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prop224: Check decoded descriptor matches the expected blinded key

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When a client decodes a descriptor, make sure it matches the expected blinded
key which is derived from the hidden service identity key.

Signed-off-by: David Goulet <dgoulet@torproject.org>
This commit is contained in:
David Goulet 2017-08-22 09:02:23 -04:00
parent 520fcdf2f3
commit 47672ec1c7
1 changed files with 11 additions and 1 deletions
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12
src/or/hs_client.c
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@ -800,6 +800,7 @@ hs_client_decode_descriptor(const char *desc_str,
{
int ret;
uint8_t subcredential[DIGEST256_LEN];
ed25519_public_key_t blinded_pubkey;
tor_assert(desc_str);
tor_assert(service_identity_pk);
@ -807,7 +808,6 @@ hs_client_decode_descriptor(const char *desc_str,
/* Create subcredential for this HS so that we can decrypt */
{
ed25519_public_key_t blinded_pubkey;
uint64_t current_time_period = hs_get_time_period_num(approx_time());
hs_build_blinded_pubkey(service_identity_pk, NULL, 0, current_time_period,
&blinded_pubkey);
@ -822,6 +822,16 @@ hs_client_decode_descriptor(const char *desc_str,
goto err;
}
/* Make sure the descriptor signing key cross certifies with the computed
* blinded key. Without this validation, anyone knowing the subcredential
* and onion address can forge a descriptor. */
if (tor_cert_checksig((*desc)->plaintext_data.signing_key_cert,
&blinded_pubkey, approx_time()) < 0) {
log_warn(LD_GENERAL, "Descriptor signing key certificate signature "
"doesn't validate with computed blinded key.");
goto err;
}
return 0;
err:
return -1;