155 lines
4.4 KiB
C
155 lines
4.4 KiB
C
/*
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* cifra - embedded cryptography library
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* Written in 2014 by Joseph Birr-Pixton <jpixton@gmail.com>
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*
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* To the extent possible under law, the author(s) have dedicated all
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* copyright and related and neighboring rights to this software to the
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* public domain worldwide. This software is distributed without any
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* warranty.
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*
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* You should have received a copy of the CC0 Public Domain Dedication
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* along with this software. If not, see
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* <http://creativecommons.org/publicdomain/zero/1.0/>.
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*/
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#include "blockwise.h"
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#include "bitops.h"
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#include "sys.h"
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#include <string.h>
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void cf_blockwise_accumulate(uint8_t *partial, size_t *npartial, size_t nblock,
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const void *inp, size_t nbytes,
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cf_blockwise_in_fn process,
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void *ctx)
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{
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cf_blockwise_accumulate_final(partial, npartial, nblock,
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inp, nbytes,
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process, process, ctx);
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}
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void cf_blockwise_accumulate_final(uint8_t *partial, size_t *npartial, size_t nblock,
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const void *inp, size_t nbytes,
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cf_blockwise_in_fn process,
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cf_blockwise_in_fn process_final,
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void *ctx)
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{
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const uint8_t *bufin = inp;
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/* If we have partial data, copy in to buffer. */
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if (*npartial && nbytes)
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{
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size_t space = nblock - *npartial;
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size_t taken = MIN(space, nbytes);
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memcpy(partial + *npartial, bufin, taken);
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bufin += taken;
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nbytes -= taken;
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*npartial += taken;
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/* If that gives us a full block, process it. */
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if (*npartial == nblock)
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{
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if (nbytes == 0)
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process_final(ctx, partial);
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else
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process(ctx, partial);
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*npartial = 0;
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}
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}
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/* now nbytes < nblock or *npartial == 0. */
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/* If we have a full block of data, process it directly. */
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while (nbytes >= nblock)
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{
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if (nbytes == nblock)
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process_final(ctx, bufin);
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else
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process(ctx, bufin);
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bufin += nblock;
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nbytes -= nblock;
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}
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/* Finally, if we have remaining data, buffer it. */
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while (nbytes)
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{
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size_t space = nblock - *npartial;
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size_t taken = MIN(space, nbytes);
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memcpy(partial + *npartial, bufin, taken);
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bufin += taken;
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nbytes -= taken;
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*npartial += taken;
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}
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}
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void cf_blockwise_acc_byte(uint8_t *partial, size_t *npartial,
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size_t nblock,
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uint8_t byte, size_t nbytes,
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cf_blockwise_in_fn process,
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void *ctx)
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{
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/* only memset the whole of the block once */
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int filled = 0;
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while (nbytes)
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{
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size_t start = *npartial;
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size_t count = MIN(nbytes, nblock - start);
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if (!filled)
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memset(partial + start, byte, count);
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if (start == 0 && count == nblock)
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filled = 1;
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if (start + count == nblock)
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{
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process(ctx, partial);
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*npartial = 0;
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} else {
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*npartial += count;
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}
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nbytes -= count;
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}
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}
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void cf_blockwise_acc_pad(uint8_t *partial, size_t *npartial,
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size_t nblock,
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uint8_t fbyte, uint8_t mbyte, uint8_t lbyte,
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size_t nbytes,
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cf_blockwise_in_fn process,
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void *ctx)
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{
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switch (nbytes)
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{
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case 0: break;
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case 1: fbyte ^= lbyte;
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cf_blockwise_accumulate(partial, npartial, nblock, &fbyte, 1, process, ctx);
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break;
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case 2:
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cf_blockwise_accumulate(partial, npartial, nblock, &fbyte, 1, process, ctx);
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cf_blockwise_accumulate(partial, npartial, nblock, &lbyte, 1, process, ctx);
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break;
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default:
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cf_blockwise_accumulate(partial, npartial, nblock, &fbyte, 1, process, ctx);
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/* If the middle and last bytes differ, then process the last byte separately.
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* Otherwise, just extend the middle block size. */
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if (lbyte != mbyte)
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{
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cf_blockwise_acc_byte(partial, npartial, nblock, mbyte, nbytes - 2, process, ctx);
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cf_blockwise_accumulate(partial, npartial, nblock, &lbyte, 1, process, ctx);
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} else {
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cf_blockwise_acc_byte(partial, npartial, nblock, mbyte, nbytes - 1, process, ctx);
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}
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break;
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}
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}
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