Track recently used totp timestamps

auth-new/auth.go

@@ -9,6 +9,7 @@ package auth
 import (
 	"time"
 
+	"git.mstar.dev/mstar/goutils/other"
 	"git.mstar.dev/mstar/goutils/sliceutils"
 	"github.com/go-webauthn/webauthn/webauthn"
 
@@ -18,7 +19,8 @@ import (
 )
 
 type Authenticator struct {
-	webauthn *webauthn.WebAuthn
+	webauthn               *webauthn.WebAuthn
+	recentlyUsedTotpTokens map[string]time.Time
 }
 type LoginNextState uint8
 
@@ -33,6 +35,17 @@ const (
 	LoginStartPasskey                              // Login starts with a passkey
 )
 
+func New(webauthnConfig *webauthn.Config) (*Authenticator, error) {
+	webauthn, err := webauthn.New(webauthnConfig)
+	if err != nil {
+		return nil, other.Error("auth", "failed to create webauthn handler", err)
+	}
+	return &Authenticator{
+		webauthn:               webauthn,
+		recentlyUsedTotpTokens: make(map[string]time.Time),
+	}, nil
+}
+
 func calcAccessExpirationTimestamp() time.Time {
 	// For now, the default expiration is one month after creation
 	// though "never" might also be a good option

auth-new/errors.go

@@ -12,6 +12,7 @@ var (
 	// A user may not login, for whatever reason
 	ErrCantLogin         = errors.New("user can't login")
 	ErrDecryptionFailure = errors.New("failed to decrypt content")
+	ErrTotpRecentlyUsed  = errors.New("totp token was used too recently")
 )
 
 type CombinedError struct {

auth-new/totp.go

@@ -1,5 +1,7 @@
 package auth
 
+// Some helpful comments from: https://waters.me/internet/google-authenticator-implementation-note-key-length-token-reuse/
+
 import (
 	"time"
 
@@ -15,11 +17,20 @@ import (
 )
 
 const totpUnverifiedSuffix = "-NOT_VERIFIED"
+const totpTokenNoLongerRecentlyUsed = time.Second * 90
 
 func (a *Authenticator) PerformTotpLogin(
 	username string,
 	totpToken string,
 ) (LoginNextState, string, error) {
+	// First check if that token has been seen recently for that user
+	if timestamp, found := a.recentlyUsedTotpTokens[totpToken+"+"+username]; found {
+		if timestamp.Add(totpTokenNoLongerRecentlyUsed).After(time.Now()) {
+			return LoginNextFailure, "", ErrTotpRecentlyUsed
+		} else {
+			delete(a.recentlyUsedTotpTokens, totpToken+"+"+username)
+		}
+	}
 	if ok, err := a.canUsernameLogin(username); !ok {
 		return 0, "", other.Error("auth", "user may not login", err)
 	}
@@ -61,6 +72,9 @@ func (a *Authenticator) PerformTotpLogin(
 			ErrInvalidCombination,
 		)
 	}
+
+	a.recentlyUsedTotpTokens[totpToken+"+"+username] = time.Now()
+
 	token := models.AccessToken{
 		User:      *acc,
 		UserId:    acc.ID,