Package2

Present in the firmware package titles (0100000000000819, 010000000000081A, 010000000000081B and 010000000000081C) and installed into eMMC storage's BCPKG2 partitions, "package2" contains the Switch kernel and the built-in system modules.

Format

Package2 is distributed in an already encrypted format. Therefore, it's not additionally encrypted when installed into the flash filesystem.

Offset	Size	Description
0x0	0x100	RSA-2048 signature (PKCS#1 v2.1 RSASSA-PSS-VERIFY with SHA256)
0x100	0x100	Encrypted header
0x200	Variable	Encrypted body

Encryption

Package2's contents are AES-CTR encrypted with a key known only by TrustZone.

The encrypted header's CTR is stored as it's first 0x10 bytes (offset 0x100). The encrypted body is divided in up to 4 sections, each one with a CTR stored inside the decrypted header.

Header

When decrypted, package2's header is as follows.

Offset	Size	Description
0x0	0x10	Header's CTR, official code copies the pre-decryption CTR over the decrypted result. Also used as metadata.
0x10	0x10	Section 0 CTR
0x20	0x10	Section 1 CTR
0x30	0x10	Section 2 CTR
0x40	0x10	Section 3 CTR
0x50	0x4	Magic "PK21"
0x54	0x4	Base offset
0x58	0x4	Always 0
0x5C	0x2	Version. HighByte must be <{maxver} and LowByte must be >{minver}, where {maxver} and {minver} are constants used by TZ updated with each package1 update.
0x5E	0x2	Padding
0x60	0x4	Section 0 size
0x64	0x4	Section 1 size
0x68	0x4	Section 2 size
0x6C	0x4	Section 3 size
0x70	0x4	Section 0 offset
0x74	0x4	Section 1 offset
0x78	0x4	Section 2 offset
0x7C	0x4	Section 3 offset
0x80	0x20	SHA-256 hash over encrypted section 0
0xA0	0x20	SHA-256 hash over encrypted section 1
0xC0	0x20	SHA-256 hash over encrypted section 2
0xE0	0x20	SHA-256 hash over encrypted section 3

Each section follows each other immediately and is encrypted with the same key used for encrypting the header. The section offsets are relative to a base, which is typically 0x80000000 pointing to the base of DRAM.

Before being decrypted, the encrypted header's CTR additionally encodes metadata used to validate package2's contents as follows:

• Size of the entire package2 with the raw header = ctr_word2 ^ ctr_word3 ^ ctr_word0
• Metadata version field = ((ctr_word1 ^ (ctr_word1 >> 16)) & 0xFF) ^ (ctr_word1 >> 24)

In [4.0.0], the metadata version field must be less or equal to 4.

Section 0

When decrypted, this section contains the plaintext Switch kernel binary.

Section 1

When decrypted, this section contains the built-in system modules encapsulated in a custom format.

INI1

Offset	Type	Description
0x0	u32	Magic "INI1"
0x4	u32	Size
0x8	u32	NumberProcesses
0xC	u32	Padding (zero)

KIP1

Kernel internal process?

Offset	Type	Description
0x0	u32	Magic "KIP1"
0x4	char[12]	Name
0x10	u64	TitleId
0x18	u32	Process category (0: regular title, 1: kernel built-in). Should be 1 here.
0x1C	u8	Main thread priority
0x1D	u8	Default CPU core
0x1E	u8	Reserved (unused)
0x1F	u8	Flags: bit0-2: compression-enable for each section, when set. Bit3: Is64Bit. Bit4: IsAddrSpace36Bit. Bit5: [2.0.0+] PoolPartitionId. Bit6, Bit7: reserved (unused)
0x20	#SectionHeader[6]	Sections: .text, .rodata, .data, .bss and two reserved (ignored) sections.
0x80	u32[0x20]	KernelCaps

SectionHeader

Offset	Type	Description
0x0	u32	OutOffset
0x4	u32	DecompressedSize
0x8	u32	CompressedSize
0xC	u32	Attribute: the size in pages of the main thread's stack for .rodata, reserved otherwise.

Compressed size can be 0 or lower than exepected, this is the case for BSS for example.

Compression

The compression used here is BLZ, with a modified footer since 3ds. The footer is now 0xC bytes instead of 0x8, and has the form u32 compressed_data_len; u32 initial_index; u32 additional_len_when_uncompressed;

Section 2

This section has a valid CTR and SHA-256 hash (over NULL) stored in the package2's header, but it's size is always 0. Likely reserved for future expansion.

Section 3

This section is not present (CTR and SHA-256 hash in package2's header are NULL). Likely reserved for future expansion.

Versions

System version	Package1 maxver constant	Package1 minver constant	Package2 version field
1.0.0	0x2	0x3	0x0104
2.0.0	0x3	0x4	0x0205
3.0.0	0x4	0x5	0x0306
3.0.2	0x5	0x6	0x0407
4.0.0	0x6	0x7	0x0508

Public Keys

Exponent

0x10001

Retail Modulus

8D 13 A7 77 6A E5 DC C0 3B 25 D0 58 E4 20 69 59
55 4B AB 70 40 08 28 07 A8 A7 FD 0F 31 2E 11 FE
47 A0 F9 9D DF 80 DB 86 5A 27 89 CD 97 6C 85 C5
6C 39 7F 41 F2 FF 24 20 C3 95 A6 F7 9D 4A 45 74
8B 5D 28 8A C6 99 35 68 85 A5 64 32 80 9F D3 48
39 A2 1D 24 67 69 DF 75 AC 12 B5 BD C3 29 90 BE
37 E4 A0 80 9A BE 36 BF 1F 2C AB 2B AD F5 97 32
9A 42 9D 09 8B 08 F0 63 47 A3 E9 1B 36 D8 2D 8A
D7 E1 54 11 95 E4 45 88 69 8A 2B 35 CE D0 A5 0B
D5 5D AC DB AF 11 4D CA B8 1E E7 01 9E F4 46 A3
8A 94 6D 76 BD 8A C8 3B D2 31 58 0C 79 A8 26 E9
D1 79 9C CB D4 2B 6A 4F C6 CC CF 90 A7 B9 98 47
FD FA 4C 6C 6F 81 87 3B CA B8 50 F6 3E 39 5D 4D
97 3F 0F 35 39 53 FB FA CD AB A8 7A 62 9A 3F F2
09 27 96 3F 07 9A 91 F7 16 BF C6 3A 82 5A 4B CF
49 50 95 8C 55 80 7E 39 B1 48 05 1E 21 C7 24 4F

Debug Modulus

00000000: B36554FB 0AB01E85 A7F6CF91 8EBA9699  ³eTû.°.…§öÏ‘Žº–™
00000010: 0D8B9169 2AEE0120 4F345C2C 4F4E37C7  .‹‘i*î. O4\,ON7Ç
00000020: F10BD4CD A17F93F1 3359CEB1 E9DD26E6  ñ.ÔÍ¡.“ñ3YαéÝ&æ
00000030: F3BB7787 467AD64E 474AD141 B7794A38  ó»w‡FzÖNGJÑA·yJ8
00000040: 066ECF61 8FCDC140 0BFA26DC C0345183  .nÏa.ÍÁ@.ú&ÜÀ4Qƒ
00000050: D93B1154 3B962732 9A95BE1E 681150A0  Ù;.T;–'2š•¾.h.P 
00000060: 6B10A883 8BF5FCBC 90847A5A 5C4352E6  k.¨ƒ‹õü¼.„zZ\CRæ
00000070: C826E9FE 06A08B53 0FAF1EC4 1C0BCF50  È&éþ. ‹S.¯.Ä..ÏP
00000080: 1AA4F35C FBF097E4 DE320A9F E35AAAB7  .¤ó\ûð—äÞ2.ŸãZª·
00000090: 447F5C33 60B90F22 2D332AE9 69793142  D.\3`¹."-3*éiy1B
000000A0: 8FE43A13 8BE726BD 08876CA6 F273F68E  .ä:.‹ç&½.‡l¦òsöŽ
000000B0: A7F2FEFB 6C28660D BDD7EB42 A878E6B8  §òþûl(f.½×ëB¨xæ¸
000000C0: 6BAEC7A9 E2406E89 2082258E 3C6A60D7  k®Ç©â@n‰ ‚%Ž<j`×
000000D0: F3568EEC 8D518A63 3C047823 0E900CB4  óVŽì.QŠc<.x#...´
000000E0: E7863B4F 8E130947 320E04B8 4D5BB046  ç†;OŽ..G2..¸M[°F
000000F0: 71B05CF4 AD634FC5 E2AC1EC4 3396097B  q°\ô.cOÅâ¬.Ä3–.{