Resource Container Format

This page describes the encrypted resource container format used by TERA.

• C/C++-like primitive types and structs will be used.

• Integers (uint8_t, int8_t, uint16_t, int16_t, etc) are little endian.

• Characters (i.e. char16_t) are UTF-16 and little endian.

• Strings (i.e. u16string) are a series of valid char16_t characters followed by a NUL character.

• Fields are laid out in the declared order with no implied padding anywhere.

Encryption

Portions of resource container files are encrypted with a 256-bit XOR cipher.

The encryption key can be extracted from a TERA client. This can be done with a running TERA process or an unpacked executable. The key appears to be static; it does not change with each client build.

Physical Structure

The overall structure can be described like this:

struct ResourceContainerFile
{
    uint8_t data[];
    ResourceContainerDirectory directory;
    ResourceContainerFooter footer;
};

Reading a resource container file requires knowing the full size of the file in advance. A reader must first seek to the footer, read it, then seek to the directory, read and decrypt it, and finally seek to the data where each file entry can be read and decrypted according to the offsets in the directory.

File Footer

A resource container file ends with this footer:

struct ResourceContainerFooter
{
    uint32_t directory_size;
    uint32_t magic;
};

directory_size is the size of the directory. This enables a reader to know how far back it must seek in order to read the directory correctly.

magic must be 0x01001fff.

Directory

Before the footer, there is a directory listing all contained files:

struct ResourceContainerDirectory
{
    ResourceContainerEntry entries[];
};

There is no way to know the number of entries in advance; a reader must keep reading entries until it has read the amount of bytes indicated in the footer's directory_size field.

Note that the entire directory is encrypted with the XOR cipher.

Entries

Each entry in the directory is of the form:

struct ResourceContainerEntry
{
    uint32_t size;
    uint32_t offset;
    u16string name;
};

size is the size of the contained file.

offset indicates where in the data section the file's contents are located. size bytes must be readable at this location. Note that the contents are encrypted with the XOR cipher.

name is the name of the file on disk.