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/* Instantiate a public key crypto key from an X.509 Certificate
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#define pr_fmt(fmt) "X.509: "fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/mpi.h>
#include <linux/asn1_decoder.h>
#include <keys/asymmetric-subtype.h>
#include <keys/asymmetric-parser.h>
#include <crypto/hash.h>
#include "asymmetric_keys.h"
#include "public_key.h"
#include "x509_parser.h"
static const
struct public_key_algorithm *x509_public_key_algorithms[PKEY_ALGO__LAST] = {
[PKEY_ALGO_DSA] = NULL,
#if defined(CONFIG_PUBLIC_KEY_ALGO_RSA) || \
defined(CONFIG_PUBLIC_KEY_ALGO_RSA_MODULE)
[PKEY_ALGO_RSA] = &RSA_public_key_algorithm,
#endif
};
/*
* Check the signature on a certificate using the provided public key
*/
static int x509_check_signature(const struct public_key *pub,
const struct x509_certificate *cert)
{
struct public_key_signature *sig;
struct crypto_shash *tfm;
struct shash_desc *desc;
size_t digest_size, desc_size;
int ret;
pr_devel("==>%s()\n", __func__);
/* Allocate the hashing algorithm we're going to need and find out how
* big the hash operational data will be.
*/
tfm = crypto_alloc_shash(pkey_hash_algo[cert->sig_hash_algo], 0, 0);
if (IS_ERR(tfm))
return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
digest_size = crypto_shash_digestsize(tfm);
/* We allocate the hash operational data storage on the end of our
* context data.
*/
ret = -ENOMEM;
sig = kzalloc(sizeof(*sig) + desc_size + digest_size, GFP_KERNEL);
if (!sig)
goto error_no_sig;
sig->pkey_hash_algo = cert->sig_hash_algo;
sig->digest = (u8 *)sig + sizeof(*sig) + desc_size;
sig->digest_size = digest_size;
desc = (void *)sig + sizeof(*sig);
desc->tfm = tfm;
desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
ret = crypto_shash_init(desc);
if (ret < 0)
goto error;
ret = -ENOMEM;
sig->rsa.s = mpi_read_raw_data(cert->sig, cert->sig_size);
if (!sig->rsa.s)
goto error;
ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, sig->digest);
if (ret < 0)
goto error_mpi;
ret = pub->algo->verify_signature(pub, sig);
pr_debug("Cert Verification: %d\n", ret);
error_mpi:
mpi_free(sig->rsa.s);
error:
kfree(sig);
error_no_sig:
crypto_free_shash(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
/*
* 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;
time_t now;
size_t srlen, sulen;
char *desc = NULL;
int ret;
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", pkey_algo[cert->pkey_algo]);
pr_devel("Cert Valid: %lu - %lu\n", cert->valid_from, cert->valid_to);
pr_devel("Cert Signature: %s + %s\n",
pkey_algo[cert->sig_pkey_algo],
pkey_hash_algo[cert->sig_hash_algo]);
if (!cert->fingerprint || !cert->authority) {
pr_warn("Cert for '%s' must have SubjKeyId and AuthKeyId extensions\n",
cert->subject);
ret = -EKEYREJECTED;
goto error_free_cert;
}
now = CURRENT_TIME.tv_sec;
if (now < cert->valid_from) {
pr_warn("Cert %s is not yet valid\n", cert->fingerprint);
ret = -EKEYREJECTED;
goto error_free_cert;
}
if (now >= cert->valid_to) {
pr_warn("Cert %s has expired\n", cert->fingerprint);
ret = -EKEYEXPIRED;
goto error_free_cert;
}
cert->pub->algo = x509_public_key_algorithms[cert->pkey_algo];
cert->pub->id_type = PKEY_ID_X509;
/* Check the signature on the key */
if (strcmp(cert->fingerprint, cert->authority) == 0) {
ret = x509_check_signature(cert->pub, cert);
if (ret < 0)
goto error_free_cert;
}
/* Propose a description */
sulen = strlen(cert->subject);
srlen = strlen(cert->fingerprint);
ret = -ENOMEM;
desc = kmalloc(sulen + 2 + srlen + 1, GFP_KERNEL);
if (!desc)
goto error_free_cert;
memcpy(desc, cert->subject, sulen);
desc[sulen] = ':';
desc[sulen + 1] = ' ';
memcpy(desc + sulen + 2, cert->fingerprint, srlen);
desc[sulen + 2 + srlen] = 0;
/* We're pinning the module by being linked against it */
__module_get(public_key_subtype.owner);
prep->type_data[0] = &public_key_subtype;
prep->type_data[1] = cert->fingerprint;
prep->payload = cert->pub;
prep->description = desc;
prep->quotalen = 100;
/* We've finished with the certificate */
cert->pub = NULL;
cert->fingerprint = NULL;
desc = NULL;
ret = 0;
error_free_cert:
x509_free_certificate(cert);
return ret;
}
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);
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