114 lines
3.7 KiB
Go
114 lines
3.7 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package x509
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import (
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"crypto/ecdsa"
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"crypto/elliptic"
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"errors"
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"fmt"
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"math/big"
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"github.com/google/certificate-transparency-go/asn1"
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)
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const ecPrivKeyVersion = 1
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// ecPrivateKey reflects an ASN.1 Elliptic Curve Private Key Structure.
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// References:
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// RFC 5915
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// SEC1 - http://www.secg.org/sec1-v2.pdf
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// Per RFC 5915 the NamedCurveOID is marked as ASN.1 OPTIONAL, however in
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// most cases it is not.
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type ecPrivateKey struct {
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Version int
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PrivateKey []byte
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NamedCurveOID asn1.ObjectIdentifier `asn1:"optional,explicit,tag:0"`
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PublicKey asn1.BitString `asn1:"optional,explicit,tag:1"`
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}
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// ParseECPrivateKey parses an ASN.1 Elliptic Curve Private Key Structure.
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func ParseECPrivateKey(der []byte) (*ecdsa.PrivateKey, error) {
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return parseECPrivateKey(nil, der)
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}
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// MarshalECPrivateKey marshals an EC private key into ASN.1, DER format.
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func MarshalECPrivateKey(key *ecdsa.PrivateKey) ([]byte, error) {
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oid, ok := OIDFromNamedCurve(key.Curve)
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if !ok {
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return nil, errors.New("x509: unknown elliptic curve")
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}
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return marshalECPrivateKeyWithOID(key, oid)
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}
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// marshalECPrivateKey marshals an EC private key into ASN.1, DER format and
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// sets the curve ID to the given OID, or omits it if OID is nil.
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func marshalECPrivateKeyWithOID(key *ecdsa.PrivateKey, oid asn1.ObjectIdentifier) ([]byte, error) {
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privateKeyBytes := key.D.Bytes()
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paddedPrivateKey := make([]byte, (key.Curve.Params().N.BitLen()+7)/8)
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copy(paddedPrivateKey[len(paddedPrivateKey)-len(privateKeyBytes):], privateKeyBytes)
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return asn1.Marshal(ecPrivateKey{
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Version: 1,
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PrivateKey: paddedPrivateKey,
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NamedCurveOID: oid,
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PublicKey: asn1.BitString{Bytes: elliptic.Marshal(key.Curve, key.X, key.Y)},
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})
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}
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// parseECPrivateKey parses an ASN.1 Elliptic Curve Private Key Structure.
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// The OID for the named curve may be provided from another source (such as
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// the PKCS8 container) - if it is provided then use this instead of the OID
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// that may exist in the EC private key structure.
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func parseECPrivateKey(namedCurveOID *asn1.ObjectIdentifier, der []byte) (key *ecdsa.PrivateKey, err error) {
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var privKey ecPrivateKey
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if _, err := asn1.Unmarshal(der, &privKey); err != nil {
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return nil, errors.New("x509: failed to parse EC private key: " + err.Error())
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}
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if privKey.Version != ecPrivKeyVersion {
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return nil, fmt.Errorf("x509: unknown EC private key version %d", privKey.Version)
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}
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var nfe NonFatalErrors
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var curve elliptic.Curve
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if namedCurveOID != nil {
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curve = namedCurveFromOID(*namedCurveOID, &nfe)
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} else {
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curve = namedCurveFromOID(privKey.NamedCurveOID, &nfe)
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}
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if curve == nil {
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return nil, errors.New("x509: unknown elliptic curve")
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}
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k := new(big.Int).SetBytes(privKey.PrivateKey)
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curveOrder := curve.Params().N
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if k.Cmp(curveOrder) >= 0 {
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return nil, errors.New("x509: invalid elliptic curve private key value")
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}
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priv := new(ecdsa.PrivateKey)
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priv.Curve = curve
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priv.D = k
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privateKey := make([]byte, (curveOrder.BitLen()+7)/8)
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// Some private keys have leading zero padding. This is invalid
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// according to [SEC1], but this code will ignore it.
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for len(privKey.PrivateKey) > len(privateKey) {
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if privKey.PrivateKey[0] != 0 {
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return nil, errors.New("x509: invalid private key length")
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}
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privKey.PrivateKey = privKey.PrivateKey[1:]
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}
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// Some private keys remove all leading zeros, this is also invalid
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// according to [SEC1] but since OpenSSL used to do this, we ignore
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// this too.
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copy(privateKey[len(privateKey)-len(privKey.PrivateKey):], privKey.PrivateKey)
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priv.X, priv.Y = curve.ScalarBaseMult(privateKey)
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return priv, nil
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}
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