
if (strcmp(option->name, "client") == 0) {
if (!parse_client_options(&ctx->extra.client, conf,
option->value))
goto err;
} else if (strcmp(option->name, "server") == 0) {
if (!parse_server_options(&ctx->extra.server, conf,
option->value))
goto err;
} else if (strcmp(option->name, "server2") == 0) {
if (!parse_server_options(&ctx->extra.server2, conf,
option->value))
goto err;
} else if (strcmp(option->name, "resume-client") == 0) {
if (!parse_client_options(&ctx->resume_extra.client, conf,
option->value))
goto err;
} else if (strcmp(option->name, "resume-server") == 0) {
if (!parse_server_options(&ctx->resume_extra.server, conf,
option->value))
goto err;
} else if (strcmp(option->name, "resume-server2") == 0) {
if (!parse_server_options(&ctx->resume_extra.server2, conf,
option->value))
goto err;
} else {
for (j = 0; j < OSSL_NELEM(ssl_test_ctx_options); j++) {
if (strcmp(option->name, ssl_test_ctx_options[j].name) == 0) {
if (!ssl_test_ctx_options[j].parse(ctx, option->value)) {
fprintf(stderr, "Bad value %s for option %s\n",
option->value, option->name);
goto err;
}
found = 1;
break;
}
}
if (!found) {
fprintf(stderr, "Unknown test option: %s\n", option->name);
goto err;
}
}
}
goto done;
err:
SSL_TEST_CTX_free(ctx);
ctx = NULL;
done:
return ctx;
}
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