Kiracı Ayrımı — A Bankasının Müşterisi B Bankasının Verisini Görmesin

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@Entity
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@Table(name = "accounts")
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public class Account {
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    @Id
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    private UUID id;
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    // Hibernate sets it on insert and adds "tenant_id = ?" to every HQL/JPQL query.
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    @TenantId
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    @Column(name = "tenant_id", nullable = false, updatable = false)
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    private String tenantId;
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    @Column(nullable = false)
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    private String iban;
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    @Column(nullable = false, precision = 19, scale = 2)
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    private BigDecimal balance;
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    protected Account() {
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    }
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}

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@Component
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class TokenTenantResolver implements CurrentTenantIdentifierResolver<String>, HibernatePropertiesCustomizer {
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    @Override
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    public String resolveCurrentTenantIdentifier() {
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        // The tenant comes from the verified token, never from the URL or the body.
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        if (SecurityContextHolder.getContext().getAuthentication() instanceof JwtAuthenticationToken jwt) {
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            return jwt.getToken().getClaimAsString("bank");
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        }
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        throw new IllegalStateException("No tenant: request is not authenticated");
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    }
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    @Override
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    public boolean validateExistingCurrentSessions() {
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        return true;
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    }
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    @Override
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    public void customize(Map<String, Object> properties) {
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        properties.put(AvailableSettings.MULTI_TENANT_IDENTIFIER_RESOLVER, this);
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    }
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}

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ALTER TABLE accounts ENABLE ROW LEVEL SECURITY;
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ALTER TABLE accounts FORCE ROW LEVEL SECURITY;  -- applies to the owner too
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-- Every query, JPQL or native, sees only the current bank's rows.
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CREATE POLICY accounts_by_bank ON accounts
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    USING (tenant_id = current_setting('app.tenant'))
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    WITH CHECK (tenant_id = current_setting('app.tenant'));
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-- The application connects as wallet_app, which does not own the table.
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GRANT SELECT, INSERT, UPDATE ON accounts TO wallet_app;

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@Component
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class TenantTransactionListener {
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    private final JdbcTemplate jdbc;
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    private final TokenTenantResolver tenants;
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    TenantTransactionListener(JdbcTemplate jdbc, TokenTenantResolver tenants) {
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        this.jdbc = jdbc;
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        this.tenants = tenants;
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    }
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    /** Called at the start of every transaction; SET LOCAL ends with it. */
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    void bindTenant() {
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        jdbc.queryForObject("SELECT set_config('app.tenant', ?, true)", String.class,
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                tenants.resolveCurrentTenantIdentifier());
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    }
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}

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@SpringBootTest
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@Testcontainers
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class TenantIsolationTest {
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    @Autowired
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    TransactionSearch search;
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    @Test
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    @WithBank("A")
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    void a_user_of_bank_a_never_sees_bank_b() {
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        TestData.loadTwoBanks("A", "B");
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        assertThat(search.find("havale"))
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                .isNotEmpty()
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                .allSatisfy(tx -> assertThat(tx.tenantId()).isEqualTo("A"));
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    }
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}