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Commit 80082b71 authored by Nick Mathewson's avatar Nick Mathewson :game_die:
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Remove rectify_client_ciphers as needless. 

We previously used this function instead of SSL_set_cipher_list() to
set up a stack of client SSL_CIPHERs for these reasons:

  A) In order to force a particular order of the results.

  B) In order to be able to include dummy entries for ciphers that
     this build of openssl did not support, so we could impersonate
     Firefox harder.

But we no longer do B, since we merged proposal 198 and stopped
lying about what ciphers we know.

And A was actually pointless, since I had misread the implementation
of SSL_set_cipher_list().  It _does_ do some internal sorting, but
that is pre-sorting on the master list of ciphers, not sorting on
the user's preferred order.
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src/common/tortls.c
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......@@ -217,16 +217,6 @@ struct tor_tls_t {
void *callback_arg;
};
#ifdef V2_HANDSHAKE_CLIENT
/** An array of fake SSL_CIPHER objects that we use in order to trick OpenSSL
* in client mode into advertising the ciphers we want. See
* rectify_client_ciphers() for details. */
static SSL_CIPHER *CLIENT_CIPHER_DUMMIES = NULL;
/** A stack of SSL_CIPHER objects, some real, some fake.
* See rectify_client_ciphers() for details. */
static STACK_OF(SSL_CIPHER) *CLIENT_CIPHER_STACK = NULL;
#endif
/** The ex_data index in which we store a pointer to an SSL object's
* corresponding tor_tls_t object. */
static int tor_tls_object_ex_data_index = -1;
......@@ -595,12 +585,6 @@ tor_tls_free_all(void)
client_tls_context = NULL;
tor_tls_context_decref(ctx);
}
#ifdef V2_HANDSHAKE_CLIENT
if (CLIENT_CIPHER_DUMMIES)
tor_free(CLIENT_CIPHER_DUMMIES);
if (CLIENT_CIPHER_STACK)
sk_SSL_CIPHER_free(CLIENT_CIPHER_STACK);
#endif
}
/** We need to give OpenSSL a callback to verify certificates. This is
......@@ -790,7 +774,6 @@ const char UNRESTRICTED_SERVER_CIPHER_LIST[] =
* (SSL3_TXT_RSA_NULL_SHA). If you do this, you won't be able to communicate
* with any of the "real" Tors, though. */
#ifdef V2_HANDSHAKE_CLIENT
#define CIPHER(id, name) name ":"
#define XCIPHER(id, name)
/** List of ciphers that clients should advertise, omitting items that
......@@ -804,28 +787,6 @@ static const char CLIENT_CIPHER_LIST[] =
#undef CIPHER
#undef XCIPHER
/** Holds a cipher that we want to advertise, and its 2-byte ID. */
typedef struct cipher_info_t { unsigned id; const char *name; } cipher_info_t;
/** A list of all the ciphers that clients should advertise, including items
* that OpenSSL might not know about. */
static const cipher_info_t CLIENT_CIPHER_INFO_LIST[] = {
#define CIPHER(id, name) { id, name },
#define XCIPHER(id, name) { id, #name },
#include "./ciphers.inc"
#undef CIPHER
#undef XCIPHER
};
/** The length of CLIENT_CIPHER_INFO_LIST and CLIENT_CIPHER_DUMMIES. */
static const int N_CLIENT_CIPHERS = ARRAY_LENGTH(CLIENT_CIPHER_INFO_LIST);
#endif
#ifndef V2_HANDSHAKE_CLIENT
#undef CLIENT_CIPHER_LIST
#define CLIENT_CIPHER_LIST (TLS1_TXT_DHE_RSA_WITH_AES_128_SHA ":" \
SSL3_TXT_EDH_RSA_DES_192_CBC3_SHA)
#endif
/** Free all storage held in <b>cert</b> */
void
tor_cert_free(tor_cert_t *cert)
......@@ -1796,149 +1757,6 @@ tor_tls_setup_session_secret_cb(tor_tls_t *tls)
#define tor_tls_setup_session_secret_cb(tls) STMT_NIL
#endif
/** Explain which ciphers we're missing. */
static void
log_unsupported_ciphers(smartlist_t *unsupported)
{
char *joined;
log_notice(LD_NET, "We weren't able to find support for all of the "
"TLS ciphersuites that we wanted to advertise. This won't "
"hurt security, but it might make your Tor (if run as a client) "
"more easy for censors to block.");
if (SSLeay() < 0x10000000L) {
log_notice(LD_NET, "To correct this, use a more recent OpenSSL, "
"built without disabling any secure ciphers or features.");
} else {
log_notice(LD_NET, "To correct this, use a version of OpenSSL "
"built with none of its ciphers disabled.");
}
joined = smartlist_join_strings(unsupported, ":", 0, NULL);
log_info(LD_NET, "The unsupported ciphers were: %s", joined);
tor_free(joined);
}
static void
set_ssl_ciphers_to_list(SSL *ssl, STACK_OF(SSL_CIPHER) *stack)
{
STACK_OF(SSL_CIPHER) *ciphers;
int r, i;
/* #1: ensure that the ssl object has its own list of ciphers. Otherwise we
* might be about to stomp the SSL_CTX ciphers list. */
r = SSL_set_cipher_list(ssl, "HIGH");
tor_assert(r);
/* #2: Grab ssl_ciphers and clear it. */
ciphers = SSL_get_ciphers(ssl);
tor_assert(ciphers);
sk_SSL_CIPHER_zero(ciphers);
/* #3: Copy the elements from stack. */
for (i = 0; i < sk_SSL_CIPHER_num(stack); ++i) {
SSL_CIPHER *c = sk_SSL_CIPHER_value(stack, i);
sk_SSL_CIPHER_push(ciphers, c);
}
}
/** Replace the ciphers on <b>ssl</b> with a new list of SSL ciphersuites:
* specifically, a list designed to mimic a common web browser. We might not
* be able to do that if OpenSSL doesn't support all the ciphers we want.
* Some of the ciphers in the list won't actually be implemented by OpenSSL:
* that's okay so long as the server doesn't select them.
*
* [If the server <b>does</b> select a bogus cipher, we won't crash or
* anything; we'll just fail later when we try to look up the cipher in
* ssl->cipher_list_by_id.]
*/
static void
rectify_client_ciphers(SSL *ssl)
{
#ifdef V2_HANDSHAKE_CLIENT
if (PREDICT_UNLIKELY(!CLIENT_CIPHER_STACK)) {
STACK_OF(SSL_CIPHER) *ciphers = SSL_get_ciphers(ssl);
/* We need to set CLIENT_CIPHER_STACK to an array of the ciphers
* we want to use/advertise. */
int i = 0, j = 0;
smartlist_t *unsupported = smartlist_new();
/* First, create a dummy SSL_CIPHER for every cipher. */
CLIENT_CIPHER_DUMMIES =
tor_malloc_zero(sizeof(SSL_CIPHER)*N_CLIENT_CIPHERS);
for (i=0; i < N_CLIENT_CIPHERS; ++i) {
CLIENT_CIPHER_DUMMIES[i].valid = 1;
/* The "3<<24" here signifies that the cipher is supposed to work with
* SSL3 and TLS1. */
CLIENT_CIPHER_DUMMIES[i].id = CLIENT_CIPHER_INFO_LIST[i].id | (3<<24);
CLIENT_CIPHER_DUMMIES[i].name = CLIENT_CIPHER_INFO_LIST[i].name;
}
CLIENT_CIPHER_STACK = sk_SSL_CIPHER_new_null();
tor_assert(CLIENT_CIPHER_STACK);
log_debug(LD_NET, "List was: %s", CLIENT_CIPHER_LIST);
for (j = 0; j < sk_SSL_CIPHER_num(ciphers); ++j) {
SSL_CIPHER *cipher = sk_SSL_CIPHER_value(ciphers, j);
log_debug(LD_NET, "Cipher %d: %lx %s", j,
SSL_CIPHER_get_id(cipher), SSL_CIPHER_get_name(cipher));
}
/* Then copy as many ciphers as we can from the good list, inserting
* dummies as needed. Let j be an index into list of ciphers we have
* (ciphers) and let i be an index into the ciphers we want
* (CLIENT_INFO_CIPHER_LIST). We are building a list of ciphers in
* CLIENT_CIPHER_STACK.
*/
for (i = j = 0; i < N_CLIENT_CIPHERS; ) {
SSL_CIPHER *cipher = NULL;
if (j < sk_SSL_CIPHER_num(ciphers))
cipher = sk_SSL_CIPHER_value(ciphers, j);
if (cipher && ((SSL_CIPHER_get_id(cipher) >> 24) & 0xff) != 3) {
/* Skip over non-v3 ciphers entirely. (This should no longer be
* needed, thanks to saying !SSLv2 above.) */
log_debug(LD_NET, "Skipping v%d cipher %s",
(int)((SSL_CIPHER_get_id(cipher)>>24) & 0xff),
SSL_CIPHER_get_name(cipher));
++j;
} else if (cipher &&
(SSL_CIPHER_get_id(cipher) & 0xffff) == CLIENT_CIPHER_INFO_LIST[i].id) {
/* "cipher" is the cipher we expect. Put it on the list. */
log_debug(LD_NET, "Found cipher %s", SSL_CIPHER_get_name(cipher));
sk_SSL_CIPHER_push(CLIENT_CIPHER_STACK, cipher);
++j;
++i;
} else if (!strcmp(CLIENT_CIPHER_DUMMIES[i].name,
"SSL_RSA_FIPS_WITH_3DES_EDE_CBC_SHA")) {
/* We found bogus cipher 0xfeff, which OpenSSL doesn't support and
* never has. For this one, we need a dummy. */
log_debug(LD_NET, "Inserting fake %s", CLIENT_CIPHER_DUMMIES[i].name);
sk_SSL_CIPHER_push(CLIENT_CIPHER_STACK, &CLIENT_CIPHER_DUMMIES[i]);
++i;
} else {
/* OpenSSL doesn't have this one. */
log_debug(LD_NET, "Completely omitting unsupported cipher %s",
CLIENT_CIPHER_INFO_LIST[i].name);
smartlist_add(unsupported, (char*) CLIENT_CIPHER_INFO_LIST[i].name);
++i;
}
}
if (smartlist_len(unsupported))
log_unsupported_ciphers(unsupported);
smartlist_free(unsupported);
}
set_ssl_ciphers_to_list(ssl, CLIENT_CIPHER_STACK);
#else
(void)ciphers;
#endif
}
/** Create a new TLS object from a file descriptor, and a flag to
* determine whether it is functioning as a server.
*/
......@@ -1978,8 +1796,6 @@ tor_tls_new(int sock, int isServer)
tor_free(result);
goto err;
}
if (!isServer)
rectify_client_ciphers(result->ssl);
result->socket = sock;
bio = BIO_new_socket(sock, BIO_NOCLOSE);
if (! bio) {
......
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