opaque.go

Documentation: github.com/ProtonMail/go-crypto/openpgp/packet

     1  // Copyright 2012 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package packet
     6  
     7  import (
     8  	"bytes"
     9  	"io"
    10  	"io/ioutil"
    11  
    12  	"github.com/ProtonMail/go-crypto/openpgp/errors"
    13  )
    14  
    15  // OpaquePacket represents an OpenPGP packet as raw, unparsed data. This is
    16  // useful for splitting and storing the original packet contents separately,
    17  // handling unsupported packet types or accessing parts of the packet not yet
    18  // implemented by this package.
    19  type OpaquePacket struct {
    20  	// Packet type
    21  	Tag uint8
    22  	// Reason why the packet was parsed opaquely
    23  	Reason error
    24  	// Binary contents of the packet data
    25  	Contents []byte
    26  }
    27  
    28  func (op *OpaquePacket) parse(r io.Reader) (err error) {
    29  	op.Contents, err = ioutil.ReadAll(r)
    30  	return
    31  }
    32  
    33  // Serialize marshals the packet to a writer in its original form, including
    34  // the packet header.
    35  func (op *OpaquePacket) Serialize(w io.Writer) (err error) {
    36  	err = serializeHeader(w, packetType(op.Tag), len(op.Contents))
    37  	if err == nil {
    38  		_, err = w.Write(op.Contents)
    39  	}
    40  	return
    41  }
    42  
    43  // Parse attempts to parse the opaque contents into a structure supported by
    44  // this package. If the packet is not known then the result will be another
    45  // OpaquePacket.
    46  func (op *OpaquePacket) Parse() (p Packet, err error) {
    47  	hdr := bytes.NewBuffer(nil)
    48  	err = serializeHeader(hdr, packetType(op.Tag), len(op.Contents))
    49  	if err != nil {
    50  		op.Reason = err
    51  		return op, err
    52  	}
    53  	p, err = Read(io.MultiReader(hdr, bytes.NewBuffer(op.Contents)))
    54  	if err != nil {
    55  		op.Reason = err
    56  		p = op
    57  	}
    58  	return
    59  }
    60  
    61  // OpaqueReader reads OpaquePackets from an io.Reader.
    62  type OpaqueReader struct {
    63  	r io.Reader
    64  }
    65  
    66  func NewOpaqueReader(r io.Reader) *OpaqueReader {
    67  	return &OpaqueReader{r: r}
    68  }
    69  
    70  // Read the next OpaquePacket.
    71  func (or *OpaqueReader) Next() (op *OpaquePacket, err error) {
    72  	tag, _, contents, err := readHeader(or.r)
    73  	if err != nil {
    74  		return
    75  	}
    76  	op = &OpaquePacket{Tag: uint8(tag), Reason: err}
    77  	err = op.parse(contents)
    78  	if err != nil {
    79  		consumeAll(contents)
    80  	}
    81  	return
    82  }
    83  
    84  // OpaqueSubpacket represents an unparsed OpenPGP subpacket,
    85  // as found in signature and user attribute packets.
    86  type OpaqueSubpacket struct {
    87  	SubType       uint8
    88  	EncodedLength []byte // Store the original encoded length for signature verifications.
    89  	Contents      []byte
    90  }
    91  
    92  // OpaqueSubpackets extracts opaque, unparsed OpenPGP subpackets from
    93  // their byte representation.
    94  func OpaqueSubpackets(contents []byte) (result []*OpaqueSubpacket, err error) {
    95  	var (
    96  		subHeaderLen int
    97  		subPacket    *OpaqueSubpacket
    98  	)
    99  	for len(contents) > 0 {
   100  		subHeaderLen, subPacket, err = nextSubpacket(contents)
   101  		if err != nil {
   102  			break
   103  		}
   104  		result = append(result, subPacket)
   105  		contents = contents[subHeaderLen+len(subPacket.Contents):]
   106  	}
   107  	return
   108  }
   109  
   110  func nextSubpacket(contents []byte) (subHeaderLen int, subPacket *OpaqueSubpacket, err error) {
   111  	// RFC 4880, section 5.2.3.1
   112  	var subLen uint32
   113  	var encodedLength []byte
   114  	if len(contents) < 1 {
   115  		goto Truncated
   116  	}
   117  	subPacket = &OpaqueSubpacket{}
   118  	switch {
   119  	case contents[0] < 192:
   120  		subHeaderLen = 2 // 1 length byte, 1 subtype byte
   121  		if len(contents) < subHeaderLen {
   122  			goto Truncated
   123  		}
   124  		encodedLength = contents[0:1]
   125  		subLen = uint32(contents[0])
   126  		contents = contents[1:]
   127  	case contents[0] < 255:
   128  		subHeaderLen = 3 // 2 length bytes, 1 subtype
   129  		if len(contents) < subHeaderLen {
   130  			goto Truncated
   131  		}
   132  		encodedLength = contents[0:2]
   133  		subLen = uint32(contents[0]-192)<<8 + uint32(contents[1]) + 192
   134  		contents = contents[2:]
   135  	default:
   136  		subHeaderLen = 6 // 5 length bytes, 1 subtype
   137  		if len(contents) < subHeaderLen {
   138  			goto Truncated
   139  		}
   140  		encodedLength = contents[0:5]
   141  		subLen = uint32(contents[1])<<24 |
   142  			uint32(contents[2])<<16 |
   143  			uint32(contents[3])<<8 |
   144  			uint32(contents[4])
   145  		contents = contents[5:]
   146  
   147  	}
   148  	if subLen > uint32(len(contents)) || subLen == 0 {
   149  		goto Truncated
   150  	}
   151  	subPacket.SubType = contents[0]
   152  	subPacket.EncodedLength = encodedLength
   153  	subPacket.Contents = contents[1:subLen]
   154  	return
   155  Truncated:
   156  	err = errors.StructuralError("subpacket truncated")
   157  	return
   158  }
   159  
   160  func (osp *OpaqueSubpacket) Serialize(w io.Writer) (err error) {
   161  	buf := make([]byte, 6)
   162  	copy(buf, osp.EncodedLength)
   163  	n := len(osp.EncodedLength)
   164  
   165  	buf[n] = osp.SubType
   166  	if _, err = w.Write(buf[:n+1]); err != nil {
   167  		return
   168  	}
   169  	_, err = w.Write(osp.Contents)
   170  	return
   171  }
   172
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