[tor-commits] [tor/master] Implement 'safe cookie authentication'
nickm at torproject.org
nickm at torproject.org
Mon Mar 26 22:53:37 UTC 2012
commit e111e371b4f44456182e7f237837a0f9466487cd
Author: Robert Ransom <rransom.8774 at gmail.com>
Date: Mon Feb 6 10:49:45 2012 -0800
Implement 'safe cookie authentication'
---
src/or/connection.c | 1 +
src/or/control.c | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++-
src/or/or.h | 6 ++
3 files changed, 164 insertions(+), 2 deletions(-)
diff --git a/src/or/connection.c b/src/or/connection.c
index a3481ec..36e192a 100644
--- a/src/or/connection.c
+++ b/src/or/connection.c
@@ -419,6 +419,7 @@ _connection_free(connection_t *conn)
}
if (conn->type == CONN_TYPE_CONTROL) {
control_connection_t *control_conn = TO_CONTROL_CONN(conn);
+ tor_free(control_conn->safecookie_client_hash);
tor_free(control_conn->incoming_cmd);
}
diff --git a/src/or/control.c b/src/or/control.c
index 1e411ec..ddfc80e 100644
--- a/src/or/control.c
+++ b/src/or/control.c
@@ -101,6 +101,12 @@ static int authentication_cookie_is_set = 0;
* read it off disk, it has permission to connect.) */
static char authentication_cookie[AUTHENTICATION_COOKIE_LEN];
+#define SAFECOOKIE_SERVER_TO_CONTROLLER_CONSTANT \
+ "Tor safe cookie authentication server-to-controller hash"
+#define SAFECOOKIE_CONTROLLER_TO_SERVER_CONSTANT \
+ "Tor safe cookie authentication controller-to-server hash"
+#define SAFECOOKIE_SERVER_NONCE_LEN DIGEST256_LEN
+
/** A sufficiently large size to record the last bootstrap phase string. */
#define BOOTSTRAP_MSG_LEN 1024
@@ -1078,6 +1084,32 @@ handle_control_authenticate(control_connection_t *conn, uint32_t len,
used_quoted_string = 1;
}
+ if (conn->safecookie_client_hash != NULL) {
+ /* The controller has chosen safe cookie authentication; the only
+ * acceptable authentication value is the controller-to-server
+ * response. */
+
+ tor_assert(authentication_cookie_is_set);
+
+ if (password_len != DIGEST256_LEN) {
+ log_warn(LD_CONTROL,
+ "Got safe cookie authentication response with wrong length "
+ "(%d)", (int)password_len);
+ errstr = "Wrong length for safe cookie response.";
+ goto err;
+ }
+
+ if (tor_memneq(conn->safecookie_client_hash, password, DIGEST256_LEN)) {
+ log_warn(LD_CONTROL,
+ "Got incorrect safe cookie authentication response");
+ errstr = "Safe cookie response did not match expected value.";
+ goto err;
+ }
+
+ tor_free(conn->safecookie_client_hash);
+ goto ok;
+ }
+
if (!options->CookieAuthentication && !options->HashedControlPassword &&
!options->HashedControlSessionPassword) {
/* if Tor doesn't demand any stronger authentication, then
@@ -2758,8 +2790,10 @@ handle_control_protocolinfo(control_connection_t *conn, uint32_t len,
int passwd = (options->HashedControlPassword != NULL ||
options->HashedControlSessionPassword != NULL);
smartlist_t *mlist = smartlist_create();
- if (cookies)
+ if (cookies) {
smartlist_add(mlist, (char*)"COOKIE");
+ smartlist_add(mlist, (char*)"SAFECOOKIE");
+ }
if (passwd)
smartlist_add(mlist, (char*)"HASHEDPASSWORD");
if (!cookies && !passwd)
@@ -2787,6 +2821,121 @@ handle_control_protocolinfo(control_connection_t *conn, uint32_t len,
return 0;
}
+/** Called when we get an AUTHCHALLENGE command. */
+static int
+handle_control_authchallenge(control_connection_t *conn, uint32_t len,
+ const char *body)
+{
+ const char *cp = body;
+ char *client_nonce;
+ size_t client_nonce_len;
+ char server_hash[DIGEST256_LEN];
+ char server_hash_encoded[HEX_DIGEST256_LEN+1];
+ char server_nonce[SAFECOOKIE_SERVER_NONCE_LEN];
+ char server_nonce_encoded[(2*SAFECOOKIE_SERVER_NONCE_LEN) + 1];
+
+ cp += strspn(cp, " \t\n\r");
+ if (!strcasecmpstart(cp, "SAFECOOKIE")) {
+ cp += strlen("SAFECOOKIE");
+ } else {
+ connection_write_str_to_buf("513 AUTHCHALLENGE only supports SAFECOOKIE "
+ "authentication", conn);
+ connection_mark_for_close(TO_CONN(conn));
+ return -1;
+ }
+
+ if (!authentication_cookie_is_set) {
+ connection_write_str_to_buf("515 Cookie authentication is disabled", conn);
+ connection_mark_for_close(TO_CONN(conn));
+ return -1;
+ }
+
+ cp += strspn(cp, " \t\n\r");
+ if (*cp == '"') {
+ const char *newcp =
+ decode_escaped_string(cp, len - (cp - body),
+ &client_nonce, &client_nonce_len);
+ if (newcp == NULL) {
+ connection_write_str_to_buf("513 Invalid quoted client nonce",
+ conn);
+ connection_mark_for_close(TO_CONN(conn));
+ return -1;
+ }
+ cp = newcp;
+ } else {
+ size_t client_nonce_encoded_len = strspn(cp, "0123456789ABCDEFabcdef");
+
+ client_nonce_len = client_nonce_encoded_len / 2;
+ client_nonce = tor_malloc_zero(client_nonce_len);
+
+ if (base16_decode(client_nonce, client_nonce_len,
+ cp, client_nonce_encoded_len) < 0) {
+ connection_write_str_to_buf("513 Invalid base16 client nonce",
+ conn);
+ connection_mark_for_close(TO_CONN(conn));
+ return -1;
+ }
+
+ cp += client_nonce_encoded_len;
+ }
+
+ cp += strspn(cp, " \t\n\r");
+ if (*cp != '\0' ||
+ cp != body + len) {
+ connection_write_str_to_buf("513 Junk at end of AUTHCHALLENGE command",
+ conn);
+ connection_mark_for_close(TO_CONN(conn));
+ tor_free(client_nonce);
+ return -1;
+ }
+
+ tor_assert(!crypto_rand(server_nonce, SAFECOOKIE_SERVER_NONCE_LEN));
+
+ /* Now compute and send the server-to-controller response, and the
+ * server's nonce. */
+ tor_assert(authentication_cookie != NULL);
+
+ {
+ size_t tmp_len = (AUTHENTICATION_COOKIE_LEN +
+ client_nonce_len +
+ SAFECOOKIE_SERVER_NONCE_LEN);
+ char *tmp = tor_malloc_zero(tmp_len);
+ char *client_hash = tor_malloc_zero(DIGEST256_LEN);
+ memcpy(tmp, authentication_cookie, AUTHENTICATION_COOKIE_LEN);
+ memcpy(tmp + AUTHENTICATION_COOKIE_LEN, client_nonce, client_nonce_len);
+ memcpy(tmp + AUTHENTICATION_COOKIE_LEN + client_nonce_len,
+ server_nonce, SAFECOOKIE_SERVER_NONCE_LEN);
+
+ crypto_hmac_sha256(server_hash,
+ SAFECOOKIE_SERVER_TO_CONTROLLER_CONSTANT,
+ strlen(SAFECOOKIE_SERVER_TO_CONTROLLER_CONSTANT),
+ tmp,
+ tmp_len);
+
+ crypto_hmac_sha256(client_hash,
+ SAFECOOKIE_CONTROLLER_TO_SERVER_CONSTANT,
+ strlen(SAFECOOKIE_CONTROLLER_TO_SERVER_CONSTANT),
+ tmp,
+ tmp_len);
+
+ conn->safecookie_client_hash = client_hash;
+
+ tor_free(tmp);
+ }
+
+ base16_encode(server_hash_encoded, sizeof(server_hash_encoded),
+ server_hash, sizeof(server_hash));
+ base16_encode(server_nonce_encoded, sizeof(server_nonce_encoded),
+ server_nonce, sizeof(server_nonce));
+
+ connection_printf_to_buf(conn,
+ "250 AUTHCHALLENGE SERVERHASH=%s "
+ "SERVERNONCE=%s\r\n",
+ server_hash_encoded,
+ server_nonce_encoded);
+ return 0;
+}
+
/** Called when we get a USEFEATURE command: parse the feature list, and
* set up the control_connection's options properly. */
static int
@@ -2888,7 +3037,10 @@ is_valid_initial_command(control_connection_t *conn, const char *cmd)
if (conn->_base.state == CONTROL_CONN_STATE_OPEN)
return 1;
if (!strcasecmp(cmd, "PROTOCOLINFO"))
- return !conn->have_sent_protocolinfo;
+ return (!conn->have_sent_protocolinfo &&
+ conn->safecookie_client_hash == NULL);
+ if (!strcasecmp(cmd, "AUTHCHALLENGE"))
+ return (conn->safecookie_client_hash == NULL);
if (!strcasecmp(cmd, "AUTHENTICATE") ||
!strcasecmp(cmd, "QUIT"))
return 1;
@@ -3104,6 +3256,9 @@ connection_control_process_inbuf(control_connection_t *conn)
} else if (!strcasecmp(conn->incoming_cmd, "PROTOCOLINFO")) {
if (handle_control_protocolinfo(conn, cmd_data_len, args))
return -1;
+ } else if (!strcasecmp(conn->incoming_cmd, "AUTHCHALLENGE")) {
+ if (handle_control_authchallenge(conn, cmd_data_len, args))
+ return -1;
} else {
connection_printf_to_buf(conn, "510 Unrecognized command \"%s\"\r\n",
conn->incoming_cmd);
diff --git a/src/or/or.h b/src/or/or.h
index c0714ee..eecd375 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -1254,6 +1254,12 @@ typedef struct control_connection_t {
* connection. */
unsigned int is_owning_control_connection:1;
+ /** If we have sent an AUTHCHALLENGE reply on this connection and
+ * have not received a successful AUTHENTICATE command, points to
+ * the value which the client must send to authenticate itself;
+ * otherwise, NULL. */
+ char *safecookie_client_hash;
+
/** Amount of space allocated in incoming_cmd. */
uint32_t incoming_cmd_len;
/** Number of bytes currently stored in incoming_cmd. */
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