fix: resolve Sscanf greedy parsing bug in VerifyPassword

internal/auth/password.go

@@ -5,6 +5,7 @@ import (
 	"crypto/subtle"
 	"encoding/base64"
 	"fmt"
+	"strings"
 
 	"golang.org/x/crypto/argon2"
 )
@@ -43,22 +44,30 @@ func HashPassword(password string) (string, error) {
 
 // VerifyPassword compares a password against an encoded Argon2id hash.
 func VerifyPassword(password, encodedHash string) (bool, error) {
-	var version int
-	var memory, time uint32
-	var threads uint8
-	var salt, hash []byte
-
-	_, err := fmt.Sscanf(encodedHash, "$argon2id$v=%d$m=%d,t=%d,p=%d$%s$%s", &version, &memory, &time, &threads, &salt, &hash)
-	if err != nil {
-		return false, fmt.Errorf("parse hash: %w", err)
+	parts := strings.Split(encodedHash, "$")
+	if len(parts) != 6 {
+		return false, fmt.Errorf("invalid hash format")
 	}
 
-	decodedSalt, err := base64.RawStdEncoding.DecodeString(string(salt))
+	var version int
+	_, err := fmt.Sscanf(parts[2], "v=%d", &version)
+	if err != nil {
+		return false, fmt.Errorf("parse version: %w", err)
+	}
+
+	var memory, time uint32
+	var threads uint8
+	_, err = fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &memory, &time, &threads)
+	if err != nil {
+		return false, fmt.Errorf("parse params: %w", err)
+	}
+
+	decodedSalt, err := base64.RawStdEncoding.DecodeString(parts[4])
 	if err != nil {
 		return false, fmt.Errorf("decode salt: %w", err)
 	}
 
-	decodedHash, err := base64.RawStdEncoding.DecodeString(string(hash))
+	decodedHash, err := base64.RawStdEncoding.DecodeString(parts[5])
 	if err != nil {
 		return false, fmt.Errorf("decode hash: %w", err)
 	}