commit e111e371b4f44456182e7f237837a0f9466487cd Author: Robert Ransom <rransom.8774@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. */