gra-projekt/Implementierung/src/md2_impls/md2_1.c

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2022-07-15 11:32:22 +02:00
#include "../../lib/md2_impls/md2_1.h"
#include "../../lib/md2_impls/md2_common.h"
void md2_checksum_1(size_t len, uint8_t* buf) {
uint8_t l = 0;
for (size_t i = 0; i < len / 16; i++) {
for (int j = 0; j < 16; j++) {
u_int8_t c = buf[i * 16 + j];
// reference is wrong. It says: Set C[j] to S[c xor L]. But it should be:
buf[len + j] ^= MD2_PI_SUBST[c ^ l];
l = buf[len + j];
}
}
}
void md2_hash_1(size_t len, const uint8_t buf[len], uint8_t out[16]) {
// === step 1 ===
int paddingNeeded = 16 - (len & 7);
uint8_t originalPadding = paddingNeeded;
len += paddingNeeded;
// printf("len: %d\n", len);
// +16 for the checksum
uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
// TODO: null check
memcpy(newBuf, buf, len - paddingNeeded);
// printBuf(len + 16, newBuf);
while (paddingNeeded > 0) {
newBuf[len - paddingNeeded] = originalPadding;
paddingNeeded--;
}
// printf("buf with padding: ");
// printBuf(len + 16, newBuf);
// === step 2 ===
md2_checksum_1(len, newBuf);
// printf("buf with cecksum: ");
// printBuf(len + 16, newBuf);
// === step 3 ===
uint8_t* messageDigestBuf = calloc(48, sizeof(uint8_t));
// TODO: add null check
// === step 4 ===
// <= because we need to hash the last block too
for (size_t i = 0; i <= (len + 16) / 16 - 1; i++) {
for (int j = 0; j < 16; j++) {
messageDigestBuf[16 + j] = newBuf[i * 16 + j];
messageDigestBuf[32 + j] =
(messageDigestBuf[16 + j] ^ messageDigestBuf[j]);
}
u_int8_t t = 0;
for (int j = 0; j < 18; j++) {
for (int k = 0; k < 48; k++) {
t = messageDigestBuf[k] = messageDigestBuf[k] ^ MD2_PI_SUBST[t];
}
t = (t + j) & 127;
}
}
// printf("messageDigestBuf: \n");
// printBuf(16, messageDigestBuf);
memcpy(out, messageDigestBuf, 16);
free(messageDigestBuf);
free(newBuf);
}