// SPDX-License-Identifier: GPL-2.0-only/* * Copyright (C) 2011 Nokia Corporation * Copyright (C) 2011 Intel Corporation * * Author: * Dmitry Kasatkin <dmitry.kasatkin@nokia.com> *                 <dmitry.kasatkin@intel.com> * * 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 <crypto/sha1.h>#include <keys/user-type.h>#include <linux/mpi.h>#include <linux/digsig.h> 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;	const uint8_t *endp;	const struct user_key_payload *ukp;	struct pubkey_hdr *pkh; 	down_read(&key->sem);	ukp = user_key_payload_locked(key); 	if (!ukp) {		/* key was revoked before we acquired its semaphore */		err = -EKEYREVOKED;		goto err1;	} 	if (ukp-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; 	for (i = 0; i < pkh->nmpi; i++) {		unsigned int remaining = endp - datap;		pkey[i] = mpi_read_from_buffer(datap, &remaining);		if (IS_ERR(pkey[i])) {			err = PTR_ERR(pkey[i]);			goto err;		}		datap += remaining;	} 	mblen = mpi_get_nbits(pkey[0]);	mlen = DIV_ROUND_UP(mblen, 8); 	if (mlen == 0) {		err = -EINVAL;		goto err;	} 	err = -ENOMEM; 	out1 = kzalloc(mlen, GFP_KERNEL);	if (!out1)		goto err; 	nret = siglen;	in = mpi_read_from_buffer(sig, &nret);	if (IS_ERR(in)) {		err = PTR_ERR(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;	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 * @siglen:	length of the signature * @data:	data * @datalen:	length of the data * * Returns 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){	struct signature_hdr *sh = (struct signature_hdr *)sig;	struct sha1_ctx ctx;	unsigned char hash[SHA1_DIGEST_SIZE];	struct key *key;	char name[20];	int err; 	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, true);		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);	} 	sha1_init(&ctx);	sha1_update(&ctx, data, datalen);	sha1_update(&ctx, sig, sizeof(*sh));	sha1_final(&ctx, hash); 	/* pass signature mpis address */	err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),			     hash, sizeof(hash)); 	key_put(key); 	return err ? -EINVAL : 0;}EXPORT_SYMBOL_GPL(digsig_verify); MODULE_LICENSE("GPL");