Защита от перебора паролей: SMTP, IMAP, веб — лимит по IP и по ящику

Один LoginGuard на все проверки пароля (SMTP AUTH, IMAP LOGIN/AUTHENTICATE,
вход в веб, смена пароля): 10 неверных с IP за 15 мин → блок 15 мин, дальше
вдвое дольше до суток; 20 неверных на ящик с разных IP → ящик закрыт, кроме
IP, с которых в него уже входили. Во время блока пароль не проверяется
(SMTP 421, IMAP BYE + NO [UNAVAILABLE], веб 429 + Retry-After); неверный
пароль — ответ через 1 с; 3 неверных в соединении — обрыв.

X-Forwarded-For веб-входа — только от прокси в частной сети, иначе
заголовок отбрасывается (подменой IP лимит не обойти).

Попутно: IMAP терял тегированный ответ после "* BYE" (LOGOUT, обрыв после
неудачных входов) — takeUntil теперь после тегированной строки.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/src/main/java/com/mailserver/config/ImapConfig.java

@@ -1,5 +1,6 @@
 package com.mailserver.config;
 
+import com.mailserver.security.LoginGuard;
 import com.mailserver.imap.DbImapStore;
 import com.mailserver.imap.ImapServer;
 import com.mailserver.imap.ImapStore;
@@ -32,7 +33,7 @@ public class ImapConfig {
 
     @Bean(initMethod = "start", destroyMethod = "stop")
     @ConditionalOnProperty(name = "mailserver.imap.enabled", havingValue = "true", matchIfMissing = true)
-    public ImapServer imapServer(ImapStore store, MailServerConfig.SmtpTlsContext tls,
+    public ImapServer imapServer(ImapStore store, MailServerConfig.SmtpTlsContext tls, LoginGuard guard,
                                  @Value("${mailserver.imap.host:0.0.0.0}") String host,
                                  @Value("${mailserver.imap.port:3143}") int port,
                                  @Value("${mailserver.smtp.hostname:localhost}") String hostname,
@@ -41,12 +42,12 @@ public class ImapConfig {
                                  @Value("${mailserver.imap.idle-timeout:30m}") Duration idleTimeout,
                                  @Value("${mailserver.imap.idle-poll:5s}") Duration idlePoll) {
         return new ImapServer(new ImapServer.Settings(host, port, hostname, authWithoutTls, tls.context(), false,
-                (int) maxLiteral.toBytes(), idleTimeout, idlePoll), store);
+                (int) maxLiteral.toBytes(), idleTimeout, idlePoll), store, guard);
     }
 
     @Bean(initMethod = "start", destroyMethod = "stop")
     @ConditionalOnExpression("'${mailserver.imap.enabled:true}' == 'true' and ${mailserver.imaps.port:0} > 0 and ${mailserver.tls.enabled:true}")
-    public ImapServer imapsServer(ImapStore store, MailServerConfig.SmtpTlsContext tls,
+    public ImapServer imapsServer(ImapStore store, MailServerConfig.SmtpTlsContext tls, LoginGuard guard,
                                   @Value("${mailserver.imap.host:0.0.0.0}") String host,
                                   @Value("${mailserver.imaps.port}") int port,
                                   @Value("${mailserver.smtp.hostname:localhost}") String hostname,
@@ -54,6 +55,6 @@ public class ImapConfig {
                                   @Value("${mailserver.imap.idle-timeout:30m}") Duration idleTimeout,
                                   @Value("${mailserver.imap.idle-poll:5s}") Duration idlePoll) {
         return new ImapServer(new ImapServer.Settings(host, port, hostname, false, tls.context(), true,
-                (int) maxLiteral.toBytes(), idleTimeout, idlePoll), store);
+                (int) maxLiteral.toBytes(), idleTimeout, idlePoll), store, guard);
     }
 }

backend/src/main/java/com/mailserver/config/LoginGuardConfig.java

@@ -0,0 +1,74 @@
+package com.mailserver.config;
+
+import com.mailserver.security.LoginGuard;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.web.server.adapter.ForwardedHeaderTransformer;
+
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/** Brute-force protection (one guard for SMTP, IMAP and the web) and whose X-Forwarded-* headers to believe. */
+@Configuration
+public class LoginGuardConfig {
+
+    @Bean
+    public LoginGuard loginGuard(@Value("${mailserver.login-guard.enabled:true}") boolean enabled,
+                                 @Value("${mailserver.login-guard.max-per-ip:10}") int maxPerIp,
+                                 @Value("${mailserver.login-guard.max-per-account:20}") int maxPerAccount,
+                                 @Value("${mailserver.login-guard.window:15m}") Duration window,
+                                 @Value("${mailserver.login-guard.block:15m}") Duration block,
+                                 @Value("${mailserver.login-guard.max-block:24h}") Duration maxBlock,
+                                 @Value("${mailserver.login-guard.known-ip-ttl:30d}") Duration knownIpTtl,
+                                 @Value("${mailserver.login-guard.trusted-ips:}") String trustedIps,
+                                 @Value("${mailserver.login-guard.failure-delay:1s}") Duration failureDelay) {
+        Set<String> trusted = Arrays.stream(trustedIps.split(","))
+                .map(String::trim).filter(s -> !s.isEmpty()).collect(Collectors.toUnmodifiableSet());
+        return new LoginGuard(new LoginGuard.Settings(enabled, maxPerIp, maxPerAccount, window, block, maxBlock,
+                knownIpTtl, trusted, failureDelay));
+    }
+
+    /**
+     * Replaces Boot's transformer (server.forward-headers-strategy=framework): X-Forwarded-* / Forwarded are believed
+     * only from a proxy in a private network (Jambotron's Caddy comes over the docker network / WireGuard). A request
+     * straight from the internet (the VM's public address) has them removed — otherwise anyone could put a new
+     * X-Forwarded-For into every login attempt and never hit the per-IP limit.
+     */
+    @Bean(name = "forwardedHeaderTransformer")
+    public ForwardedHeaderTransformer forwardedHeaderTransformer() {
+        return new TrustedProxyHeaderTransformer();
+    }
+
+    static final class TrustedProxyHeaderTransformer extends ForwardedHeaderTransformer {
+
+        private final ForwardedHeaderTransformer stripOnly = new ForwardedHeaderTransformer();
+
+        TrustedProxyHeaderTransformer() {
+            stripOnly.setRemoveOnly(true);
+        }
+
+        @Override
+        public ServerHttpRequest apply(ServerHttpRequest request) {
+            return privatePeer(request.getRemoteAddress()) ? super.apply(request) : stripOnly.apply(request);
+        }
+    }
+
+    /** Loopback, 10/8, 172.16/12, 192.168/16, link-local, IPv6 fc00::/7. */
+    static boolean privatePeer(InetSocketAddress peer) {
+        if (peer == null || peer.getAddress() == null) {
+            return false;
+        }
+        InetAddress a = peer.getAddress();
+        if (a.isLoopbackAddress() || a.isSiteLocalAddress() || a.isLinkLocalAddress()) {
+            return true;
+        }
+        byte[] b = a.getAddress();
+        return b.length == 16 && (b[0] & 0xfe) == 0xfc;
+    }
+}

backend/src/main/java/com/mailserver/config/MailServerConfig.java

@@ -1,5 +1,6 @@
 package com.mailserver.config;
 
+import com.mailserver.security.LoginGuard;
 import com.mailserver.delivery.SmtpDeliveryClient;
 import com.mailserver.smtp.MailRouter;
 import com.mailserver.smtp.SmtpServer;
@@ -39,7 +40,7 @@ public class MailServerConfig {
 
     @Bean(initMethod = "start", destroyMethod = "stop")
     @ConditionalOnProperty(name = "mailserver.smtp.enabled", havingValue = "true", matchIfMissing = true)
-    public SmtpServer smtpServer(MailRouter router, SmtpTlsContext tls,
+    public SmtpServer smtpServer(MailRouter router, SmtpTlsContext tls, LoginGuard guard,
                                  @Value("${mailserver.smtp.host:0.0.0.0}") String host,
                                  @Value("${mailserver.smtp.port:3025}") int port,
                                  @Value("${mailserver.smtp.hostname:localhost}") String hostname,
@@ -47,20 +48,20 @@ public class MailServerConfig {
                                  @Value("${mailserver.smtp.auth-without-tls:false}") boolean authWithoutTls,
                                  @Value("${mailserver.smtp.idle-timeout:5m}") Duration idleTimeout) {
         return new SmtpServer(new SmtpServer.Settings(host, port, hostname, maxBytes, authWithoutTls, idleTimeout,
-                tls.context(), false), router);
+                tls.context(), false), router, guard);
     }
 
     /** Implicit TLS (RFC 8314, usually port 465) — only when mailserver.smtps.port is set and TLS is on. */
     @Bean(initMethod = "start", destroyMethod = "stop")
     @ConditionalOnExpression("${mailserver.smtps.port:0} > 0 and ${mailserver.tls.enabled:true}")
-    public SmtpServer smtpsServer(MailRouter router, SmtpTlsContext tls,
+    public SmtpServer smtpsServer(MailRouter router, SmtpTlsContext tls, LoginGuard guard,
                                   @Value("${mailserver.smtp.host:0.0.0.0}") String host,
                                   @Value("${mailserver.smtps.port}") int port,
                                   @Value("${mailserver.smtp.hostname:localhost}") String hostname,
                                   @Value("${mailserver.smtp.max-message-bytes:26214400}") long maxBytes,
                                   @Value("${mailserver.smtp.idle-timeout:5m}") Duration idleTimeout) {
         return new SmtpServer(new SmtpServer.Settings(host, port, hostname, maxBytes, false, idleTimeout,
-                tls.context(), true), router);
+                tls.context(), true), router, guard);
     }
 
     /**