github.com/sean-/go@v0.0.0-20151219100004-97f854cd7bb6/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  // ParsePKCS1PrivateKey returns an RSA private key from its ASN.1 PKCS#1 DER encoded form.
    39  func ParsePKCS1PrivateKey(der []byte) (key *rsa.PrivateKey, err error) {
    40  	var priv pkcs1PrivateKey
    41  	rest, err := asn1.Unmarshal(der, &priv)
    42  	if len(rest) > 0 {
    43  		err = asn1.SyntaxError{Msg: "trailing data"}
    44  		return
    45  	}
    46  	if err != nil {
    47  		return
    48  	}
    49  
    50  	if priv.Version > 1 {
    51  		return nil, errors.New("x509: unsupported private key version")
    52  	}
    53  
    54  	if priv.N.Sign() <= 0 || priv.D.Sign() <= 0 || priv.P.Sign() <= 0 || priv.Q.Sign() <= 0 {
    55  		return nil, errors.New("x509: private key contains zero or negative value")
    56  	}
    57  
    58  	key = new(rsa.PrivateKey)
    59  	key.PublicKey = rsa.PublicKey{
    60  		E: priv.E,
    61  		N: priv.N,
    62  	}
    63  
    64  	key.D = priv.D
    65  	key.Primes = make([]*big.Int, 2+len(priv.AdditionalPrimes))
    66  	key.Primes[0] = priv.P
    67  	key.Primes[1] = priv.Q
    68  	for i, a := range priv.AdditionalPrimes {
    69  		if a.Prime.Sign() <= 0 {
    70  			return nil, errors.New("x509: private key contains zero or negative prime")
    71  		}
    72  		key.Primes[i+2] = a.Prime
    73  		// We ignore the other two values because rsa will calculate
    74  		// them as needed.
    75  	}
    76  
    77  	err = key.Validate()
    78  	if err != nil {
    79  		return nil, err
    80  	}
    81  	key.Precompute()
    82  
    83  	return
    84  }
    85  
    86  // MarshalPKCS1PrivateKey converts a private key to ASN.1 DER encoded form.
    87  func MarshalPKCS1PrivateKey(key *rsa.PrivateKey) []byte {
    88  	key.Precompute()
    89  
    90  	version := 0
    91  	if len(key.Primes) > 2 {
    92  		version = 1
    93  	}
    94  
    95  	priv := pkcs1PrivateKey{
    96  		Version: version,
    97  		N:       key.N,
    98  		E:       key.PublicKey.E,
    99  		D:       key.D,
   100  		P:       key.Primes[0],
   101  		Q:       key.Primes[1],
   102  		Dp:      key.Precomputed.Dp,
   103  		Dq:      key.Precomputed.Dq,
   104  		Qinv:    key.Precomputed.Qinv,
   105  	}
   106  
   107  	priv.AdditionalPrimes = make([]pkcs1AdditionalRSAPrime, len(key.Precomputed.CRTValues))
   108  	for i, values := range key.Precomputed.CRTValues {
   109  		priv.AdditionalPrimes[i].Prime = key.Primes[2+i]
   110  		priv.AdditionalPrimes[i].Exp = values.Exp
   111  		priv.AdditionalPrimes[i].Coeff = values.Coeff
   112  	}
   113  
   114  	b, _ := asn1.Marshal(priv)
   115  	return b
   116  }
   117  
   118  // rsaPublicKey reflects the ASN.1 structure of a PKCS#1 public key.
   119  type rsaPublicKey struct {
   120  	N *big.Int
   121  	E int
   122  }