/*
 * 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 manipulation\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;
}