feat(security): enforce strict host validation and authorized origin checks on ccsp routes

modules/cybercore-core/src/main/java/br/com/cybercore/signer/core/protocol/CcspServer.java

@@ -1046,7 +1046,45 @@ public class CcspServer {
         return false;
     }
 
+    private boolean validateHost(HttpExchange exchange) throws IOException {
+        String hostHeader = exchange.getRequestHeaders().getFirst("Host");
+        if (hostHeader == null || hostHeader.isBlank()) {
+            logger.warn("Requisição CCSP rejeitada: cabeçalho 'Host' ausente.");
+            sendErrorResponse(exchange, 403, "INVALID_HOST", "Cabeçalho Host é obrigatório.");
+            return false;
+        }
+
+        String rawHost = hostHeader.trim();
+        String host;
+        if (rawHost.startsWith("[")) {
+            int closingBracket = rawHost.indexOf(']');
+            if (closingBracket != -1) {
+                host = rawHost.substring(0, closingBracket + 1);
+            } else {
+                host = rawHost;
+            }
+        } else {
+            int colonIdx = rawHost.indexOf(':');
+            host = colonIdx != -1 ? rawHost.substring(0, colonIdx) : rawHost;
+        }
+
+        boolean isAllowedHost = "127.0.0.1".equalsIgnoreCase(host)
+                || "localhost".equalsIgnoreCase(host)
+                || "[::1]".equalsIgnoreCase(host);
+
+        if (!isAllowedHost) {
+            logger.warn("ALERTA DE SEGURANÇA: Requisição CCSP rejeitada por suspeita de DNS Rebinding. Host: '{}'", hostHeader);
+            sendErrorResponse(exchange, 403, CcspErrorCode.INVALID_ORIGIN.name(), "Host não autorizado para loopback local.");
+            return false;
+        }
+        return true;
+    }
+
     private boolean handleCors(HttpExchange exchange) throws IOException {
+        if (!validateHost(exchange)) {
+            return true;
+        }
+
         String path = exchange.getRequestURI().getPath();
         String origin = getOrigin(exchange);
 

modules/cybercore-core/src/test/java/br/com/cybercore/signer/core/protocol/CcspServerTest.java

@@ -615,4 +615,42 @@ class CcspServerTest {
         assertThat(resp.body()).contains("\"signed_xml\":");
         assertThat(resp.body()).contains("QualifyingProperties");
     }
+
+    @Test
+    @DisplayName("Requisição com cabeçalho Host não-loopback (DNS Rebinding) deve ser rejeitada com 403")
+    void testDnsRebindingHostRejection() throws Exception {
+        int port = server.getPort();
+        try (java.net.Socket socket = new java.net.Socket("127.0.0.1", port);
+             java.io.OutputStream out = socket.getOutputStream();
+             java.io.BufferedReader in = new java.io.BufferedReader(new java.io.InputStreamReader(socket.getInputStream()))) {
+
+            String rawRequest = "GET /ccsp/v1/status HTTP/1.1\r\n" +
+                    "Host: evil.attacker.com\r\n" +
+                    "Connection: close\r\n\r\n";
+            out.write(rawRequest.getBytes(StandardCharsets.UTF_8));
+            out.flush();
+
+            String statusLine = in.readLine();
+            assertThat(statusLine).contains("403");
+        }
+    }
+
+    @Test
+    @DisplayName("Requisição com cabeçalho Host loopback válido deve ser aceita")
+    void testValidLoopbackHostAcceptance() throws Exception {
+        int port = server.getPort();
+        try (java.net.Socket socket = new java.net.Socket("127.0.0.1", port);
+             java.io.OutputStream out = socket.getOutputStream();
+             java.io.BufferedReader in = new java.io.BufferedReader(new java.io.InputStreamReader(socket.getInputStream()))) {
+
+            String rawRequest = "GET /ccsp/v1/status HTTP/1.1\r\n" +
+                    "Host: 127.0.0.1:" + port + "\r\n" +
+                    "Connection: close\r\n\r\n";
+            out.write(rawRequest.getBytes(StandardCharsets.UTF_8));
+            out.flush();
+
+            String statusLine = in.readLine();
+            assertThat(statusLine).contains("200");
+        }
+    }
 }