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keygen.go
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keygen.go
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package gokey
import (
"crypto"
"crypto/elliptic"
"errors"
"io"
"strings"
"unicode"
deterministicEcdsaKeygen "github.com/cloudflare/gokey/ecdsa"
deterministicRsaKeygen "github.com/cloudflare/gokey/rsa"
"golang.org/x/crypto/ed25519"
)
type KeyType int
const (
EC256 KeyType = iota
EC384
EC521
RSA2048
RSA4096
X25519
ED25519
)
//go:generate stringer -type KeyType
type KeyGen struct {
rng io.Reader
}
type PasswordSpec struct {
Length int
Upper int
Lower int
Digits int
Special int
AllowedSpecial string
}
func (spec *PasswordSpec) Valid() bool {
if spec.AllowedSpecial != "" {
for _, c := range spec.AllowedSpecial {
if !unicode.IsSymbol(c) && !unicode.IsPunct(c) {
return false
}
}
}
return spec.Length >= spec.Upper+spec.Lower+spec.Digits+spec.Special
}
func allowed(num, fromSpec int) bool {
if num > 0 && fromSpec == 0 {
return false
}
if num < fromSpec {
return false
}
return true
}
func (spec *PasswordSpec) Compliant(password string) bool {
var upper, lower, digits, special int
for _, c := range password {
if unicode.IsUpper(c) {
upper++
}
if unicode.IsLower(c) {
lower++
}
if unicode.IsDigit(c) {
digits++
}
if unicode.IsSymbol(c) || unicode.IsPunct(c) {
if spec.AllowedSpecial == "" {
special++
} else {
if strings.ContainsRune(spec.AllowedSpecial, c) {
special++
} else {
return false
}
}
}
}
if !allowed(upper, spec.Upper) || !allowed(lower, spec.Lower) || !allowed(digits, spec.Digits) || !allowed(special, spec.Special) {
return false
}
return true
}
const chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890`~!@#$%^&*()-_=+[{]}\\|;:'\",<.>/?"
func randRange(rng io.Reader, max byte) (byte, error) {
var base [1]byte
for {
_, err := io.ReadFull(rng, base[:])
if err != nil {
return 0, err
}
if 255 == base[0] {
continue
}
rem := 255 % max
buck := 255 / max
if base[0] < 255-rem {
return base[0] / buck, nil
}
}
}
func (keygen *KeyGen) genRandStr(length int) (string, error) {
bytes := make([]byte, length)
for i := 0; i < length; i++ {
pos, err := randRange(keygen.rng, byte(len(chars)))
if err != nil {
return "", err
}
bytes[i] = chars[pos]
}
return string(bytes), nil
}
func (keygen *KeyGen) GeneratePassword(spec *PasswordSpec) (string, error) {
if !spec.Valid() {
return "", errors.New("invalid password specification")
}
for {
password, err := keygen.genRandStr(spec.Length)
if err != nil {
return "", err
}
if spec.Compliant(password) {
return password, nil
}
}
}
func (keygen *KeyGen) generateRsa(kt KeyType) (crypto.PrivateKey, error) {
bits := 0
switch kt {
case RSA2048:
bits = 2048
case RSA4096:
bits = 4096
default:
return nil, errors.New("invalid RSA key size requested")
}
return deterministicRsaKeygen.GenerateKey(keygen.rng, bits)
}
func (keygen *KeyGen) generateEc(kt KeyType) (crypto.PrivateKey, error) {
var curve elliptic.Curve
switch kt {
case EC256:
curve = elliptic.P256()
case EC384:
curve = elliptic.P384()
case EC521:
curve = elliptic.P521()
default:
return nil, errors.New("invalid EC key size requested")
}
return deterministicEcdsaKeygen.GenerateKey(curve, keygen.rng)
}
func (keygen *KeyGen) generate25519(kt KeyType) (crypto.PrivateKey, error) {
switch kt {
case X25519:
var privKey [32]byte
_, err := io.ReadFull(keygen.rng, privKey[:])
// from https://cr.yp.to/ecdh.html
privKey[0] &= 248
privKey[31] &= 127
privKey[31] |= 64
return x25519PrivateKey(privKey[:]), err
case ED25519:
_, privKey, err := ed25519.GenerateKey(keygen.rng)
return &privKey, err
}
return nil, errors.New("invalid key type requested")
}
func (keygen *KeyGen) GenerateKey(kt KeyType) (crypto.PrivateKey, error) {
switch kt {
case EC256, EC384, EC521:
return keygen.generateEc(kt)
case RSA2048, RSA4096:
return keygen.generateRsa(kt)
case X25519, ED25519:
return keygen.generate25519(kt)
}
return nil, errors.New("invalid key type requested")
}