commit f156156d56ec61394eb814397c33557762870809 Author: Nick Mathewson nickm@torproject.org Date: Thu Sep 22 11:22:11 2016 -0400

Audit use of tor_tls_cert_get_key().

This function is allowed to return NULL if the certified key isn't RSA. But in a couple of places we were treating this as a bug or internal error, and in one other place we weren't checking for it at all!

Caught by Isis during code review for #15055. The serious bug was only on the 15055 branch, thank goodness. --- src/common/tortls.c | 2 +- src/or/channeltls.c | 10 +++------- src/or/torcert.c | 3 +++ 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/src/common/tortls.c b/src/common/tortls.c index eb24411..e3550b2 100644 --- a/src/common/tortls.c +++ b/src/common/tortls.c @@ -814,7 +814,7 @@ tor_tls_get_my_client_auth_key(void)

/** * Return a newly allocated copy of the public key that a certificate - * certifies. Return NULL if the cert's key is not RSA. + * certifies. Watch out! This returns NULL if the cert's key is not RSA. */ crypto_pk_t * tor_tls_cert_get_key(tor_x509_cert_t *cert) diff --git a/src/or/channeltls.c b/src/or/channeltls.c index f5b81f0..a3e1f8c 100644 --- a/src/or/channeltls.c +++ b/src/or/channeltls.c @@ -1955,9 +1955,7 @@ channel_tls_process_certs_cell(var_cell_t *cell, channel_tls_t *chan)

identity_rcvd = tor_tls_cert_get_key(id_cert); if (!identity_rcvd) { - //LCOV_EXCL_START - ERR("Internal error: Couldn't get RSA key from ID cert."); - //LCOV_EXCL_STOP + ERR("Couldn't get RSA key from ID cert."); } memcpy(chan->conn->handshake_state->authenticated_rsa_peer_id, id_digests->d[DIGEST_SHA1], DIGEST_LEN); @@ -2242,10 +2240,8 @@ channel_tls_process_authenticate_cell(var_cell_t *cell, channel_tls_t *chan) size_t keysize; int signed_len;

- if (BUG(!pk)) { - // LCOV_EXCL_START - ERR("Internal error: couldn't get RSA key from AUTH cert."); - // LCOV_EXCL_STOP + if (! pk) { + ERR("Couldn't get RSA key from AUTH cert."); } crypto_digest256(d, (char*)auth, V3_AUTH_BODY_LEN, DIGEST_SHA256);

diff --git a/src/or/torcert.c b/src/or/torcert.c index d100298..69f50aa 100644 --- a/src/or/torcert.c +++ b/src/or/torcert.c @@ -559,6 +559,9 @@ or_handshake_certs_ed25519_ok(int severity, ERR("Missing RSA->Ed25519 crosscert"); } crypto_pk_t *rsa_id_key = tor_tls_cert_get_key(rsa_id_cert); + if (!rsa_id_key) { + ERR("RSA ID cert had no RSA key"); + }

if (rsa_ed25519_crosscert_check(certs->ed_rsa_crosscert, certs->ed_rsa_crosscert_len,