// SPDX-License-Identifier: GPL-2.0-or-later
/* In-software asymmetric public-key crypto subtype
*
* See Documentation/crypto/asymmetric-keys.rst
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*/
#define pr_fmt(fmt) "PKEY: "fmt
#include <crypto/akcipher.h>
#include <crypto/public_key.h>
#include <crypto/sig.h>
#include <keys/asymmetric-subtype.h>
#include <linux/asn1.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/string.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_sensitive(key->key);
kfree(key->params);
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);
}
/*
* Given a public_key, and an encoding and hash_algo to be used for signing
* and/or verification with that key, determine the name of the corresponding
* akcipher algorithm. Also check that encoding and hash_algo are allowed.
*/
static int
software_key_determine_akcipher(const struct public_key *pkey,
const char *encoding, const char *hash_algo,
char alg_name[CRYPTO_MAX_ALG_NAME], bool *sig,
enum kernel_pkey_operation op)
{
int n;
*sig = true;
if (!encoding)
return -EINVAL;
if (strcmp(pkey->pkey_algo, "rsa") == 0) {
/*
* RSA signatures usually use EMSA-PKCS1-1_5 [RFC3447 sec 8.2].
*/
if (strcmp(encoding, "pkcs1") == 0) {
*sig = op == kernel_pkey_sign ||
op == kernel_pkey_verify;
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)
return -EINVAL;
/*
* Raw RSA cannot differentiate between different hash
* algorithms.
*/
if (hash_algo)
return -EINVAL;
*sig = false;
} else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
if (strcmp(encoding, "x962") != 0)
return -EINVAL;
/*
* ECDSA signatures are taken over a raw hash, so they don't
* differentiate between different hash algorithms. That means
* that the verifier should hard-code a specific hash algorithm.
* Unfortunately, in practice ECDSA is used with multiple SHAs,
* so we have to allow all of them and not just one.
*/
if (!hash_algo)
return -EINVAL;
if (strcmp(hash_algo, "sha1") != 0 &&
strcmp(hash_algo, "sha224") != 0 &&
strcmp(hash_algo, "sha256") != 0 &&
strcmp(hash_algo, "sha384") != 0 &&
strcmp(hash_algo, "sha512") != 0 &&
strcmp(hash_algo, "sha3-256") != 0 &&
strcmp(hash_algo, "sha3-384") != 0 &&
strcmp(hash_algo, "sha3-512") != 0)
return -EINVAL;
} else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
if (strcmp(encoding, "raw") != 0)
return -EINVAL;
if (!hash_algo)
return -EINVAL;
if (strcmp(hash_algo, "streebog256") != 0 &&
strcmp(hash_algo, "streebog512") != 0)
return -EINVAL;
} else {
/* Unknown public key algorithm */
return -ENOPKG;
}
if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
return -EINVAL;
return 0;
}
static u8 *pkey_pack_u32(u8 *dst, u32 val)
{
memcpy(dst, &val, sizeof(val));
return dst + sizeof(val);
}
/*
* 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];
struct crypto_sig *sig;
u8 *key, *ptr;
int ret, len;
bool issig;
ret = software_key_determine_akcipher(pkey, params->encoding,
params->hash_algo, alg_name,
&issig, kernel_pkey_sign);
if (ret < 0)
return ret;
key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
GFP_KERNEL);
if (!key)
return -ENOMEM;
memcpy(key, pkey->key, pkey->keylen);
ptr = key + pkey->keylen;
ptr = pkey_pack_u32(ptr, pkey->algo);
ptr = pkey_pack_u32(ptr, pkey->paramlen);
memcpy(ptr, pkey->params, pkey->paramlen);
if (issig) {
sig = crypto_alloc_sig(alg_name, 0, 0);
if (IS_ERR(sig)) {
ret = PTR_ERR(sig);
goto error_free_key;
}
if (pkey->key_is_private)
ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
else
ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
if (ret < 0)
goto error_free_tfm;
len = crypto_sig_maxsize(sig);
info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
if (pkey->key_is_private)
info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
if (strcmp(params->encoding, "pkcs1") == 0) {
info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
if (pkey->key_is_private)
info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
}
} else {
tfm = crypto_alloc_akcipher(alg_name, 0, 0);
if (IS_ERR(tfm)) {
ret = PTR_ERR(tfm);
goto error_free_key;
}
if (pkey->key_is_private)
ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
else
ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
if (ret < 0)
goto error_free_tfm;
len = crypto_akcipher_maxsize(tfm);
info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
if (pkey->key_is_private)
info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
}
info->key_size = len * 8;
if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
int slen = len;
/*
* ECDSA key sizes are much smaller than RSA, and thus could
* operate on (hashed) inputs that are larger than key size.
* For example SHA384-hashed input used with secp256r1
* based keys. Set max_data_size to be at least as large as
* the largest supported hash size (SHA512)
*/
info->max_data_size = 64;
/*
* Verify takes ECDSA-Sig (described in RFC 5480) as input,
* which is actually 2 'key_size'-bit integers encoded in
* ASN.1. Account for the ASN.1 encoding overhead here.
*
* NIST P192/256/384 may prepend a '0' to a coordinate to
* indicate a positive integer. NIST P521 never needs it.
*/
if (strcmp(pkey->pkey_algo, "ecdsa-nist-p521") != 0)
slen += 1;
/* Length of encoding the x & y coordinates */
slen = 2 * (slen + 2);
/*
* If coordinate encoding takes at least 128 bytes then an
* additional byte for length encoding is needed.
*/
info->max_sig_size = 1 + (slen >= 128) + 1 + slen;
} else {
info->max_data_size = len;
info->max_sig_size = len;
}
info->max_enc_size = len;
info->max_dec_size = len;
ret = 0;
error_free_tfm:
if (issig)
crypto_free_sig(sig);
else
crypto_free_akcipher(tfm);
error_free_key:
kfree_sensitive(key);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
/*
* Do encryption, decryption and signing ops.
*/
static int software_key_eds_op(struct kernel_pkey_params *params,
const void *in, void *out)
{
const struct public_key *pkey = params->key->payload.data[asym_crypto];
char alg_name[CRYPTO_MAX_ALG_NAME];
struct crypto_akcipher *tfm;
struct crypto_sig *sig;
char *key, *ptr;
bool issig;
int ksz;
int ret;
pr_devel("==>%s()\n", __func__);
ret = software_key_determine_akcipher(pkey, params->encoding,
params->hash_algo, alg_name,
&issig, params->op);
if (ret < 0)
return ret;
key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
GFP_KERNEL);
if (!key)
return -ENOMEM;
memcpy(key, pkey->key, pkey->keylen);
ptr = key + pkey->keylen;
ptr = pkey_pack_u32(ptr, pkey->algo);
ptr = pkey_pack_u32(ptr, pkey->paramlen);
memcpy(ptr, pkey->params, pkey->paramlen);
if (issig) {
sig = crypto_alloc_sig(alg_name, 0, 0);
if (IS_ERR(sig)) {
ret = PTR_ERR(sig);
goto error_free_key;
}
if (pkey->key_is_private)
ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
else
ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
if (ret)
goto error_free_tfm;
ksz = crypto_sig_maxsize(sig);
} else {
tfm = crypto_alloc_akcipher(alg_name, 0, 0);
if (IS_ERR(tfm)) {
ret = PTR_ERR(tfm);
goto error_free_key;
}
if (pkey->key_is_private)
ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
else
ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
if (ret)
goto error_free_tfm;
ksz = crypto_akcipher_maxsize(tfm);
}
ret = -EINVAL;
/* Perform the encryption calculation. */
switch (params->op) {
case kernel_pkey_encrypt:
if (issig)
break;
ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
out, params->out_len);
break;
case kernel_pkey_decrypt:
if (issig)
break;
ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
out, params->out_len);
break;
case kernel_pkey_sign:
if (!issig)
break;
ret = crypto_sig_sign(sig, in, params->in_len,
out, params->out_len);
break;
default:
BUG();
}
if (ret == 0)
ret = ksz;
error_free_tfm:
if (issig)
crypto_free_sig(sig);
else
crypto_free_akcipher(tfm);
error_free_key:
kfree_sensitive(key);
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)
{
char alg_name[CRYPTO_MAX_ALG_NAME];
struct crypto_sig *tfm;
char *key, *ptr;
bool issig;
int ret;
pr_devel("==>%s()\n", __func__);
BUG_ON(!pkey);
BUG_ON(!sig);
BUG_ON(!sig->s);
/*
* If the signature specifies a public key algorithm, it *must* match
* the key's actual public key algorithm.
*
* Small exception: ECDSA signatures don't specify the curve, but ECDSA
* keys do. So the strings can mismatch slightly in that case:
* "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
*/
if (sig->pkey_algo) {
if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
(strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
strcmp(sig->pkey_algo, "ecdsa") != 0))
return -EKEYREJECTED;
}
ret = software_key_determine_akcipher(pkey, sig->encoding,
sig->hash_algo, alg_name,
&issig, kernel_pkey_verify);
if (ret < 0)
return ret;
tfm = crypto_alloc_sig(alg_name, 0, 0);
if (IS_ERR(tfm))
return PTR_ERR(tfm);
key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
GFP_KERNEL);
if (!key) {
ret = -ENOMEM;
goto error_free_tfm;
}
memcpy(key, pkey->key, pkey->keylen);
ptr = key + pkey->keylen;
ptr = pkey_pack_u32(ptr, pkey->algo);
ptr = pkey_pack_u32(ptr, pkey->paramlen);
memcpy(ptr, pkey->params, pkey->paramlen);
if (pkey->key_is_private)
ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
else
ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
if (ret)
goto error_free_key;
ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
sig->digest, sig->digest_size);
error_free_key:
kfree_sensitive(key);
error_free_tfm:
crypto_free_sig(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,
.eds_op = software_key_eds_op,
.verify_signature = public_key_verify_signature_2,
};
EXPORT_SYMBOL_GPL(public_key_subtype);
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