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Add helpers for handling Ed25519 key (un)marshalling
This implements the encoding of Ed25519 keys as defined in https://datatracker.ietf.org/doc/draft-ietf-curdle-pkix-04.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,133 @@ | ||
| package derhelpers | ||
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| import ( | ||
| "crypto" | ||
| "crypto/x509/pkix" | ||
| "encoding/asn1" | ||
| "errors" | ||
|
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| "golang.org/x/crypto/ed25519" | ||
| ) | ||
|
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| var errEd25519WrongID = errors.New("incorrect object identifier") | ||
| var errEd25519WrongKeyType = errors.New("incorrect key type") | ||
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| // ed25519OID is the OID for the Ed25519 signature scheme: see | ||
| // https://datatracker.ietf.org/doc/draft-ietf-curdle-pkix-04. | ||
| var ed25519OID = asn1.ObjectIdentifier{1, 3, 101, 112} | ||
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| // subjectPublicKeyInfo reflects the ASN.1 object defined in the X.509 standard. | ||
| // | ||
| // This is defined in crypto/x509 as "publicKeyInfo". | ||
| type subjectPublicKeyInfo struct { | ||
| Algorithm pkix.AlgorithmIdentifier | ||
| PublicKey asn1.BitString | ||
| } | ||
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| // MarshalEd25519PublicKey creates a DER-encoded SubjectPublicKeyInfo for an | ||
| // ed25519 public key, as defined in | ||
| // https://tools.ietf.org/html/draft-ietf-curdle-pkix-04. This is analagous to | ||
| // MarshalPKIXPublicKey in crypto/x509, which doesn't currently support Ed25519. | ||
| func MarshalEd25519PublicKey(pk crypto.PublicKey) ([]byte, error) { | ||
| pub, ok := pk.(ed25519.PublicKey) | ||
| if !ok { | ||
| return nil, errEd25519WrongKeyType | ||
| } | ||
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| spki := subjectPublicKeyInfo{ | ||
| Algorithm: pkix.AlgorithmIdentifier{ | ||
| Algorithm: ed25519OID, | ||
| }, | ||
| PublicKey: asn1.BitString{ | ||
| BitLength: len(pub) * 8, | ||
| Bytes: pub, | ||
| }, | ||
| } | ||
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| return asn1.Marshal(spki) | ||
| } | ||
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| // ParseEd25519PublicKey returns the Ed25519 public key encoded by the input. | ||
| func ParseEd25519PublicKey(der []byte) (crypto.PublicKey, error) { | ||
| var spki subjectPublicKeyInfo | ||
| if rest, err := asn1.Unmarshal(der, &spki); err != nil { | ||
| return nil, err | ||
| } else if len(rest) > 0 { | ||
| return nil, errors.New("SubjectPublicKeyInfo too long") | ||
| } | ||
|
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| if !spki.Algorithm.Algorithm.Equal(ed25519OID) { | ||
| return nil, errEd25519WrongID | ||
| } | ||
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| if spki.PublicKey.BitLength != ed25519.PublicKeySize*8 { | ||
| return nil, errors.New("SubjectPublicKeyInfo PublicKey length mismatch") | ||
| } | ||
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| return ed25519.PublicKey(spki.PublicKey.Bytes), nil | ||
| } | ||
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| // oneAsymmetricKey reflects the ASN.1 structure for storing private keys in | ||
| // https://tools.ietf.org/html/draft-ietf-curdle-pkix-04, excluding the optional | ||
| // fields, which we don't use here. | ||
| // | ||
| // This is identical to pkcs8 in crypto/x509. | ||
| type oneAsymmetricKey struct { | ||
| Version int | ||
| Algorithm pkix.AlgorithmIdentifier | ||
| PrivateKey []byte | ||
| } | ||
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| // curvePrivateKey is the innter type of the PrivateKey field of | ||
| // oneAsymmetricKey. | ||
| type curvePrivateKey []byte | ||
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| // MarshalEd25519PrivateKey returns a DER encdoing of the input private key as | ||
| // specified in https://tools.ietf.org/html/draft-ietf-curdle-pkix-04. | ||
| func MarshalEd25519PrivateKey(sk crypto.PrivateKey) ([]byte, error) { | ||
| priv, ok := sk.(ed25519.PrivateKey) | ||
| if !ok { | ||
| return nil, errEd25519WrongKeyType | ||
| } | ||
|
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| // Marshal the innter CurvePrivateKey. | ||
| curvePrivateKey, err := asn1.Marshal(priv.Seed()) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
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| // Marshal the OneAsymmetricKey. | ||
| asym := oneAsymmetricKey{ | ||
| Version: 0, | ||
| Algorithm: pkix.AlgorithmIdentifier{ | ||
| Algorithm: ed25519OID, | ||
| }, | ||
| PrivateKey: curvePrivateKey, | ||
| } | ||
| return asn1.Marshal(asym) | ||
| } | ||
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| // ParseEd25519PrivateKey returns the Ed25519 private key encoded by the input. | ||
| func ParseEd25519PrivateKey(der []byte) (crypto.PrivateKey, error) { | ||
| asym := new(oneAsymmetricKey) | ||
| if rest, err := asn1.Unmarshal(der, asym); err != nil { | ||
| return nil, err | ||
| } else if len(rest) > 0 { | ||
| return nil, errors.New("OneAsymmetricKey too long") | ||
| } | ||
|
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| // Check that the key type is correct. | ||
| if !asym.Algorithm.Algorithm.Equal(ed25519OID) { | ||
| return nil, errEd25519WrongID | ||
| } | ||
|
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| // Unmarshal the inner CurvePrivateKey. | ||
| seed := new(curvePrivateKey) | ||
| if rest, err := asn1.Unmarshal(asym.PrivateKey, seed); err != nil { | ||
| return nil, err | ||
| } else if len(rest) > 0 { | ||
| return nil, errors.New("CurvePrivateKey too long") | ||
| } | ||
|
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||
| return ed25519.NewKeyFromSeed(*seed), nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,99 @@ | ||
| package derhelpers | ||
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| import ( | ||
| "bytes" | ||
| "encoding/pem" | ||
| "testing" | ||
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| "golang.org/x/crypto/ed25519" | ||
| ) | ||
|
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| var testPubKey = `-----BEGIN PUBLIC KEY----- | ||
| MCowBQYDK2VwAyEAGb9ECWmEzf6FQbrBZ9w7lshQhqowtrbLDFw4rXAxZuE= | ||
| -----END PUBLIC KEY----- | ||
| ` | ||
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| var testPrivKey = `-----BEGIN PRIVATE KEY----- | ||
| MC4CAQAwBQYDK2VwBCIEINTuctv5E1hK1bbY8fdp+K06/nwoy/HU++CXqI9EdVhC | ||
| -----END PRIVATE KEY-----` | ||
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| func TestParseMarshalEd25519PublicKey(t *testing.T) { | ||
| block, rest := pem.Decode([]byte(testPubKey)) | ||
| if len(rest) > 0 { | ||
| t.Fatal("pem.Decode(); len(rest) > 0, want 0") | ||
| } | ||
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| pk, err := ParseEd25519PublicKey(block.Bytes) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
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| if pkLen := len(pk.(ed25519.PublicKey)); pkLen != 32 { | ||
| t.Fatalf("len(pk): got %d: want %d", pkLen, 32) | ||
| } | ||
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| der, err := MarshalEd25519PublicKey(pk) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
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| if !bytes.Equal(der, block.Bytes) { | ||
| t.Errorf("got %d bytes:\n%v \nwant %d bytes:\n%v", | ||
| len(der), der, len(block.Bytes), block.Bytes) | ||
| } | ||
| } | ||
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| func TestParseMarshalEd25519PrivateKey(t *testing.T) { | ||
| block, rest := pem.Decode([]byte(testPrivKey)) | ||
| if len(rest) > 0 { | ||
| t.Fatal("pem.Decode(); len(rest) > 0, want 0") | ||
| } | ||
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| sk, err := ParseEd25519PrivateKey(block.Bytes) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
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| if skLen := len(sk.(ed25519.PrivateKey)); skLen != 64 { | ||
| t.Fatalf("len(sk): got %d: want %d", skLen, 64) | ||
| } | ||
|
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| der, err := MarshalEd25519PrivateKey(sk) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
|
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| if !bytes.Equal(der, block.Bytes) { | ||
| t.Errorf("got %d bytes:\n%v \nwant %d bytes:\n%v", | ||
| len(der), der, len(block.Bytes), block.Bytes) | ||
| } | ||
| } | ||
|
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| func TestKeyPair(t *testing.T) { | ||
| block, rest := pem.Decode([]byte(testPrivKey)) | ||
| if len(rest) > 0 { | ||
| t.Fatal("pem.Decode(); len(rest) > 0, want 0") | ||
| } | ||
|
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| sk, err := ParseEd25519PrivateKey(block.Bytes) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
|
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| block, rest = pem.Decode([]byte(testPubKey)) | ||
| if len(rest) > 0 { | ||
| t.Fatal("pem.Decode(); len(rest) > 0, want 0") | ||
| } | ||
|
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| pub, err := ParseEd25519PublicKey(block.Bytes) | ||
| if err != nil { | ||
| t.Fatal(err) | ||
| } | ||
|
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| pk := pub.(ed25519.PublicKey) | ||
| pk2 := sk.(ed25519.PrivateKey).Public().(ed25519.PublicKey) | ||
| if !bytes.Equal(pk, pk2) { | ||
| t.Errorf("pk %d bytes:\n%v \nsk.Public() %d bytes:\n%v", | ||
| len(pk), pk, len(pk2), pk2) | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,3 @@ | ||
| -----BEGIN PRIVATE KEY----- | ||
| MC4CAQAwBQYDK2VwBCIEIEHfDC6M85b3uVU5GO82Y5D6Qkx5YehoCe2T1auTbTFN | ||
| -----END PRIVATE KEY----- |
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