Add PKCS8 marshaling to PKI (#3518)

builtin/logical/pki/cert_util.go

@@ -2,20 +2,23 @@ package pki
 
 import (
 	"bytes"
+	"crypto"
 	"crypto/ecdsa"
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/sha1"
 	"crypto/x509"
 	"crypto/x509/pkix"
 	"encoding/asn1"
+	"encoding/base64"
 	"encoding/pem"
 	"fmt"
 	"net"
 	"regexp"
 	"strings"
 	"time"
 
+	"github.com/hashicorp/errwrap"
 	"github.com/hashicorp/vault/helper/certutil"
 	"github.com/hashicorp/vault/helper/errutil"
 	"github.com/hashicorp/vault/helper/parseutil"
@@ -1183,3 +1186,66 @@ NameCheck:
 
 	return fmt.Errorf("name %q disallowed by CA's permitted DNS domains", badName)
 }
+
+func convertRespToPKCS8(resp *logical.Response) error {
+	privRaw, ok := resp.Data["private_key"]
+	if !ok {
+		return nil
+	}
+	priv, ok := privRaw.(string)
+	if !ok {
+		return fmt.Errorf("error converting response to pkcs8: could not parse original value as string")
+	}
+
+	privKeyTypeRaw, ok := resp.Data["private_key_type"]
+	if !ok {
+		return fmt.Errorf("error converting response to pkcs8: %q not found in response", "private_key_type")
+	}
+	privKeyType, ok := privKeyTypeRaw.(certutil.PrivateKeyType)
+	if !ok {
+		return fmt.Errorf("error converting response to pkcs8: could not parse original type value as string")
+	}
+
+	var keyData []byte
+	var pemUsed bool
+	var err error
+	var signer crypto.Signer
+
+	block, _ := pem.Decode([]byte(priv))
+	if block == nil {
+		keyData, err = base64.StdEncoding.DecodeString(priv)
+		if err != nil {
+			return errwrap.Wrapf("error converting response to pkcs8: error decoding original value: {{err}}", err)
+		}
+	} else {
+		keyData = block.Bytes
+		pemUsed = true
+	}
+
+	switch privKeyType {
+	case certutil.RSAPrivateKey:
+		signer, err = x509.ParsePKCS1PrivateKey(keyData)
+	case certutil.ECPrivateKey:
+		signer, err = x509.ParseECPrivateKey(keyData)
+	default:
+		return fmt.Errorf("unknown private key type %q", privKeyType)
+	}
+	if err != nil {
+		return errwrap.Wrapf("error converting response to pkcs8: error parsing previous key: {{err}}", err)
+	}
+
+	keyData, err = certutil.MarshalPKCS8PrivateKey(signer)
+	if err != nil {
+		return errwrap.Wrapf("error converting response to pkcs8: error marshaling pkcs8 key: {{err}}", err)
+	}
+
+	if pemUsed {
+		block.Type = "PRIVATE KEY"
+		block.Bytes = keyData
+		resp.Data["private_key"] = string(pem.EncodeToMemory(block))
+	} else {
+		resp.Data["private_key"] = base64.StdEncoding.EncodeToString(keyData)
+	}
+
+	return nil
+}

builtin/logical/pki/fields.go

@@ -22,6 +22,17 @@ key and issuing cert will be appended to the
 certificate pem. Defaults to "pem".`,
 	}
 
+	fields["private_key_format"] = &framework.FieldSchema{
+		Type:    framework.TypeString,
+		Default: "der",
+		Description: `Format for the returned private key.
+Generally the default will be controlled by the "format"
+parameter as either base64-encoded DER or PEM-encoded DER.
+However, this can be set to "pkcs8" to have the returned
+private key contain base64-encoded pkcs8 or PEM-encoded
+pkcs8 instead. Defaults to "der".`,
+	}
+
 	fields["ip_sans"] = &framework.FieldSchema{
 		Type: framework.TypeString,
 		Description: `The requested IP SANs, if any, in a

builtin/logical/pki/path_intermediate.go

@@ -106,6 +106,13 @@ func (b *backend) pathGenerateIntermediate(
 		}
 	}
 
+	if data.Get("private_key_format").(string) == "pkcs8" {
+		err = convertRespToPKCS8(resp)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	cb := &certutil.CertBundle{}
 	cb.PrivateKey = csrb.PrivateKey
 	cb.PrivateKeyType = csrb.PrivateKeyType

builtin/logical/pki/path_issue_sign.go

@@ -268,6 +268,13 @@ func (b *backend) pathIssueSignCert(
 		resp.Secret.TTL = parsedBundle.Certificate.NotAfter.Sub(time.Now())
 	}
 
+	if data.Get("private_key_format").(string) == "pkcs8" {
+		err = convertRespToPKCS8(resp)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	if !role.NoStore {
 		err = req.Storage.Put(&logical.StorageEntry{
 			Key:   "certs/" + normalizeSerial(cb.SerialNumber),

builtin/logical/pki/path_root.go

@@ -188,6 +188,13 @@ func (b *backend) pathCAGenerateRoot(
 		}
 	}
 
+	if data.Get("private_key_format").(string) == "pkcs8" {
+		err = convertRespToPKCS8(resp)
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	// Store it as the CA bundle
 	entry, err = logical.StorageEntryJSON("config/ca_bundle", cb)
 	if err != nil {

helper/certutil/pkcs8.go

@@ -0,0 +1,119 @@
+// 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 certutil
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"errors"
+	"fmt"
+)
+
+var (
+	oidNamedCurveP224 = asn1.ObjectIdentifier{1, 3, 132, 0, 33}
+	oidNamedCurveP256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 3, 1, 7}
+	oidNamedCurveP384 = asn1.ObjectIdentifier{1, 3, 132, 0, 34}
+	oidNamedCurveP521 = asn1.ObjectIdentifier{1, 3, 132, 0, 35}
+
+	oidPublicKeyRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
+	oidPublicKeyDSA   = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 1}
+	oidPublicKeyECDSA = asn1.ObjectIdentifier{1, 2, 840, 10045, 2, 1}
+)
+
+// 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.
+}
+
+type ecPrivateKey struct {
+	Version       int
+	PrivateKey    []byte
+	NamedCurveOID asn1.ObjectIdentifier `asn1:"optional,explicit,tag:0"`
+	PublicKey     asn1.BitString        `asn1:"optional,explicit,tag:1"`
+}
+
+// MarshalPKCS8PrivateKey converts a private key to PKCS#8 encoded form.
+// The following key types are supported: *rsa.PrivateKey, *ecdsa.PublicKey.
+// Unsupported key types result in an error.
+//
+// See RFC 5208.
+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 = x509.MarshalPKCS1PrivateKey(k)
+
+	case *ecdsa.PrivateKey:
+		oid, ok := oidFromNamedCurve(k.Curve)
+		if !ok {
+			return nil, errors.New("x509: unknown curve while marshalling 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())
+		}
+
+	default:
+		return nil, fmt.Errorf("x509: unknown key type while marshalling PKCS#8: %T", key)
+	}
+
+	return asn1.Marshal(privKey)
+}
+
+func oidFromNamedCurve(curve elliptic.Curve) (asn1.ObjectIdentifier, bool) {
+	switch curve {
+	case elliptic.P224():
+		return oidNamedCurveP224, true
+	case elliptic.P256():
+		return oidNamedCurveP256, true
+	case elliptic.P384():
+		return oidNamedCurveP384, true
+	case elliptic.P521():
+		return oidNamedCurveP521, true
+	}
+
+	return nil, false
+}
+
+// marshalECPrivateKey marshals an EC private key into ASN.1, DER format and
+// sets the curve ID to the given OID, or omits it if OID is nil.
+func marshalECPrivateKeyWithOID(key *ecdsa.PrivateKey, oid asn1.ObjectIdentifier) ([]byte, error) {
+	privateKeyBytes := key.D.Bytes()
+	paddedPrivateKey := make([]byte, (key.Curve.Params().N.BitLen()+7)/8)
+	copy(paddedPrivateKey[len(paddedPrivateKey)-len(privateKeyBytes):], privateKeyBytes)
+
+	return asn1.Marshal(ecPrivateKey{
+		Version:       1,
+		PrivateKey:    paddedPrivateKey,
+		NamedCurveOID: oid,
+		PublicKey:     asn1.BitString{Bytes: elliptic.Marshal(key.Curve, key.X, key.Y)},
+	})
+}

helper/certutil/pkcs8_test.go

@@ -0,0 +1,110 @@
+// 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 certutil
+
+import (
+	"bytes"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/hex"
+	"reflect"
+	"testing"
+)
+
+// Generated using:
+//   openssl genrsa 1024 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8RSAPrivateKeyHex = `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`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp224r1 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8P224PrivateKeyHex = `3078020100301006072a8648ce3d020106052b810400210461305f020101041cca3d72b3e88fed2684576dad9b80a9180363a5424986900e3abcab3fa13c033a0004f8f2a6372872a4e61263ed893afb919576a4cacfecd6c081a2cbc76873cf4ba8530703c6042b3a00e2205087e87d2435d2e339e25702fae1`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp256r1 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8P256PrivateKeyHex = `308187020100301306072a8648ce3d020106082a8648ce3d030107046d306b0201010420dad6b2f49ca774c36d8ae9517e935226f667c929498f0343d2424d0b9b591b43a14403420004b9c9b90095476afe7b860d8bd43568cab7bcb2eed7b8bf2fa0ce1762dd20b04193f859d2d782b1e4cbfd48492f1f533113a6804903f292258513837f07fda735`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp384r1 | openssl pkcs8 -topk8 -nocrypt
+var pkcs8P384PrivateKeyHex = `3081b6020100301006072a8648ce3d020106052b8104002204819e30819b02010104309bf832f6aaaeacb78ce47ffb15e6fd0fd48683ae79df6eca39bfb8e33829ac94aa29d08911568684c2264a08a4ceb679a164036200049070ad4ed993c7770d700e9f6dc2baa83f63dd165b5507f98e8ff29b5d2e78ccbe05c8ddc955dbf0f7497e8222cfa49314fe4e269459f8e880147f70d785e530f2939e4bf9f838325bb1a80ad4cf59272ae0e5efe9a9dc33d874492596304bd3`
+
+// Generated using:
+//   openssl ecparam -genkey -name secp521r1 | openssl pkcs8 -topk8 -nocrypt
+//
+// Note that OpenSSL will truncate the private key if it can (i.e. it emits it
+// like an integer, even though it's an OCTET STRING field). Thus if you
+// regenerate this you may, randomly, find that it's a byte shorter than
+// expected and the Go test will fail to recreate it exactly.
+var pkcs8P521PrivateKeyHex = `3081ee020100301006072a8648ce3d020106052b810400230481d63081d3020101044200cfe0b87113a205cf291bb9a8cd1a74ac6c7b2ebb8199aaa9a5010d8b8012276fa3c22ac913369fa61beec2a3b8b4516bc049bde4fb3b745ac11b56ab23ac52e361a1818903818600040138f75acdd03fbafa4f047a8e4b272ba9d555c667962b76f6f232911a5786a0964e5edea6bd21a6f8725720958de049c6e3e6661c1c91b227cebee916c0319ed6ca003db0a3206d372229baf9dd25d868bf81140a518114803ce40c1855074d68c4e9dab9e65efba7064c703b400f1767f217dac82715ac1f6d88c74baf47a7971de4ea`
+
+func TestPKCS8(t *testing.T) {
+	tests := []struct {
+		name    string
+		keyHex  string
+		keyType reflect.Type
+		curve   elliptic.Curve
+	}{
+		{
+			name:    "RSA private key",
+			keyHex:  pkcs8RSAPrivateKeyHex,
+			keyType: reflect.TypeOf(&rsa.PrivateKey{}),
+		},
+		{
+			name:    "P-224 private key",
+			keyHex:  pkcs8P224PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P224(),
+		},
+		{
+			name:    "P-256 private key",
+			keyHex:  pkcs8P256PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P256(),
+		},
+		{
+			name:    "P-384 private key",
+			keyHex:  pkcs8P384PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P384(),
+		},
+		{
+			name:    "P-521 private key",
+			keyHex:  pkcs8P521PrivateKeyHex,
+			keyType: reflect.TypeOf(&ecdsa.PrivateKey{}),
+			curve:   elliptic.P521(),
+		},
+	}
+
+	for _, test := range tests {
+		derBytes, err := hex.DecodeString(test.keyHex)
+		if err != nil {
+			t.Errorf("%s: failed to decode hex: %s", test.name, err)
+			continue
+		}
+		privKey, err := x509.ParsePKCS8PrivateKey(derBytes)
+		if err != nil {
+			t.Errorf("%s: failed to decode PKCS#8: %s", test.name, err)
+			continue
+		}
+		if reflect.TypeOf(privKey) != test.keyType {
+			t.Errorf("%s: decoded PKCS#8 returned unexpected key type: %T", test.name, privKey)
+			continue
+		}
+		if ecKey, isEC := privKey.(*ecdsa.PrivateKey); isEC && ecKey.Curve != test.curve {
+			t.Errorf("%s: decoded PKCS#8 returned unexpected curve %#v", test.name, ecKey.Curve)
+			continue
+		}
+		reserialised, err := MarshalPKCS8PrivateKey(privKey)
+		if err != nil {
+			t.Errorf("%s: failed to marshal into PKCS#8: %s", test.name, err)
+			continue
+		}
+		if !bytes.Equal(derBytes, reserialised) {
+			t.Errorf("%s: marshalled PKCS#8 didn't match original: got %x, want %x", test.name, reserialised, derBytes)
+			continue
+		}
+	}
+}