378 lines
11 KiB
Go
378 lines
11 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package openpgp
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import (
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"crypto"
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"hash"
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"io"
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"strconv"
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"time"
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"golang.org/x/crypto/openpgp/armor"
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"golang.org/x/crypto/openpgp/errors"
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"golang.org/x/crypto/openpgp/packet"
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"golang.org/x/crypto/openpgp/s2k"
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)
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// DetachSign signs message with the private key from signer (which must
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// already have been decrypted) and writes the signature to w.
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// If config is nil, sensible defaults will be used.
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func DetachSign(w io.Writer, signer *Entity, message io.Reader, config *packet.Config) error {
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return detachSign(w, signer, message, packet.SigTypeBinary, config)
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}
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// ArmoredDetachSign signs message with the private key from signer (which
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// must already have been decrypted) and writes an armored signature to w.
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// If config is nil, sensible defaults will be used.
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func ArmoredDetachSign(w io.Writer, signer *Entity, message io.Reader, config *packet.Config) (err error) {
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return armoredDetachSign(w, signer, message, packet.SigTypeBinary, config)
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}
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// DetachSignText signs message (after canonicalising the line endings) with
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// the private key from signer (which must already have been decrypted) and
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// writes the signature to w.
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// If config is nil, sensible defaults will be used.
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func DetachSignText(w io.Writer, signer *Entity, message io.Reader, config *packet.Config) error {
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return detachSign(w, signer, message, packet.SigTypeText, config)
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}
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// ArmoredDetachSignText signs message (after canonicalising the line endings)
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// with the private key from signer (which must already have been decrypted)
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// and writes an armored signature to w.
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// If config is nil, sensible defaults will be used.
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func ArmoredDetachSignText(w io.Writer, signer *Entity, message io.Reader, config *packet.Config) error {
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return armoredDetachSign(w, signer, message, packet.SigTypeText, config)
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}
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func armoredDetachSign(w io.Writer, signer *Entity, message io.Reader, sigType packet.SignatureType, config *packet.Config) (err error) {
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out, err := armor.Encode(w, SignatureType, nil)
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if err != nil {
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return
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}
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err = detachSign(out, signer, message, sigType, config)
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if err != nil {
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return
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}
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return out.Close()
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}
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func detachSign(w io.Writer, signer *Entity, message io.Reader, sigType packet.SignatureType, config *packet.Config) (err error) {
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if signer.PrivateKey == nil {
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return errors.InvalidArgumentError("signing key doesn't have a private key")
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}
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if signer.PrivateKey.Encrypted {
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return errors.InvalidArgumentError("signing key is encrypted")
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}
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sig := new(packet.Signature)
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sig.SigType = sigType
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sig.PubKeyAlgo = signer.PrivateKey.PubKeyAlgo
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sig.Hash = config.Hash()
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sig.CreationTime = config.Now()
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sig.IssuerKeyId = &signer.PrivateKey.KeyId
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h, wrappedHash, err := hashForSignature(sig.Hash, sig.SigType)
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if err != nil {
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return
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}
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io.Copy(wrappedHash, message)
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err = sig.Sign(h, signer.PrivateKey, config)
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if err != nil {
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return
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}
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return sig.Serialize(w)
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}
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// FileHints contains metadata about encrypted files. This metadata is, itself,
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// encrypted.
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type FileHints struct {
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// IsBinary can be set to hint that the contents are binary data.
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IsBinary bool
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// FileName hints at the name of the file that should be written. It's
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// truncated to 255 bytes if longer. It may be empty to suggest that the
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// file should not be written to disk. It may be equal to "_CONSOLE" to
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// suggest the data should not be written to disk.
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FileName string
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// ModTime contains the modification time of the file, or the zero time if not applicable.
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ModTime time.Time
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}
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// SymmetricallyEncrypt acts like gpg -c: it encrypts a file with a passphrase.
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// The resulting WriteCloser must be closed after the contents of the file have
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// been written.
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// If config is nil, sensible defaults will be used.
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func SymmetricallyEncrypt(ciphertext io.Writer, passphrase []byte, hints *FileHints, config *packet.Config) (plaintext io.WriteCloser, err error) {
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if hints == nil {
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hints = &FileHints{}
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}
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key, err := packet.SerializeSymmetricKeyEncrypted(ciphertext, passphrase, config)
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if err != nil {
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return
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}
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w, err := packet.SerializeSymmetricallyEncrypted(ciphertext, config.Cipher(), key, config)
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if err != nil {
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return
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}
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literaldata := w
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if algo := config.Compression(); algo != packet.CompressionNone {
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var compConfig *packet.CompressionConfig
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if config != nil {
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compConfig = config.CompressionConfig
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}
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literaldata, err = packet.SerializeCompressed(w, algo, compConfig)
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if err != nil {
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return
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}
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}
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var epochSeconds uint32
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if !hints.ModTime.IsZero() {
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epochSeconds = uint32(hints.ModTime.Unix())
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}
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return packet.SerializeLiteral(literaldata, hints.IsBinary, hints.FileName, epochSeconds)
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}
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// intersectPreferences mutates and returns a prefix of a that contains only
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// the values in the intersection of a and b. The order of a is preserved.
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func intersectPreferences(a []uint8, b []uint8) (intersection []uint8) {
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var j int
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for _, v := range a {
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for _, v2 := range b {
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if v == v2 {
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a[j] = v
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j++
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break
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}
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}
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}
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return a[:j]
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}
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func hashToHashId(h crypto.Hash) uint8 {
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v, ok := s2k.HashToHashId(h)
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if !ok {
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panic("tried to convert unknown hash")
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}
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return v
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}
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// Encrypt encrypts a message to a number of recipients and, optionally, signs
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// it. hints contains optional information, that is also encrypted, that aids
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// the recipients in processing the message. The resulting WriteCloser must
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// be closed after the contents of the file have been written.
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// If config is nil, sensible defaults will be used.
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func Encrypt(ciphertext io.Writer, to []*Entity, signed *Entity, hints *FileHints, config *packet.Config) (plaintext io.WriteCloser, err error) {
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var signer *packet.PrivateKey
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if signed != nil {
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signKey, ok := signed.signingKey(config.Now())
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if !ok {
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return nil, errors.InvalidArgumentError("no valid signing keys")
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}
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signer = signKey.PrivateKey
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if signer == nil {
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return nil, errors.InvalidArgumentError("no private key in signing key")
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}
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if signer.Encrypted {
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return nil, errors.InvalidArgumentError("signing key must be decrypted")
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}
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}
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// These are the possible ciphers that we'll use for the message.
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candidateCiphers := []uint8{
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uint8(packet.CipherAES128),
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uint8(packet.CipherAES256),
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uint8(packet.CipherCAST5),
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}
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// These are the possible hash functions that we'll use for the signature.
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candidateHashes := []uint8{
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hashToHashId(crypto.SHA256),
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hashToHashId(crypto.SHA512),
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hashToHashId(crypto.SHA1),
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hashToHashId(crypto.RIPEMD160),
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}
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// In the event that a recipient doesn't specify any supported ciphers
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// or hash functions, these are the ones that we assume that every
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// implementation supports.
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defaultCiphers := candidateCiphers[len(candidateCiphers)-1:]
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defaultHashes := candidateHashes[len(candidateHashes)-1:]
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encryptKeys := make([]Key, len(to))
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for i := range to {
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var ok bool
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encryptKeys[i], ok = to[i].encryptionKey(config.Now())
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if !ok {
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return nil, errors.InvalidArgumentError("cannot encrypt a message to key id " + strconv.FormatUint(to[i].PrimaryKey.KeyId, 16) + " because it has no encryption keys")
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}
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sig := to[i].primaryIdentity().SelfSignature
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preferredSymmetric := sig.PreferredSymmetric
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if len(preferredSymmetric) == 0 {
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preferredSymmetric = defaultCiphers
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}
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preferredHashes := sig.PreferredHash
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if len(preferredHashes) == 0 {
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preferredHashes = defaultHashes
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}
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candidateCiphers = intersectPreferences(candidateCiphers, preferredSymmetric)
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candidateHashes = intersectPreferences(candidateHashes, preferredHashes)
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}
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if len(candidateCiphers) == 0 || len(candidateHashes) == 0 {
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return nil, errors.InvalidArgumentError("cannot encrypt because recipient set shares no common algorithms")
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}
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cipher := packet.CipherFunction(candidateCiphers[0])
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// If the cipher specified by config is a candidate, we'll use that.
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configuredCipher := config.Cipher()
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for _, c := range candidateCiphers {
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cipherFunc := packet.CipherFunction(c)
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if cipherFunc == configuredCipher {
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cipher = cipherFunc
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break
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}
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}
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var hash crypto.Hash
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for _, hashId := range candidateHashes {
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if h, ok := s2k.HashIdToHash(hashId); ok && h.Available() {
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hash = h
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break
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}
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}
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// If the hash specified by config is a candidate, we'll use that.
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if configuredHash := config.Hash(); configuredHash.Available() {
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for _, hashId := range candidateHashes {
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if h, ok := s2k.HashIdToHash(hashId); ok && h == configuredHash {
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hash = h
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break
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}
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}
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}
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if hash == 0 {
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hashId := candidateHashes[0]
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name, ok := s2k.HashIdToString(hashId)
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if !ok {
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name = "#" + strconv.Itoa(int(hashId))
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}
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return nil, errors.InvalidArgumentError("cannot encrypt because no candidate hash functions are compiled in. (Wanted " + name + " in this case.)")
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}
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symKey := make([]byte, cipher.KeySize())
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if _, err := io.ReadFull(config.Random(), symKey); err != nil {
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return nil, err
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}
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for _, key := range encryptKeys {
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if err := packet.SerializeEncryptedKey(ciphertext, key.PublicKey, cipher, symKey, config); err != nil {
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return nil, err
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}
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}
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encryptedData, err := packet.SerializeSymmetricallyEncrypted(ciphertext, cipher, symKey, config)
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if err != nil {
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return
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}
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if signer != nil {
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ops := &packet.OnePassSignature{
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SigType: packet.SigTypeBinary,
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Hash: hash,
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PubKeyAlgo: signer.PubKeyAlgo,
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KeyId: signer.KeyId,
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IsLast: true,
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}
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if err := ops.Serialize(encryptedData); err != nil {
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return nil, err
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}
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}
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if hints == nil {
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hints = &FileHints{}
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}
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w := encryptedData
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if signer != nil {
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// If we need to write a signature packet after the literal
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// data then we need to stop literalData from closing
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// encryptedData.
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w = noOpCloser{encryptedData}
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}
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var epochSeconds uint32
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if !hints.ModTime.IsZero() {
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epochSeconds = uint32(hints.ModTime.Unix())
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}
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literalData, err := packet.SerializeLiteral(w, hints.IsBinary, hints.FileName, epochSeconds)
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if err != nil {
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return nil, err
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}
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if signer != nil {
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return signatureWriter{encryptedData, literalData, hash, hash.New(), signer, config}, nil
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}
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return literalData, nil
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}
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// signatureWriter hashes the contents of a message while passing it along to
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// literalData. When closed, it closes literalData, writes a signature packet
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// to encryptedData and then also closes encryptedData.
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type signatureWriter struct {
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encryptedData io.WriteCloser
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literalData io.WriteCloser
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hashType crypto.Hash
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h hash.Hash
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signer *packet.PrivateKey
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config *packet.Config
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}
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func (s signatureWriter) Write(data []byte) (int, error) {
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s.h.Write(data)
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return s.literalData.Write(data)
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}
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func (s signatureWriter) Close() error {
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sig := &packet.Signature{
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SigType: packet.SigTypeBinary,
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PubKeyAlgo: s.signer.PubKeyAlgo,
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Hash: s.hashType,
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CreationTime: s.config.Now(),
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IssuerKeyId: &s.signer.KeyId,
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}
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if err := sig.Sign(s.h, s.signer, s.config); err != nil {
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return err
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}
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if err := s.literalData.Close(); err != nil {
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return err
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}
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if err := sig.Serialize(s.encryptedData); err != nil {
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return err
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}
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return s.encryptedData.Close()
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}
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// noOpCloser is like an ioutil.NopCloser, but for an io.Writer.
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// TODO: we have two of these in OpenPGP packages alone. This probably needs
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// to be promoted somewhere more common.
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type noOpCloser struct {
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w io.Writer
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}
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func (c noOpCloser) Write(data []byte) (n int, err error) {
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return c.w.Write(data)
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}
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func (c noOpCloser) Close() error {
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return nil
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}
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