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dnssec_keygen.go
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dnssec_keygen.go
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package dns
import (
"crypto/dsa"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"math/big"
)
// Generate generates a DNSKEY of the given bit size.
// The public part is put inside the DNSKEY record.
// The Algorithm in the key must be set as this will define
// what kind of DNSKEY will be generated.
// The ECDSA algorithms imply a fixed keysize, in that case
// bits should be set to the size of the algorithm.
func (k *DNSKEY) Generate(bits int) (PrivateKey, error) {
switch k.Algorithm {
case DSA, DSANSEC3SHA1:
if bits != 1024 {
return nil, ErrKeySize
}
case RSAMD5, RSASHA1, RSASHA256, RSASHA1NSEC3SHA1:
if bits < 512 || bits > 4096 {
return nil, ErrKeySize
}
case RSASHA512:
if bits < 1024 || bits > 4096 {
return nil, ErrKeySize
}
case ECDSAP256SHA256:
if bits != 256 {
return nil, ErrKeySize
}
case ECDSAP384SHA384:
if bits != 384 {
return nil, ErrKeySize
}
}
switch k.Algorithm {
case DSA, DSANSEC3SHA1:
params := new(dsa.Parameters)
if err := dsa.GenerateParameters(params, rand.Reader, dsa.L1024N160); err != nil {
return nil, err
}
priv := new(dsa.PrivateKey)
priv.PublicKey.Parameters = *params
err := dsa.GenerateKey(priv, rand.Reader)
if err != nil {
return nil, err
}
k.setPublicKeyDSA(params.Q, params.P, params.G, priv.PublicKey.Y)
return (*DSAPrivateKey)(priv), nil
case RSAMD5, RSASHA1, RSASHA256, RSASHA512, RSASHA1NSEC3SHA1:
priv, err := rsa.GenerateKey(rand.Reader, bits)
if err != nil {
return nil, err
}
k.setPublicKeyRSA(priv.PublicKey.E, priv.PublicKey.N)
return (*RSAPrivateKey)(priv), nil
case ECDSAP256SHA256, ECDSAP384SHA384:
var c elliptic.Curve
switch k.Algorithm {
case ECDSAP256SHA256:
c = elliptic.P256()
case ECDSAP384SHA384:
c = elliptic.P384()
}
priv, err := ecdsa.GenerateKey(c, rand.Reader)
if err != nil {
return nil, err
}
k.setPublicKeyECDSA(priv.PublicKey.X, priv.PublicKey.Y)
return (*ECDSAPrivateKey)(priv), nil
default:
return nil, ErrAlg
}
}
// Set the public key (the value E and N)
func (k *DNSKEY) setPublicKeyRSA(_E int, _N *big.Int) bool {
if _E == 0 || _N == nil {
return false
}
buf := exponentToBuf(_E)
buf = append(buf, _N.Bytes()...)
k.PublicKey = toBase64(buf)
return true
}
// Set the public key for Elliptic Curves
func (k *DNSKEY) setPublicKeyECDSA(_X, _Y *big.Int) bool {
if _X == nil || _Y == nil {
return false
}
var intlen int
switch k.Algorithm {
case ECDSAP256SHA256:
intlen = 32
case ECDSAP384SHA384:
intlen = 48
}
k.PublicKey = toBase64(curveToBuf(_X, _Y, intlen))
return true
}
// Set the public key for DSA
func (k *DNSKEY) setPublicKeyDSA(_Q, _P, _G, _Y *big.Int) bool {
if _Q == nil || _P == nil || _G == nil || _Y == nil {
return false
}
buf := dsaToBuf(_Q, _P, _G, _Y)
k.PublicKey = toBase64(buf)
return true
}
// Set the public key (the values E and N) for RSA
// RFC 3110: Section 2. RSA Public KEY Resource Records
func exponentToBuf(_E int) []byte {
var buf []byte
i := big.NewInt(int64(_E))
if len(i.Bytes()) < 256 {
buf = make([]byte, 1)
buf[0] = uint8(len(i.Bytes()))
} else {
buf = make([]byte, 3)
buf[0] = 0
buf[1] = uint8(len(i.Bytes()) >> 8)
buf[2] = uint8(len(i.Bytes()))
}
buf = append(buf, i.Bytes()...)
return buf
}
// Set the public key for X and Y for Curve. The two
// values are just concatenated.
func curveToBuf(_X, _Y *big.Int, intlen int) []byte {
buf := intToBytes(_X, intlen)
buf = append(buf, intToBytes(_Y, intlen)...)
return buf
}
// Set the public key for X and Y for Curve. The two
// values are just concatenated.
func dsaToBuf(_Q, _P, _G, _Y *big.Int) []byte {
t := divRoundUp(divRoundUp(_G.BitLen(), 8)-64, 8)
buf := []byte{byte(t)}
buf = append(buf, intToBytes(_Q, 20)...)
buf = append(buf, intToBytes(_P, 64+t*8)...)
buf = append(buf, intToBytes(_G, 64+t*8)...)
buf = append(buf, intToBytes(_Y, 64+t*8)...)
return buf
}