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![Stefan Berger](/assets/img/avatar_default.png)
Adjust the calculation of the maximum signature size for support of NIST P521. While existing curves may prepend a 0 byte to their coordinates (to make the number positive), NIST P521 will not do this since only the first bit in the most significant byte is used. If the encoding of the x & y coordinates requires at least 128 bytes then an additional byte is needed for the encoding of the length. Take this into account when calculating the maximum signature size. Reviewed-by: Lukas Wunner <lukas@wunner.de> Tested-by: Lukas Wunner <lukas@wunner.de> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
489 lines
12 KiB
C
489 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* In-software asymmetric public-key crypto subtype
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*
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* See Documentation/crypto/asymmetric-keys.rst
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#define pr_fmt(fmt) "PKEY: "fmt
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#include <crypto/akcipher.h>
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#include <crypto/public_key.h>
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#include <crypto/sig.h>
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#include <keys/asymmetric-subtype.h>
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#include <linux/asn1.h>
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#include <linux/err.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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MODULE_DESCRIPTION("In-software asymmetric public-key subtype");
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MODULE_AUTHOR("Red Hat, Inc.");
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MODULE_LICENSE("GPL");
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/*
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* Provide a part of a description of the key for /proc/keys.
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*/
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static void public_key_describe(const struct key *asymmetric_key,
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struct seq_file *m)
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{
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struct public_key *key = asymmetric_key->payload.data[asym_crypto];
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if (key)
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seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
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}
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/*
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* Destroy a public key algorithm key.
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*/
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void public_key_free(struct public_key *key)
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{
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if (key) {
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kfree_sensitive(key->key);
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kfree(key->params);
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kfree(key);
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}
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}
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EXPORT_SYMBOL_GPL(public_key_free);
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/*
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* Destroy a public key algorithm key.
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*/
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static void public_key_destroy(void *payload0, void *payload3)
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{
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public_key_free(payload0);
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public_key_signature_free(payload3);
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}
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/*
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* Given a public_key, and an encoding and hash_algo to be used for signing
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* and/or verification with that key, determine the name of the corresponding
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* akcipher algorithm. Also check that encoding and hash_algo are allowed.
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*/
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static int
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software_key_determine_akcipher(const struct public_key *pkey,
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const char *encoding, const char *hash_algo,
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char alg_name[CRYPTO_MAX_ALG_NAME], bool *sig,
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enum kernel_pkey_operation op)
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{
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int n;
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*sig = true;
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if (!encoding)
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return -EINVAL;
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if (strcmp(pkey->pkey_algo, "rsa") == 0) {
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/*
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* RSA signatures usually use EMSA-PKCS1-1_5 [RFC3447 sec 8.2].
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*/
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if (strcmp(encoding, "pkcs1") == 0) {
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*sig = op == kernel_pkey_sign ||
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op == kernel_pkey_verify;
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if (!hash_algo) {
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n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
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"pkcs1pad(%s)",
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pkey->pkey_algo);
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} else {
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n = snprintf(alg_name, CRYPTO_MAX_ALG_NAME,
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"pkcs1pad(%s,%s)",
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pkey->pkey_algo, hash_algo);
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}
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return n >= CRYPTO_MAX_ALG_NAME ? -EINVAL : 0;
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}
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if (strcmp(encoding, "raw") != 0)
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return -EINVAL;
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/*
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* Raw RSA cannot differentiate between different hash
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* algorithms.
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*/
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if (hash_algo)
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return -EINVAL;
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*sig = false;
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} else if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
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if (strcmp(encoding, "x962") != 0)
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return -EINVAL;
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/*
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* ECDSA signatures are taken over a raw hash, so they don't
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* differentiate between different hash algorithms. That means
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* that the verifier should hard-code a specific hash algorithm.
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* Unfortunately, in practice ECDSA is used with multiple SHAs,
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* so we have to allow all of them and not just one.
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*/
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if (!hash_algo)
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return -EINVAL;
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if (strcmp(hash_algo, "sha1") != 0 &&
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strcmp(hash_algo, "sha224") != 0 &&
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strcmp(hash_algo, "sha256") != 0 &&
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strcmp(hash_algo, "sha384") != 0 &&
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strcmp(hash_algo, "sha512") != 0 &&
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strcmp(hash_algo, "sha3-256") != 0 &&
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strcmp(hash_algo, "sha3-384") != 0 &&
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strcmp(hash_algo, "sha3-512") != 0)
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return -EINVAL;
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} else if (strcmp(pkey->pkey_algo, "sm2") == 0) {
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if (strcmp(encoding, "raw") != 0)
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return -EINVAL;
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if (!hash_algo)
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return -EINVAL;
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if (strcmp(hash_algo, "sm3") != 0)
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return -EINVAL;
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} else if (strcmp(pkey->pkey_algo, "ecrdsa") == 0) {
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if (strcmp(encoding, "raw") != 0)
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return -EINVAL;
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if (!hash_algo)
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return -EINVAL;
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if (strcmp(hash_algo, "streebog256") != 0 &&
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strcmp(hash_algo, "streebog512") != 0)
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return -EINVAL;
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} else {
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/* Unknown public key algorithm */
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return -ENOPKG;
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}
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if (strscpy(alg_name, pkey->pkey_algo, CRYPTO_MAX_ALG_NAME) < 0)
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return -EINVAL;
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return 0;
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}
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static u8 *pkey_pack_u32(u8 *dst, u32 val)
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{
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memcpy(dst, &val, sizeof(val));
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return dst + sizeof(val);
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}
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/*
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* Query information about a key.
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*/
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static int software_key_query(const struct kernel_pkey_params *params,
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struct kernel_pkey_query *info)
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{
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struct crypto_akcipher *tfm;
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struct public_key *pkey = params->key->payload.data[asym_crypto];
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char alg_name[CRYPTO_MAX_ALG_NAME];
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struct crypto_sig *sig;
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u8 *key, *ptr;
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int ret, len;
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bool issig;
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ret = software_key_determine_akcipher(pkey, params->encoding,
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params->hash_algo, alg_name,
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&issig, kernel_pkey_sign);
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if (ret < 0)
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return ret;
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key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
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GFP_KERNEL);
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if (!key)
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return -ENOMEM;
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memcpy(key, pkey->key, pkey->keylen);
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ptr = key + pkey->keylen;
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ptr = pkey_pack_u32(ptr, pkey->algo);
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ptr = pkey_pack_u32(ptr, pkey->paramlen);
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memcpy(ptr, pkey->params, pkey->paramlen);
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if (issig) {
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sig = crypto_alloc_sig(alg_name, 0, 0);
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if (IS_ERR(sig)) {
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ret = PTR_ERR(sig);
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goto error_free_key;
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}
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if (pkey->key_is_private)
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ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
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else
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ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
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if (ret < 0)
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goto error_free_tfm;
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len = crypto_sig_maxsize(sig);
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info->supported_ops = KEYCTL_SUPPORTS_VERIFY;
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if (pkey->key_is_private)
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info->supported_ops |= KEYCTL_SUPPORTS_SIGN;
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if (strcmp(params->encoding, "pkcs1") == 0) {
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info->supported_ops |= KEYCTL_SUPPORTS_ENCRYPT;
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if (pkey->key_is_private)
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info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
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}
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} else {
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tfm = crypto_alloc_akcipher(alg_name, 0, 0);
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if (IS_ERR(tfm)) {
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ret = PTR_ERR(tfm);
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goto error_free_key;
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}
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if (pkey->key_is_private)
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ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
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else
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ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
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if (ret < 0)
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goto error_free_tfm;
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len = crypto_akcipher_maxsize(tfm);
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info->supported_ops = KEYCTL_SUPPORTS_ENCRYPT;
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if (pkey->key_is_private)
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info->supported_ops |= KEYCTL_SUPPORTS_DECRYPT;
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}
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info->key_size = len * 8;
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if (strncmp(pkey->pkey_algo, "ecdsa", 5) == 0) {
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int slen = len;
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/*
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* ECDSA key sizes are much smaller than RSA, and thus could
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* operate on (hashed) inputs that are larger than key size.
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* For example SHA384-hashed input used with secp256r1
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* based keys. Set max_data_size to be at least as large as
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* the largest supported hash size (SHA512)
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*/
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info->max_data_size = 64;
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/*
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* Verify takes ECDSA-Sig (described in RFC 5480) as input,
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* which is actually 2 'key_size'-bit integers encoded in
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* ASN.1. Account for the ASN.1 encoding overhead here.
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*
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* NIST P192/256/384 may prepend a '0' to a coordinate to
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* indicate a positive integer. NIST P521 never needs it.
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*/
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if (strcmp(pkey->pkey_algo, "ecdsa-nist-p521") != 0)
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slen += 1;
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/* Length of encoding the x & y coordinates */
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slen = 2 * (slen + 2);
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/*
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* If coordinate encoding takes at least 128 bytes then an
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* additional byte for length encoding is needed.
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*/
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info->max_sig_size = 1 + (slen >= 128) + 1 + slen;
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} else {
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info->max_data_size = len;
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info->max_sig_size = len;
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}
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info->max_enc_size = len;
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info->max_dec_size = len;
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ret = 0;
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error_free_tfm:
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if (issig)
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crypto_free_sig(sig);
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else
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crypto_free_akcipher(tfm);
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error_free_key:
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kfree_sensitive(key);
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pr_devel("<==%s() = %d\n", __func__, ret);
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return ret;
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}
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/*
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* Do encryption, decryption and signing ops.
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*/
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static int software_key_eds_op(struct kernel_pkey_params *params,
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const void *in, void *out)
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{
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const struct public_key *pkey = params->key->payload.data[asym_crypto];
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char alg_name[CRYPTO_MAX_ALG_NAME];
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struct crypto_akcipher *tfm;
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struct crypto_sig *sig;
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char *key, *ptr;
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bool issig;
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int ksz;
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int ret;
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pr_devel("==>%s()\n", __func__);
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ret = software_key_determine_akcipher(pkey, params->encoding,
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params->hash_algo, alg_name,
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&issig, params->op);
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if (ret < 0)
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return ret;
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key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
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GFP_KERNEL);
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if (!key)
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return -ENOMEM;
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memcpy(key, pkey->key, pkey->keylen);
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ptr = key + pkey->keylen;
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ptr = pkey_pack_u32(ptr, pkey->algo);
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ptr = pkey_pack_u32(ptr, pkey->paramlen);
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memcpy(ptr, pkey->params, pkey->paramlen);
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if (issig) {
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sig = crypto_alloc_sig(alg_name, 0, 0);
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if (IS_ERR(sig)) {
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ret = PTR_ERR(sig);
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goto error_free_key;
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}
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if (pkey->key_is_private)
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ret = crypto_sig_set_privkey(sig, key, pkey->keylen);
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else
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ret = crypto_sig_set_pubkey(sig, key, pkey->keylen);
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if (ret)
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goto error_free_tfm;
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ksz = crypto_sig_maxsize(sig);
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} else {
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tfm = crypto_alloc_akcipher(alg_name, 0, 0);
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if (IS_ERR(tfm)) {
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ret = PTR_ERR(tfm);
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goto error_free_key;
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}
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if (pkey->key_is_private)
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ret = crypto_akcipher_set_priv_key(tfm, key, pkey->keylen);
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else
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ret = crypto_akcipher_set_pub_key(tfm, key, pkey->keylen);
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if (ret)
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goto error_free_tfm;
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ksz = crypto_akcipher_maxsize(tfm);
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}
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ret = -EINVAL;
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/* Perform the encryption calculation. */
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switch (params->op) {
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case kernel_pkey_encrypt:
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if (issig)
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break;
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ret = crypto_akcipher_sync_encrypt(tfm, in, params->in_len,
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out, params->out_len);
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break;
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case kernel_pkey_decrypt:
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if (issig)
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break;
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ret = crypto_akcipher_sync_decrypt(tfm, in, params->in_len,
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out, params->out_len);
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break;
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case kernel_pkey_sign:
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if (!issig)
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break;
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ret = crypto_sig_sign(sig, in, params->in_len,
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out, params->out_len);
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break;
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default:
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BUG();
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}
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if (ret == 0)
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ret = ksz;
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error_free_tfm:
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if (issig)
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crypto_free_sig(sig);
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else
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crypto_free_akcipher(tfm);
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error_free_key:
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kfree_sensitive(key);
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pr_devel("<==%s() = %d\n", __func__, ret);
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return ret;
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}
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/*
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* Verify a signature using a public key.
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*/
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int public_key_verify_signature(const struct public_key *pkey,
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const struct public_key_signature *sig)
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{
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char alg_name[CRYPTO_MAX_ALG_NAME];
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struct crypto_sig *tfm;
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char *key, *ptr;
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bool issig;
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int ret;
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pr_devel("==>%s()\n", __func__);
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BUG_ON(!pkey);
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BUG_ON(!sig);
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BUG_ON(!sig->s);
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/*
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* If the signature specifies a public key algorithm, it *must* match
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* the key's actual public key algorithm.
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*
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* Small exception: ECDSA signatures don't specify the curve, but ECDSA
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* keys do. So the strings can mismatch slightly in that case:
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* "ecdsa-nist-*" for the key, but "ecdsa" for the signature.
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*/
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if (sig->pkey_algo) {
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if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 &&
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(strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 ||
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strcmp(sig->pkey_algo, "ecdsa") != 0))
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return -EKEYREJECTED;
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}
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ret = software_key_determine_akcipher(pkey, sig->encoding,
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sig->hash_algo, alg_name,
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&issig, kernel_pkey_verify);
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if (ret < 0)
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return ret;
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tfm = crypto_alloc_sig(alg_name, 0, 0);
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if (IS_ERR(tfm))
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return PTR_ERR(tfm);
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key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen,
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GFP_KERNEL);
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if (!key) {
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ret = -ENOMEM;
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goto error_free_tfm;
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}
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memcpy(key, pkey->key, pkey->keylen);
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ptr = key + pkey->keylen;
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ptr = pkey_pack_u32(ptr, pkey->algo);
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ptr = pkey_pack_u32(ptr, pkey->paramlen);
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memcpy(ptr, pkey->params, pkey->paramlen);
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if (pkey->key_is_private)
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ret = crypto_sig_set_privkey(tfm, key, pkey->keylen);
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else
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ret = crypto_sig_set_pubkey(tfm, key, pkey->keylen);
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if (ret)
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goto error_free_key;
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ret = crypto_sig_verify(tfm, sig->s, sig->s_size,
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sig->digest, sig->digest_size);
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error_free_key:
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kfree_sensitive(key);
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error_free_tfm:
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crypto_free_sig(tfm);
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pr_devel("<==%s() = %d\n", __func__, ret);
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if (WARN_ON_ONCE(ret > 0))
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ret = -EINVAL;
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return ret;
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}
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EXPORT_SYMBOL_GPL(public_key_verify_signature);
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static int public_key_verify_signature_2(const struct key *key,
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const struct public_key_signature *sig)
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{
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const struct public_key *pk = key->payload.data[asym_crypto];
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return public_key_verify_signature(pk, sig);
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}
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/*
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* Public key algorithm asymmetric key subtype
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*/
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struct asymmetric_key_subtype public_key_subtype = {
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.owner = THIS_MODULE,
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.name = "public_key",
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.name_len = sizeof("public_key") - 1,
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.describe = public_key_describe,
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.destroy = public_key_destroy,
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.query = software_key_query,
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.eds_op = software_key_eds_op,
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.verify_signature = public_key_verify_signature_2,
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};
|
|
EXPORT_SYMBOL_GPL(public_key_subtype);
|