Remedy Archive System

File Format
Name	Remedy Archive System
Ontology	Electronic File Formats Game data files Remedy Archive System
Extension(s)	.ras
Released	2001

Remedy Archive System is used to store game data for Remedy Entertainment games such as Max Payne and Max Payne 2. The metadata (central directory) following the header is encrypted.

Identification

Files begin with signature bytes 52 41 53 00.

Format details

Numbers are in little-endian byte order.

The file's header has the following structure:

struct RASHeader {
  uint8_t magic[4]; // "RAS\0"
  uint32_t encryptionKey;
};

The next section of the header must be decrypted first:

// decrypted structure
struct RASMetadata {
  uint32_t fileCount;
  uint32_t dirCount;
  uint32_t fileListLength;
  uint32_t dirListLength;
  float32_t version; // binary32 according to IEEE 754
  uint32_t unknown5;
  uint32_t unknown6;
  uint32_t unknown7;
  uint32_t compatibility;
};

The following version and compatibility values are known:

Version	Compatibility	Game
1.2	3	Max Payne

What follows are fileListLength encrypted bytes of file metadata that can be decrypted using encryptionKey. (It is not necessary to remember the last value of key from decrypting RASMetadata.) Each entry has the following structure:

// decrypted structure
struct RASFileListEntry {
  char name[]; // NUL-terminated
  uint32_t unknown0;
  uint32_t unknown1;
  uint32_t unknown2;
  uint32_t unknown3;
  uint32_t unknown4;
  uint32_t unknown5;
  uint32_t unknown6;
  uint32_t unknown7;
  uint32_t unknown8;
  uint32_t unknown9;
};

Next is a directory list of dirCount elements which must be decrypted similarly.

// decrypted structure
struct RASDirListEntry {
  char name[]; // NUL-terminated
  uint16_t unknown0;
  uint16_t unknown1;
  uint16_t unknown2;
  uint16_t unknown3;
  uint16_t unknown4;
  uint16_t unknown5;
  uint16_t unknown6;
  uint16_t unknown7;
};

Each directory is listed with its full name which starts and ends with a backslash (\). The top-most directory is named \.

Encryption

Depending on the generation of the RAS file format, different encryption schemes are used.

RAS1 (Max Payne)

void decrypt(uint8_t *buf, size_t count, int32_t key) {
  size_t i;
  uint8_t a;
  uint8_t b;

  if (key == 0) {
    key = 1;
  }
  for (i = 0; i < count; i++) {
    uint8_t a = buf[i];
    uint8_t b = ((uint8_t)(i % 5)) & 7;
    buf[i] = rotateLeftByte(a, b);
    key = key * 171 + (key / 177) * -30269;
    buf[i] = (uint8_t)((((((int8_t)i) + 3) * 6) ^ buf[i]) + ((int8_t)key));
  }
}

If your programming language doesn't support the rotateLeftByte operation, it can be emulated using:

uint8_t rotateLeftByte(uint8_t a, uint8_t b) {
  return (a << b) | (a >> (8 - b));
}