sdls

type AuthAlgorithm uint8

type ChannelID struct {
	// TFVN is the Transfer Frame Version Number: 0 for TM, 1 for TC and AOS
	// (each per its own numbering), 12 (0b1100) for USLP.
	TFVN uint8

	// SCID is the Spacecraft Identifier.
	SCID uint16

	// VCID is the Virtual Channel Identifier.
	VCID uint8

	// MAPID extends the GVCID to a GMAP_ID for TC and USLP. Set it to NoMAP
	// when the frames have no MAP, or when the binding stops at the virtual
	// channel. The zero value is MAP 0, a real MAP: fill this field
	// explicitly.
	MAPID int
}

type FieldLengths struct {
	IV     int // Initialization Vector, clause 4.1.1.3
	SeqNum int // anti-replay Sequence Number, clause 4.1.1.4
	PadLen int // Pad Length, clause 4.1.1.5
	MAC    int // Message Authentication Code in the trailer, clause 4.1.2.3
}

type Mode uint8

type SALookup func(spi uint16) (*SecurityAssociation, error)

type SecurityAssociation struct {
	// SPI identifies this SA on the wire (clause 4.2.2.3). 0 and 65535 are reserved.
	SPI uint16

	// Mode is the single service type this SA performs (clause 4.2.2.4).
	Mode Mode

	// Key is the caller-supplied AES-256 key: exactly 32 octets. The SA does
	// not copy it, load it, or store it anywhere; key management is out of
	// scope for this package.
	Key []byte

	// AuthAlgorithm selects the MAC algorithm when Mode is Authentication. It
	// is ignored for AuthenticatedEncryption, which is always AES-GCM.
	AuthAlgorithm AuthAlgorithm

	// FieldLengths is the wire layout of this SA's header and trailer fields.
	FieldLengths FieldLengths

	// AuthMask is the authentication bit mask of clause 4.2.2.6.2, applied with a
	// bitwise AND to the frame header and security header before the MAC is
	// computed. It must be at least as long as the frame header plus the
	// security header.
	//
	// The mask depends on the frame type; clause 4.2.2.6.2 sets the rules. Use the
	// per-frame-type constructors (BaselineAuthMaskTM, BaselineAuthMaskTC,
	// BaselineAuthMaskAOS, BaselineAuthMaskUSLP) which apply the mandatory
	// exclusions: the TM Master Channel Frame Count, the AOS Frame Header
	// Error Control, the Insert Zone, and the Initialization Vector.
	//
	// A nil mask means "authenticate every octet of the frame header". That
	// is stricter than clause 4.2.2.6.2 requires, and for TM and AOS it violates
	// the mandatory exclusions: a field rewritten downstream (the TM MCFC,
	// the AOS FHEC) would break the MAC at the receiver. Leave the mask nil
	// only when the frame header you pass contains no such field. The
	// Initialization Vector is excluded from the MAC either way:
	// Clause 4.2.2.6.2 h) makes that mandatory, so this package enforces it
	// regardless of the mask supplied.
	AuthMask []byte

	// Channels lists the channels this SA is bound to, as clause 4.2.2.2 requires
	// an SA to serve an agreed set of Global Virtual Channels or Global MAP
	// IDs. ProcessSecurityForChannel refuses a frame whose channel is not in
	// the list (clause 4.2.4.3). An empty list declares no binding: the check is
	// skipped, and plain ProcessSecurity never performs it.
	Channels []ChannelID

	// SeqWindow is the sequence number window of clause 2.3.2.3.3: a positive delta
	// beyond which a received counter is discarded. Zero disables the
	// anti-replay check entirely, which is only appropriate for testing.
	SeqWindow uint64
	// contains filtered or unexported fields
}

type SecurityHeader struct {
	SPI       uint16
	IV        []byte // clause 4.1.1.3
	SeqNum    []byte // clause 4.1.1.4
	PadLength []byte // clause 4.1.1.5
}