// SPDX-License-Identifier: GPL-2.0-or-later
/* Instantiate a public key crypto key from an X.509 Certificate
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*/
#define pr_fmt(fmt) "X.509: "fmt
#include <crypto/hash.h>
#include <keys/asymmetric-parser.h>
#include <keys/asymmetric-subtype.h>
#include <keys/system_keyring.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/string.h>
#include "asymmetric_keys.h"
#include "x509_parser.h"
/*
* Set up the signature parameters in an X.509 certificate. This involves
* digesting the signed data and extracting the signature.
*/
int x509_get_sig_params(struct x509_certificate *cert)
{
struct public_key_signature *sig = cert->sig;
struct crypto_shash *tfm;
struct shash_desc *desc;
size_t desc_size;
int ret;
pr_devel("==>%s()\n", __func__);
sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
if (!sig->s)
return -ENOMEM;
sig->s_size = cert->raw_sig_size;
/* Allocate the hashing algorithm we're going to need and find out how
* big the hash operational data will be.
*/
tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
if (IS_ERR(tfm)) {
if (PTR_ERR(tfm) == -ENOENT) {
cert->unsupported_sig = true;
return 0;
}
return PTR_ERR(tfm);
}
desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
sig->digest_size = crypto_shash_digestsize(tfm);
ret = -ENOMEM;
sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
if (!sig->digest)
goto error;
desc = kzalloc(desc_size, GFP_KERNEL);
if (!desc)
goto error;
desc->tfm = tfm;
ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size,
sig->digest);
if (ret < 0)
goto error_2;
ret = is_hash_blacklisted(sig->digest, sig->digest_size,
BLACKLIST_HASH_X509_TBS);
if (ret == -EKEYREJECTED) {
pr_err("Cert %*phN is blacklisted\n",
sig->digest_size, sig->digest);
cert->blacklisted = true;
ret = 0;
}
error_2:
kfree(desc);
error:
crypto_free_shash(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
/*
* 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;
}
if (cert->unsupported_sig) {
ret = 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;
}
/*
* Attempt to parse a data blob for a key as an X509 certificate.
*/
static int x509_key_preparse(struct key_preparsed_payload *prep)
{
struct x509_certificate *cert __free(x509_free_certificate);
struct asymmetric_key_ids *kids __free(kfree) = NULL;
char *p, *desc __free(kfree) = NULL;
const char *q;
size_t srlen, sulen;
cert = x509_cert_parse(prep->data, prep->datalen);
if (IS_ERR(cert))
return PTR_ERR(cert);
pr_devel("Cert Issuer: %s\n", cert->issuer);
pr_devel("Cert Subject: %s\n", cert->subject);
pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
cert->pub->id_type = "X509";
if (cert->unsupported_sig) {
public_key_signature_free(cert->sig);
cert->sig = NULL;
} else {
pr_devel("Cert Signature: %s + %s\n",
cert->sig->pkey_algo, cert->sig->hash_algo);
}
/* Don't permit addition of blacklisted keys */
if (cert->blacklisted)
return -EKEYREJECTED;
/* Propose a description */
sulen = strlen(cert->subject);
if (cert->raw_skid) {
srlen = cert->raw_skid_size;
q = cert->raw_skid;
} else {
srlen = cert->raw_serial_size;
q = cert->raw_serial;
}
desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
if (!desc)
return -ENOMEM;
p = memcpy(desc, cert->subject, sulen);
p += sulen;
*p++ = ':';
*p++ = ' ';
p = bin2hex(p, q, srlen);
*p = 0;
kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
if (!kids)
return -ENOMEM;
kids->id[0] = cert->id;
kids->id[1] = cert->skid;
kids->id[2] = asymmetric_key_generate_id(cert->raw_subject,
cert->raw_subject_size,
"", 0);
if (IS_ERR(kids->id[2]))
return PTR_ERR(kids->id[2]);
/* We're pinning the module by being linked against it */
__module_get(public_key_subtype.owner);
prep->payload.data[asym_subtype] = &public_key_subtype;
prep->payload.data[asym_key_ids] = kids;
prep->payload.data[asym_crypto] = cert->pub;
prep->payload.data[asym_auth] = cert->sig;
prep->description = desc;
prep->quotalen = 100;
/* We've finished with the certificate */
cert->pub = NULL;
cert->id = NULL;
cert->skid = NULL;
cert->sig = NULL;
desc = NULL;
kids = NULL;
return 0;
}
static struct asymmetric_key_parser x509_key_parser = {
.owner = THIS_MODULE,
.name = "x509",
.parse = x509_key_preparse,
};
/*
* Module stuff
*/
static int __init x509_key_init(void)
{
return register_asymmetric_key_parser(&x509_key_parser);
}
static void __exit x509_key_exit(void)
{
unregister_asymmetric_key_parser(&x509_key_parser);
}
module_init(x509_key_init);
module_exit(x509_key_exit);
MODULE_DESCRIPTION("X.509 certificate parser");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL");
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