crypto.c

/*
 * Copyright (c) 2011 Alex Hornung <alex@alexhornung.com>.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
#include <sys/types.h>
#include <sys/param.h>
#include <inttypes.h>

#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>

#include "crc32.h"
#include "tcplay.h"

int
tc_cipher_chain_populate_keys(struct tc_cipher_chain *cipher_chain,
    unsigned char *key)
{
	int total_key_bytes, used_key_bytes;
	struct tc_cipher_chain *dummy_chain;

	/*
	 * We need to determine the total key bytes as the key locations
	 * depend on it.
	 */
	total_key_bytes = tc_cipher_chain_klen(cipher_chain);

	/*
	 * Now we need to get prepare the keys, as the keys are in
	 * forward order with respect to the cipher cascade, but
	 * the actual decryption is in reverse cipher cascade order.
	 */
	used_key_bytes = 0;
	for (dummy_chain = cipher_chain;
	    dummy_chain != NULL;
	    dummy_chain = dummy_chain->next) {
		dummy_chain->key = alloc_safe_mem(dummy_chain->cipher->klen);
		if (dummy_chain->key == NULL) {
			tc_log(1, "tc_decrypt: Could not allocate key "
			    "memory\n");
			return ENOMEM;
		}

		/* XXX: here we assume XTS operation! */
		memcpy(dummy_chain->key,
		    key + used_key_bytes/2,
		    dummy_chain->cipher->klen/2);
		memcpy(dummy_chain->key + dummy_chain->cipher->klen/2,
		    key + (total_key_bytes/2) + used_key_bytes/2,
		    dummy_chain->cipher->klen/2);

		/* Remember how many key bytes we've seen */
		used_key_bytes += dummy_chain->cipher->klen;
	}

	return 0;
}

int
tc_cipher_chain_free_keys(struct tc_cipher_chain *cipher_chain)
{
	for (; cipher_chain != NULL; cipher_chain = cipher_chain->next) {
		if (cipher_chain->key != NULL) {
			free_safe_mem(cipher_chain->key);
			cipher_chain->key = NULL;
		}
	}

	return 0;
}

int
tc_encrypt(struct tc_cipher_chain *cipher_chain, unsigned char *key,
    unsigned char *iv,
    unsigned char *in, int in_len, unsigned char *out)
{
	struct tc_cipher_chain *chain_start;
	int err;

	chain_start = cipher_chain;

	if ((err = tc_cipher_chain_populate_keys(cipher_chain, key)))
		return err;

#ifdef DEBUG
	printf("tc_encrypt: starting chain\n");
#endif

	/*
	 * Now process the actual decryption, in forward cascade order.
	 */
	for (;
	    cipher_chain != NULL;
	    cipher_chain = cipher_chain->next) {
#ifdef DEBUG
		printf("tc_encrypt: Currently using cipher %s\n",
		    cipher_chain->cipher->name);
#endif

		err = syscrypt(cipher_chain->cipher, cipher_chain->key,
		    cipher_chain->cipher->klen, iv, in, out, in_len, 1);

		/* Deallocate this key, since we won't need it anymore */
		free_safe_mem(cipher_chain->key);
		cipher_chain->key = NULL;

		if (err != 0) {
			tc_cipher_chain_free_keys(chain_start);
			return err;
		}

		/* Set next input buffer as current output buffer */
		in = out;
	}

	tc_cipher_chain_free_keys(chain_start);

	return 0;
}

int
tc_decrypt(struct tc_cipher_chain *cipher_chain, unsigned char *key,
    unsigned char *iv,
    unsigned char *in, int in_len, unsigned char *out)
{
	struct tc_cipher_chain *chain_start;
	int err;

	chain_start = cipher_chain;

	if ((err = tc_cipher_chain_populate_keys(cipher_chain, key)))
		return err;

#ifdef DEBUG
	printf("tc_decrypt: starting chain!\n");
#endif

	/*
	 * Now process the actual decryption, in reverse cascade order; so
	 * first find the last element in the chain.
	 */
	for (; cipher_chain->next != NULL; cipher_chain = cipher_chain->next)
		;
	for (;
	    cipher_chain != NULL;
	    cipher_chain = cipher_chain->prev) {
#ifdef DEBUG
		printf("tc_decrypt: Currently using cipher %s\n",
		    cipher_chain->cipher->name);
#endif

		err = syscrypt(cipher_chain->cipher, cipher_chain->key,
		    cipher_chain->cipher->klen, iv, in, out, in_len, 0);

		/* Deallocate this key, since we won't need it anymore */
		free_safe_mem(cipher_chain->key);
		cipher_chain->key = NULL;

		if (err != 0) {
			tc_cipher_chain_free_keys(chain_start);
			return err;
		}

		/* Set next input buffer as current output buffer */
		in = out;
	}

	tc_cipher_chain_free_keys(chain_start);

	return 0;
}

int
apply_keyfiles(unsigned char *pass, size_t pass_memsz, const char *keyfiles[],
    int nkeyfiles)
{
	int pl, k;
	unsigned char *kpool;
	unsigned char *kdata;
	int kpool_idx;
	size_t i, kdata_sz;
	uint32_t crc;

	if (pass_memsz < MAX_PASSSZ) {
		tc_log(1, "Not enough memory for password manipluation\n");
		return ENOMEM;
	}

	pl = strlen((char *)pass);
	memset(pass+pl, 0, MAX_PASSSZ-pl);

	if ((kpool = alloc_safe_mem(KPOOL_SZ)) == NULL) {
		tc_log(1, "Error allocating memory for keyfile pool\n");
		return ENOMEM;
	}

	memset(kpool, 0, KPOOL_SZ);

	for (k = 0; k < nkeyfiles; k++) {
#ifdef DEBUG
		printf("Loading keyfile %s into kpool\n", keyfiles[k]);
#endif
		kpool_idx = 0;
		crc = ~0U;
		kdata_sz = MAX_KFILE_SZ;

		if ((kdata = read_to_safe_mem(keyfiles[k], 0, &kdata_sz)) == NULL) {
			tc_log(1, "Error reading keyfile %s content\n",
			    keyfiles[k]);
			free_safe_mem(kpool);
			return EIO;
		}

		for (i = 0; i < kdata_sz; i++) {
			crc = crc32_intermediate(crc, kdata[i]);

			kpool[kpool_idx++] += (unsigned char)(crc >> 24);
			kpool[kpool_idx++] += (unsigned char)(crc >> 16);
			kpool[kpool_idx++] += (unsigned char)(crc >> 8);
			kpool[kpool_idx++] += (unsigned char)(crc);

			/* Wrap around */
			if (kpool_idx == KPOOL_SZ)
				kpool_idx = 0;
		}

		free_safe_mem(kdata);
	}

#ifdef DEBUG
	printf("Applying kpool to passphrase\n");
#endif
	/* Apply keyfile pool to passphrase */
	for (i = 0; i < KPOOL_SZ; i++)
		pass[i] += kpool[i];

	free_safe_mem(kpool);

	return 0;
}