feat: migrate passwords from SHA-256 to bcrypt

- Replace SHA-256 hex hashing with bcrypt (cost 10) for password storage
- VerifyPassword now uses bcrypt.CompareHashAndPassword
- HashPassword returns (string, error) instead of string
- Add IsBcryptHash helper to detect legacy hashes for future migration
- Remove duplicate verifyPassword from api.go (already done in prev commit)
- Promote golang.org/x/crypto to direct dependency

go.mod

@@ -1,6 +1,6 @@
 module gitea.mrixs.me/Mrixs/MrixsCraft-server
 
-go 1.22
+go 1.25.0
 
 require github.com/jackc/pgx/v5 v5.6.0
 
@@ -8,7 +8,7 @@ require (
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
 	github.com/jackc/puddle/v2 v2.2.1 // indirect
-	golang.org/x/crypto v0.17.0 // indirect
-	golang.org/x/sync v0.1.0 // indirect
-	golang.org/x/text v0.14.0 // indirect
+	golang.org/x/crypto v0.52.0
+	golang.org/x/sync v0.20.0 // indirect
+	golang.org/x/text v0.37.0 // indirect
 )

internal/api/api.go

@@ -179,7 +179,11 @@ func (h *Handler) register(w http.ResponseWriter, r *http.Request) {
 	}
 
 	uuid := auth.GenerateUUID()
-	passwordHash := auth.HashPassword(req.Password)
+	passwordHash, err := auth.HashPassword(req.Password)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "Failed to hash password")
+		return
+	}
 
 	_, err = h.db.Pool().Exec(r.Context(),
 		`INSERT INTO users (username, email, password_hash, uuid, role)

internal/auth/auth.go

@@ -4,16 +4,17 @@ package auth
 import (
 	"context"
 	"crypto/rand"
-	"crypto/sha256"
-	"crypto/subtle"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
 	"strings"
 	"time"
 
+	"golang.org/x/crypto/bcrypt"
+
 	"gitea.mrixs.me/Mrixs/MrixsCraft-server/internal/config"
 	"gitea.mrixs.me/Mrixs/MrixsCraft-server/internal/database"
 )
@@ -380,10 +381,10 @@ func ExtractBearer(h string) string {
 	return ""
 }
 
-// VerifyPassword checks a plaintext password against a SHA-256 hex hash.
+// VerifyPassword checks a plaintext password against a stored bcrypt hash.
 func VerifyPassword(password, hash string) bool {
-	h := sha256.Sum256([]byte(password))
-	return subtle.ConstantTimeCompare([]byte(hex.EncodeToString(h[:])), []byte(hash)) == 1
+	err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
+	return err == nil
 }
 
 // GenerateToken creates a random hex token (16 bytes → 32 hex chars).
@@ -406,12 +407,24 @@ func writeError(w http.ResponseWriter, status int, err, msg string) {
 	})
 }
 
-// HashPassword returns the SHA-256 hex of a password for storage.
-func HashPassword(password string) string {
-	h := sha256.Sum256([]byte(password))
-	return hex.EncodeToString(h[:])
+// HashPassword returns a bcrypt hash of the password for storage.
+func HashPassword(password string) (string, error) {
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return "", fmt.Errorf("hashing password: %w", err)
+	}
+	return string(hash), nil
 }
 
+// IsBcryptHash reports whether the given hash looks like a bcrypt hash
+// (starts with $2a$, $2b$, or $2y$). Used to detect legacy SHA-256 hashes.
+func IsBcryptHash(hash string) bool {
+	return strings.HasPrefix(hash, "$2a$") || strings.HasPrefix(hash, "$2b$") || strings.HasPrefix(hash, "$2y$")
+}
+
+// ErrPasswordHashing is returned when bcrypt hashing fails.
+var ErrPasswordHashing = errors.New("password hashing failed")
+
 // GenerateUUID creates a random UUID v4-like string.
 func GenerateUUID() string {
 	b := make([]byte, 16)