crypto/x509: add function to marshal EC private keys.

This complements the parsing function that we already have.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/10426043

diff --git a/src/pkg/crypto/x509/sec1.go b/src/pkg/crypto/x509/sec1.go
index 3a0e29a03e3dbf45ca552164e1eb36480e9464ab..7de66754eeb082a0d3984cf571a5e849c53249a3 100644 (file)
--- a/src/pkg/crypto/x509/sec1.go
+++ b/src/pkg/crypto/x509/sec1.go
@@ -33,6 +33,20 @@ func ParseECPrivateKey(der []byte) (key *ecdsa.PrivateKey, err error) {
        return parseECPrivateKey(nil, der)
 }
 
+// MarshalECPrivateKey marshals an EC private key into ASN.1, DER format.
+func MarshalECPrivateKey(key *ecdsa.PrivateKey) ([]byte, error) {
+       oid, ok := oidFromNamedCurve(key.Curve)
+       if !ok {
+               return nil, errors.New("x509: unknown elliptic curve")
+       }
+       return asn1.Marshal(ecPrivateKey{
+               Version:       1,
+               PrivateKey:    key.D.Bytes(),
+               NamedCurveOID: oid,
+               PublicKey:     asn1.BitString{Bytes: elliptic.Marshal(key.Curve, key.X, key.Y)},
+       })
+}
+
 // parseECPrivateKey parses an ASN.1 Elliptic Curve Private Key Structure.
 // The OID for the named curve may be provided from another source (such as
 // the PKCS8 container) - if it is provided then use this instead of the OID

diff --git a/src/pkg/crypto/x509/sec1_test.go b/src/pkg/crypto/x509/sec1_test.go
index 7135699d28325ff78187c57aad22ee6479957547..95f18e77de0e4d58aaa10e98d42b8c3657029c28 100644 (file)
--- a/src/pkg/crypto/x509/sec1_test.go
+++ b/src/pkg/crypto/x509/sec1_test.go
@@ -5,6 +5,7 @@
 package x509
 
 import (
+       "bytes"
        "encoding/hex"
        "testing"
 )
@@ -15,8 +16,15 @@ var ecPrivateKeyHex = `3081a40201010430bdb9839c08ee793d1157886a7a758a3c8b2a17a4d
 
 func TestParseECPrivateKey(t *testing.T) {
        derBytes, _ := hex.DecodeString(ecPrivateKeyHex)
-       _, err := ParseECPrivateKey(derBytes)
+       key, err := ParseECPrivateKey(derBytes)
        if err != nil {
                t.Errorf("failed to decode EC private key: %s", err)
        }
+       serialized, err := MarshalECPrivateKey(key)
+       if err != nil {
+               t.Fatalf("failed to encode EC private key: %s", err)
+       }
+       if !bytes.Equal(serialized, derBytes) {
+               t.Fatalf("serialized key differs: got %x, want %x", serialized, derBytes)
+       }
 }