Difference between revisions of "NCA"
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| − | | Crypto Type, must be 0-2. Only used stating with [[3.0.0]]. Normally 0. 2 = supported starting with [[3.0.0]]. | + | | Crypto Type, must be 0-2. Only used stating with [[3.0.0]]. Normally 0. 2 = Crypto supported starting with [[3.0.0]]. |
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| − | | Crypto-Type2. 0x3 = | + | | Crypto-Type2. 0x3 = Crypto supported starting with [[3.0.1]]. |
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| 0x230 | | 0x230 | ||
Revision as of 01:03, 1 October 2017
The entire raw NCAs are encrypted.
The only known area which is not encrypted in the raw NCA is the logo section, when the NCA includes that section. Everything else documented on this page is for the plaintext version of that data.
Encryption
The first {at least 0xC00 bytes} are encrypted with AES-XTS with sector size 0x200, at least 6 sectors in total. Everything in this region uses same keydata.
Header
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x100 | RSA-2048 signature over the 0x200-bytes starting at offset 0x200 using fixed key. |
| 0x100 | 0x100 | RSA-2048 signature over the 0x200-bytes starting at offset 0x200 using key from NPDM, or zeroes if not a program. |
| 0x200 | 0x4 | Magicnum "NCA3" |
| 0x204 | 0x1 | 0 for system NCAs. 1 for a NCA from gamecard. |
| 0x205 | 0x1 | Content Type (0=Program, 1=Meta, 2=Control, 3=Manual, 4=Data) |
| 0x206 | 0x1 | Crypto Type, must be 0-2. Only used stating with 3.0.0. Normally 0. 2 = Crypto supported starting with 3.0.0. |
| 0x207 | 0x1 | Key index, must be 0-2. |
| 0x208 | 0x8 | Size of the entire NCA. |
| 0x210 | 0x8 | titleID |
| 0x21C | 0x4 | sdk_version. byte0 is normally 0? Compared with a required minimum-value(0x000B0000). Matches this string from codebin: "FS_ACCESS: { sdk_version: {byte3}.{byte2}.{byte1}, ...". |
| 0x220 | 0x1 | Crypto-Type2. 0x3 = Crypto supported starting with 3.0.1. |
| 0x230 | 0x10 | Rights ID (Ticket) |
| 0x240 | 0x10*0x4(0x40) | Table for each section, see below. |
| 0x280 | 0x20*0x4(0x80) | Table of SHA256 hashes, over each 0x200-byte Section Header Block. |
| 0x300 | 0x10*0x4(0x40) | Key area |
The header is 0x400-bytes, at NCA+0.
When the above "Crypto Type" field is 0x2 on >=v3.0, different {crypto/keydata} is used for the sections' data. With system content, this is used with every ncatype except ncatype0. The only other exception is {data-content} for the firm titles: this is required in order for older-system-versions to install it.
Crypto-Type2 0x3(with the above crypto-type value) is used for all 3.0.1 sysmodules and the System_Version_Title.
With 3.0.2, all updated titles use the crypto from 3.0.1 for non-ncatype0, except for firm {data-content}.
Note: in some cases various game content uses the above newer crypto as well.
The keyindex passed to the contentkey-generation funcptr is determined as follows:
- Pre-3.0.0: The ncahdr keyindex field(0x207) is passed directly.
- 3.0.0+: It's determined using ncahdr keyindex(0x207) and "Crypto Type"(0x206). The end result is basically the same, except when ncahdr_x206 == 0x2, final_index is new_base_index+ncahdr_keyindex. Actual implementation loads index from u32_array[ncahdr_crypto_type], where the address of u32_array is different for each ncahdr_keyindex.
Section Table Entry
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x4 | Media offset |
| 0x4 | 0x4 | Media end-offset |
| 0x8 | 0x4 | Unknown |
| 0xC | 0x4 | Unknown |
Entry size is 0x10-bytes.
Media offset is absoluteoffset/{mediasize}, where mediasize is hard-coded to 0x200.
Section Header Block
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x1 | ? |
| 0x1 | 0x1 | ? |
| 0x2 | 0x1 | ? |
| 0x3 | 0x1 | Filesystem type. 0x2 = PFS0, 0x3 = RomFS, everything else is invalid. |
| 0x4 | 0x1 | Crypto type. 0 and >4 are invalid. 1 = none(plaintext from raw NCA). 2 = other crypto. 3 = regular crypto. 4 = unknown. |
| 0x5 | 0x1 | Padding? |
| 0x8 | FS-specific superblock. | |
| 0x100 | ? | Optional BKTR header. Can be used with any section, but only known to be used with game-updates RomFS. |
The Section Header Block for each section is at absoluteoffset+0x400+(sectionid*0x200), where sectionid corresponds to the index used with the entry/hash tables.
The total size is 0x200-bytes.
PFS0 superblock
| Offset | Size | Description |
|---|---|---|
| 0x8 | 0x20 | SHA256 hash over the hash-table at section-start+0 with the below hash-table size. |
| 0x28 | 0x4 | Block size in bytes. |
| 0x2C | 0x4 | Must be 0x2. |
| 0x30 | 0x8 | Offset of hash-table. Normally zero? |
| 0x38 | 0x8 | Size of hash-table. |
| 0x40 | 0x8 | Offset relative to section-start where the PFS0 header is located. |
| 0x48 | 0x8 | Actual byte-size of the PFS0 filesystem relative to the PFS0 header. |
| 0x50 | 0xF4 | Normally zeros. |
| 0x144 | ? | 0x1? |
| 0x148 | 0xB8 | Normally zeros. |
This documents the structure of Section Header Block +0 for PFS0.
RomFS superblock
| Offset | Size | Description |
|---|---|---|
| 0x8 | 0xE0 | IVFC header. Basically the same as Savegames IVFC except with 2 more levels and +0x0C is non-zero, see below. |
This documents the structure of Section Header Block +0 for RomFS.
IVFC
| Start | Length | Description |
|---|---|---|
| 0x00 | 4 | Magic ("IVFC") |
| 0x04 | 4 | Magic Number (0x20000) |
| 0x08 | 4 | Master hash size? |
| 0x0C | 4 | Usually 7? Unknown, could be related to total number of levels maybe? |
| 0x10 | 8 | Level 1 offset |
| 0x18 | 8 | Level 1 size |
| 0x20 | 4 | Level 1 block size, in log2 |
| 0x24 | 4 | Reserved |
| 0x28 | 8 | Level 2 offset |
| 0x30 | 8 | Level 2 size |
| 0x38 | 4 | Level 2 block size, in log2. |
| 0x3C | 4 | Reserved |
| 0x40 | 8 | Level 3 offset |
| 0x48 | 8 | Level 3 size |
| 0x50 | 4 | Level 3 block size, in log2. |
| 0x54 | 4 | Reserved |
| 0x58 | 8 | Level 4 offset |
| 0x60 | 8 | Level 4 size |
| 0x68 | 4 | Level 4 block size, in log2. |
| 0x6C | 4 | Reserved |
| 0x70 | 8 | Level 5 offset |
| 0x78 | 8 | Level 5 size |
| 0x80 | 4 | Level 5 block size, in log2. |
| 0x84 | 4 | Reserved |
| 0x88 | 8 | Level 6 offset |
| 0x90 | 8 | Level 6 size |
| 0x98 | 4 | Level 6 block size, in log2. |
| 0x9C | 4 | Reserved |
| 0xA0 | 32 | Unknown, reserved? |
| 0xC0 | 32 | Hash |
BKTR
| Start | Length | Description |
|---|---|---|
| 0x0 | 0x8 | Offset |
| 0x8 | 0x8 | Size |
| 0x10 | 0x4 | "BKTR" |
| 0x14 | 0x4 | u32, must be <=1. |
| 0x18 | 0x4 | s32, must be >=1. |
| 0x1C | 0x4 | ? |
| 0x20 | 0x20 | Same as the above 0x20-bytes except with different data. |
| 0x40 | 0x4? | ? |
| 0x44 | 0x4? | ? |
Using this header is enabled when offset 0x8 in this header is non-zero.
The above byte-offsets are relative to the start of the section-data.
The two sections specified by the two BKTR entries are usually(?) at the very end of the section data(section_endoffset-{size of BKTR sections}).
Logo section
This is a PFS0. See here for the mounted-FS logo contents.
ExeFS section
This is a PFS0.
See here for mounted-FS ExeFS contents.
PFS0
| Offset | Size | Description |
|---|---|---|
| {Hash-table offset from superblock} | {Hash-table size from superblock} | Table of SHA256 hashes. |
| {Hash-table <offset+size> from superblock} | Zeros for alignment to {alignment size}. | |
| {PFS0 offset from superblock} | {PFS0 size from superblock} | The actual PFS0. |
This is the FS which has magicnum "PFS0" at header+0. This is very similar to HFS0. A tool for extracting this FS is available here.
The hash table is hashes for every {Block size from superblock} starting at the PFS0 header. The size used for the last hash is {PFS0 filesystem size from superblock} - offset_relativeto_header.
See also the PFS0 superblock above.
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x4 | "PFS0" Magic |
| 0x4 | 0x4 | Number of files |
| 0x8 | 0x4 | Size of the string table |
| 0xC | 0x4 | Zero/Reserved |
| 0x10 | X | File Entry Table |
| 0x10 + X | Y | String Table |
| 0x10 + X + Y | Z | Raw File Data |
Where File Entry Table consists of Number of Files FileEntries:
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x8 | Offset of file in Data |
| 0x8 | 0x8 | Size of file in Data |
| 0x10 | 0x4 | Offset of filename in String Table |
| 0x14 | 0x4 | Normally zero? |