Content.bin file structure
The content.bin file structure
VC games and Wii channels, when saved to a SD card, will be stored in a file named "private/wii/title/XXXX/content.bin", where XXXX is the four-character name of the game/channel.
A program to help parse and analyze the structure of content.bin files, parse-channel.c, is available here: http://pastebin.com/f6ea7673f. Put it in the same directory as a compiled version of segher's Wii tools, since it depends on them.
The general layout of this file is as follows. Most of the data here is sketchy, at best.
|0x0640||Part A: Encrypted header|
|variable, padded to 64-byte boundary||Part B: Encrypted channel logo/preview|
|0x70, padded to 64-byte boundary||Part C: Cleartext "Bk" header|
|0x1E4 + num_contents*0x24, padded to 64-byte boundary||Part D: Cleartext TMD block, including content_records for the following files|
|num_contents*variable, padded to 64-byte boundary||Part E: Encrypted data contents|
|0x340||Part F: Cleartext certificates|
Part A: Encrypted header
The header is encrypted by the SD key and SD IV. When decrypted, it contains the following structure: (* means the field is discussed below)
|0x000||0x007||8||Title ID (which is 00 01 00 01 followed by the four-character code)|
|0x008||0x00B||4||Size of part B|
|0x00C||0x01B||16||MD5 Hash of header|
|0x01C||0x02B||16||unknown_1 (crypto usage, md5 hash of something?)|
|0x080||0x09B||28||* IMET data|
|0x09C||0x0EF||42||Channel name in Unicode, padded with 00 (Japanse version -- can be empty).|
|0x0F0||0x143||42||Channel name in Unicode, padded with 00 (English version).|
|0x144||0x197||42||Channel name in Unicode, padded with 00 (German version).|
|0x198||0x1EB||42||Channel name in Unicode, padded with 00 (French version).|
|0x1EC||0x23F||42||Channel name in Unicode, padded with 00 (Spanish version).|
|0x240||0x293||42||Channel name in Unicode, padded with 00 (Italian version).|
|0x294||0x2E7||42||Channel name in Unicode, padded with 00 (Dutch version).|
|0x2E8||0x63F||0x358||* Padding (normally zero)|
This value looks almost like the four-letter code of a channel/game. I have found HADP on most files, but HAGP on Super Mario/NES and '\0UPD' (that is, the first byte is 00, then UPD) on two N64-games.
- Title-ID-reference_1 and Title-ID-reference_2
These two looks like two Title-ID:s. On most files I have analyzed they are: 00 01 00 08 HALP and 00 01 00 08 HAKP (this is from a PAL Wii). However, on Super Mario/NES I found 00 01 00 02 HAFP and 00 01 00 02 HAGA. A guess is that they might stipulate some kind of dependencies on system files.
If the guess about depencencies is correct, then this might be a padding field which is zero only if not more than two dependencies are needed.
- IMET data
The IMET data follows a quite strict format, with a few changes between files. I don't have any good idea what those changes represent. The only major difference is found i Metroid Prime 3 Preview, which have everyting zero except the "IMET" header. The values indicated below is for all other files I've studied, which was non-zero.
|0x000||0x003||4||IMET header "IMET"|
|0x004||0x00B||8||Fixed value, always 00 00 06 00 00 00 00 03.|
|0x00C||0x017||12||Three 32-bit numbers (sizes?), typically in the range of 0x84BC to 0x56318.|
|0x018||0x01B||4||Flags? This is normally just zero, but Everybody Votes has 0050 0000 and Mii Contest has 0060 4100.|
- Padding (normally zero)
For Metroid Prime 3 Preview, this field was not completely zero. The three bytes with positions 0x313, 0x367 and 0x3BB was 0x20 instead of 0. My guess is that this doesn't matter, but then again, it could have something to do with the weird IMET data of MP3preview.
Part B: Encrypted Encrypted channel logo/preview
This part is is also encrypted by the SD key and SD IV. The precise format of this part has not yet been fully analyzed. It seems to contain code/data for displaying the animated logo/channel preview in the channel selector.
Part C: Cleartext "Bk" header
This part is not encrypted. It is similar to the Bk header found in savegames, but the contents only partially match. The header could also be exactly 0x80 long; the size of 0x70 is a guess based on the first field being a size parameter.
|0x000||0x003||4||Size of this part (presumably; always 0x70)|
|0x004||0x007||4||Magic word, always 0x42 0x6B 0x00 0x01 (Bk..)|
|0x016||0x021||12||Not yet analyzed, first byte is 0x03 or 0x02. On VCs, this always starts with 0x02 0xE0 and ends with 0x63 0x00.|
Part D: Cleartext TMD block
This part is not encrypted. It is well described on the TMD file format page. Some things to note:
- Only the tmd struct is included here, not the certificates.
- As described on the TMD file format page, after the main struct (with a size of 0x1E4), there follows an array of content_record structs.
- There is as many structs as the num_contents field in the tmd struct indicates. For VC, this seems to be always 7.
- The type and size file of the content_record is of special interest, since they describe part E.
- If type is 0x80 0x01, then the content is included in part E, and the size of the content is given by the size field.
- Otherwise, type will be 0x00 0x01, and the content is (presumably) shared between VCs and stored elsewere on the Wii.
Part E: Encrypted data contents
This part is encrypted. The encryption key is currently unknown. It might be unique to the Wii which saved the VC. It consists of several separate "files", one for each of the contents with the 0x80 type flag in the TMD content_record, padded to 64-byte boundary.
- This part is probably the same for every Wii, but unique to each VC. It's probably encrypted with the title key, stored in a ticket somewhere. Bushing 03:42, 11 February 2008 (PST)
Part F: Cleartext certificates
This part is not encrypted. The exact details of this field is not yet analyzed, but it is likely related to the chain of certificates as described on the TMD file format page.