pdu

package
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 Go to latest Published: Jun 16, 2026 License: MIT Imports: 6 Imported by: 0

Documentation

Overview

Package pdu models connection-oriented DCE/RPC protocol data units (PDUs): the 16-byte common header and the Bind, Bind_Ack, Bind_Nak, Request, Response, and Fault bodies ([C706] section 12, [MS-RPCE] section 2.2).

Each PDU type embeds the common Header and represents a whole PDU. Marshal returns the complete on-the-wire bytes (header included) and sets the header's frag_length; Unmarshal parses a complete PDU and returns the number of bytes consumed.

Only the little-endian data representation (DREP first byte 0x10) is supported, which is what Windows and Samba always send; a big-endian DREP is rejected on Unmarshal rather than silently mis-parsed.

Index

Constants

View Source 
const (
	ResultAcceptance        uint16 = 0
	ResultUserRejection     uint16 = 1
	ResultProviderRejection uint16 = 2
	ResultNegotiateAck      uint16 = 3 // [MS-RPCE] bind-time feature negotiation
)

Presentation context negotiation result codes (p_cont_def_result_t), as returned in the result field of each p_result_t in a bind_ack PDU.

References:

View Source 
const (
	ReasonNotSpecified                         uint16 = 0
	ReasonAbstractSyntaxNotSupported           uint16 = 1
	ReasonProposedTransferSyntaxesNotSupported uint16 = 2
	ReasonLocalLimitExceeded                   uint16 = 3
)

Provider reject reasons (p_provider_reason_t / p_reject_reason_t).

Reference: [C706] section 12.6.3.1: https://pubs.opengroup.org/onlinepubs/9629399/chap12.htm

View Source 
const (
	NCASStatusOK             uint32 = 0x00000000
	NCASOpRngError           uint32 = 0x1C010002 // nca_s_op_rng_error: invalid opnum
	NCASUnkIf                uint32 = 0x1C010003 // nca_s_unk_if: unknown interface
	NCASProtoError           uint32 = 0x1C01000B // nca_s_proto_error
	NCASFaultIntDivByZero    uint32 = 0x1C000001 // nca_s_fault_int_div_by_zero
	NCASFaultAddrError       uint32 = 0x1C000002 // nca_s_fault_addr_error
	NCASFaultNDR             uint32 = 0x000006F7 // nca_s_fault_ndr: NDR could not decode
	NCASFaultAccessDenied    uint32 = 0x00000005 // nca_s_fault_access_denied
	NCASFaultContextMismatch uint32 = 0x1C00001A // nca_s_fault_context_mismatch
)

Common connection-oriented RPC fault status codes (nca_* / rpc_s_*). This is a subset; unknown codes are reported numerically by FaultStatus.String.

References:

View Source 
const HeaderSize = 16

HeaderSize is the size, in bytes, of the connection-oriented common header.

Variables

View Source 
var DataRepresentationLittleEndian = [4]byte{0x10, 0x00, 0x00, 0x00}

DataRepresentationLittleEndian is the canonical packed_drep for little-endian integers, ASCII characters, and IEEE floating point.

Functions

This section is empty.

Types

type Bind 

type Bind struct {
	Header       Header
	MaxXmitFrag  uint16
	MaxRecvFrag  uint16
	AssocGroupID uint32
	ContextList  []ContextElement
}

Bind is a bind PDU: it proposes the maximum fragment sizes, an association group, and a list of presentation contexts to negotiate.

References:

func (*Bind) Marshal 

func (b *Bind) Marshal() ([]byte, error)

Marshal serializes the complete bind PDU, filling in the header's packet type and frag_length.

func (*Bind) String 

func (b *Bind) String() string

String returns a one-line summary.

func (*Bind) Unmarshal 

func (b *Bind) Unmarshal(data []byte) (int, error)

Unmarshal parses a complete bind PDU and returns the bytes consumed.

type BindAck 

type BindAck struct {
	Header           Header
	MaxXmitFrag      uint16
	MaxRecvFrag      uint16
	AssocGroupID     uint32
	SecondaryAddress string // port_spec, without the trailing NUL
	Results          []PresentationResult
}

BindAck is a bind_ack PDU: the server's response to a bind, echoing the negotiated fragment sizes and reporting per-context negotiation results.

References:

func (*BindAck) Accepted 

func (b *BindAck) Accepted() bool

Accepted reports whether at least one presentation context was accepted.

func (*BindAck) Marshal 

func (b *BindAck) Marshal() ([]byte, error)

Marshal serializes the complete bind_ack PDU, including the 4-byte alignment pad after the secondary address.

func (*BindAck) String 

func (b *BindAck) String() string

String returns a one-line summary.

func (*BindAck) Unmarshal 

func (b *BindAck) Unmarshal(data []byte) (int, error)

Unmarshal parses a complete bind_ack PDU and returns the bytes consumed.

type BindNak 

type BindNak struct {
	Header       Header
	RejectReason uint16
	Versions     []ProtocolVersion
}

BindNak is a bind_nak PDU: the server's rejection of a bind, with a reason and the list of RPC protocol versions it supports.

Reference: [C706] section 12.6.3.1 ("The bind_nak PDU"): https://pubs.opengroup.org/onlinepubs/9629399/chap12.htm

func (*BindNak) Marshal 

func (b *BindNak) Marshal() ([]byte, error)

Marshal serializes the complete bind_nak PDU.

func (*BindNak) String 

func (b *BindNak) String() string

String returns a one-line summary.

func (*BindNak) Unmarshal 

func (b *BindNak) Unmarshal(data []byte) (int, error)

Unmarshal parses a complete bind_nak PDU and returns the bytes consumed.

type ContextElement 

type ContextElement struct {
	ContextID        uint16
	AbstractSyntax   syntax.SyntaxID
	TransferSyntaxes []syntax.SyntaxID
}

ContextElement is a single presentation context proposed in a bind (or alter_context) PDU: a context id, an abstract syntax (the target interface), and one or more candidate transfer syntaxes (p_cont_elem_t).

References:

func (*ContextElement) Marshal 

func (c *ContextElement) Marshal() ([]byte, error)

Marshal serializes a presentation context element.

func (*ContextElement) Unmarshal 

func (c *ContextElement) Unmarshal(data []byte) (int, error)

Unmarshal parses a presentation context element and returns the bytes consumed.

type Fault 

type Fault struct {
	Header      Header
	AllocHint   uint32
	ContextID   uint16
	CancelCount uint8
	Status      uint32
	Stub        []byte
}

Fault is a fault PDU: it reports that a call failed, carrying a status code and any error stub data.

References:

func (*Fault) Error 

func (f *Fault) Error() string

Error implements the error interface so a Fault can be returned directly from a call. The message includes the mnemonic status code.

func (*Fault) Marshal 

func (f *Fault) Marshal() ([]byte, error)

Marshal serializes the complete fault PDU.

func (*Fault) String 

func (f *Fault) String() string

String returns a one-line summary.

func (*Fault) Unmarshal 

func (f *Fault) Unmarshal(data []byte) (int, error)

Unmarshal parses a complete fault PDU and returns the bytes consumed.

type FaultStatus 

type FaultStatus uint32

FaultStatus is a fault PDU status code, with a descriptive String.

func (FaultStatus) String 

func (s FaultStatus) String() string

String returns a mnemonic for known status codes, otherwise the hex value. 

type Header struct {
	RPCVersion         uint8
	RPCVersionMinor    uint8
	PacketType         PacketType
	PacketFlags        PFCFlags
	DataRepresentation [4]byte
	FragLength         uint16
	AuthLength         uint16
	CallID             uint32
}

Header is the connection-oriented common header present at the start of every PDU.

References:

func NewHeader 

func NewHeader(pt PacketType, flags PFCFlags, callID uint32) Header

NewHeader returns a header initialized for protocol version 5.0 with little-endian data representation and the given packet type, flags, and call id.

func PeekHeader 

func PeekHeader(data []byte) (*Header, error)

PeekHeader parses just the common header from the front of a complete PDU buffer. It is a convenience for dispatching on PacketType before fully unmarshalling.

func (*Header) Marshal 

func (h *Header) Marshal() ([]byte, error)

Marshal serializes the header into its 16-byte wire form.

func (*Header) String 

func (h *Header) String() string

String returns a human-readable one-line summary of the header.

func (*Header) Unmarshal 

func (h *Header) Unmarshal(data []byte) (int, error)

Unmarshal parses a header from the start of data and returns the bytes consumed (always HeaderSize on success).

type PFCFlags 

type PFCFlags uint8

PFCFlags is the set of PFC_* flags carried in the pfc_flags field of the common header.

References: 

const (
	// PFCFirstFrag marks the first fragment of a multi-fragment PDU.
	PFCFirstFrag PFCFlags = 0x01
	// PFCLastFrag marks the last fragment of a multi-fragment PDU.
	PFCLastFrag PFCFlags = 0x02
	// PFCPendingCancel signals a pending cancel (request) or a cancel was pending
	// (response).
	PFCPendingCancel PFCFlags = 0x04
	// PFCReserved is reserved.
	PFCReserved PFCFlags = 0x08
	// PFCConcMpx indicates support for concurrent multiplexing on the connection.
	PFCConcMpx PFCFlags = 0x10
	// PFCDidNotExecute indicates the server did not execute the call (response/fault).
	PFCDidNotExecute PFCFlags = 0x20
	// PFCMaybe indicates a "maybe" call with no response expected.
	PFCMaybe PFCFlags = 0x40
	// PFCObjectUuid indicates an object UUID is present in the PDU body.
	PFCObjectUuid PFCFlags = 0x80
)

func (PFCFlags) Has 

func (f PFCFlags) Has(flag PFCFlags) bool

Has reports whether all bits in flag are set.

func (PFCFlags) String 

func (f PFCFlags) String() string

String returns a "|"-joined list of set flag names.

type PacketType 

type PacketType uint8

PacketType identifies the kind of a connection-oriented DCE/RPC PDU, as carried in the ptype field of the common header.

References: 

const (
	PacketTypeRequest          PacketType = 0
	PacketTypePing             PacketType = 1
	PacketTypeResponse         PacketType = 2
	PacketTypeFault            PacketType = 3
	PacketTypeWorking          PacketType = 4
	PacketTypeNoCall           PacketType = 5
	PacketTypeReject           PacketType = 6
	PacketTypeAck              PacketType = 7
	PacketTypeClCancel         PacketType = 8
	PacketTypeFack             PacketType = 9
	PacketTypeCancelAck        PacketType = 10
	PacketTypeBind             PacketType = 11
	PacketTypeBindAck          PacketType = 12
	PacketTypeBindNak          PacketType = 13
	PacketTypeAlterContext     PacketType = 14
	PacketTypeAlterContextResp PacketType = 15
	PacketTypeShutdown         PacketType = 17
	PacketTypeCoCancel         PacketType = 18
	PacketTypeOrphaned         PacketType = 19
)

func (PacketType) String 

func (t PacketType) String() string

String returns the mnemonic name of the packet type.

type PresentationResult 

type PresentationResult struct {
	Result         uint16
	Reason         uint16
	TransferSyntax syntax.SyntaxID
}

PresentationResult is one server response in a bind_ack p_result_list (p_result_t): the negotiation result, an optional reason, and the accepted transfer syntax.

Reference: [C706] section 12.6.3.1 ("The bind_ack PDU"): https://pubs.opengroup.org/onlinepubs/9629399/chap12.htm

func (*PresentationResult) Marshal 

func (r *PresentationResult) Marshal() ([]byte, error)

Marshal serializes a single presentation result (24 bytes).

func (*PresentationResult) Unmarshal 

func (r *PresentationResult) Unmarshal(data []byte) (int, error)

Unmarshal parses a single presentation result and returns the bytes consumed.

type ProtocolVersion 

type ProtocolVersion struct {
	Major uint8
	Minor uint8
}

ProtocolVersion is one supported RPC protocol version (p_rt_version_t).

type Request 

type Request struct {
	Header     Header
	AllocHint  uint32
	ContextID  uint16
	Opnum      uint16
	ObjectUUID *guid.GUID // present iff PFC_OBJECT_UUID is set
	Stub       []byte
}

Request is a request PDU: it carries a method call (opnum) and its marshalled arguments (stub data) to the server.

When the PFC_OBJECT_UUID flag is set, a 16-byte object UUID precedes the stub data; otherwise it is absent. Stub data is 8-octet aligned, which the fixed 8-byte body (plus an optional 16-byte object UUID) already satisfies.

Reference: [C706] section 12.6.3.1 ("The request PDU"): https://pubs.opengroup.org/onlinepubs/9629399/chap12.htm

func (*Request) Marshal 

func (r *Request) Marshal() ([]byte, error)

Marshal serializes the complete request PDU. If ObjectUUID is non-nil the PFC_OBJECT_UUID flag is set automatically. AllocHint defaults to len(Stub) when left zero.

func (*Request) String 

func (r *Request) String() string

String returns a one-line summary.

func (*Request) Unmarshal 

func (r *Request) Unmarshal(data []byte) (int, error)

Unmarshal parses a complete request PDU and returns the bytes consumed.

type Response 

type Response struct {
	Header      Header
	AllocHint   uint32
	ContextID   uint16
	CancelCount uint8
	Stub        []byte
}

Response is a response PDU: it carries the marshalled return values (stub data) of a successful call back to the client.

Reference: [C706] section 12.6.3.1 ("The response PDU"): https://pubs.opengroup.org/onlinepubs/9629399/chap12.htm

func (*Response) Marshal 

func (r *Response) Marshal() ([]byte, error)

Marshal serializes the complete response PDU.

func (*Response) String 

func (r *Response) String() string

String returns a one-line summary.

func (*Response) Unmarshal 

func (r *Response) Unmarshal(data []byte) (int, error)

Unmarshal parses a complete response PDU and returns the bytes consumed.

Source Files

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