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

00000000: 8D13A777 6AE5DCC0 3B25D058 E4206959  ..§wjåÜÀ;%ÐXä iY
00000010: 554BAB70 40082807 A8A7FD0F 312E11FE  UK«p@.(.¨§ý.1..þ
00000020: 47A0F99D DF80DB86 5A2789CD 976C85C5  G ù.߀ۆZ'‰Í—l…Å
00000030: 6C397F41 F2FF2420 C395A6F7 9D4A4574  l9.Aòÿ$ Õ¦÷.JEt
00000040: 8B5D288A C6993568 85A56432 809FD348  ‹](ŠÆ™5h…¥d2€ŸÓH
00000050: 39A21D24 6769DF75 AC12B5BD C32990BE  9¢.$gißu¬.µ½Ã).¾
00000060: 37E4A080 9ABE36BF 1F2CAB2B ADF59732  7ä €š¾6¿.,«+.õ—2
00000070: 9A429D09 8B08F063 47A3E91B 36D82D8A  šB..‹.ðcG£é.6Ø-Š
00000080: D7E15411 95E44588 698A2B35 CED0A50B  ×áT.•äEˆiŠ+5ÎÐ¥.
00000090: D55DACDB AF114DCA B81EE701 9EF446A3  Õ]¬Û¯.Mʸ.ç.žôF£
000000A0: 8A946D76 BD8AC83B D231580C 79A826E9  Š”mv½ŠÈ;Ò1X.y¨&é
000000B0: D1799CCB D42B6A4F C6CCCF90 A7B99847  ÑyœËÔ+jOÆÌÏ.§¹˜G
000000C0: FDFA4C6C 6F81873B CAB850F6 3E395D4D  ýúLlo.‡;ʸPö>9]M
000000D0: 973F0F35 3953FBFA CDABA87A 629A3FF2  —?.59SûúÍ«¨zbš?ò
000000E0: 0927963F 079A91F7 16BFC63A 825A4BCF  .'–?.š‘÷.¿Æ:‚ZKÏ
000000F0: 4950958C 55807E39 B148051E 21C7244F  IP•ŒU€~9±H..!Ç$O

Debug Modulus

B3 65 54 FB 0A B0 1E 85 A7 F6 CF 91 8E BA 96 99
0D 8B 91 69 2A EE 01 20 4F 34 5C 2C 4F 4E 37 C7
F1 0B D4 CD A1 7F 93 F1 33 59 CE B1 E9 DD 26 E6
F3 BB 77 87 46 7A D6 4E 47 4A D1 41 B7 79 4A 38
06 6E CF 61 8F CD C1 40 0B FA 26 DC C0 34 51 83
D9 3B 11 54 3B 96 27 32 9A 95 BE 1E 68 11 50 A0
6B 10 A8 83 8B F5 FC BC 90 84 7A 5A 5C 43 52 E6
C8 26 E9 FE 06 A0 8B 53 0F AF 1E C4 1C 0B CF 50
1A A4 F3 5C FB F0 97 E4 DE 32 0A 9F E3 5A AA B7
44 7F 5C 33 60 B9 0F 22 2D 33 2A E9 69 79 31 42
8F E4 3A 13 8B E7 26 BD 08 87 6C A6 F2 73 F6 8E
A7 F2 FE FB 6C 28 66 0D BD D7 EB 42 A8 78 E6 B8
6B AE C7 A9 E2 40 6E 89 20 82 25 8E 3C 6A 60 D7
F3 56 8E EC 8D 51 8A 63 3C 04 78 23 0E 90 0C B4
E7 86 3B 4F 8E 13 09 47 32 0E 04 B8 4D 5B B0 46
71 B0 5C F4 AD 63 4F C5 E2 AC 1E C4 33 96 09 7B