github.com/graybobo/golang.org-package-offline-cache@v0.0.0-20200626051047-6608995c132f/x/crypto/openpgp/packet/opaque.go (about)

     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  	"golang.org/x/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  	Contents []byte
    89  }
    90  
    91  // OpaqueSubpackets extracts opaque, unparsed OpenPGP subpackets from
    92  // their byte representation.
    93  func OpaqueSubpackets(contents []byte) (result []*OpaqueSubpacket, err error) {
    94  	var (
    95  		subHeaderLen int
    96  		subPacket    *OpaqueSubpacket
    97  	)
    98  	for len(contents) > 0 {
    99  		subHeaderLen, subPacket, err = nextSubpacket(contents)
   100  		if err != nil {
   101  			break
   102  		}
   103  		result = append(result, subPacket)
   104  		contents = contents[subHeaderLen+len(subPacket.Contents):]
   105  	}
   106  	return
   107  }
   108  
   109  func nextSubpacket(contents []byte) (subHeaderLen int, subPacket *OpaqueSubpacket, err error) {
   110  	// RFC 4880, section 5.2.3.1
   111  	var subLen uint32
   112  	if len(contents) < 1 {
   113  		goto Truncated
   114  	}
   115  	subPacket = &OpaqueSubpacket{}
   116  	switch {
   117  	case contents[0] < 192:
   118  		subHeaderLen = 2 // 1 length byte, 1 subtype byte
   119  		if len(contents) < subHeaderLen {
   120  			goto Truncated
   121  		}
   122  		subLen = uint32(contents[0])
   123  		contents = contents[1:]
   124  	case contents[0] < 255:
   125  		subHeaderLen = 3 // 2 length bytes, 1 subtype
   126  		if len(contents) < subHeaderLen {
   127  			goto Truncated
   128  		}
   129  		subLen = uint32(contents[0]-192)<<8 + uint32(contents[1]) + 192
   130  		contents = contents[2:]
   131  	default:
   132  		subHeaderLen = 6 // 5 length bytes, 1 subtype
   133  		if len(contents) < subHeaderLen {
   134  			goto Truncated
   135  		}
   136  		subLen = uint32(contents[1])<<24 |
   137  			uint32(contents[2])<<16 |
   138  			uint32(contents[3])<<8 |
   139  			uint32(contents[4])
   140  		contents = contents[5:]
   141  	}
   142  	if subLen > uint32(len(contents)) || subLen == 0 {
   143  		goto Truncated
   144  	}
   145  	subPacket.SubType = contents[0]
   146  	subPacket.Contents = contents[1:subLen]
   147  	return
   148  Truncated:
   149  	err = errors.StructuralError("subpacket truncated")
   150  	return
   151  }
   152  
   153  func (osp *OpaqueSubpacket) Serialize(w io.Writer) (err error) {
   154  	buf := make([]byte, 6)
   155  	n := serializeSubpacketLength(buf, len(osp.Contents)+1)
   156  	buf[n] = osp.SubType
   157  	if _, err = w.Write(buf[:n+1]); err != nil {
   158  		return
   159  	}
   160  	_, err = w.Write(osp.Contents)
   161  	return
   162  }