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/* RSA asymmetric public-key algorithm [RFC3447]
*
* 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) "RSA: "fmt
#include <linux/module.h>
#include <linux/slab.h>
#include <crypto/akcipher.h>
#include <crypto/public_key.h>
#include <crypto/algapi.h>
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("RSA Public Key Algorithm");
#define kenter(FMT, ...) \
pr_devel("==> %s("FMT")\n", __func__, ##__VA_ARGS__)
#define kleave(FMT, ...) \
pr_devel("<== %s()"FMT"\n", __func__, ##__VA_ARGS__)
/*
* Hash algorithm OIDs plus ASN.1 DER wrappings [RFC4880 sec 5.2.2].
*/
static const u8 RSA_digest_info_MD5[] = {
0x30, 0x20, 0x30, 0x0C, 0x06, 0x08,
0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* OID */
0x05, 0x00, 0x04, 0x10
};
static const u8 RSA_digest_info_SHA1[] = {
0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
0x2B, 0x0E, 0x03, 0x02, 0x1A,
0x05, 0x00, 0x04, 0x14
};
static const u8 RSA_digest_info_RIPE_MD_160[] = {
0x30, 0x21, 0x30, 0x09, 0x06, 0x05,
0x2B, 0x24, 0x03, 0x02, 0x01,
0x05, 0x00, 0x04, 0x14
};
static const u8 RSA_digest_info_SHA224[] = {
0x30, 0x2d, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x04,
0x05, 0x00, 0x04, 0x1C
};
static const u8 RSA_digest_info_SHA256[] = {
0x30, 0x31, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01,
0x05, 0x00, 0x04, 0x20
};
static const u8 RSA_digest_info_SHA384[] = {
0x30, 0x41, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x02,
0x05, 0x00, 0x04, 0x30
};
static const u8 RSA_digest_info_SHA512[] = {
0x30, 0x51, 0x30, 0x0d, 0x06, 0x09,
0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03,
0x05, 0x00, 0x04, 0x40
};
static const struct {
const u8 *data;
size_t size;
} RSA_ASN1_templates[PKEY_HASH__LAST] = {
#define _(X) { RSA_digest_info_##X, sizeof(RSA_digest_info_##X) }
[HASH_ALGO_MD5] = _(MD5),
[HASH_ALGO_SHA1] = _(SHA1),
[HASH_ALGO_RIPE_MD_160] = _(RIPE_MD_160),
[HASH_ALGO_SHA256] = _(SHA256),
[HASH_ALGO_SHA384] = _(SHA384),
[HASH_ALGO_SHA512] = _(SHA512),
[HASH_ALGO_SHA224] = _(SHA224),
#undef _
};
struct rsa_completion {
struct completion completion;
int err;
};
/*
* Perform the RSA signature verification.
* @H: Value of hash of data and metadata
* @EM: The computed signature value
* @k: The size of EM (EM[0] is an invalid location but should hold 0x00)
* @hash_size: The size of H
* @asn1_template: The DigestInfo ASN.1 template
* @asn1_size: Size of asm1_template[]
*/
static int rsa_verify(const u8 *H, const u8 *EM, size_t k, size_t hash_size,
const u8 *asn1_template, size_t asn1_size)
{
unsigned PS_end, T_offset, i;
kenter(",,%zu,%zu,%zu", k, hash_size, asn1_size);
if (k < 2 + 1 + asn1_size + hash_size)
return -EBADMSG;
/* Decode the EMSA-PKCS1-v1_5
* note: leading zeros are stirpped by the RSA implementation */
if (EM[0] != 0x01) {
kleave(" = -EBADMSG [EM[0] == %02u]", EM[0]);
return -EBADMSG;
}
T_offset = k - (asn1_size + hash_size);
PS_end = T_offset - 1;
if (EM[PS_end] != 0x00) {
kleave(" = -EBADMSG [EM[T-1] == %02u]", EM[PS_end]);
return -EBADMSG;
}
for (i = 1; i < PS_end; i++) {
if (EM[i] != 0xff) {
kleave(" = -EBADMSG [EM[PS%x] == %02u]", i - 2, EM[i]);
return -EBADMSG;
}
}
if (crypto_memneq(asn1_template, EM + T_offset, asn1_size) != 0) {
kleave(" = -EBADMSG [EM[T] ASN.1 mismatch]");
return -EBADMSG;
}
if (crypto_memneq(H, EM + T_offset + asn1_size, hash_size) != 0) {
kleave(" = -EKEYREJECTED [EM[T] hash mismatch]");
return -EKEYREJECTED;
}
kleave(" = 0");
return 0;
}
static void public_key_verify_done(struct crypto_async_request *req, int err)
{
struct rsa_completion *compl = req->data;
if (err == -EINPROGRESS)
return;
compl->err = err;
complete(&compl->completion);
}
int rsa_verify_signature(const struct public_key *pkey,
const struct public_key_signature *sig)
{
struct crypto_akcipher *tfm;
struct akcipher_request *req;
struct rsa_completion compl;
struct scatterlist sig_sg, sg_out;
void *outbuf = NULL;
unsigned int outlen = 0;
int ret = -ENOMEM;
tfm = crypto_alloc_akcipher("rsa", 0, 0);
if (IS_ERR(tfm))
goto error_out;
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 = -EINVAL;
outlen = crypto_akcipher_maxsize(tfm);
if (!outlen)
goto error_free_req;
/* initlialzie out buf */
ret = -ENOMEM;
outbuf = kmalloc(outlen, GFP_KERNEL);
if (!outbuf)
goto error_free_req;
sg_init_one(&sig_sg, sig->s, sig->s_size);
sg_init_one(&sg_out, outbuf, outlen);
akcipher_request_set_crypt(req, &sig_sg, &sg_out, sig->s_size, outlen);
init_completion(&compl.completion);
akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
CRYPTO_TFM_REQ_MAY_SLEEP,
public_key_verify_done, &compl);
ret = crypto_akcipher_verify(req);
if (ret == -EINPROGRESS) {
wait_for_completion(&compl.completion);
ret = compl.err;
}
if (ret)
goto error_free_req;
/*
* Output from the operation is an encoded message (EM) of
* length k octets.
*/
outlen = req->dst_len;
ret = rsa_verify(sig->digest, outbuf, outlen, sig->digest_size,
RSA_ASN1_templates[sig->pkey_hash_algo].data,
RSA_ASN1_templates[sig->pkey_hash_algo].size);
error_free_req:
akcipher_request_free(req);
error_free_tfm:
crypto_free_akcipher(tfm);
error_out:
kfree(outbuf);
return ret;
}
EXPORT_SYMBOL_GPL(rsa_verify_signature);
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