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- /* ===================================================================
- *
- * Copyright (c) 2014, Legrandin <helderijs@gmail.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 HOLDER 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 "common.h"
- FAKE_INIT(raw_ofb)
- #include "block_base.h"
- #define ERR_OFB_IV_LEN ((3 << 16) | 1)
- #define MAX_BLOCK_LEN 16
- typedef struct {
- BlockBase *cipher;
- /** How many bytes at the beginning of the key stream
- * have already been used.
- */
- size_t usedKeyStream;
- uint8_t keyStream[MAX_BLOCK_LEN];
- } OfbModeState;
- EXPORT_SYM int OFB_start_operation(BlockBase *cipher,
- const uint8_t iv[],
- size_t iv_len,
- OfbModeState **pResult)
- {
- if ((NULL == cipher) || (NULL == iv) || (NULL == pResult))
- return ERR_NULL;
- if (cipher->block_len > MAX_BLOCK_LEN)
- return ERR_BLOCK_SIZE;
- if (cipher->block_len != iv_len)
- return ERR_OFB_IV_LEN;
- *pResult = calloc(1, sizeof(OfbModeState));
- if (NULL == *pResult)
- return ERR_MEMORY;
- (*pResult)->cipher = cipher;
- (*pResult)->usedKeyStream = cipher->block_len;
- memcpy((*pResult)->keyStream, iv, iv_len);
- return 0;
- }
- EXPORT_SYM int OFB_encrypt(OfbModeState *ofbState,
- const uint8_t *in,
- uint8_t *out,
- size_t data_len)
- {
- size_t block_len;
- uint8_t oldKeyStream[MAX_BLOCK_LEN];
- if ((NULL == ofbState) || (NULL == in) || (NULL == out))
- return ERR_NULL;
- block_len = ofbState->cipher->block_len;
- if (block_len > MAX_BLOCK_LEN)
- return ERR_BLOCK_SIZE;
- while (data_len > 0) {
- size_t i;
- size_t keyStreamToUse;
- if (ofbState->usedKeyStream == block_len) {
- int result;
- memcpy(oldKeyStream, ofbState->keyStream, block_len);
- result = ofbState->cipher->encrypt(ofbState->cipher,
- oldKeyStream,
- ofbState->keyStream,
- block_len);
- if (0 != result)
- return result;
- ofbState->usedKeyStream = 0;
- }
- keyStreamToUse = MIN(data_len, block_len - ofbState->usedKeyStream);
- for (i=0; i<keyStreamToUse; i++)
- *out++ = *in++ ^ ofbState->keyStream[i + ofbState->usedKeyStream];
- data_len -= keyStreamToUse;
- ofbState->usedKeyStream += keyStreamToUse;
- }
- return 0;
- }
- EXPORT_SYM int OFB_decrypt(OfbModeState *ofbState,
- const uint8_t *in,
- uint8_t *out,
- size_t data_len)
- {
- return OFB_encrypt(ofbState, in, out, data_len);
- }
- EXPORT_SYM int OFB_stop_operation(OfbModeState *state)
- {
- if (NULL == state)
- return ERR_NULL;
- state->cipher->destructor(state->cipher);
- free(state);
- return 0;
- }
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