/*
* Check the new certificate against the ones in the trust keyring. If one of
* those is the signing key and validates the new certificate, then mark the
* new certificate as being trusted.
*
* Return 0 if the new certificate was successfully validated, 1 if we couldn't
* find a matching parent certificate in the trusted list and an error if there
* is a matching certificate but the signature check fails.
*/
static int x509_validate_trust(struct x509_certificate *cert,
struct key *trust_keyring)
{
struct key *key;
int ret = 1;
if (!trust_keyring)
return -EOPNOTSUPP;
if (ca_keyid && !asymmetric_key_id_partial(cert->akid_skid, ca_keyid))
return -EPERM;
key = x509_request_asymmetric_key(trust_keyring, cert->akid_skid,
false);
if (!IS_ERR(key)) {
if (!use_builtin_keys
|| test_bit(KEY_FLAG_BUILTIN, &key->flags))
ret = x509_check_signature(key->payload.data, cert);
key_put(key);
}
return ret;
}
/**
* Check the trust on one PKCS#7 SignedInfo block.
*/
static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
struct pkcs7_signed_info *sinfo,
struct key *trust_keyring)
{
struct public_key_signature *sig = &sinfo->sig;
struct x509_certificate *x509, *last = NULL, *p;
struct key *key;
bool trusted;
int ret;
kenter(",%u,", sinfo->index);
if (sinfo->unsupported_crypto) {
kleave(" = -ENOPKG [cached]");
return -ENOPKG;
}
for (x509 = sinfo->signer; x509; x509 = x509->signer) {
if (x509->seen) {
if (x509->verified) {
trusted = x509->trusted;
goto verified;
}
kleave(" = -ENOKEY [cached]");
return -ENOKEY;
}
x509->seen = true;
/* Look to see if this certificate is present in the trusted
* keys.
*/
key = x509_request_asymmetric_key(trust_keyring, x509->id,
false);
if (!IS_ERR(key)) {
/* One of the X.509 certificates in the PKCS#7 message
* is apparently the same as one we already trust.
* Verify that the trusted variant can also validate
* the signature on the descendant.
*/
pr_devel("sinfo %u: Cert %u as key %x\n",
sinfo->index, x509->index, key_serial(key));
goto matched;
}
if (key == ERR_PTR(-ENOMEM))
return -ENOMEM;
/* Self-signed certificates form roots of their own, and if we
* don't know them, then we can't accept them.
*/
if (x509->next == x509) {
kleave(" = -ENOKEY [unknown self-signed]");
return -ENOKEY;
}
might_sleep();
last = x509;
sig = &last->sig;
}
/* No match - see if the root certificate has a signer amongst the
* trusted keys.
*/
if (last && last->authority) {
key = x509_request_asymmetric_key(trust_keyring, last->authority,
false);
if (!IS_ERR(key)) {
x509 = last;
pr_devel("sinfo %u: Root cert %u signer is key %x\n",
sinfo->index, x509->index, key_serial(key));
goto matched;
}
if (PTR_ERR(key) != -ENOKEY)
return PTR_ERR(key);
}
/* As a last resort, see if we have a trusted public key that matches
* the signed info directly.
*/
key = x509_request_asymmetric_key(trust_keyring,
sinfo->signing_cert_id,
false);
if (!IS_ERR(key)) {
pr_devel("sinfo %u: Direct signer is key %x\n",
sinfo->index, key_serial(key));
x509 = NULL;
goto matched;
}
if (PTR_ERR(key) != -ENOKEY)
return PTR_ERR(key);
kleave(" = -ENOKEY [no backref]");
return -ENOKEY;
matched:
ret = verify_signature(key, sig);
trusted = test_bit(KEY_FLAG_TRUSTED, &key->flags);
key_put(key);
if (ret < 0) {
if (ret == -ENOMEM)
return ret;
kleave(" = -EKEYREJECTED [verify %d]", ret);
return -EKEYREJECTED;
}
verified:
if (x509) {
x509->verified = true;
for (p = sinfo->signer; p != x509; p = p->signer) {
p->verified = true;
p->trusted = trusted;
}
}
sinfo->trusted = trusted;
kleave(" = 0");
return 0;
}