Add 'twofactor/' from commit 'c999bf35b0e47de4f63d59abbe0d7efc76c13ced'

git-subtree-dir: twofactor
git-subtree-mainline: 4dc135cfe0
git-subtree-split: c999bf35b0

twofactor/hotp.go

@@ -0,0 +1,103 @@
+package twofactor
+
+import (
+	"crypto"
+	"crypto/sha1"
+	"encoding/base32"
+	"io"
+	"net/url"
+	"strconv"
+	"strings"
+)
+
+// HOTP represents an RFC-4226 Hash-based One Time Password instance.
+type HOTP struct {
+	*OATH
+}
+
+// Type returns OATH_HOTP.
+func (otp *HOTP) Type() Type {
+	return OATH_HOTP
+}
+
+// NewHOTP takes the key, the initial counter value, and the number
+// of digits (typically 6 or 8) and returns a new HOTP instance.
+func NewHOTP(key []byte, counter uint64, digits int) *HOTP {
+	return &HOTP{
+		OATH: &OATH{
+			key:     key,
+			counter: counter,
+			size:    digits,
+			hash:    sha1.New,
+			algo:    crypto.SHA1,
+		},
+	}
+}
+
+// OTP returns the next OTP and increments the counter.
+func (otp *HOTP) OTP() string {
+	code := otp.OATH.OTP(otp.counter)
+	otp.counter++
+	return code
+}
+
+// URL returns an HOTP URL (i.e. for putting in a QR code).
+func (otp *HOTP) URL(label string) string {
+	return otp.OATH.URL(otp.Type(), label)
+}
+
+// SetProvider sets up the provider component of the OTP URL.
+func (otp *HOTP) SetProvider(provider string) {
+	otp.provider = provider
+}
+
+// GenerateGoogleHOTP generates a new HOTP instance as used by
+// Google Authenticator.
+func GenerateGoogleHOTP() *HOTP {
+	key := make([]byte, sha1.Size)
+	if _, err := io.ReadFull(PRNG, key); err != nil {
+		return nil
+	}
+	return NewHOTP(key, 0, 6)
+}
+
+func hotpFromURL(u *url.URL) (*HOTP, string, error) {
+	label := u.Path[1:]
+	v := u.Query()
+
+	secret := strings.ToUpper(v.Get("secret"))
+	if secret == "" {
+		return nil, "", ErrInvalidURL
+	}
+
+	var digits = 6
+	if sdigit := v.Get("digits"); sdigit != "" {
+		tmpDigits, err := strconv.ParseInt(sdigit, 10, 8)
+		if err != nil {
+			return nil, "", err
+		}
+		digits = int(tmpDigits)
+	}
+
+	var counter uint64 = 0
+	if scounter := v.Get("counter"); scounter != "" {
+		var err error
+		counter, err = strconv.ParseUint(scounter, 10, 64)
+		if err != nil {
+			return nil, "", err
+		}
+	}
+
+	key, err := base32.StdEncoding.DecodeString(Pad(secret))
+	if err != nil {
+		// assume secret isn't base32 encoded
+		key = []byte(secret)
+	}
+	otp := NewHOTP(key, counter, digits)
+	return otp, label, nil
+}
+
+// QR generates a new QR code for the HOTP.
+func (otp *HOTP) QR(label string) ([]byte, error) {
+	return otp.OATH.QR(otp.Type(), label)
+}