commit e56d7a3809611e85b48474f27b3feb461e82e109 Author: Nick Mathewson nickm@torproject.org Date: Wed Oct 5 10:33:39 2011 -0400

Give tor_cert_get_id_digests() fail-fast behavior

Right now we can take the digests only of an RSA key, and only expect to take the digests of an RSA key. The old tor_cert_get_id_digests() would return a good set of digests for an RSA key, and an all-zero one for a non-RSA key. This behavior is too error-prone: it carries the risk that we will someday check two non-RSA keys for equality and conclude that they must be equal because they both have the same (zero) "digest".

Instead, let's have tor_cert_get_id_digests() return NULL for keys we can't handle, and make its callers explicitly test for NULL. --- src/common/tortls.c | 10 ++++++++-- src/or/command.c | 9 ++++++++- src/or/connection_or.c | 11 ++++++++--- 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/common/tortls.c b/src/common/tortls.c index 247e9ee..9600464 100644 --- a/src/common/tortls.c +++ b/src/common/tortls.c @@ -102,6 +102,7 @@ struct tor_cert_t { X509 *cert; uint8_t *encoded; size_t encoded_len; + unsigned pkey_digests_set : 1; digests_t cert_digests; digests_t pkey_digests; }; @@ -734,6 +735,7 @@ tor_cert_new(X509 *x509_cert) (rsa = EVP_PKEY_get1_RSA(pkey))) { crypto_pk_env_t *pk = _crypto_new_pk_env_rsa(rsa); crypto_pk_get_all_digests(pk, &cert->pkey_digests); + cert->pkey_digests_set = 1; crypto_free_pk_env(pk); EVP_PKEY_free(pkey); } @@ -794,11 +796,15 @@ tor_cert_get_der(const tor_cert_t *cert, *size_out = cert->encoded_len; }

-/** Return a set of digests for the public key in <b>cert</b>. */ +/** Return a set of digests for the public key in <b>cert</b>, or NULL if this + * cert's public key is not one we know how to take the digest of. */ const digests_t * tor_cert_get_id_digests(const tor_cert_t *cert) { - return &cert->pkey_digests; + if (cert->pkey_digests_set) + return &cert->pkey_digests; + else + return NULL; }

/** Return a set of digests for the public key in <b>cert</b>. */ diff --git a/src/or/command.c b/src/or/command.c index 91486c1..c1e2f5e 100644 --- a/src/or/command.c +++ b/src/or/command.c @@ -939,8 +939,12 @@ command_process_cert_cell(var_cell_t *cell, or_connection_t *conn)

conn->handshake_state->authenticated = 1; { - crypto_pk_env_t *identity_rcvd = tor_tls_cert_get_key(id_cert); const digests_t *id_digests = tor_cert_get_id_digests(id_cert); + crypto_pk_env_t *identity_rcvd; + if (!id_digests) + ERR("Couldn't compute digests for key in ID cert"); + + identity_rcvd = tor_tls_cert_get_key(id_cert); memcpy(conn->handshake_state->authenticated_peer_id, id_digests->d[DIGEST_SHA1], DIGEST_LEN); connection_or_set_circid_type(conn, identity_rcvd); @@ -1172,6 +1176,9 @@ command_process_authenticate_cell(var_cell_t *cell, or_connection_t *conn) const digests_t *id_digests = tor_cert_get_id_digests(conn->handshake_state->id_cert);

+ /* This must exist; we checked key type when reading the cert. */ + tor_assert(id_digests); + memcpy(conn->handshake_state->authenticated_peer_id, id_digests->d[DIGEST_SHA1], DIGEST_LEN);

diff --git a/src/or/connection_or.c b/src/or/connection_or.c index 7cdea82..a5b965b 100644 --- a/src/or/connection_or.c +++ b/src/or/connection_or.c @@ -2060,12 +2060,17 @@ connection_or_compute_authenticate_cell_body(or_connection_t *conn,

{ const tor_cert_t *id_cert=NULL, *link_cert=NULL; + const digests_t *my_digests, *their_digests; const uint8_t *my_id, *their_id, *client_id, *server_id; if (tor_tls_get_my_certs(0, &link_cert, &id_cert)) return -1; - my_id = (uint8_t*)tor_cert_get_id_digests(id_cert)->d[DIGEST_SHA256]; - their_id = (uint8_t*) - tor_cert_get_id_digests(conn->handshake_state->id_cert)->d[DIGEST_SHA256]; + my_digests = tor_cert_get_id_digests(id_cert); + their_digests = tor_cert_get_id_digests(conn->handshake_state->id_cert); + tor_assert(my_digests); + tor_assert(their_digests); + my_id = (uint8_t*)my_digests->d[DIGEST_SHA256]; + their_id = (uint8_t*)their_digests->d[DIGEST_SHA256]; + client_id = server ? their_id : my_id; server_id = server ? my_id : their_id;