From 3003b010e22f64d92fd9526945484052d8e25445 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simon=20Lukas=20=7E=20Znox=20/=20Pl=C3=A4nkler?=
 <60503970+Plaenkler@users.noreply.github.com>
Date: Fri, 11 Aug 2023 20:34:05 +0200
Subject: [PATCH 1/2] [ADD] Possibility to regenerate key

---
 otp.go       |  5 ++++-
 totp/totp.go | 17 ++++++++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/otp.go b/otp.go
index 02b08f3..d66823d 100644
--- a/otp.go
+++ b/otp.go
@@ -46,6 +46,9 @@ var ErrGenerateMissingIssuer = errors.New("Issuer must be set")
 // When generating a Key, the Account Name must be set.
 var ErrGenerateMissingAccountName = errors.New("AccountName must be set")
 
+// When regenerating a Key, the Secret must be set.
+var ErrRegenerateMissingSecret = errors.New("Secret must be set")
+
 // Key represents an TOTP or HTOP key.
 type Key struct {
 	orig string
@@ -55,8 +58,8 @@ type Key struct {
 // NewKeyFromURL creates a new Key from an TOTP or HOTP url.
 //
 // The URL format is documented here:
-//   https://github.com/google/google-authenticator/wiki/Key-Uri-Format
 //
+//	https://github.com/google/google-authenticator/wiki/Key-Uri-Format
 func NewKeyFromURL(orig string) (*Key, error) {
 	s := strings.TrimSpace(orig)
 
diff --git a/totp/totp.go b/totp/totp.go
index a2fb7d5..d37a790 100644
--- a/totp/totp.go
+++ b/totp/totp.go
@@ -18,10 +18,11 @@
 package totp
 
 import (
+	"io"
+
 	"github.com/pquerna/otp"
 	"github.com/pquerna/otp/hotp"
 	"github.com/pquerna/otp/internal"
-	"io"
 
 	"crypto/rand"
 	"encoding/base32"
@@ -205,3 +206,17 @@ func Generate(opts GenerateOpts) (*otp.Key, error) {
 
 	return otp.NewKeyFromURL(u.String())
 }
+
+// Restores a key from a secret opts.Secret must be set
+func Regenerate(opts GenerateOpts) (*otp.Key, error) {
+	if opts.SecretSize == 0 {
+		return nil, otp.ErrRegenerateMissingSecret
+	}
+	var secret []byte
+	_, err := base32.StdEncoding.Decode(secret, opts.Secret)
+	if err != nil {
+		return nil, err
+	}
+	opts.Secret = secret
+	return Generate(opts)
+}

From 7e6936b68a0a773fd67d624da55c93106fc23979 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simon=20Lukas=20=7E=20Znox=20/=20Pl=C3=A4nkler?=
 <60503970+Plaenkler@users.noreply.github.com>
Date: Mon, 4 Sep 2023 00:16:45 +0200
Subject: [PATCH 2/2] [FIX] Secret size

---
 totp/totp.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/totp/totp.go b/totp/totp.go
index d37a790..76f32c8 100644
--- a/totp/totp.go
+++ b/totp/totp.go
@@ -212,7 +212,7 @@ func Regenerate(opts GenerateOpts) (*otp.Key, error) {
 	if opts.SecretSize == 0 {
 		return nil, otp.ErrRegenerateMissingSecret
 	}
-	var secret []byte
+	secret := make([]byte, base32.StdEncoding.DecodedLen(len(opts.Secret)))
 	_, err := base32.StdEncoding.Decode(secret, opts.Secret)
 	if err != nil {
 		return nil, err