img3

type Header struct {
	Magic        [4]byte // ASCII_LE("Img3")
	FullSize     uint32  // full size of fw image
	SizeNoPack   uint32  // size of fw image without header
	SigCheckArea uint32  // although that is just my name for it, this is the
	// size of the start of the data section (the code) up to
	// the start of the RSA signature (SHSH section)
	Ident [4]byte // identifier of image, used when bootrom is parsing images

}

type Img3 struct {
	Header
	Tags []Tag // continues until end of file
}

type KBAG128 struct {
	KBagHeader
	EncIV  [16]byte // IV for the firmware file, encrypted with the GID Key
	EncKey [16]byte // Key for the firmware file, encrypted with the GID Key
}

type KBAG192 struct {
	KBagHeader
	EncIV  [16]byte // IV for the firmware file, encrypted with the GID Key
	EncKey [24]byte // Key for the firmware file, encrypted with the GID Key
}

type KBAG256 struct {
	KBagHeader
	EncIV  [16]byte // IV for the firmware file, encrypted with the GID Key
	EncKey [32]byte // Key for the firmware file, encrypted with the GID Key
}

type KBagData struct {
	CryptState uint32
	AESType    uint32
	IV         []byte
	Key        []byte
}

type KBagHeader struct {
	CryptState uint32 // 1 if encrypted with GID Key, 2 if encrypted with Development GID Key
	AESType    uint32 // 0x80 = aes128, 0xc0 = aes192, 0x100 = aes256
}

type Tag struct {
	TagHeader
	Data []byte // [dataLength]
	Pad  []byte // Typically padded to 4 byte multiple [totalLength - dataLength - 12]
}

type TagHeader struct {
	Magic       [4]byte // see below
	TotalLength uint32  // length of tag including "magic" and these two length values
	DataLength  uint32  // length of tag data
}