117 lines
3.9 KiB
Go
117 lines
3.9 KiB
Go
package ndr
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import (
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"encoding/binary"
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"fmt"
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)
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/*
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Serialization Version 1
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https://msdn.microsoft.com/en-us/library/cc243563.aspx
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Common Header - https://msdn.microsoft.com/en-us/library/cc243890.aspx
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8 bytes in total:
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- First byte - Version: Must equal 1
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- Second byte - 1st 4 bits: Endianess (0=Big; 1=Little); 2nd 4 bits: Character Encoding (0=ASCII; 1=EBCDIC)
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- 3rd - Floating point representation (This does not seem to be the case in examples for Microsoft test sources)
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- 4th - Common Header Length: Must equal 8
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- 5th - 8th - Filler: MUST be set to 0xcccccccc on marshaling, and SHOULD be ignored during unmarshaling.
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Private Header - https://msdn.microsoft.com/en-us/library/cc243919.aspx
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8 bytes in total:
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- First 4 bytes - Indicates the length of a serialized top-level type in the octet stream. It MUST include the padding length and exclude the header itself.
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- Second 4 bytes - Filler: MUST be set to 0 (zero) during marshaling, and SHOULD be ignored during unmarshaling.
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*/
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const (
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protocolVersion uint8 = 1
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commonHeaderBytes uint16 = 8
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bigEndian = 0
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littleEndian = 1
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ascii uint8 = 0
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ebcdic uint8 = 1
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ieee uint8 = 0
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vax uint8 = 1
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cray uint8 = 2
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ibm uint8 = 3
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)
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// CommonHeader implements the NDR common header: https://msdn.microsoft.com/en-us/library/cc243889.aspx
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type CommonHeader struct {
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Version uint8
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Endianness binary.ByteOrder
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CharacterEncoding uint8
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FloatRepresentation uint8
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HeaderLength uint16
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Filler []byte
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}
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// PrivateHeader implements the NDR private header: https://msdn.microsoft.com/en-us/library/cc243919.aspx
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type PrivateHeader struct {
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ObjectBufferLength uint32
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Filler []byte
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}
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func (dec *Decoder) readCommonHeader() error {
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// Version
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vb, err := dec.r.ReadByte()
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if err != nil {
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return Malformed{EText: "could not read first byte of common header for version"}
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}
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dec.ch.Version = uint8(vb)
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if dec.ch.Version != protocolVersion {
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return Malformed{EText: fmt.Sprintf("byte stream does not indicate a RPC Type serialization of version %v", protocolVersion)}
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}
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// Read Endianness & Character Encoding
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eb, err := dec.r.ReadByte()
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if err != nil {
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return Malformed{EText: "could not read second byte of common header for endianness"}
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}
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endian := int(eb >> 4 & 0xF)
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if endian != 0 && endian != 1 {
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return Malformed{EText: "common header does not indicate a valid endianness"}
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}
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dec.ch.CharacterEncoding = uint8(vb & 0xF)
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if dec.ch.CharacterEncoding != 0 && dec.ch.CharacterEncoding != 1 {
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return Malformed{EText: "common header does not indicate a valid character encoding"}
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}
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switch endian {
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case littleEndian:
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dec.ch.Endianness = binary.LittleEndian
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case bigEndian:
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dec.ch.Endianness = binary.BigEndian
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}
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// Common header length
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lb, err := dec.readBytes(2)
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if err != nil {
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return Malformed{EText: fmt.Sprintf("could not read common header length: %v", err)}
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}
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dec.ch.HeaderLength = dec.ch.Endianness.Uint16(lb)
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if dec.ch.HeaderLength != commonHeaderBytes {
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return Malformed{EText: "common header does not indicate a valid length"}
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}
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// Filler bytes
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dec.ch.Filler, err = dec.readBytes(4)
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if err != nil {
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return Malformed{EText: fmt.Sprintf("could not read common header filler: %v", err)}
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}
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return nil
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}
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func (dec *Decoder) readPrivateHeader() error {
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// The next 8 bytes after the common header comprise the RPC type marshalling private header for constructed types.
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err := binary.Read(dec.r, dec.ch.Endianness, &dec.ph.ObjectBufferLength)
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if err != nil {
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return Malformed{EText: "could not read private header object buffer length"}
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}
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if dec.ph.ObjectBufferLength%8 != 0 {
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return Malformed{EText: "object buffer length not a multiple of 8"}
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}
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// Filler bytes
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dec.ph.Filler, err = dec.readBytes(4)
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if err != nil {
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return Malformed{EText: fmt.Sprintf("could not read private header filler: %v", err)}
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}
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return nil
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}
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