diff options
Diffstat (limited to 'src/or/relay_crypto.c')
| -rw-r--r-- | src/or/relay_crypto.c | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/src/or/relay_crypto.c b/src/or/relay_crypto.c new file mode 100644 index 0000000000..e0992a3014 --- /dev/null +++ b/src/or/relay_crypto.c @@ -0,0 +1,202 @@ +/* Copyright (c) 2001 Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2018, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +#include "or.h" +#include "config.h" +#include "relay_crypto.h" +#include "relay.h" + +/** Update digest from the payload of cell. Assign integrity part to + * cell. + */ +static void +relay_set_digest(crypto_digest_t *digest, cell_t *cell) +{ + char integrity[4]; + relay_header_t rh; + + crypto_digest_add_bytes(digest, (char*)cell->payload, CELL_PAYLOAD_SIZE); + crypto_digest_get_digest(digest, integrity, 4); +// log_fn(LOG_DEBUG,"Putting digest of %u %u %u %u into relay cell.", +// integrity[0], integrity[1], integrity[2], integrity[3]); + relay_header_unpack(&rh, cell->payload); + memcpy(rh.integrity, integrity, 4); + relay_header_pack(cell->payload, &rh); +} + +/** Does the digest for this circuit indicate that this cell is for us? + * + * Update digest from the payload of cell (with the integrity part set + * to 0). If the integrity part is valid, return 1, else restore digest + * and cell to their original state and return 0. + */ +static int +relay_digest_matches(crypto_digest_t *digest, cell_t *cell) +{ + uint32_t received_integrity, calculated_integrity; + relay_header_t rh; + crypto_digest_checkpoint_t backup_digest; + + crypto_digest_checkpoint(&backup_digest, digest); + + relay_header_unpack(&rh, cell->payload); + memcpy(&received_integrity, rh.integrity, 4); + memset(rh.integrity, 0, 4); + relay_header_pack(cell->payload, &rh); + +// log_fn(LOG_DEBUG,"Reading digest of %u %u %u %u from relay cell.", +// received_integrity[0], received_integrity[1], +// received_integrity[2], received_integrity[3]); + + crypto_digest_add_bytes(digest, (char*) cell->payload, CELL_PAYLOAD_SIZE); + crypto_digest_get_digest(digest, (char*) &calculated_integrity, 4); + + int rv = 1; + + if (calculated_integrity != received_integrity) { +// log_fn(LOG_INFO,"Recognized=0 but bad digest. Not recognizing."); +// (%d vs %d).", received_integrity, calculated_integrity); + /* restore digest to its old form */ + crypto_digest_restore(digest, &backup_digest); + /* restore the relay header */ + memcpy(rh.integrity, &received_integrity, 4); + relay_header_pack(cell->payload, &rh); + rv = 0; + } + + memwipe(&backup_digest, 0, sizeof(backup_digest)); + return rv; +} + +/** Apply <b>cipher</b> to CELL_PAYLOAD_SIZE bytes of <b>in</b> + * (in place). + * + * Note that we use the same operation for encrypting and for decrypting. + */ +static void +relay_crypt_one_payload(crypto_cipher_t *cipher, uint8_t *in) +{ + crypto_cipher_crypt_inplace(cipher, (char*) in, CELL_PAYLOAD_SIZE); +} + +/** Do the appropriate en/decryptions for <b>cell</b> arriving on + * <b>circ</b> in direction <b>cell_direction</b>. + * + * If cell_direction == CELL_DIRECTION_IN: + * - If we're at the origin (we're the OP), for hops 1..N, + * decrypt cell. If recognized, stop. + * - Else (we're not the OP), encrypt one hop. Cell is not recognized. + * + * If cell_direction == CELL_DIRECTION_OUT: + * - decrypt one hop. Check if recognized. + * + * If cell is recognized, set *recognized to 1, and set + * *layer_hint to the hop that recognized it. + * + * Return -1 to indicate that we should mark the circuit for close, + * else return 0. + */ +int +relay_decrypt_cell(circuit_t *circ, cell_t *cell, + cell_direction_t cell_direction, + crypt_path_t **layer_hint, char *recognized) +{ + relay_header_t rh; + + tor_assert(circ); + tor_assert(cell); + tor_assert(recognized); + tor_assert(cell_direction == CELL_DIRECTION_IN || + cell_direction == CELL_DIRECTION_OUT); + + if (cell_direction == CELL_DIRECTION_IN) { + if (CIRCUIT_IS_ORIGIN(circ)) { /* We're at the beginning of the circuit. + * We'll want to do layered decrypts. */ + crypt_path_t *thishop, *cpath = TO_ORIGIN_CIRCUIT(circ)->cpath; + thishop = cpath; + if (thishop->state != CPATH_STATE_OPEN) { + log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, + "Relay cell before first created cell? Closing."); + return -1; + } + do { /* Remember: cpath is in forward order, that is, first hop first. */ + tor_assert(thishop); + + /* decrypt one layer */ + relay_crypt_one_payload(thishop->b_crypto, cell->payload); + + relay_header_unpack(&rh, cell->payload); + if (rh.recognized == 0) { + /* it's possibly recognized. have to check digest to be sure. */ + if (relay_digest_matches(thishop->b_digest, cell)) { + *recognized = 1; + *layer_hint = thishop; + return 0; + } + } + + thishop = thishop->next; + } while (thishop != cpath && thishop->state == CPATH_STATE_OPEN); + log_fn(LOG_PROTOCOL_WARN, LD_OR, + "Incoming cell at client not recognized. Closing."); + return -1; + } else { + /* We're in the middle. Encrypt one layer. */ + relay_crypt_one_payload(TO_OR_CIRCUIT(circ)->p_crypto, cell->payload); + } + } else /* cell_direction == CELL_DIRECTION_OUT */ { + /* We're in the middle. Decrypt one layer. */ + + relay_crypt_one_payload(TO_OR_CIRCUIT(circ)->n_crypto, cell->payload); + + relay_header_unpack(&rh, cell->payload); + if (rh.recognized == 0) { + /* it's possibly recognized. have to check digest to be sure. */ + if (relay_digest_matches(TO_OR_CIRCUIT(circ)->n_digest, cell)) { + *recognized = 1; + return 0; + } + } + } + return 0; +} + +/** + * Encrypt a cell <b>cell</b> that we are creating, and sending outbound on + * <b>circ</b> until the hop corresponding to <b>layer_hint</b>. + */ +void +relay_encrypt_cell_outbound(cell_t *cell, + origin_circuit_t *circ, + crypt_path_t *layer_hint) +{ + crypt_path_t *thishop; /* counter for repeated crypts */ + relay_set_digest(layer_hint->f_digest, cell); + + thishop = layer_hint; + /* moving from farthest to nearest hop */ + do { + tor_assert(thishop); + log_debug(LD_OR,"encrypting a layer of the relay cell."); + relay_crypt_one_payload(thishop->f_crypto, cell->payload); + + thishop = thishop->prev; + } while (thishop != circ->cpath->prev); +} + +/** + * Encrypt a cell <b>cell</b> that we are creating, and sending on + * <b>circuit</b> to the origin. + */ +void +relay_encrypt_cell_inbound(cell_t *cell, + or_circuit_t *or_circ) +{ + relay_set_digest(or_circ->p_digest, cell); + /* encrypt one layer */ + relay_crypt_one_payload(or_circ->p_crypto, cell->payload); +} + |