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/* Copyright (c) 2014, The Tor Project, Inc. */
/* See LICENSE for licensing information */
#include "torcert.h"
#include "crypto.h"
#include "ed25519_cert.h"
#include "torlog.h"
#include "util.h"
#include "compat.h"
/** Helper for tor_cert_create(): signs any 32 bytes, not just an ed25519
* key.
*/
static tor_cert_t *
tor_cert_sign_impl(const ed25519_keypair_t *signing_key,
uint8_t cert_type,
uint8_t signed_key_type,
const uint8_t signed_key_info[32],
time_t now, time_t lifetime,
uint32_t flags)
{
tor_cert_t *torcert = NULL;
ed25519_cert_t *cert = ed25519_cert_new();
cert->cert_type = cert_type;
cert->exp_field = (uint32_t) CEIL_DIV(now + lifetime, 3600);
cert->cert_key_type = signed_key_type;
memcpy(cert->certified_key, signed_key_info, 32);
if (flags & CERT_FLAG_INCLUDE_SIGNING_KEY) {
ed25519_cert_extension_t *ext = ed25519_cert_extension_new();
ext->ext_type = CERTEXT_SIGNED_WITH_KEY;
memcpy(ext->un_signing_key, signing_key->pubkey.pubkey, 32);
ed25519_cert_add_ext(cert, ext);
++cert->n_extensions;
}
const ssize_t alloc_len = ed25519_cert_encoded_len(cert);
tor_assert(alloc_len > 0);
uint8_t *encoded = tor_malloc(alloc_len);
const ssize_t real_len = ed25519_cert_encode(encoded, alloc_len, cert);
if (real_len < 0)
goto err;
tor_assert(real_len == alloc_len);
tor_assert(real_len > ED25519_SIG_LEN);
uint8_t *sig = encoded + (real_len - ED25519_SIG_LEN);
tor_assert(tor_mem_is_zero((char*)sig, ED25519_SIG_LEN));
ed25519_signature_t signature;
if (ed25519_sign(&signature, encoded,
real_len-ED25519_SIG_LEN, signing_key)<0) {
log_warn(LD_BUG, "Can't sign certificate");
goto err;
}
memcpy(sig, signature.sig, ED25519_SIG_LEN);
torcert = tor_cert_parse(encoded, real_len);
if (! torcert) {
log_warn(LD_BUG, "Generated a certificate we cannot parse");
goto err;
}
if (tor_cert_checksig(torcert, &signing_key->pubkey, now) < 0) {
log_warn(LD_BUG, "Generated a certificate whose signature we can't check");
goto err;
}
tor_free(encoded);
return torcert;
err:
tor_cert_free(torcert);
ed25519_cert_free(cert);
tor_free(encoded);
return NULL;
}
/**
* Create and return a new new certificate of type <b>cert_type</b> to
* authenticate <b>signed_key</b> using the key <b>signing_key</b>. The
* certificate should remain valid for at least <b>lifetime</b> seconds after
* <b>now</b>.
*
* If CERT_FLAG_INCLUDE_SIGNING_KEY is set in <b>flags</b>, embed
* the public part of <b>signing_key</b> in the certificate.
*/
tor_cert_t *
tor_cert_create(const ed25519_keypair_t *signing_key,
uint8_t cert_type,
const ed25519_public_key_t *signed_key,
time_t now, time_t lifetime,
uint32_t flags)
{
return tor_cert_sign_impl(signing_key, cert_type,
SIGNED_KEY_TYPE_ED25519, signed_key->pubkey,
now, lifetime, flags);
}
/** Release all storage held for <b>cert</>. */
void
tor_cert_free(tor_cert_t *cert)
{
if (! cert)
return;
if (cert->encoded)
memwipe(cert->encoded, 0, cert->encoded_len);
tor_free(cert->encoded);
memwipe(cert, 0, sizeof(tor_cert_t));
tor_free(cert);
}
/** Parse a certificate encoded with <b>len</b> bytes in <b>encoded</b>. */
tor_cert_t *
tor_cert_parse(const uint8_t *encoded, const size_t len)
{
tor_cert_t *cert = NULL;
ed25519_cert_t *parsed = NULL;
ssize_t got_len = ed25519_cert_parse(&parsed, encoded, len);
if (got_len < 0 || (size_t) got_len != len)
goto err;
cert = tor_malloc_zero(sizeof(tor_cert_t));
cert->encoded = tor_memdup(encoded, len);
cert->encoded_len = len;
memcpy(cert->signed_key.pubkey, parsed->certified_key, 32);
cert->valid_until = parsed->exp_field * 3600;
cert->cert_type = parsed->cert_type;
for (unsigned i = 0; i < ed25519_cert_getlen_ext(parsed); ++i) {
ed25519_cert_extension_t *ext = ed25519_cert_get_ext(parsed, i);
if (ext->ext_type == CERTEXT_SIGNED_WITH_KEY) {
if (cert->signing_key_included)
goto err;
cert->signing_key_included = 1;
memcpy(cert->signing_key.pubkey, ext->un_signing_key, 32);
} else if (ext->ext_flags & CERTEXT_FLAG_AFFECTS_VALIDATION) {
/* Unrecognized extension with affects_validation set */
goto err;
}
}
return cert;
err:
ed25519_cert_free(parsed);
tor_cert_free(cert);
return NULL;
}
/** Fill in <b>checkable_out</b> with the information needed to check
* the signature on <b>cert</b> with <b>pubkey</b>. */
int
tor_cert_get_checkable_sig(ed25519_checkable_t *checkable_out,
const tor_cert_t *cert,
const ed25519_public_key_t *pubkey)
{
if (! pubkey) {
if (cert->signing_key_included)
pubkey = &cert->signing_key;
else
return -1;
}
checkable_out->msg = cert->encoded;
checkable_out->pubkey = pubkey;
tor_assert(cert->encoded_len > ED25519_SIG_LEN);
const size_t signed_len = cert->encoded_len - ED25519_SIG_LEN;
checkable_out->len = signed_len;
memcpy(checkable_out->signature.sig,
cert->encoded + signed_len, ED25519_SIG_LEN);
return 0;
}
/** Validates the signature on <b>cert</b> with <b>pubkey</b> relative to
* the current time <b>now</b>. Return 0 on success, -1 on failure.
* Sets flags in <b>cert</b> as appropriate.
*/
int
tor_cert_checksig(tor_cert_t *cert,
const ed25519_public_key_t *pubkey, time_t now)
{
ed25519_checkable_t checkable;
int okay;
if (now > cert->valid_until) {
cert->cert_expired = 1;
return -1;
}
if (tor_cert_get_checkable_sig(&checkable, cert, pubkey) < 0)
return -1;
if (ed25519_checksig_batch(&okay, &checkable, 1) < 0) {
cert->sig_bad = 1;
return -1;
} else {
cert->sig_ok = 1;
memcpy(cert->signing_key.pubkey, checkable.pubkey->pubkey, 32);
cert->cert_valid = 1;
return 0;
}
}
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