86 lines
2.6 KiB
Go
86 lines
2.6 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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// START CT CHANGES
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"src.agwa.name/ctwatch/ct/asn1"
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// START CT CHANGES
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"errors"
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"fmt"
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"math/big"
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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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// RFC5915
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// SEC1 - http://www.secg.org/download/aid-780/sec1-v2.pdf
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// Per RFC5915 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) (key *ecdsa.PrivateKey, err 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 asn1.Marshal(ecPrivateKey{
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Version: 1,
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PrivateKey: key.D.Bytes(),
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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 curve elliptic.Curve
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if namedCurveOID != nil {
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curve = namedCurveFromOID(*namedCurveOID)
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} else {
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curve = namedCurveFromOID(privKey.NamedCurveOID)
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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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if k.Cmp(curve.Params().N) >= 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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priv.X, priv.Y = curve.ScalarBaseMult(privKey.PrivateKey)
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return priv, nil
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}
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