Initial import.

Basic HOTP functionality.

otp.go

@@ -0,0 +1,61 @@
+package twofactor
+
+import (
+	"crypto/rand"
+	"fmt"
+	"hash"
+)
+
+type Type uint
+
+const (
+	OATH_HOTP = iota
+	OATH_TOTP
+)
+
+var PRNG = rand.Reader
+
+// Type OTP represents a one-time password token -- whether a
+// software taken (as in the case of Google Authenticator) or a
+// hardware token (as in the case of a YubiKey).
+type OTP interface {
+	// Returns the current counter value; the meaning of the
+	// returned value is algorithm-specific.
+	Counter() uint64
+
+	// Set the counter to a specific value.
+	SetCounter(uint64)
+
+	// the secret key contained in the OTP
+	Key() []byte
+
+	// generate a new OTP
+	OTP() string
+
+	// the output size of the OTP
+	Size() int
+
+	// the hash function used by the OTP
+	Hash() func() hash.Hash
+
+	// URL generates a Google Authenticator url (or perhaps some other url)
+	URL(string) string
+
+	// QR outputs a byte slice containing a PNG-encoded QR code
+	// of the URL.
+	QR(string) ([]byte, error)
+
+	// Returns the type of this OTP.
+	Type() Type
+}
+
+func OTPString(otp OTP) string {
+	var typeName string
+	switch otp.Type() {
+	case OATH_HOTP:
+		typeName = "OATH-HOTP"
+	case OATH_TOTP:
+		typeName = "OATH-TOTP"
+	}
+	return fmt.Sprintf("%s, %d", typeName, otp.Size())
+}