gra-projekt/Implementierung/src/md2_impls/md2_3.c

#include "../../lib/md2_impls/md2_3.h"

#include "../../lib/md2_impls/md2_common.h"

void process_hash(size_t len, uint8_t buf[len], uint8_t messageDigestBuf[48]) {
  for (size_t i = 0; i < (len + 16) / 16 - 1; i++) {
    for (int j = 0; j < 16; j++) {
      messageDigestBuf[16 + j] = buf[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) % 256;
    }
  }
}

void process_checksum(size_t len, uint8_t buf[len], uint8_t checksum[16]) {
  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:
      l = checksum[j] ^= MD2_PI_SUBST[c ^ l];
    }
  }
}

// DUPLICATE CODE FROM md2_2.c
// int apply_padding(size_t len, uint8_t buf[len]) {
//   int paddingNeeded = 16 - (len % 16);
//   uint8_t originalPadding = paddingNeeded;
//   len += paddingNeeded;

//   while (paddingNeeded > 0) {
//     buf[len - paddingNeeded] = originalPadding;
//     paddingNeeded--;
//   }
//   return len;
// }

// unused!
void md2_checksum_3(size_t _, uint8_t* __) {}

void md2_hash_3(size_t len, const uint8_t buf[len], uint8_t out[16]) {
  // === step 1 ===
  int paddingNeeded = 16 - (len % 16);
  uint8_t originalPadding = paddingNeeded;
  len += paddingNeeded;

  uint8_t* newBuf = calloc(len + 16, sizeof(uint8_t));
  if (newBuf == NULL) {
    return;
  }

  memcpy(newBuf, buf, len - paddingNeeded);

  while (paddingNeeded > 0) {
    newBuf[len - paddingNeeded] = originalPadding;
    paddingNeeded--;
  }

  // === step 3 ===
  uint8_t* messageDigestBuf = calloc(48, sizeof(uint8_t));
  if (messageDigestBuf == NULL) {
    return;
  }

  // === step 4 ===
  uint8_t* checksum = calloc(16, sizeof(uint8_t));
  if (checksum == NULL) {
    return;
  }

  int hashPipe[2];
  int checksumPipe[2];

  if (pipe(hashPipe) == -1 || pipe(checksumPipe) == -1) {
    return;
  }

  pid_t pid_1, pid_2;
  (pid_1 = fork()) && (pid_2 = fork());

  if (pid_1 == 0) {
    // Child 1 process
    close(hashPipe[0]);
    process_hash(len, newBuf, messageDigestBuf);
    write(hashPipe[1], messageDigestBuf, 48);
    exit(0);

  } else if (pid_2 == 0) {
    // Child 2 process
    close(checksumPipe[0]);
    process_checksum(len, newBuf, checksum);
    write(checksumPipe[1], checksum, 16);
    exit(0);
  } else {
    // int status;
    // Parent process
    close(hashPipe[1]);
    close(checksumPipe[1]);

    waitpid(pid_1, NULL, 0);
    waitpid(pid_2, NULL, 0);

    read(hashPipe[0], messageDigestBuf, 48);
    read(checksumPipe[0], checksum, 16);

    process_hash(16, checksum, messageDigestBuf);
    memcpy(out, messageDigestBuf, 16);

    // free(data);
    free(messageDigestBuf);
    free(checksum);
  }

  // process_block_checksum(data, checksum, &l);
  // process_block_hash(data, messageDigestBuf);

  // process_block_checksum(data, checksum, &l);
  // process_block_hash(data, messageDigestBuf);
}