restic/vendor/golang.org/x/crypto/openpgp/read.go
Alexander Neumann 6e1a3987b7 Add 'self-update' command
This commit adds a command called `self-update` which downloads the
latest released version of restic from GitHub and replacing the current
binary with it. It does not rely on any external program (so it'll work
everywhere), but still verifies the GPG signature using the embedded GPG
public key.

By default, the `self-update` command is hidden behind the `selfupdate`
built tag, which is only set when restic is built using `build.go`. The
reason for this is that downstream distributions will then not include
the command by default, so users are encouraged to use the
platform-specific distribution mechanism.
2018-08-12 23:34:47 +02:00

442 lines
13 KiB
Go

// 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 openpgp implements high level operations on OpenPGP messages.
package openpgp // import "golang.org/x/crypto/openpgp"
import (
"crypto"
_ "crypto/sha256"
"hash"
"io"
"strconv"
"golang.org/x/crypto/openpgp/armor"
"golang.org/x/crypto/openpgp/errors"
"golang.org/x/crypto/openpgp/packet"
)
// SignatureType is the armor type for a PGP signature.
var SignatureType = "PGP SIGNATURE"
// readArmored reads an armored block with the given type.
func readArmored(r io.Reader, expectedType string) (body io.Reader, err error) {
block, err := armor.Decode(r)
if err != nil {
return
}
if block.Type != expectedType {
return nil, errors.InvalidArgumentError("expected '" + expectedType + "', got: " + block.Type)
}
return block.Body, nil
}
// MessageDetails contains the result of parsing an OpenPGP encrypted and/or
// signed message.
type MessageDetails struct {
IsEncrypted bool // true if the message was encrypted.
EncryptedToKeyIds []uint64 // the list of recipient key ids.
IsSymmetricallyEncrypted bool // true if a passphrase could have decrypted the message.
DecryptedWith Key // the private key used to decrypt the message, if any.
IsSigned bool // true if the message is signed.
SignedByKeyId uint64 // the key id of the signer, if any.
SignedBy *Key // the key of the signer, if available.
LiteralData *packet.LiteralData // the metadata of the contents
UnverifiedBody io.Reader // the contents of the message.
// If IsSigned is true and SignedBy is non-zero then the signature will
// be verified as UnverifiedBody is read. The signature cannot be
// checked until the whole of UnverifiedBody is read so UnverifiedBody
// must be consumed until EOF before the data can be trusted. Even if a
// message isn't signed (or the signer is unknown) the data may contain
// an authentication code that is only checked once UnverifiedBody has
// been consumed. Once EOF has been seen, the following fields are
// valid. (An authentication code failure is reported as a
// SignatureError error when reading from UnverifiedBody.)
SignatureError error // nil if the signature is good.
Signature *packet.Signature // the signature packet itself, if v4 (default)
SignatureV3 *packet.SignatureV3 // the signature packet if it is a v2 or v3 signature
decrypted io.ReadCloser
}
// A PromptFunction is used as a callback by functions that may need to decrypt
// a private key, or prompt for a passphrase. It is called with a list of
// acceptable, encrypted private keys and a boolean that indicates whether a
// passphrase is usable. It should either decrypt a private key or return a
// passphrase to try. If the decrypted private key or given passphrase isn't
// correct, the function will be called again, forever. Any error returned will
// be passed up.
type PromptFunction func(keys []Key, symmetric bool) ([]byte, error)
// A keyEnvelopePair is used to store a private key with the envelope that
// contains a symmetric key, encrypted with that key.
type keyEnvelopePair struct {
key Key
encryptedKey *packet.EncryptedKey
}
// ReadMessage parses an OpenPGP message that may be signed and/or encrypted.
// The given KeyRing should contain both public keys (for signature
// verification) and, possibly encrypted, private keys for decrypting.
// If config is nil, sensible defaults will be used.
func ReadMessage(r io.Reader, keyring KeyRing, prompt PromptFunction, config *packet.Config) (md *MessageDetails, err error) {
var p packet.Packet
var symKeys []*packet.SymmetricKeyEncrypted
var pubKeys []keyEnvelopePair
var se *packet.SymmetricallyEncrypted
packets := packet.NewReader(r)
md = new(MessageDetails)
md.IsEncrypted = true
// The message, if encrypted, starts with a number of packets
// containing an encrypted decryption key. The decryption key is either
// encrypted to a public key, or with a passphrase. This loop
// collects these packets.
ParsePackets:
for {
p, err = packets.Next()
if err != nil {
return nil, err
}
switch p := p.(type) {
case *packet.SymmetricKeyEncrypted:
// This packet contains the decryption key encrypted with a passphrase.
md.IsSymmetricallyEncrypted = true
symKeys = append(symKeys, p)
case *packet.EncryptedKey:
// This packet contains the decryption key encrypted to a public key.
md.EncryptedToKeyIds = append(md.EncryptedToKeyIds, p.KeyId)
switch p.Algo {
case packet.PubKeyAlgoRSA, packet.PubKeyAlgoRSAEncryptOnly, packet.PubKeyAlgoElGamal:
break
default:
continue
}
var keys []Key
if p.KeyId == 0 {
keys = keyring.DecryptionKeys()
} else {
keys = keyring.KeysById(p.KeyId)
}
for _, k := range keys {
pubKeys = append(pubKeys, keyEnvelopePair{k, p})
}
case *packet.SymmetricallyEncrypted:
se = p
break ParsePackets
case *packet.Compressed, *packet.LiteralData, *packet.OnePassSignature:
// This message isn't encrypted.
if len(symKeys) != 0 || len(pubKeys) != 0 {
return nil, errors.StructuralError("key material not followed by encrypted message")
}
packets.Unread(p)
return readSignedMessage(packets, nil, keyring)
}
}
var candidates []Key
var decrypted io.ReadCloser
// Now that we have the list of encrypted keys we need to decrypt at
// least one of them or, if we cannot, we need to call the prompt
// function so that it can decrypt a key or give us a passphrase.
FindKey:
for {
// See if any of the keys already have a private key available
candidates = candidates[:0]
candidateFingerprints := make(map[string]bool)
for _, pk := range pubKeys {
if pk.key.PrivateKey == nil {
continue
}
if !pk.key.PrivateKey.Encrypted {
if len(pk.encryptedKey.Key) == 0 {
pk.encryptedKey.Decrypt(pk.key.PrivateKey, config)
}
if len(pk.encryptedKey.Key) == 0 {
continue
}
decrypted, err = se.Decrypt(pk.encryptedKey.CipherFunc, pk.encryptedKey.Key)
if err != nil && err != errors.ErrKeyIncorrect {
return nil, err
}
if decrypted != nil {
md.DecryptedWith = pk.key
break FindKey
}
} else {
fpr := string(pk.key.PublicKey.Fingerprint[:])
if v := candidateFingerprints[fpr]; v {
continue
}
candidates = append(candidates, pk.key)
candidateFingerprints[fpr] = true
}
}
if len(candidates) == 0 && len(symKeys) == 0 {
return nil, errors.ErrKeyIncorrect
}
if prompt == nil {
return nil, errors.ErrKeyIncorrect
}
passphrase, err := prompt(candidates, len(symKeys) != 0)
if err != nil {
return nil, err
}
// Try the symmetric passphrase first
if len(symKeys) != 0 && passphrase != nil {
for _, s := range symKeys {
key, cipherFunc, err := s.Decrypt(passphrase)
if err == nil {
decrypted, err = se.Decrypt(cipherFunc, key)
if err != nil && err != errors.ErrKeyIncorrect {
return nil, err
}
if decrypted != nil {
break FindKey
}
}
}
}
}
md.decrypted = decrypted
if err := packets.Push(decrypted); err != nil {
return nil, err
}
return readSignedMessage(packets, md, keyring)
}
// readSignedMessage reads a possibly signed message if mdin is non-zero then
// that structure is updated and returned. Otherwise a fresh MessageDetails is
// used.
func readSignedMessage(packets *packet.Reader, mdin *MessageDetails, keyring KeyRing) (md *MessageDetails, err error) {
if mdin == nil {
mdin = new(MessageDetails)
}
md = mdin
var p packet.Packet
var h hash.Hash
var wrappedHash hash.Hash
FindLiteralData:
for {
p, err = packets.Next()
if err != nil {
return nil, err
}
switch p := p.(type) {
case *packet.Compressed:
if err := packets.Push(p.Body); err != nil {
return nil, err
}
case *packet.OnePassSignature:
if !p.IsLast {
return nil, errors.UnsupportedError("nested signatures")
}
h, wrappedHash, err = hashForSignature(p.Hash, p.SigType)
if err != nil {
md = nil
return
}
md.IsSigned = true
md.SignedByKeyId = p.KeyId
keys := keyring.KeysByIdUsage(p.KeyId, packet.KeyFlagSign)
if len(keys) > 0 {
md.SignedBy = &keys[0]
}
case *packet.LiteralData:
md.LiteralData = p
break FindLiteralData
}
}
if md.SignedBy != nil {
md.UnverifiedBody = &signatureCheckReader{packets, h, wrappedHash, md}
} else if md.decrypted != nil {
md.UnverifiedBody = checkReader{md}
} else {
md.UnverifiedBody = md.LiteralData.Body
}
return md, nil
}
// hashForSignature returns a pair of hashes that can be used to verify a
// signature. The signature may specify that the contents of the signed message
// should be preprocessed (i.e. to normalize line endings). Thus this function
// returns two hashes. The second should be used to hash the message itself and
// performs any needed preprocessing.
func hashForSignature(hashId crypto.Hash, sigType packet.SignatureType) (hash.Hash, hash.Hash, error) {
if !hashId.Available() {
return nil, nil, errors.UnsupportedError("hash not available: " + strconv.Itoa(int(hashId)))
}
h := hashId.New()
switch sigType {
case packet.SigTypeBinary:
return h, h, nil
case packet.SigTypeText:
return h, NewCanonicalTextHash(h), nil
}
return nil, nil, errors.UnsupportedError("unsupported signature type: " + strconv.Itoa(int(sigType)))
}
// checkReader wraps an io.Reader from a LiteralData packet. When it sees EOF
// it closes the ReadCloser from any SymmetricallyEncrypted packet to trigger
// MDC checks.
type checkReader struct {
md *MessageDetails
}
func (cr checkReader) Read(buf []byte) (n int, err error) {
n, err = cr.md.LiteralData.Body.Read(buf)
if err == io.EOF {
mdcErr := cr.md.decrypted.Close()
if mdcErr != nil {
err = mdcErr
}
}
return
}
// signatureCheckReader wraps an io.Reader from a LiteralData packet and hashes
// the data as it is read. When it sees an EOF from the underlying io.Reader
// it parses and checks a trailing Signature packet and triggers any MDC checks.
type signatureCheckReader struct {
packets *packet.Reader
h, wrappedHash hash.Hash
md *MessageDetails
}
func (scr *signatureCheckReader) Read(buf []byte) (n int, err error) {
n, err = scr.md.LiteralData.Body.Read(buf)
scr.wrappedHash.Write(buf[:n])
if err == io.EOF {
var p packet.Packet
p, scr.md.SignatureError = scr.packets.Next()
if scr.md.SignatureError != nil {
return
}
var ok bool
if scr.md.Signature, ok = p.(*packet.Signature); ok {
scr.md.SignatureError = scr.md.SignedBy.PublicKey.VerifySignature(scr.h, scr.md.Signature)
} else if scr.md.SignatureV3, ok = p.(*packet.SignatureV3); ok {
scr.md.SignatureError = scr.md.SignedBy.PublicKey.VerifySignatureV3(scr.h, scr.md.SignatureV3)
} else {
scr.md.SignatureError = errors.StructuralError("LiteralData not followed by Signature")
return
}
// The SymmetricallyEncrypted packet, if any, might have an
// unsigned hash of its own. In order to check this we need to
// close that Reader.
if scr.md.decrypted != nil {
mdcErr := scr.md.decrypted.Close()
if mdcErr != nil {
err = mdcErr
}
}
}
return
}
// CheckDetachedSignature takes a signed file and a detached signature and
// returns the signer if the signature is valid. If the signer isn't known,
// ErrUnknownIssuer is returned.
func CheckDetachedSignature(keyring KeyRing, signed, signature io.Reader) (signer *Entity, err error) {
var issuerKeyId uint64
var hashFunc crypto.Hash
var sigType packet.SignatureType
var keys []Key
var p packet.Packet
packets := packet.NewReader(signature)
for {
p, err = packets.Next()
if err == io.EOF {
return nil, errors.ErrUnknownIssuer
}
if err != nil {
return nil, err
}
switch sig := p.(type) {
case *packet.Signature:
if sig.IssuerKeyId == nil {
return nil, errors.StructuralError("signature doesn't have an issuer")
}
issuerKeyId = *sig.IssuerKeyId
hashFunc = sig.Hash
sigType = sig.SigType
case *packet.SignatureV3:
issuerKeyId = sig.IssuerKeyId
hashFunc = sig.Hash
sigType = sig.SigType
default:
return nil, errors.StructuralError("non signature packet found")
}
keys = keyring.KeysByIdUsage(issuerKeyId, packet.KeyFlagSign)
if len(keys) > 0 {
break
}
}
if len(keys) == 0 {
panic("unreachable")
}
h, wrappedHash, err := hashForSignature(hashFunc, sigType)
if err != nil {
return nil, err
}
if _, err := io.Copy(wrappedHash, signed); err != nil && err != io.EOF {
return nil, err
}
for _, key := range keys {
switch sig := p.(type) {
case *packet.Signature:
err = key.PublicKey.VerifySignature(h, sig)
case *packet.SignatureV3:
err = key.PublicKey.VerifySignatureV3(h, sig)
default:
panic("unreachable")
}
if err == nil {
return key.Entity, nil
}
}
return nil, err
}
// CheckArmoredDetachedSignature performs the same actions as
// CheckDetachedSignature but expects the signature to be armored.
func CheckArmoredDetachedSignature(keyring KeyRing, signed, signature io.Reader) (signer *Entity, err error) {
body, err := readArmored(signature, SignatureType)
if err != nil {
return
}
return CheckDetachedSignature(keyring, signed, body)
}