pkcs8.go

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package x509
     6  
     7  import (
     8  	"crypto/ecdsa"
     9  	"crypto/ed25519"
    10  	"crypto/rsa"
    11  	"crypto/x509/pkix"
    12  	"encoding/asn1"
    13  	"errors"
    14  	"fmt"
    15  )
    16  
    17  // pkcs8 reflects an ASN.1, PKCS #8 PrivateKey. See
    18  // ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-8/pkcs-8v1_2.asn
    19  // and RFC 5208.
    20  type pkcs8 struct {
    21  	Version    int
    22  	Algo       pkix.AlgorithmIdentifier
    23  	PrivateKey []byte
    24  	// optional attributes omitted.
    25  }
    26  
    27  // ParsePKCS8PrivateKey parses an unencrypted private key in PKCS #8, ASN.1 DER form.
    28  //
    29  // It returns a *rsa.PrivateKey, a *ecdsa.PrivateKey, or a ed25519.PrivateKey.
    30  // More types might be supported in the future.
    31  //
    32  // This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
    33  func ParsePKCS8PrivateKey(der []byte) (key any, err error) {
    34  	var privKey pkcs8
    35  	if _, err := asn1.Unmarshal(der, &privKey); err != nil {
    36  		if _, err := asn1.Unmarshal(der, &ecPrivateKey{}); err == nil {
    37  			return nil, errors.New("x509: failed to parse private key (use ParseECPrivateKey instead for this key format)")
    38  		}
    39  		if _, err := asn1.Unmarshal(der, &pkcs1PrivateKey{}); err == nil {
    40  			return nil, errors.New("x509: failed to parse private key (use ParsePKCS1PrivateKey instead for this key format)")
    41  		}
    42  		return nil, err
    43  	}
    44  	switch {
    45  	case privKey.Algo.Algorithm.Equal(oidPublicKeyRSA):
    46  		key, err = ParsePKCS1PrivateKey(privKey.PrivateKey)
    47  		if err != nil {
    48  			return nil, errors.New("x509: failed to parse RSA private key embedded in PKCS#8: " + err.Error())
    49  		}
    50  		return key, nil
    51  
    52  	case privKey.Algo.Algorithm.Equal(oidPublicKeyECDSA):
    53  		bytes := privKey.Algo.Parameters.FullBytes
    54  		namedCurveOID := new(asn1.ObjectIdentifier)
    55  		if _, err := asn1.Unmarshal(bytes, namedCurveOID); err != nil {
    56  			namedCurveOID = nil
    57  		}
    58  		key, err = parseECPrivateKey(namedCurveOID, privKey.PrivateKey)
    59  		if err != nil {
    60  			return nil, errors.New("x509: failed to parse EC private key embedded in PKCS#8: " + err.Error())
    61  		}
    62  		return key, nil
    63  
    64  	case privKey.Algo.Algorithm.Equal(oidPublicKeyEd25519):
    65  		if l := len(privKey.Algo.Parameters.FullBytes); l != 0 {
    66  			return nil, errors.New("x509: invalid Ed25519 private key parameters")
    67  		}
    68  		var curvePrivateKey []byte
    69  		if _, err := asn1.Unmarshal(privKey.PrivateKey, &curvePrivateKey); err != nil {
    70  			return nil, fmt.Errorf("x509: invalid Ed25519 private key: %v", err)
    71  		}
    72  		if l := len(curvePrivateKey); l != ed25519.SeedSize {
    73  			return nil, fmt.Errorf("x509: invalid Ed25519 private key length: %d", l)
    74  		}
    75  		return ed25519.NewKeyFromSeed(curvePrivateKey), nil
    76  
    77  	default:
    78  		return nil, fmt.Errorf("x509: PKCS#8 wrapping contained private key with unknown algorithm: %v", privKey.Algo.Algorithm)
    79  	}
    80  }
    81  
    82  // MarshalPKCS8PrivateKey converts a private key to PKCS #8, ASN.1 DER form.
    83  //
    84  // The following key types are currently supported: *rsa.PrivateKey, *ecdsa.PrivateKey
    85  // and ed25519.PrivateKey. Unsupported key types result in an error.
    86  //
    87  // This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
    88  func MarshalPKCS8PrivateKey(key any) ([]byte, error) {
    89  	var privKey pkcs8
    90  
    91  	switch k := key.(type) {
    92  	case *rsa.PrivateKey:
    93  		privKey.Algo = pkix.AlgorithmIdentifier{
    94  			Algorithm:  oidPublicKeyRSA,
    95  			Parameters: asn1.NullRawValue,
    96  		}
    97  		privKey.PrivateKey = MarshalPKCS1PrivateKey(k)
    98  
    99  	case *ecdsa.PrivateKey:
   100  		oid, ok := oidFromNamedCurve(k.Curve)
   101  		if !ok {
   102  			return nil, errors.New("x509: unknown curve while marshaling to PKCS#8")
   103  		}
   104  
   105  		oidBytes, err := asn1.Marshal(oid)
   106  		if err != nil {
   107  			return nil, errors.New("x509: failed to marshal curve OID: " + err.Error())
   108  		}
   109  
   110  		privKey.Algo = pkix.AlgorithmIdentifier{
   111  			Algorithm: oidPublicKeyECDSA,
   112  			Parameters: asn1.RawValue{
   113  				FullBytes: oidBytes,
   114  			},
   115  		}
   116  
   117  		if privKey.PrivateKey, err = marshalECPrivateKeyWithOID(k, nil); err != nil {
   118  			return nil, errors.New("x509: failed to marshal EC private key while building PKCS#8: " + err.Error())
   119  		}
   120  
   121  	case ed25519.PrivateKey:
   122  		privKey.Algo = pkix.AlgorithmIdentifier{
   123  			Algorithm: oidPublicKeyEd25519,
   124  		}
   125  		curvePrivateKey, err := asn1.Marshal(k.Seed())
   126  		if err != nil {
   127  			return nil, fmt.Errorf("x509: failed to marshal private key: %v", err)
   128  		}
   129  		privKey.PrivateKey = curvePrivateKey
   130  
   131  	default:
   132  		return nil, fmt.Errorf("x509: unknown key type while marshaling PKCS#8: %T", key)
   133  	}
   134  
   135  	return asn1.Marshal(privKey)
   136  }
   137
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