1package dns
2
3import (
4	"crypto"
5	"crypto/dsa"
6	"crypto/ecdsa"
7	"crypto/rsa"
8	"math/big"
9	"strconv"
10
11	"golang.org/x/crypto/ed25519"
12)
13
14const format = "Private-key-format: v1.3\n"
15
16var bigIntOne = big.NewInt(1)
17
18// PrivateKeyString converts a PrivateKey to a string. This string has the same
19// format as the private-key-file of BIND9 (Private-key-format: v1.3).
20// It needs some info from the key (the algorithm), so its a method of the DNSKEY
21// It supports rsa.PrivateKey, ecdsa.PrivateKey and dsa.PrivateKey
22func (r *DNSKEY) PrivateKeyString(p crypto.PrivateKey) string {
23	algorithm := strconv.Itoa(int(r.Algorithm))
24	algorithm += " (" + AlgorithmToString[r.Algorithm] + ")"
25
26	switch p := p.(type) {
27	case *rsa.PrivateKey:
28		modulus := toBase64(p.PublicKey.N.Bytes())
29		e := big.NewInt(int64(p.PublicKey.E))
30		publicExponent := toBase64(e.Bytes())
31		privateExponent := toBase64(p.D.Bytes())
32		prime1 := toBase64(p.Primes[0].Bytes())
33		prime2 := toBase64(p.Primes[1].Bytes())
34		// Calculate Exponent1/2 and Coefficient as per: http://en.wikipedia.org/wiki/RSA#Using_the_Chinese_remainder_algorithm
35		// and from: http://code.google.com/p/go/issues/detail?id=987
36		p1 := new(big.Int).Sub(p.Primes[0], bigIntOne)
37		q1 := new(big.Int).Sub(p.Primes[1], bigIntOne)
38		exp1 := new(big.Int).Mod(p.D, p1)
39		exp2 := new(big.Int).Mod(p.D, q1)
40		coeff := new(big.Int).ModInverse(p.Primes[1], p.Primes[0])
41
42		exponent1 := toBase64(exp1.Bytes())
43		exponent2 := toBase64(exp2.Bytes())
44		coefficient := toBase64(coeff.Bytes())
45
46		return format +
47			"Algorithm: " + algorithm + "\n" +
48			"Modulus: " + modulus + "\n" +
49			"PublicExponent: " + publicExponent + "\n" +
50			"PrivateExponent: " + privateExponent + "\n" +
51			"Prime1: " + prime1 + "\n" +
52			"Prime2: " + prime2 + "\n" +
53			"Exponent1: " + exponent1 + "\n" +
54			"Exponent2: " + exponent2 + "\n" +
55			"Coefficient: " + coefficient + "\n"
56
57	case *ecdsa.PrivateKey:
58		var intlen int
59		switch r.Algorithm {
60		case ECDSAP256SHA256:
61			intlen = 32
62		case ECDSAP384SHA384:
63			intlen = 48
64		}
65		private := toBase64(intToBytes(p.D, intlen))
66		return format +
67			"Algorithm: " + algorithm + "\n" +
68			"PrivateKey: " + private + "\n"
69
70	case *dsa.PrivateKey:
71		T := divRoundUp(divRoundUp(p.PublicKey.Parameters.G.BitLen(), 8)-64, 8)
72		prime := toBase64(intToBytes(p.PublicKey.Parameters.P, 64+T*8))
73		subprime := toBase64(intToBytes(p.PublicKey.Parameters.Q, 20))
74		base := toBase64(intToBytes(p.PublicKey.Parameters.G, 64+T*8))
75		priv := toBase64(intToBytes(p.X, 20))
76		pub := toBase64(intToBytes(p.PublicKey.Y, 64+T*8))
77		return format +
78			"Algorithm: " + algorithm + "\n" +
79			"Prime(p): " + prime + "\n" +
80			"Subprime(q): " + subprime + "\n" +
81			"Base(g): " + base + "\n" +
82			"Private_value(x): " + priv + "\n" +
83			"Public_value(y): " + pub + "\n"
84
85	case ed25519.PrivateKey:
86		private := toBase64(p.Seed())
87		return format +
88			"Algorithm: " + algorithm + "\n" +
89			"PrivateKey: " + private + "\n"
90
91	default:
92		return ""
93	}
94}
95