/*
* Check for self-signedness in an X.509 cert and if found, check the signature
* immediately if we can.
*/
int x509_check_for_self_signed(struct x509_certificate *cert)
{
int ret = 0;
pr_devel("==>%s()\n", __func__);
if (cert->raw_subject_size != cert->raw_issuer_size ||
memcmp(cert->raw_subject, cert->raw_issuer,
cert->raw_issuer_size) != 0)
goto not_self_signed;
if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
/* If the AKID is present it may have one or two parts. If
* both are supplied, both must match.
*/
bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
if (!a && !b)
goto not_self_signed;
ret = -EKEYREJECTED;
if (((a && !b) || (b && !a)) &&
cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
goto out;
}
ret = -EKEYREJECTED;
if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
goto out;
ret = public_key_verify_signature(cert->pub, cert->sig);
if (ret < 0) {
if (ret == -ENOPKG) {
cert->unsupported_sig = true;
ret = 0;
}
goto out;
}
pr_devel("Cert Self-signature verified");
cert->self_signed = true;
out:
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
not_self_signed:
pr_devel("<==%s() = 0 [not]\n", __func__);
return 0;
}
/*
* Check the signature on a certificate using the provided public key
*/
int x509_check_signature(const struct public_key *pub,
struct x509_certificate *cert)
{
int ret;
pr_devel("==>%s()\n", __func__);
ret = x509_get_sig_params(cert);
if (ret < 0)
return ret;
ret = public_key_verify_signature(pub, &cert->sig);
pr_debug("Cert Verification: %d\n", ret);
return ret;
}
/*
* Verify one signed information block from a PKCS#7 message.
*/
static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
struct pkcs7_signed_info *sinfo)
{
int ret;
kenter(",%u", sinfo->index);
/* First of all, digest the data in the PKCS#7 message and the
* signed information block
*/
ret = pkcs7_digest(pkcs7, sinfo);
if (ret < 0)
return ret;
/* Find the key for the signature if there is one */
ret = pkcs7_find_key(pkcs7, sinfo);
if (ret < 0)
return ret;
if (!sinfo->signer)
return 0;
pr_devel("Using X.509[%u] for sig %u\n",
sinfo->signer->index, sinfo->index);
/* Check that the PKCS#7 signing time is valid according to the X.509
* certificate. We can't, however, check against the system clock
* since that may not have been set yet and may be wrong.
*/
if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) {
if (sinfo->signing_time < sinfo->signer->valid_from ||
sinfo->signing_time > sinfo->signer->valid_to) {
pr_warn("Message signed outside of X.509 validity window\n");
return -EKEYREJECTED;
}
}
/* Verify the PKCS#7 binary against the key */
ret = public_key_verify_signature(sinfo->signer->pub, &sinfo->sig);
if (ret < 0)
return ret;
pr_devel("Verified signature %u\n", sinfo->index);
/* Verify the internal certificate chain */
return pkcs7_verify_sig_chain(pkcs7, sinfo);
}
/**
* 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;
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)
goto verified;
kleave(" = -ENOKEY [cached]");
return -ENOKEY;
}
x509->seen = true;
/* Look to see if this certificate is present in the trusted
* keys.
*/
key = find_asymmetric_key(trust_keyring,
x509->id, x509->skid, 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->signer == 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->sig->auth_ids[0] || last->sig->auth_ids[1])) {
key = find_asymmetric_key(trust_keyring,
last->sig->auth_ids[0],
last->sig->auth_ids[1],
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 = find_asymmetric_key(trust_keyring,
sinfo->sig->auth_ids[0], NULL, 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 = public_key_verify_signature(key->public_key, sig);
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;
}
kleave(" = 0");
return 0;
}
static int public_key_verify_signature_2(const struct key *key,
const struct public_key_signature *sig)
{
const struct public_key *pk = key->payload.data;
return public_key_verify_signature(pk, sig);
}
/*
* Verify the internal certificate chain as best we can.
*/
static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7,
struct pkcs7_signed_info *sinfo)
{
struct public_key_signature *sig;
struct x509_certificate *x509 = sinfo->signer, *p;
struct asymmetric_key_id *auth;
int ret;
kenter("");
for (p = pkcs7->certs; p; p = p->next)
p->seen = false;
for (;;) {
pr_debug("verify %s: %*phN\n",
x509->subject,
x509->raw_serial_size, x509->raw_serial);
x509->seen = true;
if (x509->unsupported_key)
goto unsupported_crypto_in_x509;
pr_debug("- issuer %s\n", x509->issuer);
sig = x509->sig;
if (sig->auth_ids[0])
pr_debug("- authkeyid.id %*phN\n",
sig->auth_ids[0]->len, sig->auth_ids[0]->data);
if (sig->auth_ids[1])
pr_debug("- authkeyid.skid %*phN\n",
sig->auth_ids[1]->len, sig->auth_ids[1]->data);
if (x509->self_signed) {
/* If there's no authority certificate specified, then
* the certificate must be self-signed and is the root
* of the chain. Likewise if the cert is its own
* authority.
*/
if (x509->unsupported_sig)
goto unsupported_crypto_in_x509;
x509->signer = x509;
pr_debug("- self-signed\n");
return 0;
}
/* Look through the X.509 certificates in the PKCS#7 message's
* list to see if the next one is there.
*/
auth = sig->auth_ids[0];
if (auth) {
pr_debug("- want %*phN\n", auth->len, auth->data);
for (p = pkcs7->certs; p; p = p->next) {
pr_debug("- cmp [%u] %*phN\n",
p->index, p->id->len, p->id->data);
if (asymmetric_key_id_same(p->id, auth))
goto found_issuer_check_skid;
}
} else {
auth = sig->auth_ids[1];
pr_debug("- want %*phN\n", auth->len, auth->data);
for (p = pkcs7->certs; p; p = p->next) {
if (!p->skid)
continue;
pr_debug("- cmp [%u] %*phN\n",
p->index, p->skid->len, p->skid->data);
if (asymmetric_key_id_same(p->skid, auth))
goto found_issuer;
}
}
/* We didn't find the root of this chain */
pr_debug("- top\n");
return 0;
found_issuer_check_skid:
/* We matched issuer + serialNumber, but if there's an
* authKeyId.keyId, that must match the CA subjKeyId also.
*/
if (sig->auth_ids[1] &&
!asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {
pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n",
sinfo->index, x509->index, p->index);
return -EKEYREJECTED;
}
found_issuer:
pr_debug("- subject %s\n", p->subject);
if (p->seen) {
pr_warn("Sig %u: X.509 chain contains loop\n",
sinfo->index);
return 0;
}
ret = public_key_verify_signature(p->pub, p->sig);
if (ret < 0)
return ret;
x509->signer = p;
if (x509 == p) {
pr_debug("- self-signed\n");
return 0;
}
x509 = p;
might_sleep();
}
unsupported_crypto_in_x509:
/* Just prune the certificate chain at this point if we lack some
* crypto module to go further. Note, however, we don't want to set
* sinfo->unsupported_crypto as the signed info block may still be
* validatable against an X.509 cert lower in the chain that we have a
* trusted copy of.
*/
return 0;
}
