github.com/mattn/go@v0.0.0-20171011075504-07f7db3ea99f/src/crypto/x509/pkcs1.go (about)

     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/rsa"
     9  	"encoding/asn1"
    10  	"errors"
    11  	"math/big"
    12  )
    13  
    14  // pkcs1PrivateKey is a structure which mirrors the PKCS#1 ASN.1 for an RSA private key.
    15  type pkcs1PrivateKey struct {
    16  	Version int
    17  	N       *big.Int
    18  	E       int
    19  	D       *big.Int
    20  	P       *big.Int
    21  	Q       *big.Int
    22  	// We ignore these values, if present, because rsa will calculate them.
    23  	Dp   *big.Int `asn1:"optional"`
    24  	Dq   *big.Int `asn1:"optional"`
    25  	Qinv *big.Int `asn1:"optional"`
    26  
    27  	AdditionalPrimes []pkcs1AdditionalRSAPrime `asn1:"optional,omitempty"`
    28  }
    29  
    30  type pkcs1AdditionalRSAPrime struct {
    31  	Prime *big.Int
    32  
    33  	// We ignore these values because rsa will calculate them.
    34  	Exp   *big.Int
    35  	Coeff *big.Int
    36  }
    37  
    38  // pkcs1PublicKey reflects the ASN.1 structure of a PKCS#1 public key.
    39  type pkcs1PublicKey struct {
    40  	N *big.Int
    41  	E int
    42  }
    43  
    44  // ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.
    45  func ParsePKCS1PrivateKey(der []byte) (*rsa.PrivateKey, error) {
    46  	var priv pkcs1PrivateKey
    47  	rest, err := asn1.Unmarshal(der, &priv)
    48  	if len(rest) > 0 {
    49  		return nil, asn1.SyntaxError{Msg: "trailing data"}
    50  	}
    51  	if err != nil {
    52  		return nil, err
    53  	}
    54  
    55  	if priv.Version > 1 {
    56  		return nil, errors.New("x509: unsupported private key version")
    57  	}
    58  
    59  	if priv.N.Sign() <= 0 || priv.D.Sign() <= 0 || priv.P.Sign() <= 0 || priv.Q.Sign() <= 0 {
    60  		return nil, errors.New("x509: private key contains zero or negative value")
    61  	}
    62  
    63  	key := new(rsa.PrivateKey)
    64  	key.PublicKey = rsa.PublicKey{
    65  		E: priv.E,
    66  		N: priv.N,
    67  	}
    68  
    69  	key.D = priv.D
    70  	key.Primes = make([]*big.Int, 2+len(priv.AdditionalPrimes))
    71  	key.Primes[0] = priv.P
    72  	key.Primes[1] = priv.Q
    73  	for i, a := range priv.AdditionalPrimes {
    74  		if a.Prime.Sign() <= 0 {
    75  			return nil, errors.New("x509: private key contains zero or negative prime")
    76  		}
    77  		key.Primes[i+2] = a.Prime
    78  		// We ignore the other two values because rsa will calculate
    79  		// them as needed.
    80  	}
    81  
    82  	err = key.Validate()
    83  	if err != nil {
    84  		return nil, err
    85  	}
    86  	key.Precompute()
    87  
    88  	return key, nil
    89  }
    90  
    91  // MarshalPKCS1PrivateKey converts a private key to ASN.1 DER encoded form.
    92  func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte {
    93  	key.Precompute()
    94  
    95  	version := 0
    96  	if len(key.Primes) > 2 {
    97  		version = 1
    98  	}
    99  
   100  	priv := pkcs1PrivateKey{
   101  		Version: version,
   102  		N:       key.N,
   103  		E:       key.PublicKey.E,
   104  		D:       key.D,
   105  		P:       key.Primes[0],
   106  		Q:       key.Primes[1],
   107  		Dp:      key.Precomputed.Dp,
   108  		Dq:      key.Precomputed.Dq,
   109  		Qinv:    key.Precomputed.Qinv,
   110  	}
   111  
   112  	priv.AdditionalPrimes = make([]pkcs1AdditionalRSAPrime, len(key.Precomputed.CRTValues))
   113  	for i, values := range key.Precomputed.CRTValues {
   114  		priv.AdditionalPrimes[i].Prime = key.Primes[2+i]
   115  		priv.AdditionalPrimes[i].Exp = values.Exp
   116  		priv.AdditionalPrimes[i].Coeff = values.Coeff
   117  	}
   118  
   119  	b, _ := asn1.Marshal(priv)
   120  	return b
   121  }