fix(security): hash password reset tokens before database storage

INF-10: Reset tokens are now SHA-256 hashed before INSERT. Validation
hashes the received token and compares against stored hash. Plain
tokens never persisted.

veza-backend-api/internal/services/password_service.go

@@ -3,8 +3,10 @@ package services
 import (
 	"context"
 	"crypto/rand"
+	"crypto/sha256"
 	"database/sql"
 	"encoding/base64"
+	"encoding/hex"
 	"fmt"
 	"strings"
 	"time"
@@ -53,6 +55,13 @@ func NewPasswordService(db *database.Database, logger *zap.Logger) *PasswordServ
 	}
 }
 
+// hashToken returns the hex-encoded SHA-256 hash of the token.
+// INF-10: Tokens are stored hashed in the DB; only the hash is persisted.
+func (ps *PasswordService) hashToken(token string) string {
+	h := sha256.Sum256([]byte(token))
+	return hex.EncodeToString(h[:])
+}
+
 // GetUserByEmail retrieves a user by email
 func (ps *PasswordService) GetUserByEmail(email string) (*UserInfo, error) {
 	ctx := context.Background()
@@ -87,12 +96,13 @@ func (ps *PasswordService) GeneratePasswordResetToken(userID uuid.UUID) (string,
 	// Set expiration (1 hour)
 	expiresAt := time.Now().Add(1 * time.Hour)
 
-	// Store in database
+	// INF-10: Store hash in DB, return plain token to user
 	ctx := context.Background()
+	tokenHash := ps.hashToken(token)
 	_, err = ps.db.ExecContext(ctx, `
 		INSERT INTO password_reset_tokens (user_id, token, expires_at, used)
 		VALUES ($1, $2, $3, FALSE)
-	`, userID, token, expiresAt)
+	`, userID, tokenHash, expiresAt)
 
 	if err != nil {
 		return "", time.Time{}, err
@@ -109,13 +119,14 @@ func (ps *PasswordService) GeneratePasswordResetToken(userID uuid.UUID) (string,
 func (ps *PasswordService) ResetPassword(token, newPassword string) error {
 	ctx := context.Background()
 
-	// Get token info
+	// INF-10: Hash received token and look up by hash
+	tokenHash := ps.hashToken(token)
 	var resetToken PasswordResetToken
 	err := ps.db.QueryRowContext(ctx, `
 		SELECT id, user_id, token, expires_at, used, created_at
 		FROM password_reset_tokens
 		WHERE token = $1 AND used = FALSE
-	`, token).Scan(
+	`, tokenHash).Scan(
 		&resetToken.ID,
 		&resetToken.UserID,
 		&resetToken.Token,