124 lines
2.5 KiB
C
124 lines
2.5 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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#include "tomcrypt_private.h"
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/**
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@file adler32.c
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Adler-32 checksum algorithm
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Written and placed in the public domain by Wei Dai
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Adapted for libtomcrypt by Steffen Jaeckel
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*/
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#ifdef LTC_ADLER32
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static const unsigned long s_adler32_base = 65521;
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void adler32_init(adler32_state *ctx)
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{
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LTC_ARGCHKVD(ctx != NULL);
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ctx->s[0] = 1;
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ctx->s[1] = 0;
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}
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void adler32_update(adler32_state *ctx, const unsigned char *input, unsigned long length)
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{
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unsigned long s1, s2;
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LTC_ARGCHKVD(ctx != NULL);
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LTC_ARGCHKVD(input != NULL);
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s1 = ctx->s[0];
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s2 = ctx->s[1];
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if (length % 8 != 0) {
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do {
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s1 += *input++;
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s2 += s1;
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length--;
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} while (length % 8 != 0);
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if (s1 >= s_adler32_base) {
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s1 -= s_adler32_base;
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}
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s2 %= s_adler32_base;
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}
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while (length > 0) {
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s1 += input[0];
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s2 += s1;
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s1 += input[1];
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s2 += s1;
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s1 += input[2];
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s2 += s1;
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s1 += input[3];
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s2 += s1;
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s1 += input[4];
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s2 += s1;
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s1 += input[5];
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s2 += s1;
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s1 += input[6];
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s2 += s1;
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s1 += input[7];
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s2 += s1;
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length -= 8;
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input += 8;
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if (s1 >= s_adler32_base) {
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s1 -= s_adler32_base;
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}
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s2 %= s_adler32_base;
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}
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LTC_ARGCHKVD(s1 < s_adler32_base);
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LTC_ARGCHKVD(s2 < s_adler32_base);
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ctx->s[0] = (unsigned short)s1;
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ctx->s[1] = (unsigned short)s2;
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}
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void adler32_finish(const adler32_state *ctx, void *hash, unsigned long size)
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{
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unsigned char* h;
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LTC_ARGCHKVD(ctx != NULL);
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LTC_ARGCHKVD(hash != NULL);
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h = hash;
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switch (size) {
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default:
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h[3] = ctx->s[0] & 0x0ff;
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/* FALLTHROUGH */
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case 3:
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h[2] = (ctx->s[0] >> 8) & 0x0ff;
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/* FALLTHROUGH */
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case 2:
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h[1] = ctx->s[1] & 0x0ff;
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/* FALLTHROUGH */
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case 1:
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h[0] = (ctx->s[1] >> 8) & 0x0ff;
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/* FALLTHROUGH */
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case 0:
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;
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}
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}
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int adler32_test(void)
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{
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#ifndef LTC_TEST
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return CRYPT_NOP;
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#else
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const void* in = "libtomcrypt";
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const unsigned char adler32[] = { 0x1b, 0xe8, 0x04, 0xba };
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unsigned char out[4];
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adler32_state ctx;
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adler32_init(&ctx);
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adler32_update(&ctx, in, XSTRLEN(in));
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adler32_finish(&ctx, out, 4);
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if (compare_testvector(adler32, 4, out, 4, "adler32", 0)) {
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return CRYPT_FAIL_TESTVECTOR;
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}
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return CRYPT_OK;
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#endif
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}
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#endif
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