diff options
Diffstat (limited to 'src/or/onion.c')
| -rw-r--r-- | src/or/onion.c | 81 |
1 files changed, 74 insertions, 7 deletions
diff --git a/src/or/onion.c b/src/or/onion.c index d6ef3673dd..a987883802 100644 --- a/src/or/onion.c +++ b/src/or/onion.c @@ -8,9 +8,62 @@ * \file onion.c * \brief Functions to queue create cells, wrap the various onionskin types, * and parse and create the CREATE cell and its allies. + * + * This module has a few functions, all related to the CREATE/CREATED + * handshake that we use on links in order to create a circuit, and the + * related EXTEND/EXTENDED handshake that we use over circuits in order to + * extend them an additional hop. + * + * In this module, we provide a set of abstractions to create a uniform + * interface over the three circuit extension handshakes that Tor has used + * over the years (TAP, CREATE_FAST, and ntor). These handshakes are + * implemented in onion_tap.c, onion_fast.c, and onion_ntor.c respectively. + * + * All[*] of these handshakes follow a similar pattern: a client, knowing + * some key from the relay it wants to extend through, generates the + * first part of a handshake. A relay receives that handshake, and sends + * a reply. Once the client handles the reply, it knows that it is + * talking to the right relay, and it shares some freshly negotiated key + * material with that relay. + * + * We sometimes call the client's part of the handshake an "onionskin". + * We do this because historically, Onion Routing used a multi-layer + * structure called an "onion" to construct circuits. Each layer of the + * onion contained key material chosen by the client, the identity of + * the next relay in the circuit, and a smaller onion, encrypted with + * the key of the next relay. When we changed Tor to use a telescoping + * circuit extension design, it corresponded to sending each layer of the + * onion separately -- as a series of onionskins. + * + * Clients invoke these functions when creating or extending a circuit, + * from circuitbuild.c. + * + * Relays invoke these functions when they receive a CREATE or EXTEND + * cell in command.c or relay.c, in order to queue the pending request. + * They also invoke them from cpuworker.c, which handles dispatching + * onionskin requests to different worker threads. + * + * <br> + * + * This module also handles: + * <ul> + * <li> Queueing incoming onionskins on the relay side before passing + * them to worker threads. + * <li>Expiring onionskins on the relay side if they have waited for + * too long. + * <li>Packaging private keys on the server side in order to pass + * them to worker threads. + * <li>Encoding and decoding CREATE, CREATED, CREATE2, and CREATED2 cells. + * <li>Encoding and decodign EXTEND, EXTENDED, EXTEND2, and EXTENDED2 + * relay cells. + * </ul> + * + * [*] The CREATE_FAST handshake is weaker than described here; see + * onion_fast.c for more information. **/ #include "or.h" +#include "circuitbuild.h" #include "circuitlist.h" #include "config.h" #include "cpuworker.h" @@ -38,9 +91,9 @@ typedef struct onion_queue_t { /** Array of queues of circuits waiting for CPU workers. An element is NULL * if that queue is empty.*/ -TOR_TAILQ_HEAD(onion_queue_head_t, onion_queue_t) - ol_list[MAX_ONION_HANDSHAKE_TYPE+1] = { - TOR_TAILQ_HEAD_INITIALIZER(ol_list[0]), /* tap */ +static TOR_TAILQ_HEAD(onion_queue_head_t, onion_queue_t) + ol_list[MAX_ONION_HANDSHAKE_TYPE+1] = +{ TOR_TAILQ_HEAD_INITIALIZER(ol_list[0]), /* tap */ TOR_TAILQ_HEAD_INITIALIZER(ol_list[1]), /* fast */ TOR_TAILQ_HEAD_INITIALIZER(ol_list[2]), /* ntor */ }; @@ -51,7 +104,7 @@ static int ol_entries[MAX_ONION_HANDSHAKE_TYPE+1]; static int num_ntors_per_tap(void); static void onion_queue_entry_remove(onion_queue_t *victim); -/* XXXX024 Check lengths vs MAX_ONIONSKIN_{CHALLENGE,REPLY}_LEN. +/* XXXX Check lengths vs MAX_ONIONSKIN_{CHALLENGE,REPLY}_LEN. * * (By which I think I meant, "make sure that no * X_ONIONSKIN_CHALLENGE/REPLY_LEN is greater than @@ -130,9 +183,12 @@ onion_pending_add(or_circuit_t *circ, create_cell_t *onionskin) time_t now = time(NULL); if (onionskin->handshake_type > MAX_ONION_HANDSHAKE_TYPE) { + /* LCOV_EXCL_START + * We should have rejected this far before this point */ log_warn(LD_BUG, "Handshake %d out of range! Dropping.", onionskin->handshake_type); return -1; + /* LCOV_EXCL_STOP */ } tmp = tor_malloc_zero(sizeof(onion_queue_t)); @@ -305,10 +361,13 @@ static void onion_queue_entry_remove(onion_queue_t *victim) { if (victim->handshake_type > MAX_ONION_HANDSHAKE_TYPE) { + /* LCOV_EXCL_START + * We should have rejected this far before this point */ log_warn(LD_BUG, "Handshake %d out of range! Dropping.", victim->handshake_type); /* XXX leaks */ return; + /* LCOV_EXCL_STOP */ } TOR_TAILQ_REMOVE(&ol_list[victim->handshake_type], victim, next); @@ -391,9 +450,12 @@ onion_handshake_state_release(onion_handshake_state_t *state) state->u.ntor = NULL; break; default: + /* LCOV_EXCL_START + * This state should not even exist. */ log_warn(LD_BUG, "called with unknown handshake state type %d", (int)state->tag); tor_fragile_assert(); + /* LCOV_EXCL_STOP */ } } @@ -429,8 +491,7 @@ onion_skin_create(int type, r = CREATE_FAST_LEN; break; case ONION_HANDSHAKE_TYPE_NTOR: - if (tor_mem_is_zero((const char*)node->curve25519_onion_key.public_key, - CURVE25519_PUBKEY_LEN)) + if (!extend_info_supports_ntor(node)) return -1; if (onion_skin_ntor_create((const uint8_t*)node->identity_digest, &node->curve25519_onion_key, @@ -441,9 +502,12 @@ onion_skin_create(int type, r = NTOR_ONIONSKIN_LEN; break; default: + /* LCOV_EXCL_START + * We should never try to create an impossible handshake type. */ log_warn(LD_BUG, "called with unknown handshake state type %d", type); tor_fragile_assert(); r = -1; + /* LCOV_EXCL_STOP */ } if (r > 0) @@ -512,9 +576,12 @@ onion_skin_server_handshake(int type, } break; default: + /* LCOV_EXCL_START + * We should have rejected this far before this point */ log_warn(LD_BUG, "called with unknown handshake state type %d", type); tor_fragile_assert(); return -1; + /* LCOV_EXCL_STOP */ } return r; @@ -527,7 +594,7 @@ onion_skin_server_handshake(int type, * <b>rend_authenticator_out</b> to the "KH" field that can be used to * establish introduction points at this hop, and return 0. On failure, * return -1, and set *msg_out to an error message if this is worth - * complaining to the usre about. */ + * complaining to the user about. */ int onion_skin_client_handshake(int type, const onion_handshake_state_t *handshake_state, |