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// 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
import (
"crypto/rsa"
"io"
"time"
"golang.org/x/crypto/openpgp/armor"
"golang.org/x/crypto/openpgp/errors"
"golang.org/x/crypto/openpgp/packet"
)
// PublicKeyType is the armor type for a PGP public key.
var PublicKeyType = "PGP PUBLIC KEY BLOCK"
// PrivateKeyType is the armor type for a PGP private key.
var PrivateKeyType = "PGP PRIVATE KEY BLOCK"
// An Entity represents the components of an OpenPGP key: a primary public key
// (which must be a signing key), one or more identities claimed by that key,
// and zero or more subkeys, which may be encryption keys.
type Entity struct {
PrimaryKey *packet.PublicKey
PrivateKey *packet.PrivateKey
Identities map[string]*Identity // indexed by Identity.Name
Revocations []*packet.Signature
Subkeys []Subkey
}
// An Identity represents an identity claimed by an Entity and zero or more
// assertions by other entities about that claim.
type Identity struct {
Name string // by convention, has the form "Full Name (comment) <email@example.com>"
UserId *packet.UserId
SelfSignature *packet.Signature
Signatures []*packet.Signature
}
// A Subkey is an additional public key in an Entity. Subkeys can be used for
// encryption.
type Subkey struct {
PublicKey *packet.PublicKey
PrivateKey *packet.PrivateKey
Sig *packet.Signature
}
// A Key identifies a specific public key in an Entity. This is either the
// Entity's primary key or a subkey.
type Key struct {
Entity *Entity
PublicKey *packet.PublicKey
PrivateKey *packet.PrivateKey
SelfSignature *packet.Signature
}
// A KeyRing provides access to public and private keys.
type KeyRing interface {
// KeysById returns the set of keys that have the given key id.
KeysById(id uint64) []Key
// KeysByIdAndUsage returns the set of keys with the given id
// that also meet the key usage given by requiredUsage.
// The requiredUsage is expressed as the bitwise-OR of
// packet.KeyFlag* values.
KeysByIdUsage(id uint64, requiredUsage byte) []Key
// DecryptionKeys returns all private keys that are valid for
// decryption.
DecryptionKeys() []Key
}
// primaryIdentity returns the Identity marked as primary or the first identity
// if none are so marked.
func (e *Entity) primaryIdentity() *Identity {
var firstIdentity *Identity
for _, ident := range e.Identities {
if firstIdentity == nil {
firstIdentity = ident
}
if ident.SelfSignature.IsPrimaryId != nil && *ident.SelfSignature.IsPrimaryId {
return ident
}
}
return firstIdentity
}
// encryptionKey returns the best candidate Key for encrypting a message to the
// given Entity.
func (e *Entity) encryptionKey(now time.Time) (Key, bool) {
candidateSubkey := -1
// Iterate the keys to find the newest key
var maxTime time.Time
for i, subkey := range e.Subkeys {
if subkey.Sig.FlagsValid &&
subkey.Sig.FlagEncryptCommunications &&
subkey.PublicKey.PubKeyAlgo.CanEncrypt() &&
!subkey.Sig.KeyExpired(now) &&
(maxTime.IsZero() || subkey.Sig.CreationTime.After(maxTime)) {
candidateSubkey = i
maxTime = subkey.Sig.CreationTime
}
}
if candidateSubkey != -1 {
subkey := e.Subkeys[candidateSubkey]
return Key{e, subkey.PublicKey, subkey.PrivateKey, subkey.Sig}, true
}
// If we don't have any candidate subkeys for encryption and
// the primary key doesn't have any usage metadata then we
// assume that the primary key is ok. Or, if the primary key is
// marked as ok to encrypt to, then we can obviously use it.
i := e.primaryIdentity()
if !i.SelfSignature.FlagsValid || i.SelfSignature.FlagEncryptCommunications &&
e.PrimaryKey.PubKeyAlgo.CanEncrypt() &&
!i.SelfSignature.KeyExpired(now) {
return Key{e, e.PrimaryKey, e.PrivateKey, i.SelfSignature}, true
}
// This Entity appears to be signing only.
return Key{}, false
}
// signingKey return the best candidate Key for signing a message with this
// Entity.
func (e *Entity) signingKey(now time.Time) (Key, bool) {
candidateSubkey := -1
for i, subkey := range e.Subkeys {
if subkey.Sig.FlagsValid &&
subkey.Sig.FlagSign &&
subkey.PublicKey.PubKeyAlgo.CanSign() &&
!subkey.Sig.KeyExpired(now) {
candidateSubkey = i
break
}
}
if candidateSubkey != -1 {
subkey := e.Subkeys[candidateSubkey]
return Key{e, subkey.PublicKey, subkey.PrivateKey, subkey.Sig}, true
}
// If we have no candidate subkey then we assume that it's ok to sign
// with the primary key.
i := e.primaryIdentity()
if !i.SelfSignature.FlagsValid || i.SelfSignature.FlagSign &&
!i.SelfSignature.KeyExpired(now) {
return Key{e, e.PrimaryKey, e.PrivateKey, i.SelfSignature}, true
}
return Key{}, false
}
// An EntityList contains one or more Entities.
type EntityList []*Entity
// KeysById returns the set of keys that have the given key id.
func (el EntityList) KeysById(id uint64) (keys []Key) {
for _, e := range el {
if e.PrimaryKey.KeyId == id {
var selfSig *packet.Signature
for _, ident := range e.Identities {
if selfSig == nil {
selfSig = ident.SelfSignature
} else if ident.SelfSignature.IsPrimaryId != nil && *ident.SelfSignature.IsPrimaryId {
selfSig = ident.SelfSignature
break
}
}
keys = append(keys, Key{e, e.PrimaryKey, e.PrivateKey, selfSig})
}
for _, subKey := range e.Subkeys {
if subKey.PublicKey.KeyId == id {
keys = append(keys, Key{e, subKey.PublicKey, subKey.PrivateKey, subKey.Sig})
}
}
}
return
}
// KeysByIdAndUsage returns the set of keys with the given id that also meet
// the key usage given by requiredUsage. The requiredUsage is expressed as
// the bitwise-OR of packet.KeyFlag* values.
func (el EntityList) KeysByIdUsage(id uint64, requiredUsage byte) (keys []Key) {
for _, key := range el.KeysById(id) {
if len(key.Entity.Revocations) > 0 {
continue
}
if key.SelfSignature.RevocationReason != nil {
continue
}
if key.SelfSignature.FlagsValid && requiredUsage != 0 {
var usage byte
if key.SelfSignature.FlagCertify {
usage |= packet.KeyFlagCertify
}
if key.SelfSignature.FlagSign {
usage |= packet.KeyFlagSign
}
if key.SelfSignature.FlagEncryptCommunications {
usage |= packet.KeyFlagEncryptCommunications
}
if key.SelfSignature.FlagEncryptStorage {
usage |= packet.KeyFlagEncryptStorage
}
if usage&requiredUsage != requiredUsage {
continue
}
}
keys = append(keys, key)
}
return
}
// DecryptionKeys returns all private keys that are valid for decryption.
func (el EntityList) DecryptionKeys() (keys []Key) {
for _, e := range el {
for _, subKey := range e.Subkeys {
if subKey.PrivateKey != nil && (!subKey.Sig.FlagsValid || subKey.Sig.FlagEncryptStorage || subKey.Sig.FlagEncryptCommunications) {
keys = append(keys, Key{e, subKey.PublicKey, subKey.PrivateKey, subKey.Sig})
}
}
}
return
}
// ReadArmoredKeyRing reads one or more public/private keys from an armor keyring file.
func ReadArmoredKeyRing(r io.Reader) (EntityList, error) {
block, err := armor.Decode(r)
if err == io.EOF {
return nil, errors.InvalidArgumentError("no armored data found")
}
if err != nil {
return nil, err
}
if block.Type != PublicKeyType && block.Type != PrivateKeyType {
return nil, errors.InvalidArgumentError("expected public or private key block, got: " + block.Type)
}
return ReadKeyRing(block.Body)
}
// ReadKeyRing reads one or more public/private keys. Unsupported keys are
// ignored as long as at least a single valid key is found.
func ReadKeyRing(r io.Reader) (el EntityList, err error) {
packets := packet.NewReader(r)
var lastUnsupportedError error
for {
var e *Entity
e, err = ReadEntity(packets)
if err != nil {
// TODO: warn about skipped unsupported/unreadable keys
if _, ok := err.(errors.UnsupportedError); ok {
lastUnsupportedError = err
err = readToNextPublicKey(packets)
} else if _, ok := err.(errors.StructuralError); ok {
// Skip unreadable, badly-formatted keys
lastUnsupportedError = err
err = readToNextPublicKey(packets)
}
if err == io.EOF {
err = nil
break
}
if err != nil {
el = nil
break
}
} else {
el = append(el, e)
}
}
if len(el) == 0 && err == nil {
err = lastUnsupportedError
}
return
}
// readToNextPublicKey reads packets until the start of the entity and leaves
// the first packet of the new entity in the Reader.
func readToNextPublicKey(packets *packet.Reader) (err error) {
var p packet.Packet
for {
p, err = packets.Next()
if err == io.EOF {
return
} else if err != nil {
if _, ok := err.(errors.UnsupportedError); ok {
err = nil
continue
}
return
}
if pk, ok := p.(*packet.PublicKey); ok && !pk.IsSubkey {
packets.Unread(p)
return
}
}
}
// ReadEntity reads an entity (public key, identities, subkeys etc) from the
// given Reader.
func ReadEntity(packets *packet.Reader) (*Entity, error) {
e := new(Entity)
e.Identities = make(map[string]*Identity)
p, err := packets.Next()
if err != nil {
return nil, err
}
var ok bool
if e.PrimaryKey, ok = p.(*packet.PublicKey); !ok {
if e.PrivateKey, ok = p.(*packet.PrivateKey); !ok {
packets.Unread(p)
return nil, errors.StructuralError("first packet was not a public/private key")
}
e.PrimaryKey = &e.PrivateKey.PublicKey
}
if !e.PrimaryKey.PubKeyAlgo.CanSign() {
return nil, errors.StructuralError("primary key cannot be used for signatures")
}
var revocations []*packet.Signature
EachPacket:
for {
p, err := packets.Next()
if err == io.EOF {
break
} else if err != nil {
return nil, err
}
switch pkt := p.(type) {
case *packet.UserId:
if err := addUserID(e, packets, pkt); err != nil {
return nil, err
}
case *packet.Signature:
if pkt.SigType == packet.SigTypeKeyRevocation {
revocations = append(revocations, pkt)
} else if pkt.SigType == packet.SigTypeDirectSignature {
// TODO: RFC4880 5.2.1 permits signatures
// directly on keys (eg. to bind additional
// revocation keys).
}
// Else, ignoring the signature as it does not follow anything
// we would know to attach it to.
case *packet.PrivateKey:
if pkt.IsSubkey == false {
packets.Unread(p)
break EachPacket
}
err = addSubkey(e, packets, &pkt.PublicKey, pkt)
if err != nil {
return nil, err
}
case *packet.PublicKey:
if pkt.IsSubkey == false {
packets.Unread(p)
break EachPacket
}
err = addSubkey(e, packets, pkt, nil)
if err != nil {
return nil, err
}
default:
// we ignore unknown packets
}
}
if len(e.Identities) == 0 {
return nil, errors.StructuralError("entity without any identities")
}
for _, revocation := range revocations {
err = e.PrimaryKey.VerifyRevocationSignature(revocation)
if err == nil {
e.Revocations = append(e.Revocations, revocation)
} else {
// TODO: RFC 4880 5.2.3.15 defines revocation keys.
return nil, errors.StructuralError("revocation signature signed by alternate key")
}
}
return e, nil
}
func addUserID(e *Entity, packets *packet.Reader, pkt *packet.UserId) error {
// Make a new Identity object, that we might wind up throwing away.
// We'll only add it if we get a valid self-signature over this
// userID.
identity := new(Identity)
identity.Name = pkt.Id
identity.UserId = pkt
for {
p, err := packets.Next()
if err == io.EOF {
break
} else if err != nil {
return err
}
sig, ok := p.(*packet.Signature)
if !ok {
packets.Unread(p)
break
}
if (sig.SigType == packet.SigTypePositiveCert || sig.SigType == packet.SigTypeGenericCert) && sig.IssuerKeyId != nil && *sig.IssuerKeyId == e.PrimaryKey.KeyId {
if err = e.PrimaryKey.VerifyUserIdSignature(pkt.Id, e.PrimaryKey, sig); err != nil {
return errors.StructuralError("user ID self-signature invalid: " + err.Error())
}
identity.SelfSignature = sig
e.Identities[pkt.Id] = identity
} else {
identity.Signatures = append(identity.Signatures, sig)
}
}
return nil
}
func addSubkey(e *Entity, packets *packet.Reader, pub *packet.PublicKey, priv *packet.PrivateKey) error {
var subKey Subkey
subKey.PublicKey = pub
subKey.PrivateKey = priv
for {
p, err := packets.Next()
if err == io.EOF {
break
} else if err != nil {
return errors.StructuralError("subkey signature invalid: " + err.Error())
}
sig, ok := p.(*packet.Signature)
if !ok {
packets.Unread(p)
break
}
if sig.SigType != packet.SigTypeSubkeyBinding && sig.SigType != packet.SigTypeSubkeyRevocation {
return errors.StructuralError("subkey signature with wrong type")
}
if err := e.PrimaryKey.VerifyKeySignature(subKey.PublicKey, sig); err != nil {
return errors.StructuralError("subkey signature invalid: " + err.Error())
}
switch sig.SigType {
case packet.SigTypeSubkeyRevocation:
subKey.Sig = sig
case packet.SigTypeSubkeyBinding:
if shouldReplaceSubkeySig(subKey.Sig, sig) {
subKey.Sig = sig
}
}
}
if subKey.Sig == nil {
return errors.StructuralError("subkey packet not followed by signature")
}
e.Subkeys = append(e.Subkeys, subKey)
return nil
}
func shouldReplaceSubkeySig(existingSig, potentialNewSig *packet.Signature) bool {
if potentialNewSig == nil {
return false
}
if existingSig == nil {
return true
}
if existingSig.SigType == packet.SigTypeSubkeyRevocation {
return false // never override a revocation signature
}
return potentialNewSig.CreationTime.After(existingSig.CreationTime)
}
const defaultRSAKeyBits = 2048
// NewEntity returns an Entity that contains a fresh RSA/RSA keypair with a
// single identity composed of the given full name, comment and email, any of
// which may be empty but must not contain any of "()<>\x00".
// If config is nil, sensible defaults will be used.
func NewEntity(name, comment, email string, config *packet.Config) (*Entity, error) {
creationTime := config.Now()
bits := defaultRSAKeyBits
if config != nil && config.RSABits != 0 {
bits = config.RSABits
}
uid := packet.NewUserId(name, comment, email)
if uid == nil {
return nil, errors.InvalidArgumentError("user id field contained invalid characters")
}
signingPriv, err := rsa.GenerateKey(config.Random(), bits)
if err != nil {
return nil, err
}
encryptingPriv, err := rsa.GenerateKey(config.Random(), bits)
if err != nil {
return nil, err
}
e := &Entity{
PrimaryKey: packet.NewRSAPublicKey(creationTime, &signingPriv.PublicKey),
PrivateKey: packet.NewRSAPrivateKey(creationTime, signingPriv),
Identities: make(map[string]*Identity),
}
isPrimaryId := true
e.Identities[uid.Id] = &Identity{
Name: uid.Id,
UserId: uid,
SelfSignature: &packet.Signature{
CreationTime: creationTime,
SigType: packet.SigTypePositiveCert,
PubKeyAlgo: packet.PubKeyAlgoRSA,
Hash: config.Hash(),
IsPrimaryId: &isPrimaryId,
FlagsValid: true,
FlagSign: true,
FlagCertify: true,
IssuerKeyId: &e.PrimaryKey.KeyId,
},
}
err = e.Identities[uid.Id].SelfSignature.SignUserId(uid.Id, e.PrimaryKey, e.PrivateKey, config)
if err != nil {
return nil, err
}
// If the user passes in a DefaultHash via packet.Config,
// set the PreferredHash for the SelfSignature.
if config != nil && config.DefaultHash != 0 {
e.Identities[uid.Id].SelfSignature.PreferredHash = []uint8{hashToHashId(config.DefaultHash)}
}
// Likewise for DefaultCipher.
if config != nil && config.DefaultCipher != 0 {
e.Identities[uid.Id].SelfSignature.PreferredSymmetric = []uint8{uint8(config.DefaultCipher)}
}
e.Subkeys = make([]Subkey, 1)
e.Subkeys[0] = Subkey{
PublicKey: packet.NewRSAPublicKey(creationTime, &encryptingPriv.PublicKey),
PrivateKey: packet.NewRSAPrivateKey(creationTime, encryptingPriv),
Sig: &packet.Signature{
CreationTime: creationTime,
SigType: packet.SigTypeSubkeyBinding,
PubKeyAlgo: packet.PubKeyAlgoRSA,
Hash: config.Hash(),
FlagsValid: true,
FlagEncryptStorage: true,
FlagEncryptCommunications: true,
IssuerKeyId: &e.PrimaryKey.KeyId,
},
}
e.Subkeys[0].PublicKey.IsSubkey = true
e.Subkeys[0].PrivateKey.IsSubkey = true
err = e.Subkeys[0].Sig.SignKey(e.Subkeys[0].PublicKey, e.PrivateKey, config)
if err != nil {
return nil, err
}
return e, nil
}
// SerializePrivate serializes an Entity, including private key material, but
// excluding signatures from other entities, to the given Writer.
// Identities and subkeys are re-signed in case they changed since NewEntry.
// If config is nil, sensible defaults will be used.
func (e *Entity) SerializePrivate(w io.Writer, config *packet.Config) (err error) {
err = e.PrivateKey.Serialize(w)
if err != nil {
return
}
for _, ident := range e.Identities {
err = ident.UserId.Serialize(w)
if err != nil {
return
}
err = ident.SelfSignature.SignUserId(ident.UserId.Id, e.PrimaryKey, e.PrivateKey, config)
if err != nil {
return
}
err = ident.SelfSignature.Serialize(w)
if err != nil {
return
}
}
for _, subkey := range e.Subkeys {
err = subkey.PrivateKey.Serialize(w)
if err != nil {
return
}
err = subkey.Sig.SignKey(subkey.PublicKey, e.PrivateKey, config)
if err != nil {
return
}
err = subkey.Sig.Serialize(w)
if err != nil {
return
}
}
return nil
}
// Serialize writes the public part of the given Entity to w, including
// signatures from other entities. No private key material will be output.
func (e *Entity) Serialize(w io.Writer) error {
err := e.PrimaryKey.Serialize(w)
if err != nil {
return err
}
for _, ident := range e.Identities {
err = ident.UserId.Serialize(w)
if err != nil {
return err
}
err = ident.SelfSignature.Serialize(w)
if err != nil {
return err
}
for _, sig := range ident.Signatures {
err = sig.Serialize(w)
if err != nil {
return err
}
}
}
for _, subkey := range e.Subkeys {
err = subkey.PublicKey.Serialize(w)
if err != nil {
return err
}
err = subkey.Sig.Serialize(w)
if err != nil {
return err
}
}
return nil
}
// SignIdentity adds a signature to e, from signer, attesting that identity is
// associated with e. The provided identity must already be an element of
// e.Identities and the private key of signer must have been decrypted if
// necessary.
// If config is nil, sensible defaults will be used.
func (e *Entity) SignIdentity(identity string, signer *Entity, config *packet.Config) error {
if signer.PrivateKey == nil {
return errors.InvalidArgumentError("signing Entity must have a private key")
}
if signer.PrivateKey.Encrypted {
return errors.InvalidArgumentError("signing Entity's private key must be decrypted")
}
ident, ok := e.Identities[identity]
if !ok {
return errors.InvalidArgumentError("given identity string not found in Entity")
}
sig := &packet.Signature{
SigType: packet.SigTypeGenericCert,
PubKeyAlgo: signer.PrivateKey.PubKeyAlgo,
Hash: config.Hash(),
CreationTime: config.Now(),
IssuerKeyId: &signer.PrivateKey.KeyId,
}
if err := sig.SignUserId(identity, e.PrimaryKey, signer.PrivateKey, config); err != nil {
return err
}
ident.Signatures = append(ident.Signatures, sig)
return nil
}
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