path: root/security/keys/encrypted-keys/encrypted.c

/*
 * Copyright (C) 2010 IBM Corporation
 * Copyright (C) 2010 Politecnico di Torino, Italy
 *                    TORSEC group -- http://security.polito.it
 *
 * Authors:
 * Mimi Zohar <zohar@us.ibm.com>
 * Roberto Sassu <roberto.sassu@polito.it>
 *
 * 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.
 *
 * See Documentation/security/keys-trusted-encrypted.txt
 */

#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/parser.h>
#include <linux/string.h>
#include <linux/err.h>
#include <keys/user-type.h>
#include <keys/trusted-type.h>
#include <keys/encrypted-type.h>
#include <linux/key-type.h>
#include <linux/random.h>
#include <linux/rcupdate.h>
#include <linux/scatterlist.h>
#include <linux/crypto.h>
#include <linux/ctype.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <crypto/aes.h>

#include "encrypted.h"
#include "ecryptfs_format.h"

static const char KEY_TRUSTED_PREFIX[] = "trusted:";
static const char KEY_USER_PREFIX[] = "user:";
static const char hash_alg[] = "sha256";
static const char hmac_alg[] = "hmac(sha256)";
static const char blkcipher_alg[] = "cbc(aes)";
static const char key_format_default[] = "default";
static const char key_format_ecryptfs[] = "ecryptfs";
static unsigned int ivsize;
static int blksize;

#define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1)
#define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1)
#define KEY_ECRYPTFS_DESC_LEN 16
#define HASH_SIZE SHA256_DIGEST_SIZE
#define MAX_DATA_SIZE 4096
#define MIN_DATA_SIZE  20

struct sdesc {
	struct shash_desc shash;
	char ctx[];
};

static struct crypto_shash *hashalg;
static struct crypto_shash *hmacalg;

enum {
	Opt_err = -1, Opt_new, Opt_load, Opt_update
};

enum {
	Opt_error = -1, Opt_default, Opt_ecryptfs
};

static const match_table_t key_format_tokens = {
	{Opt_default, "default"},
	{Opt_ecryptfs, "ecryptfs"},
	{Opt_error, NULL}
};

static const match_table_t key_tokens = {
	{Opt_new, "new"},
	{Opt_load, "load"},
	{Opt_update, "update"},
	{Opt_err, NULL}
};

static int aes_get_sizes(void)
{
	struct crypto_blkcipher *tfm;

	tfm = crypto_alloc_blkcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(tfm)) {
		pr_err("encrypted_key: failed to alloc_cipher (%ld)\n",
		       PTR_ERR(tfm));
		return PTR_ERR(tfm);
	}
	ivsize = crypto_blkcipher_ivsize(tfm);
	blksize = crypto_blkcipher_blocksize(tfm);
	crypto_free_blkcipher(tfm);
	return 0;
}

/*
 * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key
 *
 * The description of a encrypted key with format 'ecryptfs' must contain
 * exactly 16 hexadecimal characters.
 *
 */
static int valid_ecryptfs_desc(const char *ecryptfs_desc)
{
	int i;

	if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) {
		pr_err("encrypted_key: key description must be %d hexadecimal "
		       "characters long\n", KEY_ECRYPTFS_DESC_LEN);
		return -EINVAL;
	}

	for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) {
		if (!isxdigit(ecryptfs_desc[i])) {
			pr_err("encrypted_key: key description must contain "
			       "only hexadecimal characters\n");
			return -EINVAL;
		}
	}

	return 0;
}

/*
 * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key
 *
 * key-type:= "trusted:" | "user:"
 * desc:= master-key description
 *
 * Verify that 'key-type' is valid and that 'desc' exists. On key update,
 * only the master key description is permitted to change, not the key-type.
 * The key-type remains constant.
 *
 * On success returns 0, otherwise -EINVAL.
 */
static int valid_master_desc(const char *new_desc, const char *orig_desc)
{
	if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
		if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
			goto out;
		if (orig_desc)
			if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
				goto out;
	} else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
		if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
			goto out;
		if (orig_desc)
			if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
				goto out;
	} else
		goto out;
	return 0;
out:
	return -EINVAL;
}