Add parsing and serializing interfaces for keyrings (#275)

* Add parsing and serializing interfaces for keyrings

* Make error check more compact

CHANGELOG.md

@@ -4,6 +4,18 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Added
+- API to serialize KeyRings to binary data:
+	```go
+	func (keyRing *KeyRing) Serialize() ([]byte, error)
+	```
+- API to parse KeyRings from binary data:
+	```go
+	func NewKeyRingFromBinary(binKeys []byte) (*KeyRing, error)
+	```
+
 ## [2.7.5] 2023-31-01
 
 ### Added

crypto/keyring.go

@@ -49,6 +49,29 @@ func (keyRing *KeyRing) AddKey(key *Key) error {
 	return nil
 }
 
+// NewKeyRingFromBinary creates a new keyring with all the keys contained in the unarmored binary data.
+// Note that it accepts only unlocked or public keys, as KeyRing cannot contain locked keys.
+func NewKeyRingFromBinary(binKeys []byte) (*KeyRing, error) {
+	entities, err := openpgp.ReadKeyRing(bytes.NewReader(binKeys))
+	if err != nil {
+		return nil, errors.Wrap(err, "gopenpgp: error in reading keyring")
+	}
+
+	keyring := &KeyRing{}
+	for _, entity := range entities {
+		key, err := NewKeyFromEntity(entity)
+		if err != nil {
+			return nil, errors.Wrap(err, "gopenpgp: error in reading keyring")
+		}
+
+		if err = keyring.AddKey(key); err != nil {
+			return nil, errors.Wrap(err, "gopenpgp: error in reading keyring")
+		}
+	}
+
+	return keyring, nil
+}
+
 // --- Extract keys from keyring
 
 // GetKeys returns openpgp keys contained in this KeyRing.
@@ -88,6 +111,25 @@ func (keyRing *KeyRing) getSigningEntity() (*openpgp.Entity, error) {
 	return signEntity, nil
 }
 
+// Serialize serializes a KeyRing to binary data.
+func (keyRing *KeyRing) Serialize() ([]byte, error) {
+	var buffer bytes.Buffer
+
+	for _, entity := range keyRing.entities {
+		var err error
+		if entity.PrivateKey == nil {
+			err = entity.Serialize(&buffer)
+		} else {
+			err = entity.SerializePrivateWithoutSigning(&buffer, nil)
+		}
+		if err != nil {
+			return nil, errors.Wrap(err, "gopenpgp: error in serializing keyring")
+		}
+	}
+
+	return buffer.Bytes(), nil
+}
+
 // --- Extract info from key
 
 // CountEntities returns the number of entities in the keyring.

crypto/keyring_test.go

@@ -148,6 +148,21 @@ func TestMultipleKeyRing(t *testing.T) {
 	assert.Exactly(t, 1, singleKeyRing.CountDecryptionEntities())
 }
 
+func TestSerializeParse(t *testing.T) {
+	serialized, err := keyRingTestMultiple.Serialize()
+	assert.Nil(t, err)
+
+	parsed, err := NewKeyRingFromBinary(serialized)
+	assert.Nil(t, err)
+
+	assert.Exactly(t, 3, len(parsed.GetKeys()))
+	for i, parsedKey := range parsed.GetKeys() {
+		expectedKey, err := keyRingTestMultiple.GetKey(i)
+		assert.Nil(t, err)
+		assert.Exactly(t, parsedKey.GetFingerprint(), expectedKey.GetFingerprint())
+	}
+}
+
 func TestClearPrivateKey(t *testing.T) {
 	keyRingCopy, err := keyRingTestMultiple.Copy()
 	if err != nil {