77 lines
2 KiB
C
77 lines
2 KiB
C
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#include "../../lib/md2_impls/md2_2.h"
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#include "../../lib/md2_impls/md2_common.h"
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void process_block_hash(uint8_t block[16], uint8_t messageDigestBuf[48]) {
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for (int j = 0; j < 16; j++) {
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messageDigestBuf[16 + j] = block[j];
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messageDigestBuf[32 + j] = (messageDigestBuf[16 + j] ^ messageDigestBuf[j]);
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}
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u_int8_t t = 0;
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for (int j = 0; j < 18; j++) {
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for (int k = 0; k < 48; k++) {
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t = messageDigestBuf[k] = messageDigestBuf[k] ^ MD2_PI_SUBST[t];
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}
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t = (t + j) % 256;
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}
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}
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void process_block_checksum(uint8_t block[16], uint8_t checksum[16],
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uint8_t* l) {
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for (int j = 0; j < 16; j++) {
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u_int8_t c = block[j];
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// reference is wrong. It says: Set C[j] to S[c xor L]. But it should be:
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(*l) = checksum[j] ^= MD2_PI_SUBST[c ^ (*l)];
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}
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}
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void md2_checksum_2(size_t len, uint8_t* buf) {
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uint8_t l = 0;
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for (size_t i = 0; i < len / 16; i++) {
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process_block_checksum(buf + (i * 16), buf + len, &l);
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}
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}
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void md2_hash_2(size_t len, const uint8_t buf[len], uint8_t out[16]) {
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// === step 1 ===
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int paddingNeeded = 16 - (len % 16);
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uint8_t originalPadding = paddingNeeded;
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len += paddingNeeded;
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// printf("len: %d\n", len);
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// +16 for the checksum
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uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
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// TODO: null check
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memcpy(newBuf, buf, len - paddingNeeded);
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// printBuf(len + 16, newBuf);
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while (paddingNeeded > 0) {
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newBuf[len - paddingNeeded] = originalPadding;
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paddingNeeded--;
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}
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// printf("buf with padding: ");
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// printBuf(len + 16, newBuf);
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// === step 3 ===
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uint8_t* messageDigestBuf = calloc(48, sizeof(uint8_t));
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// === step 4 ===
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uint8_t l = 0;
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// <= because we need to hash the last block too
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for (size_t i = 0; i < len / 16; i++) {
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process_block_checksum(newBuf + (i * 16), newBuf + len, &l);
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process_block_hash(newBuf + (i * 16), messageDigestBuf);
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}
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process_block_hash(newBuf + len, messageDigestBuf);
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memcpy(out, messageDigestBuf, 16);
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free(newBuf);
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}
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