Add fork of Go 1.15-dev's crypto/x509

Snapshotted from Go commit 619c7a48a38b28b521591b490fd14ccb7ea5e821
(https://go-review.googlesource.com/c/go/+/229762,
"crypto/x509: add x509omitbundledroots build tag to not embed roots")

With 975c01342a25899962969833d8b2873dc8856a4f
(https://go-review.googlesource.com/c/go/+/220721) removed, because it
depends on other stuff in Go std that doesn't yet exist in a Go
release.

Also, add a subset fork of Go's internal/testenv, for use by x509's tests.

tempfork/x509/pkcs8.go

@@ -0,0 +1,136 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package x509
+
+import (
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/rsa"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+)
+
+// pkcs8 reflects an ASN.1, PKCS#8 PrivateKey. See
+// ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-8/pkcs-8v1_2.asn
+// and RFC 5208.
+type pkcs8 struct {
+	Version    int
+	Algo       pkix.AlgorithmIdentifier
+	PrivateKey []byte
+	// optional attributes omitted.
+}
+
+// ParsePKCS8PrivateKey parses an unencrypted private key in PKCS#8, ASN.1 DER form.
+//
+// It returns a *rsa.PrivateKey, a *ecdsa.PrivateKey, or a ed25519.PrivateKey.
+// More types might be supported in the future.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
+func ParsePKCS8PrivateKey(der []byte) (key interface{}, err error) {
+	var privKey pkcs8
+	if _, err := asn1.Unmarshal(der, &privKey); err != nil {
+		if _, err := asn1.Unmarshal(der, &ecPrivateKey{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParseECPrivateKey instead for this key format)")
+		}
+		if _, err := asn1.Unmarshal(der, &pkcs1PrivateKey{}); err == nil {
+			return nil, errors.New("x509: failed to parse private key (use ParsePKCS1PrivateKey instead for this key format)")
+		}
+		return nil, err
+	}
+	switch {
+	case privKey.Algo.Algorithm.Equal(oidPublicKeyRSA):
+		key, err = ParsePKCS1PrivateKey(privKey.PrivateKey)
+		if err != nil {
+			return nil, errors.New("x509: failed to parse RSA private key embedded in PKCS#8: " + err.Error())
+		}
+		return key, nil
+
+	case privKey.Algo.Algorithm.Equal(oidPublicKeyECDSA):
+		bytes := privKey.Algo.Parameters.FullBytes
+		namedCurveOID := new(asn1.ObjectIdentifier)
+		if _, err := asn1.Unmarshal(bytes, namedCurveOID); err != nil {
+			namedCurveOID = nil
+		}
+		key, err = parseECPrivateKey(namedCurveOID, privKey.PrivateKey)
+		if err != nil {
+			return nil, errors.New("x509: failed to parse EC private key embedded in PKCS#8: " + err.Error())
+		}
+		return key, nil
+
+	case privKey.Algo.Algorithm.Equal(oidPublicKeyEd25519):
+		if l := len(privKey.Algo.Parameters.FullBytes); l != 0 {
+			return nil, errors.New("x509: invalid Ed25519 private key parameters")
+		}
+		var curvePrivateKey []byte
+		if _, err := asn1.Unmarshal(privKey.PrivateKey, &curvePrivateKey); err != nil {
+			return nil, fmt.Errorf("x509: invalid Ed25519 private key: %v", err)
+		}
+		if l := len(curvePrivateKey); l != ed25519.SeedSize {
+			return nil, fmt.Errorf("x509: invalid Ed25519 private key length: %d", l)
+		}
+		return ed25519.NewKeyFromSeed(curvePrivateKey), nil
+
+	default:
+		return nil, fmt.Errorf("x509: PKCS#8 wrapping contained private key with unknown algorithm: %v", privKey.Algo.Algorithm)
+	}
+}
+
+// MarshalPKCS8PrivateKey converts a private key to PKCS#8, ASN.1 DER form.
+//
+// The following key types are currently supported: *rsa.PrivateKey, *ecdsa.PrivateKey
+// and ed25519.PrivateKey. Unsupported key types result in an error.
+//
+// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
+func MarshalPKCS8PrivateKey(key interface{}) ([]byte, error) {
+	var privKey pkcs8
+
+	switch k := key.(type) {
+	case *rsa.PrivateKey:
+		privKey.Algo = pkix.AlgorithmIdentifier{
+			Algorithm:  oidPublicKeyRSA,
+			Parameters: asn1.NullRawValue,
+		}
+		privKey.PrivateKey = MarshalPKCS1PrivateKey(k)
+
+	case *ecdsa.PrivateKey:
+		oid, ok := oidFromNamedCurve(k.Curve)
+		if !ok {
+			return nil, errors.New("x509: unknown curve while marshaling to PKCS#8")
+		}
+
+		oidBytes, err := asn1.Marshal(oid)
+		if err != nil {
+			return nil, errors.New("x509: failed to marshal curve OID: " + err.Error())
+		}
+
+		privKey.Algo = pkix.AlgorithmIdentifier{
+			Algorithm: oidPublicKeyECDSA,
+			Parameters: asn1.RawValue{
+				FullBytes: oidBytes,
+			},
+		}
+
+		if privKey.PrivateKey, err = marshalECPrivateKeyWithOID(k, nil); err != nil {
+			return nil, errors.New("x509: failed to marshal EC private key while building PKCS#8: " + err.Error())
+		}
+
+	case ed25519.PrivateKey:
+		privKey.Algo = pkix.AlgorithmIdentifier{
+			Algorithm: oidPublicKeyEd25519,
+		}
+		curvePrivateKey, err := asn1.Marshal(k.Seed())
+		if err != nil {
+			return nil, fmt.Errorf("x509: failed to marshal private key: %v", err)
+		}
+		privKey.PrivateKey = curvePrivateKey
+
+	default:
+		return nil, fmt.Errorf("x509: unknown key type while marshaling PKCS#8: %T", key)
+	}
+
+	return asn1.Marshal(privKey)
+}