nstool/README.md

Nintendo Switch Tool (NSTool)

General purpose reading/extraction tool for Nintendo Switch file formats.

Supported File Formats

• PartitionFs (PFS0) (.pfs0)
• Sha256PartitionFs (HFS0) (.hfs0)
• RomFs (.romfs)
• Nintendo Submission Package (.nsp)
• Nintendo Content Archive (.nca)
• NX GameCard Image (.xci)
• Meta (META) (.npdm)
• Nintendo Application Control Property (.nacp)
• Content Metadata (.cnmt)
• ES Certificate (.cert)
• ES Ticket (v2 only) (.tik)
• Nintendo Shared Object (NSO0) (.nso)
• Nintendo Relocatable Object (NRO0) (.nro)
• Initial Program Bundle (INI1) (.ini)
• Initial Program (KIP1) (.kip)

Usage

General usage

The default mode of NSTool is to show general information about a file.

To display general information the usage is as follows:

nstool some_file.bin

However not all information is shown in this mode; file-layout, key data and properties set to default values are omitted.

Alternative output modes

To output file-layout information, use the --showlayout option:

nstool --showlayout some_file.bin

To output key data generation and selection, use the --showkeys option:

nstool --showkeys some_file.bin

To output all information, enable the verbose output mode with the -v or --verbose option:

nstool -v some_file.bin

Specify File Type

NSTool will in most cases correctly identify the file type. However you can override this and manually specify the file type with the -t or --intype option:

nstool -t cnmt some_file.bin

In that example cnmt was selected, NSTool would process the file as Content Metadata. See below for a list of supported file type codes:

Code	Description
gc, xci	NX GameCard Image
nsp	Nintendo Submission Package
pfs	PartitionFs
hfs	Sha256PartitionFs
romfs	RomFs
nca	Nintendo Content Archive
meta, npdm	Meta (.npdm)
cnmt	Content Metadata
nso	Nintendo Shared Object
nro	Nintendo Relocatable Object
ini	Initial Program Bundle
kip	Initial Program
nacp	Nintendo Application Control Property
cert	ES Certificate
tik	ES Ticket
aset, asset	Homebrew NRO Asset Binary

Validate Input File

Some file types have signatures/hashes/fields that can be validated by NSTool, but this mode isn't enabled by default.

To validate files with NSTool, enable the verify mode with the -y or --verify option:

nstool -y some_file.bin

See the below table for file types that support optional validation:

File Type	Validation	Comments
ES Certificate	Signature	If certificate is part of a certificate chain it will validate it as part of that chain. Root signed certificates are verified with user supplied Root public key.
ES Ticket	Signature	If the user specifies a certificate chain with --cert option, the ticket will be verified against that certificate chain.
NX GameCard Image	XCI Header Signature, HFS0 Hashes	XCI header signature is verified with user supplied XCI Header public key.
META	AccessControlInfo fields, AccessControlInfoDesc signature	AccessControlInfo fields are validated against the AccessControlInfoDesc. AccessControlInfoDesc signature is verfied with the appropriate user supplied ACID public key.
NCA	Header Signature[0], Header Signature[1]	Header Signature[0] is verified with the appropriate user supplied NCA Header public key. Header Signature[1] is verified only in Program titles, by retrieving the with public key from the AccessControlInfoDesc stored in the code partition.

• As of Nintendo Switch Firmware 9.0.0, Nintendo retroactively added key generations for some public keys, including NCA Header and ACID public keys, so the various generations for these public keys will have to be supplied by the user
• As of NSTool v1.6.0 the public key(s) for Root Certificate, XCI Header, ACID and NCA Header are built-in, and will be used if the user does not supply the public key in a key file.

Encrypted Files

Some Nintendo Switch files are partially or completely encrypted. These require the user to supply the encryption keys to NSTool so that it can process them.

NX GameCard Image

The GameCard ExtendedHeader is encrypted with one of 8 keys, specified by the KekIndex in the GameCard Header. It isn't required to extract game data, it just contains metadata.

Only two keys are currently defined:

KeyIndex	Name	Description
00	Production	Usually selected for prod images. Some dev images use this key index.
01	Development	Usually selected for dev images. This was changed from key index 00 at some point.

In order to read the XCI Extended Header, the header key(s) must be defined in prod.keys/dev.keys.

Define these keys in both prod.keys and dev.keys (Prod and dev share the same keydata).

xci_header_key_00 = <32 char AES128 key here>
xci_header_key_01 = <32 char AES128 key here>

Nintendo Content Archive

Nintendo Content Archive (NCA) files have both an encrypted header and content. The encrypted header determines the layout/format/encryption method of the content, which contains the game data.

In order to read the NCA header, the header key must be defined in prod.keys/dev.keys.

This can be explicitly:

nca_header_key = <64 char AES128-XTS key-data here>

Or allow NSTool to derive it from key sources:

master_key_00 = <32 char AES128 key-data here>
aes_kek_generation_source = <32 char AES128 key-data here>
aes_key_generation_source = <32 char AES128 key-data here>
nca_header_kek_source = <32 char AES128 key-data here>
nca_header_key_source = <64 char AES128 key-data here>

In order to read the NCA content, the content key must be determined. Unlike the header key which is fixed, each NCA will have a unique content key.

Content keys are either:

1. "Internal", where they are encrypted the NCA Header KeyArea
2. "External", where they are encrypted in an external Ticket file (.tik) (external content keys are sometimes called title keys)

Internal Content Key

Decrypting the content key from the NCA Header Key Area requires the appropriate nca_key_area_key to be defined in prod.keys/dev.keys. However for security reasons Nintendo revises this key periodically, and within each key revision there are 3 separate keys for different categories of applications.

It's best to define as many of these as possible, to reduce the number of times you need to edit the keyfiles.

So for a given key revision these key area keys can be defined explicitly (## represents the key revision in hexadecimal):

nca_key_area_key_application_## = <32 char AES128 key-data here>
nca_key_area_key_ocean_##       = <32 char AES128 key-data here>
nca_key_area_key_system_##      = <32 char AES128 key-data here>

Or allow NSTool to derive them from key sources: (## represents the key revision in hexadecimal):

master_key_##                       = <32 char AES128 key-data here>
aes_kek_generation_source           = <32 char AES128 key-data here>
aes_key_generation_source           = <32 char AES128 key-data here>
nca_key_area_key_application_source = <32 char AES128 key-data here>
nca_key_area_key_ocean_source       = <32 char AES128 key-data here>
nca_key_area_key_system_source      = <32 char AES128 key-data here>

External Content Key

For NCAs that use an external content key, the user must supplied the key to NSTool.

Most NCAs that use an external content key will be bundled with a ticket file (*.tik) that contains the content key in an encrypted form.

The ticket can be supplied by the user using the --tik option:

nstool --tik <32 char rightsid>.tik <32 char contentid>.nca

This however requires the the appropriate commonkey to be defined in prod.keys/dev.keys to decrypt the content key in the ticket. However for security reasons Nintendo revises this key periodically. So it's best to define as many of these as possible, to reduce the number of times you need to edit the keyfiles.

So for a given key revision the common key can be defined explicitly (## represents the key revision in hexadecimal):

ticket_commonkey_## = <32 char AES128 key-data here>

Or allow NSTool to derive them from key sources: (## represents the key revision in hexadecimal):

master_key_##           = <32 char AES128 key-data here>
ticket_commonkey_source = <32 char AES128 key-data here>

Alternatively you can supply the raw encrypted content key (also called a title key) directly with the --titlekey option:

nstool --titlekey <32 char AES128 key-data here> <32 char contentid>.nca

It is also possible to supply the decrypted content key directly with the --contentkey option:

nstool --contentkey <32 char AES128 key-data here> <32 char contentid>.nca

Scene tickets

Please note that "Scene" tickets have been known to have errors. If you have issues using the --tik option, try passing the raw encrypted titlekey directly with the --titlekey option. The titlekey can be found by reading the ticket with NSTool:

nstool <32 char rightsid>.tik

Dealing with ticket errors

If the ticket is personalised (encrypted with console unique RSA key), NSTool will not support it. You will need to use extract the title key with another tool and pass the encrypted title key directly with the --titlekey option.

External Keys

NSTool doesn't embed any keys that are copyright protected. However keys can be imported via various keyset files.

See SWITCH_KEYS.md for more info.

Building

See BUILDING.md.