/* Module signature checker * * 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. */ #include <linux/kernel.h>#include <linux/err.h>#include <crypto/public_key.h>#include <crypto/hash.h>#include <keys/asymmetric-type.h>#include <keys/system_keyring.h>#include "module-internal.h" /* * Module signature information block. * * The constituents of the signature section are, in order: * *	- Signer's name *	- Key identifier *	- Signature data *	- Information block */struct module_signature {	u8	algo;		/* Public-key crypto algorithm [enum pkey_algo] */	u8	hash;		/* Digest algorithm [enum hash_algo] */	u8	id_type;	/* Key identifier type [enum pkey_id_type] */	u8	signer_len;	/* Length of signer's name */	u8	key_id_len;	/* Length of key identifier */	u8	__pad[3];	__be32	sig_len;	/* Length of signature data */}; /* * Digest the module contents. */static struct public_key_signature *mod_make_digest(enum hash_algo hash,						    const void *mod,						    unsigned long modlen){	struct public_key_signature *pks;	struct crypto_shash *tfm;	struct shash_desc *desc;	size_t digest_size, desc_size;	int ret; 	pr_devel("==>%s()\n", __func__);		/* Allocate the hashing algorithm we're going to need and find out how	 * big the hash operational data will be.	 */	tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);	if (IS_ERR(tfm))		return (PTR_ERR(tfm) == -ENOENT) ? ERR_PTR(-ENOPKG) : ERR_CAST(tfm); 	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);	digest_size = crypto_shash_digestsize(tfm); 	/* We allocate the hash operational data storage on the end of our	 * context data and the digest output buffer on the end of that.	 */	ret = -ENOMEM;	pks = kzalloc(digest_size + sizeof(*pks) + desc_size, GFP_KERNEL);	if (!pks)		goto error_no_pks; 	pks->pkey_hash_algo	= hash;	pks->digest		= (u8 *)pks + sizeof(*pks) + desc_size;	pks->digest_size	= digest_size; 	desc = (void *)pks + sizeof(*pks);	desc->tfm   = tfm;	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; 	ret = crypto_shash_init(desc);	if (ret < 0)		goto error; 	ret = crypto_shash_finup(desc, mod, modlen, pks->digest);	if (ret < 0)		goto error; 	crypto_free_shash(tfm);	pr_devel("<==%s() = ok\n", __func__);	return pks; error:	kfree(pks);error_no_pks:	crypto_free_shash(tfm);	pr_devel("<==%s() = %d\n", __func__, ret);	return ERR_PTR(ret);} /* * Extract an MPI array from the signature data.  This represents the actual * signature.  Each raw MPI is prefaced by a BE 2-byte value indicating the * size of the MPI in bytes. * * RSA signatures only have one MPI, so currently we only read one. */static int mod_extract_mpi_array(struct public_key_signature *pks,				 const void *data, size_t len){	size_t nbytes;	MPI mpi; 	if (len < 3)		return -EBADMSG;	nbytes = ((const u8 *)data)[0] << 8 | ((const u8 *)data)[1];	data += 2;	len -= 2;	if (len != nbytes)		return -EBADMSG; 	mpi = mpi_read_raw_data(data, nbytes);	if (!mpi)		return -ENOMEM;	pks->mpi[0] = mpi;	pks->nr_mpi = 1;	return 0;} /* * Request an asymmetric key. */static struct key *request_asymmetric_key(const char *signer, size_t signer_len,					  const u8 *key_id, size_t key_id_len){	key_ref_t key;	size_t i;	char *id, *q; 	pr_devel("==>%s(,%zu,,%zu)\n", __func__, signer_len, key_id_len); 	/* Construct an identifier. */	id = kmalloc(signer_len + 2 + key_id_len * 2 + 1, GFP_KERNEL);	if (!id)		return ERR_PTR(-ENOKEY); 	memcpy(id, signer, signer_len); 	q = id + signer_len;	*q++ = ':';	*q++ = ' ';	for (i = 0; i < key_id_len; i++) {		*q++ = hex_asc[*key_id >> 4];		*q++ = hex_asc[*key_id++ & 0x0f];	} 	*q = 0; 	pr_debug("Look up: \"%s\"\n", id); 	key = keyring_search(make_key_ref(system_trusted_keyring, 1),			     &key_type_asymmetric, id);	if (IS_ERR(key))		pr_warn("Request for unknown module key '%s' err %ld\n",			id, PTR_ERR(key));	kfree(id); 	if (IS_ERR(key)) {		switch (PTR_ERR(key)) {			/* Hide some search errors */		case -EACCES:		case -ENOTDIR:		case -EAGAIN:			return ERR_PTR(-ENOKEY);		default:			return ERR_CAST(key);		}	} 	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key_ref_to_ptr(key)));	return key_ref_to_ptr(key);} /* * Verify the signature on a module. */int mod_verify_sig(const void *mod, unsigned long *_modlen){	struct public_key_signature *pks;	struct module_signature ms;	struct key *key;	const void *sig;	size_t modlen = *_modlen, sig_len;	int ret; 	pr_devel("==>%s(,%zu)\n", __func__, modlen); 	if (modlen <= sizeof(ms))		return -EBADMSG; 	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));	modlen -= sizeof(ms); 	sig_len = be32_to_cpu(ms.sig_len);	if (sig_len >= modlen)		return -EBADMSG;	modlen -= sig_len;	if ((size_t)ms.signer_len + ms.key_id_len >= modlen)		return -EBADMSG;	modlen -= (size_t)ms.signer_len + ms.key_id_len; 	*_modlen = modlen;	sig = mod + modlen; 	/* For the moment, only support RSA and X.509 identifiers */	if (ms.algo != PKEY_ALGO_RSA ||	    ms.id_type != PKEY_ID_X509)		return -ENOPKG; 	if (ms.hash >= PKEY_HASH__LAST ||	    !hash_algo_name[ms.hash])		return -ENOPKG; 	key = request_asymmetric_key(sig, ms.signer_len,				     sig + ms.signer_len, ms.key_id_len);	if (IS_ERR(key))		return PTR_ERR(key); 	pks = mod_make_digest(ms.hash, mod, modlen);	if (IS_ERR(pks)) {		ret = PTR_ERR(pks);		goto error_put_key;	} 	ret = mod_extract_mpi_array(pks, sig + ms.signer_len + ms.key_id_len,				    sig_len);	if (ret < 0)		goto error_free_pks; 	ret = verify_signature(key, pks);	pr_devel("verify_signature() = %d\n", ret); error_free_pks:	mpi_free(pks->rsa.s);	kfree(pks);error_put_key:	key_put(key);	pr_devel("<==%s() = %d\n", __func__, ret);	return ret;	}