Add CRC32 checksum for Yakuza: Like a Dragon

ylad_encrypt.c

@@ -0,0 +1,97 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+static const char Key[]  = "STarYZgr3DL11";
+static const int  KeyLen = 13;
+
+// https://stackoverflow.com/a/21001712
+unsigned int crc32b(unsigned char *message) {
+   int i, j;
+   unsigned int byte, crc, mask;
+
+   i = 0;
+   crc = 0xFFFFFFFF;
+   while (message[i] != 0) {
+      byte = message[i];            // Get next byte.
+      crc = crc ^ byte;
+      for (j = 7; j >= 0; j--) {    // Do eight times.
+         mask = -(crc & 1);
+         crc = (crc >> 1) ^ (0xEDB88320 & mask);
+      }
+      i = i + 1;
+   }
+   return ~crc;
+}
+
+uint32_t calculate(char *data, uint64_t sz)
+{
+    return crc32b(data);
+}
+
+int main(int argc, char **argv)
+{
+    FILE *in, *out;
+    unsigned char *data, *outname, *filename, *ext;
+    size_t sz;
+    uint32_t checksum;
+
+    if (argc != 2)
+    {
+        printf("Usage: %s in.json\n", argv[0]);
+        return 0;
+    }
+
+    if ((in = fopen(argv[1], "rb")) == NULL)
+    {
+        perror("Error");
+        return 1;
+    }
+
+    // get filename without extension
+    filename = malloc(sizeof(argv[1]));
+    strcpy(filename, argv[1]);
+    ext = strchr(filename, '.');
+    filename[(int)(ext - filename)] = '\0';
+
+    outname = strcat(filename, ".sav");
+
+    if ((out = fopen(outname, "wb")) == NULL)
+    {
+        perror("Error");
+        fclose(in);
+        return 1;
+    }
+
+    printf("Writing %s to %s...\n", argv[1], outname);
+
+    fseek(in, 0, SEEK_END);
+    sz = ftell(in);
+    data = malloc(sz + 4);
+    rewind(in);
+    fread(data, 1, sz, in);
+    fclose(in);
+
+    // calculate checksum
+    checksum = calculate(data, (uint64_t)sz);
+
+    // encrypt
+    for (int i = 0; i < sz; i++)
+        data[i] ^= Key[i % KeyLen];
+
+    // add checksum
+    data[sz] = checksum;
+    data[sz + 1] = checksum >> 8;
+    data[sz + 2] = checksum >> 16;
+    data[sz + 3] = checksum >> 24;
+
+    fwrite(data, 1, sz + 4, out);
+
+    free(data);
+    fclose(out);
+
+    puts("Done!");
+
+    return 0;
+}