/* * Copyright (C) 2011 Nokia Corporation * Copyright (C) 2011 Intel Corporation * * Author: * Dmitry Kasatkin <dmitry.kasatkin@nokia.com> *                 <dmitry.kasatkin@intel.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, version 2 of the License. * * File: sign.c *	implements signature (RSA) verification *	pkcs decoding is based on LibTomCrypt code */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/err.h>#include <linux/module.h>#include <linux/slab.h>#include <linux/key.h>#include <linux/crypto.h>#include <crypto/hash.h>#include <crypto/sha.h>#include <keys/user-type.h>#include <linux/mpi.h>#include <linux/digsig.h> static struct crypto_shash *shash; static const char *pkcs_1_v1_5_decode_emsa(const unsigned char *msg,						unsigned long  msglen,						unsigned long  modulus_bitlen,						unsigned long *outlen){	unsigned long modulus_len, ps_len, i; 	modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0); 	/* test message size */	if ((msglen > modulus_len) || (modulus_len < 11))		return NULL; 	/* separate encoded message */	if (msg[0] != 0x00 || msg[1] != 0x01)		return NULL; 	for (i = 2; i < modulus_len - 1; i++)		if (msg[i] != 0xFF)			break; 	/* separator check */	if (msg[i] != 0)		/* There was no octet with hexadecimal value 0x00		to separate ps from m. */		return NULL; 	ps_len = i - 2; 	*outlen = (msglen - (2 + ps_len + 1)); 	return msg + 2 + ps_len + 1;} /* * RSA Signature verification with public key */static int digsig_verify_rsa(struct key *key,		    const char *sig, int siglen,		       const char *h, int hlen){	int err = -EINVAL;	unsigned long len;	unsigned long mlen, mblen;	unsigned nret, l;	int head, i;	unsigned char *out1 = NULL;	const char *m;	MPI in = NULL, res = NULL, pkey[2];	uint8_t *p, *datap, *endp;	struct user_key_payload *ukp;	struct pubkey_hdr *pkh; 	down_read(&key->sem);	ukp = key->payload.data; 	if (ukp->datalen < sizeof(*pkh))		goto err1; 	pkh = (struct pubkey_hdr *)ukp->data; 	if (pkh->version != 1)		goto err1; 	if (pkh->algo != PUBKEY_ALGO_RSA)		goto err1; 	if (pkh->nmpi != 2)		goto err1; 	datap = pkh->mpi;	endp = ukp->data + ukp->datalen; 	err = -ENOMEM; 	for (i = 0; i < pkh->nmpi; i++) {		unsigned int remaining = endp - datap;		pkey[i] = mpi_read_from_buffer(datap, &remaining);		if (!pkey[i])			goto err;		datap += remaining;	} 	mblen = mpi_get_nbits(pkey[0]);	mlen = DIV_ROUND_UP(mblen, 8); 	if (mlen == 0)		goto err; 	out1 = kzalloc(mlen, GFP_KERNEL);	if (!out1)		goto err; 	nret = siglen;	in = mpi_read_from_buffer(sig, &nret);	if (!in)		goto err; 	res = mpi_alloc(mpi_get_nlimbs(in) * 2);	if (!res)		goto err; 	err = mpi_powm(res, in, pkey[1], pkey[0]);	if (err)		goto err; 	if (mpi_get_nlimbs(res) * BYTES_PER_MPI_LIMB > mlen) {		err = -EINVAL;		goto err;	} 	p = mpi_get_buffer(res, &l, NULL);	if (!p) {		err = -EINVAL;		goto err;	} 	len = mlen;	head = len - l;	memset(out1, 0, head);	memcpy(out1 + head, p, l); 	kfree(p); 	m = pkcs_1_v1_5_decode_emsa(out1, len, mblen, &len); 	if (!m || len != hlen || memcmp(m, h, hlen))		err = -EINVAL; err:	mpi_free(in);	mpi_free(res);	kfree(out1);	while (--i >= 0)		mpi_free(pkey[i]);err1:	up_read(&key->sem); 	return err;} /** * digsig_verify() - digital signature verification with public key * @keyring:	keyring to search key in * @sig:	digital signature * @sigen:	length of the signature * @data:	data * @datalen:	length of the data * @return:	0 on success, -EINVAL otherwise * * Verifies data integrity against digital signature. * Currently only RSA is supported. * Normally hash of the content is used as a data for this function. * */int digsig_verify(struct key *keyring, const char *sig, int siglen,						const char *data, int datalen){	int err = -ENOMEM;	struct signature_hdr *sh = (struct signature_hdr *)sig;	struct shash_desc *desc = NULL;	unsigned char hash[SHA1_DIGEST_SIZE];	struct key *key;	char name[20]; 	if (siglen < sizeof(*sh) + 2)		return -EINVAL; 	if (sh->algo != PUBKEY_ALGO_RSA)		return -ENOTSUPP; 	sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid)); 	if (keyring) {		/* search in specific keyring */		key_ref_t kref;		kref = keyring_search(make_key_ref(keyring, 1UL),						&key_type_user, name);		if (IS_ERR(kref))			key = ERR_CAST(kref);		else			key = key_ref_to_ptr(kref);	} else {		key = request_key(&key_type_user, name, NULL);	}	if (IS_ERR(key)) {		pr_err("key not found, id: %s\n", name);		return PTR_ERR(key);	} 	desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash),		       GFP_KERNEL);	if (!desc)		goto err; 	desc->tfm = shash;	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; 	crypto_shash_init(desc);	crypto_shash_update(desc, data, datalen);	crypto_shash_update(desc, sig, sizeof(*sh));	crypto_shash_final(desc, hash); 	kfree(desc); 	/* pass signature mpis address */	err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),			     hash, sizeof(hash)); err:	key_put(key); 	return err ? -EINVAL : 0;}EXPORT_SYMBOL_GPL(digsig_verify); static int __init digsig_init(void){	shash = crypto_alloc_shash("sha1", 0, 0);	if (IS_ERR(shash)) {		pr_err("shash allocation failed\n");		return  PTR_ERR(shash);	} 	return 0; } static void __exit digsig_cleanup(void){	crypto_free_shash(shash);} module_init(digsig_init);module_exit(digsig_cleanup); MODULE_LICENSE("GPL");