Make SSL certificate validation respect wildcards

src/main/java/com/microsoft/sqlserver/jdbc/IOBuffer.java

@@ -1400,27 +1400,66 @@ private String parseCommonName(String distinguishedName) {
             return commonName;
         }
 
-        private boolean validateServerName(String nameInCert) throws CertificateException {
+        private boolean validateServerName(String nameInCert) {
             // Failed to get the common name from DN or empty CN
             if (null == nameInCert) {
-                if (logger.isLoggable(Level.FINER))
+                if (logger.isLoggable(Level.FINER)) {
                     logger.finer(logContext + " Failed to parse the name from the certificate or name is empty.");
+                }
                 return false;
             }
-
+            // We do not allow wildcards in IDNs (xn--).
+            if (!nameInCert.startsWith("xn--") && nameInCert.contains("*")) {
+                int hostIndex = 0, certIndex = 0, match = 0, startIndex = -1, periodCount = 0;
+                while (hostIndex < hostName.length()) {
+                    if ('.' == hostName.charAt(hostIndex)) {
+                        periodCount++;
+                    }
+                    if (certIndex < nameInCert.length() && hostName.charAt(hostIndex) == nameInCert.charAt(certIndex)) {
+                        hostIndex++;
+                        certIndex++;
+                    } else if (certIndex < nameInCert.length() && '*' == nameInCert.charAt(certIndex)) {
+                        startIndex = certIndex;
+                        match = hostIndex;
+                        certIndex++;
+                    } else if (startIndex != -1 && 0 == periodCount) {
+                        certIndex = startIndex + 1;
+                        match++;
+                        hostIndex = match;
+                    } else {
+                        logFailMessage(nameInCert);
+                        return false;
+                    }
+                }
+                if (nameInCert.length() == certIndex && periodCount > 1) {
+                    logSuccessMessage(nameInCert);
+                    return true;
+                } else {
+                    logFailMessage(nameInCert);
+                    return false;
+                }
+            }
             // Verify that the name in certificate matches exactly with the host name
             if (!nameInCert.equals(hostName)) {
-                if (logger.isLoggable(Level.FINER))
-                    logger.finer(logContext + " The name in certificate " + nameInCert
-                            + " does not match with the server name " + hostName + ".");
+                logFailMessage(nameInCert);
                 return false;
             }
+            logSuccessMessage(nameInCert);
+            return true;
+        }
 
-            if (logger.isLoggable(Level.FINER))
+        private void logFailMessage(String nameInCert) {
+            if (logger.isLoggable(Level.FINER)) {
+                logger.finer(logContext + " The name in certificate " + nameInCert
+                        + " does not match with the server name " + hostName + ".");
+            }
+        }
+
+        private void logSuccessMessage(String nameInCert) {
+            if (logger.isLoggable(Level.FINER)) {
                 logger.finer(logContext + " The name in certificate:" + nameInCert + " validated against server name "
                         + hostName + ".");
-
-            return true;
+            }
         }
 
         public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
@@ -4591,8 +4630,8 @@ void writeTVPRows(TVP value) throws SQLServerException {
                         SQLServerError databaseError = new SQLServerError();
                         databaseError.setFromTDS(tdsReader);
 
-                        SQLServerException.makeFromDatabaseError(con, null, databaseError.getErrorMessage(), databaseError,
-                                false);
+                        SQLServerException.makeFromDatabaseError(con, null, databaseError.getErrorMessage(),
+                                databaseError, false);
                     }
 
                     command.setInterruptsEnabled(true);

src/test/java/com/microsoft/sqlserver/jdbc/SSLCertificateValidation.java

@@ -0,0 +1,138 @@
+/*
+ * Microsoft JDBC Driver for SQL Server Copyright(c) Microsoft Corporation All rights reserved. This program is made
+ * available under the terms of the MIT License. See the LICENSE file in the project root for more information.
+ */
+
+package com.microsoft.sqlserver.jdbc;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+
+import org.junit.jupiter.api.Test;
+import org.junit.platform.runner.JUnitPlatform;
+import org.junit.runner.RunWith;
+
+
+@RunWith(JUnitPlatform.class)
+public class SSLCertificateValidation {
+
+    /**
+     * Tests our internal method, validateServerName() against different possible names in SSL certificate.
+     * 
+     * @throws Exception
+     */
+    @Test
+    public void testValidateServerName() throws Exception {
+
+        String serverName = "msjdbc.database.windows.net";
+        String serverName2 = "bbbbuuzzuzzzzzz.example.net";
+        String serverName3 = "xn--ms.database.windows.net";
+
+        // Set up the HostNameOverrideX509TrustManager object using reflection
+        TDSChannel tdsc = new TDSChannel(new SQLServerConnection("someConnectionProperty"));
+        Class<?> hsoClass = Class.forName("com.microsoft.sqlserver.jdbc.TDSChannel$HostNameOverrideX509TrustManager");
+        Constructor<?> constructor = hsoClass.getDeclaredConstructors()[0];
+        constructor.setAccessible(true);
+        Object hsoObject = constructor.newInstance(null, tdsc, null, serverName);
+        Method method = hsoObject.getClass().getDeclaredMethod("validateServerName", String.class);
+        method.setAccessible(true);
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = msjdbc.database.windows.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "msjdbc.database.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = msjdbc***.database.windows.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "msjdbc***.database.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = ms*bc.database.windows.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "ms*bc.database.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = *bc.database.windows.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "*bc.database.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = ms*.database.windows.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "ms*.database.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = *jd*.database.windows.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "*jd*.database.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = ms.*.net
+        // Expected result: false
+        assertFalse((boolean) method.invoke(hsoObject, "ms.*.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = msjdbc.asd*dsa.windows.net
+        // Expected result: false
+        assertFalse((boolean) method.invoke(hsoObject, "msjdbc.asd*dsa.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = .*.windows.net
+        // Expected result: false
+        assertFalse((boolean) method.invoke(hsoObject, ".*.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = msjdbc.*.windows.net
+        // Expected result: false
+        assertFalse((boolean) method.invoke(hsoObject, "msjdbc.*.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = *.*.windows.net
+        // Expected result: false
+        // Note: multiple wildcards are not allowed, so this case shouldn't happen, but we still make sure to fail this.
+        assertFalse((boolean) method.invoke(hsoObject, "*.*.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = *.com
+        // Expected result: false
+        // A cert with * plus a top-level domain is not allowed.
+        assertFalse((boolean) method.invoke(hsoObject, "*.com"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = xn--ms*.database.windows.net
+        // Expected result: fail
+        assertFalse((boolean) method.invoke(hsoObject, "xn--ms*.database.windows.net"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = *
+        // Expected result: fail
+        assertFalse((boolean) method.invoke(hsoObject, "*"));
+
+        // Server Name = msjdbc.database.windows.net
+        // SAN = ms*atabase.windows.net
+        // Expected result: fail
+        assertFalse((boolean) method.invoke(hsoObject, "ms*atabase.windows.net"));
+
+        hsoObject = constructor.newInstance(null, tdsc, null, serverName2);
+        method = hsoObject.getClass().getDeclaredMethod("validateServerName", String.class);
+        method.setAccessible(true);
+
+        // Server Name = bbbbuuzzuzzzzzz.example.net
+        // SAN = b*zzz.example.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "b*zzz.example.net"));
+
+        hsoObject = constructor.newInstance(null, tdsc, null, serverName3);
+        method = hsoObject.getClass().getDeclaredMethod("validateServerName", String.class);
+        method.setAccessible(true);
+
+        // Server Name = xn--ms.database.windows.net
+        // SAN = xn--ms.database.windows.net
+        // Expected result: true
+        assertTrue((boolean) method.invoke(hsoObject, "xn--ms.database.windows.net"));
+    }
+}