// Copyright 2011 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // Package packet implements parsing and serialization of OpenPGP packets, as // specified in RFC 4880. package packet // import "golang.org/x/crypto/openpgp/packet" import ( "bufio" "crypto/aes" "crypto/cipher" "crypto/des" "golang.org/x/crypto/cast5" "golang.org/x/crypto/openpgp/errors" "io" "math/big" ) // readFull is the same as io.ReadFull except that reading zero bytes returns // ErrUnexpectedEOF rather than EOF. func readFull(r io.Reader, buf []byte) (n int, err error) { n, err = io.ReadFull(r, buf) if err == io.EOF { err = io.ErrUnexpectedEOF } return } // readLength reads an OpenPGP length from r. See RFC 4880, section 4.2.2. func readLength(r io.Reader) (length int64, isPartial bool, err error) { var buf [4]byte _, err = readFull(r, buf[:1]) if err != nil { return } switch { case buf[0] < 192: length = int64(buf[0]) case buf[0] < 224: length = int64(buf[0]-192) << 8 _, err = readFull(r, buf[0:1]) if err != nil { return } length += int64(buf[0]) + 192 case buf[0] < 255: length = int64(1) << (buf[0] & 0x1f) isPartial = true default: _, err = readFull(r, buf[0:4]) if err != nil { return } length = int64(buf[0])<<24 | int64(buf[1])<<16 | int64(buf[2])<<8 | int64(buf[3]) } return } // partialLengthReader wraps an io.Reader and handles OpenPGP partial lengths. // The continuation lengths are parsed and removed from the stream and EOF is // returned at the end of the packet. See RFC 4880, section 4.2.2.4. type partialLengthReader struct { r io.Reader remaining int64 isPartial bool } func (r *partialLengthReader) Read(p []byte) (n int, err error) { for r.remaining == 0 { if !r.isPartial { return 0, io.EOF } r.remaining, r.isPartial, err = readLength(r.r) if err != nil { return 0, err } } toRead := int64(len(p)) if toRead > r.remaining { toRead = r.remaining } n, err = r.r.Read(p[:int(toRead)]) r.remaining -= int64(n) if n < int(toRead) && err == io.EOF { err = io.ErrUnexpectedEOF } return } // partialLengthWriter writes a stream of data using OpenPGP partial lengths. // See RFC 4880, section 4.2.2.4. type partialLengthWriter struct { w io.WriteCloser lengthByte [1]byte } func (w *partialLengthWriter) Write(p []byte) (n int, err error) { for len(p) > 0 { for power := uint(14); power < 32; power-- { l := 1 << power if len(p) >= l { w.lengthByte[0] = 224 + uint8(power) _, err = w.w.Write(w.lengthByte[:]) if err != nil { return } var m int m, err = w.w.Write(p[:l]) n += m if err != nil { return } p = p[l:] break } } } return } func (w *partialLengthWriter) Close() error { w.lengthByte[0] = 0 _, err := w.w.Write(w.lengthByte[:]) if err != nil { return err } return w.w.Close() } // A spanReader is an io.LimitReader, but it returns ErrUnexpectedEOF if the // underlying Reader returns EOF before the limit has been reached. type spanReader struct { r io.Reader n int64 } func (l *spanReader) Read(p []byte) (n int, err error) { if l.n <= 0 { return 0, io.EOF } if int64(len(p)) > l.n { p = p[0:l.n] } n, err = l.r.Read(p) l.n -= int64(n) if l.n > 0 && err == io.EOF { err = io.ErrUnexpectedEOF } return } // readHeader parses a packet header and returns an io.Reader which will return // the contents of the packet. See RFC 4880, section 4.2. func readHeader(r io.Reader) (tag packetType, length int64, contents io.Reader, err error) { var buf [4]byte _, err = io.ReadFull(r, buf[:1]) if err != nil { return } if buf[0]&0x80 == 0 { err = errors.StructuralError("tag byte does not have MSB set") return } if buf[0]&0x40 == 0 { // Old format packet tag = packetType((buf[0] & 0x3f) >> 2) lengthType := buf[0] & 3 if lengthType == 3 { length = -1 contents = r return } lengthBytes := 1 << lengthType _, err = readFull(r, buf[0:lengthBytes]) if err != nil { return } for i := 0; i < lengthBytes; i++ { length <<= 8 length |= int64(buf[i]) } contents = &spanReader{r, length} return } // New format packet tag = packetType(buf[0] & 0x3f) length, isPartial, err := readLength(r) if err != nil { return } if isPartial { contents = &partialLengthReader{ remaining: length, isPartial: true, r: r, } length = -1 } else { contents = &spanReader{r, length} } return } // serializeHeader writes an OpenPGP packet header to w. See RFC 4880, section // 4.2. func serializeHeader(w io.Writer, ptype packetType, length int) (err error) { var buf [6]byte var n int buf[0] = 0x80 | 0x40 | byte(ptype) if length < 192 { buf[1] = byte(length) n = 2 } else if length < 8384 { length -= 192 buf[1] = 192 + byte(length>>8) buf[2] = byte(length) n = 3 } else { buf[1] = 255 buf[2] = byte(length >> 24) buf[3] = byte(length >> 16) buf[4] = byte(length >> 8) buf[5] = byte(length) n = 6 } _, err = w.Write(buf[:n]) return } // serializeStreamHeader writes an OpenPGP packet header to w where the // length of the packet is unknown. It returns a io.WriteCloser which can be // used to write the contents of the packet. See RFC 4880, section 4.2. func serializeStreamHeader(w io.WriteCloser, ptype packetType) (out io.WriteCloser, err error) { var buf [1]byte buf[0] = 0x80 | 0x40 | byte(ptype) _, err = w.Write(buf[:]) if err != nil { return } out = &partialLengthWriter{w: w} return } // Packet represents an OpenPGP packet. Users are expected to try casting // instances of this interface to specific packet types. type Packet interface { parse(io.Reader) error } // consumeAll reads from the given Reader until error, returning the number of // bytes read. func consumeAll(r io.Reader) (n int64, err error) { var m int var buf [1024]byte for { m, err = r.Read(buf[:]) n += int64(m) if err == io.EOF { err = nil return } if err != nil { return } } panic("unreachable") } // packetType represents the numeric ids of the different OpenPGP packet types. See // http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-2 type packetType uint8 const ( packetTypeEncryptedKey packetType = 1 packetTypeSignature packetType = 2 packetTypeSymmetricKeyEncrypted packetType = 3 packetTypeOnePassSignature packetType = 4 packetTypePrivateKey packetType = 5 packetTypePublicKey packetType = 6 packetTypePrivateSubkey packetType = 7 packetTypeCompressed packetType = 8 packetTypeSymmetricallyEncrypted packetType = 9 packetTypeLiteralData packetType = 11 packetTypeUserId packetType = 13 packetTypePublicSubkey packetType = 14 packetTypeUserAttribute packetType = 17 packetTypeSymmetricallyEncryptedMDC packetType = 18 ) // peekVersion detects the version of a public key packet about to // be read. A bufio.Reader at the original position of the io.Reader // is returned. func peekVersion(r io.Reader) (bufr *bufio.Reader, ver byte, err error) { bufr = bufio.NewReader(r) var verBuf []byte if verBuf, err = bufr.Peek(1); err != nil { return } ver = verBuf[0] return } // Read reads a single OpenPGP packet from the given io.Reader. If there is an // error parsing a packet, the whole packet is consumed from the input. func Read(r io.Reader) (p Packet, err error) { tag, _, contents, err := readHeader(r) if err != nil { return } switch tag { case packetTypeEncryptedKey: p = new(EncryptedKey) case packetTypeSignature: var version byte // Detect signature version if contents, version, err = peekVersion(contents); err != nil { return } if version < 4 { p = new(SignatureV3) } else { p = new(Signature) } case packetTypeSymmetricKeyEncrypted: p = new(SymmetricKeyEncrypted) case packetTypeOnePassSignature: p = new(OnePassSignature) case packetTypePrivateKey, packetTypePrivateSubkey: pk := new(PrivateKey) if tag == packetTypePrivateSubkey { pk.IsSubkey = true } p = pk case packetTypePublicKey, packetTypePublicSubkey: var version byte if contents, version, err = peekVersion(contents); err != nil { return } isSubkey := tag == packetTypePublicSubkey if version < 4 { p = &PublicKeyV3{IsSubkey: isSubkey} } else { p = &PublicKey{IsSubkey: isSubkey} } case packetTypeCompressed: p = new(Compressed) case packetTypeSymmetricallyEncrypted: p = new(SymmetricallyEncrypted) case packetTypeLiteralData: p = new(LiteralData) case packetTypeUserId: p = new(UserId) case packetTypeUserAttribute: p = new(UserAttribute) case packetTypeSymmetricallyEncryptedMDC: se := new(SymmetricallyEncrypted) se.MDC = true p = se default: err = errors.UnknownPacketTypeError(tag) } if p != nil { err = p.parse(contents) } if err != nil { consumeAll(contents) } return } // SignatureType represents the different semantic meanings of an OpenPGP // signature. See RFC 4880, section 5.2.1. type SignatureType uint8 const ( SigTypeBinary SignatureType = 0 SigTypeText = 1 SigTypeGenericCert = 0x10 SigTypePersonaCert = 0x11 SigTypeCasualCert = 0x12 SigTypePositiveCert = 0x13 SigTypeSubkeyBinding = 0x18 SigTypePrimaryKeyBinding = 0x19 SigTypeDirectSignature = 0x1F SigTypeKeyRevocation = 0x20 SigTypeSubkeyRevocation = 0x28 ) // PublicKeyAlgorithm represents the different public key system specified for // OpenPGP. See // http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-12 type PublicKeyAlgorithm uint8 const ( PubKeyAlgoRSA PublicKeyAlgorithm = 1 PubKeyAlgoRSAEncryptOnly PublicKeyAlgorithm = 2 PubKeyAlgoRSASignOnly PublicKeyAlgorithm = 3 PubKeyAlgoElGamal PublicKeyAlgorithm = 16 PubKeyAlgoDSA PublicKeyAlgorithm = 17 // RFC 6637, Section 5. PubKeyAlgoECDH PublicKeyAlgorithm = 18 PubKeyAlgoECDSA PublicKeyAlgorithm = 19 ) // CanEncrypt returns true if it's possible to encrypt a message to a public // key of the given type. func (pka PublicKeyAlgorithm) CanEncrypt() bool { switch pka { case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoElGamal: return true } return false } // CanSign returns true if it's possible for a public key of the given type to // sign a message. func (pka PublicKeyAlgorithm) CanSign() bool { switch pka { case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoDSA, PubKeyAlgoECDSA: return true } return false } // CipherFunction represents the different block ciphers specified for OpenPGP. See // http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-13 type CipherFunction uint8 const ( Cipher3DES CipherFunction = 2 CipherCAST5 CipherFunction = 3 CipherAES128 CipherFunction = 7 CipherAES192 CipherFunction = 8 CipherAES256 CipherFunction = 9 ) // KeySize returns the key size, in bytes, of cipher. func (cipher CipherFunction) KeySize() int { switch cipher { case Cipher3DES: return 24 case CipherCAST5: return cast5.KeySize case CipherAES128: return 16 case CipherAES192: return 24 case CipherAES256: return 32 } return 0 } // blockSize returns the block size, in bytes, of cipher. func (cipher CipherFunction) blockSize() int { switch cipher { case Cipher3DES: return des.BlockSize case CipherCAST5: return 8 case CipherAES128, CipherAES192, CipherAES256: return 16 } return 0 } // new returns a fresh instance of the given cipher. func (cipher CipherFunction) new(key []byte) (block cipher.Block) { switch cipher { case Cipher3DES: block, _ = des.NewTripleDESCipher(key) case CipherCAST5: block, _ = cast5.NewCipher(key) case CipherAES128, CipherAES192, CipherAES256: block, _ = aes.NewCipher(key) } return } // readMPI reads a big integer from r. The bit length returned is the bit // length that was specified in r. This is preserved so that the integer can be // reserialized exactly. func readMPI(r io.Reader) (mpi []byte, bitLength uint16, err error) { var buf [2]byte _, err = readFull(r, buf[0:]) if err != nil { return } bitLength = uint16(buf[0])<<8 | uint16(buf[1]) numBytes := (int(bitLength) + 7) / 8 mpi = make([]byte, numBytes) _, err = readFull(r, mpi) return } // mpiLength returns the length of the given *big.Int when serialized as an // MPI. func mpiLength(n *big.Int) (mpiLengthInBytes int) { mpiLengthInBytes = 2 /* MPI length */ mpiLengthInBytes += (n.BitLen() + 7) / 8 return } // writeMPI serializes a big integer to w. func writeMPI(w io.Writer, bitLength uint16, mpiBytes []byte) (err error) { _, err = w.Write([]byte{byte(bitLength >> 8), byte(bitLength)}) if err == nil { _, err = w.Write(mpiBytes) } return } // writeBig serializes a *big.Int to w. func writeBig(w io.Writer, i *big.Int) error { return writeMPI(w, uint16(i.BitLen()), i.Bytes()) } // CompressionAlgo Represents the different compression algorithms // supported by OpenPGP (except for BZIP2, which is not currently // supported). See Section 9.3 of RFC 4880. type CompressionAlgo uint8 const ( CompressionNone CompressionAlgo = 0 CompressionZIP CompressionAlgo = 1 CompressionZLIB CompressionAlgo = 2 )