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/* In-software asymmetric public-key crypto subtype
*
* See Documentation/crypto/asymmetric-keys.txt
*
* 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) "PKEY: "fmt
#include <linux/module.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/scatterlist.h>
#include <keys/asymmetric-subtype.h>
#include <crypto/public_key.h>
#include <crypto/akcipher.h>
MODULE_DESCRIPTION("In-software asymmetric public-key subtype");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL");
/*
* Provide a part of a description of the key for /proc/keys.
*/
static void public_key_describe(const struct key *asymmetric_key,
struct seq_file *m)
{
struct public_key *key = asymmetric_key->payload.data[asym_crypto];
if (key)
seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
}
/*
* Destroy a public key algorithm key.
*/
void public_key_free(struct public_key *key)
{
if (key) {
kfree(key->key);
kfree(key);
}
}
EXPORT_SYMBOL_GPL(public_key_free);
/*
* Destroy a public key algorithm key.
*/
static void public_key_destroy(void *payload0, void *payload3)
{
public_key_free(payload0);
public_key_signature_free(payload3);
}
/*
* Determine the crypto algorithm name.
*/
static
int software_key_determine_akcipher(const char *encoding,
const char *hash_algo,
const struct public_key *pkey,
char alg_name[CRYPTO_MAX_ALG_NAME])
{
int n;
if (strcmp(encoding, "pkcs1") == 0) {
/* The data wangled by the RSA algorithm is typically padded
* and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447
* sec 8.2].
*/
if (!hash_algo)
n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
"pkcs1pad(%s)",
pkey->pkey_algo);
else
n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
"pkcs1pad(%s,%s)",
pkey->pkey_algo, hash_algo);
return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
}
if (strcmp(encoding, "raw") == 0) {
strcpy(alg_name, pkey->pkey_algo);
return 0;
}
return -ENOPKG;
}
/*
* Query information about a key.
*/
static int software_key_query(const struct kernel_pkey_params *params,
struct kernel_pkey_query *info)
{
struct crypto_akcipher *tfm;
struct public_key *pkey = params->key->payload.data[asym_crypto];
char alg_name[CRYPTO_MAX_ALG_NAME];
int ret, len;
ret = software_key_determine_akcipher(params->encoding,
params->hash_algo,
pkey, alg_name);
if (ret < 0)
return ret;
tfm = crypto_alloc_akcipher(alg_name, 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
if (ret < 0)
goto error_free_tfm;
len = crypto_akcipher_maxsize(tfm);
info->key_size = len * 8;
info->max_data_size = len;
info->max_sig_size = len;
info->max_enc_size = len;
info->max_dec_size = len;
info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
ret = 0;
error_free_tfm:
crypto_free_akcipher(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
/*
* Verify a signature using a public key.
*/
int public_key_verify_signature(const struct public_key *pkey,
const struct public_key_signature *sig)
{
struct crypto_wait cwait;
struct crypto_akcipher *tfm;
struct akcipher_request *req;
struct scatterlist sig_sg, digest_sg;
char alg_name[CRYPTO_MAX_ALG_NAME];
void *output;
unsigned int outlen;
int ret;
pr_devel("==>%s()\n", __func__);
BUG_ON(!pkey);
BUG_ON(!sig);
BUG_ON(!sig->s);
ret = software_key_determine_akcipher(sig->encoding,
sig->hash_algo,
pkey, alg_name);
if (ret < 0)
return ret;
tfm = crypto_alloc_akcipher(alg_name, 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
ret = -ENOMEM;
req = akcipher_request_alloc(tfm, GFP_KERNEL);
if (!req)
goto error_free_tfm;
ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
if (ret)
goto error_free_req;
ret = -ENOMEM;
outlen = crypto_akcipher_maxsize(tfm);
output = kmalloc(outlen, GFP_KERNEL);
if (!output)
goto error_free_req;
sg_init_one(&sig_sg, sig->s, sig->s_size);
sg_init_one(&digest_sg, output, outlen);
akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
outlen);
crypto_init_wait(&cwait);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &cwait);
/* Perform the verification calculation. This doesn't actually do the
* verification, but rather calculates the hash expected by the
* signature and returns that to us.
*/
ret = crypto_wait_req(crypto_akcipher_verify(req), &cwait);
if (ret)
goto out_free_output;
/* Do the actual verification step. */
if (req->dst_len != sig->digest_size ||
memcmp(sig->digest, output, sig->digest_size) != 0)
ret = -EKEYREJECTED;
out_free_output:
kfree(output);
error_free_req:
akcipher_request_free(req);
error_free_tfm:
crypto_free_akcipher(tfm);
pr_devel("<==%s() = %d\n", __func__, ret);
if (WARN_ON_ONCE(ret > 0))
ret = -EINVAL;
return ret;
}
EXPORT_SYMBOL_GPL(public_key_verify_signature);
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[asym_crypto];
return public_key_verify_signature(pk, sig);
}
/*
* Public key algorithm asymmetric key subtype
*/
struct asymmetric_key_subtype public_key_subtype = {
.owner = THIS_MODULE,
.name = "public_key",
.name_len = sizeof("public_key") - 1,
.describe = public_key_describe,
.destroy = public_key_destroy,
.query = software_key_query,
.verify_signature = public_key_verify_signature_2,
};
EXPORT_SYMBOL_GPL(public_key_subtype);
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