[client-v2, jdbc-v2] Implement SSL Modes

client-v2/src/main/java/com/clickhouse/client/api/Client.java

@@ -12,6 +12,7 @@
 import com.clickhouse.client.api.data_formats.internal.ProcessParser;
 import com.clickhouse.client.api.enums.Protocol;
 import com.clickhouse.client.api.enums.ProxyType;
+import com.clickhouse.client.api.enums.SSLMode;
 import com.clickhouse.client.api.http.ClickHouseHttpProto;
 import com.clickhouse.client.api.insert.InsertResponse;
 import com.clickhouse.client.api.insert.InsertSettings;
@@ -755,6 +756,34 @@
             return this;
         }
 
+        /**
+         * Defines how strictly the client verifies a server identity on secure connections.
+         *
+         * <p>Supported modes:</p>
+         * <ul>
+         *     <li>{@link SSLMode#DISABLED} - SSL is not used; only meaningful with plain protocols</li>
+         *     <li>{@link SSLMode#TRUST} - encrypt, but accept any server certificate and skip
+         *     hostname verification; a configured trust store or CA certificate is ignored (a warning
+         *     is logged), while a client certificate/key is still applied for mTLS</li>
+         *     <li>{@link SSLMode#VERIFY_CA} - validate the server certificate chain, but skip
+         *     hostname verification</li>
+         *     <li>{@link SSLMode#STRICT} - full verification of the certificate chain and the
+         *     hostname (default)</li>
+         * </ul>
+         *
+         * <p>The mode applies only when a secure protocol is in use - for the HTTP transport that
+         * means an {@code https://} endpoint. Setting any mode does <b>not</b> make the client use
+         * encryption on a plain HTTP endpoint: the endpoint scheme always decides whether the
+         * connection is encrypted.</p>
+         *
+         * @param sslMode ssl mode
+         * @return same instance of the builder
+         */
+        public Builder setSSLMode(SSLMode sslMode) {
+            this.configuration.put(ClientConfigProperties.SSL_MODE.getKey(), sslMode.name());
+            return this;
+        }
+
         /**
          * Configure client to use server timezone for date/datetime columns. Default is true.
          * If this options is selected then server timezone should be set as well.
@@ -1127,7 +1156,7 @@
             return this;
         }
 
         public Client build() {
             // check if endpoint are empty. so can not initiate client
             if (this.endpoints.isEmpty()) {
                 throw new IllegalArgumentException("At least one endpoint is required");
@@ -1140,6 +1169,36 @@
                 throw new ClientMisconfigurationException("Trust store and certificates cannot be used together");
             }
 
+            // A trust store and a CA certificate are not rejected here: for VERIFY_CA/STRICT the trust
+            // store takes precedence and the CA certificate is ignored with a warning (see createSSLContext).
+
+            // Resolve ssl_mode case-insensitively and normalize it to the canonical enum name so that
+            // downstream parsing is consistent and an unknown value is reported as a misconfiguration
+            // here instead of failing later with a generic enum-parsing error.
+            String sslModeValue = configuration.get(ClientConfigProperties.SSL_MODE.getKey());
+            if (sslModeValue != null) {
+                SSLMode sslMode;
+                try {
+                    sslMode = SSLMode.fromValue(sslModeValue);
+                } catch (IllegalArgumentException e) {
+                    throw new ClientMisconfigurationException("Invalid value '" + sslModeValue + "' for '"
+                            + ClientConfigProperties.SSL_MODE.getKey() + "'", e);
+                }
+                configuration.put(ClientConfigProperties.SSL_MODE.getKey(), sslMode.name());
+
+                // SSLMode.DISABLED does not turn encryption off - the endpoint scheme decides that. So it
+                // contradicts a secure (https) endpoint and must be rejected here, before the client is created.
+                if (sslMode == SSLMode.DISABLED) {
+                    for (Endpoint endpoint : this.endpoints) {
+                        if ("https".equalsIgnoreCase(endpoint.getURI().getScheme())) {
+                            throw new ClientMisconfigurationException("SSL mode '" + SSLMode.DISABLED
+                                    + "' cannot be used with a secure (https) endpoint. Use '" + SSLMode.TRUST
+                                    + "' to trust all certificates or use plain HTTP.");
+                        }
+                    }
+                }
+            }
+
             // Check timezone settings
             String useTimeZoneValue = this.configuration.get(ClientConfigProperties.USE_TIMEZONE.getKey());
             String serverTimeZoneValue = this.configuration.get(ClientConfigProperties.SERVER_TIMEZONE.getKey());

client-v2/src/main/java/com/clickhouse/client/api/ClientConfigProperties.java

@@ -1,6 +1,7 @@
 package com.clickhouse.client.api;
 
 import com.clickhouse.client.api.data_formats.internal.AbstractBinaryFormatReader;
+import com.clickhouse.client.api.enums.SSLMode;
 import com.clickhouse.client.api.internal.ClickHouseLZ4OutputStream;
 import com.clickhouse.data.ClickHouseDataType;
 import com.clickhouse.data.ClickHouseFormat;
@@ -115,6 +116,8 @@ public enum ClientConfigProperties {
 
     SSL_CERTIFICATE("sslcert", String.class),
 
+    SSL_MODE("ssl_mode", SSLMode.class, SSLMode.STRICT.name()),
+
     RETRY_ON_FAILURE("retry", Integer.class, "3"),
 
     INPUT_OUTPUT_FORMAT("format", ClickHouseFormat.class),

client-v2/src/main/java/com/clickhouse/client/api/enums/SSLMode.java

@@ -0,0 +1,65 @@
+package com.clickhouse.client.api.enums;
+
+/**
+ * Defines how strictly the client verifies a server identity when a secure protocol is used.
+ *
+ * <p>The mode affects only connections that are already using a secure transport (for example,
+ * an {@code https://} endpoint). It does <b>not</b> enable encryption for plain protocols - an
+ * {@code http://} endpoint stays unencrypted whatever the mode is.</p>
+ *
+ * <p>Modes from the least to the most strict:</p>
+ * <ul>
+ *     <li>{@link #DISABLED} - SSL is not used. Plain protocols only.</li>
+ *     <li>{@link #TRUST} - the hostname is not verified and any server certificate is accepted, which
+ *     is susceptible to MITM attacks - use that only for testing or in fully trusted environments. A
+ *     configured trust store or CA certificate has no effect in this mode and is ignored (a warning is
+ *     logged); a configured client certificate/key is still applied for mTLS.</li>
+ *     <li>{@link #VERIFY_CA} - the server certificate chain is validated against the trust material
+ *     (default JVM trust store, configured trust store, or a CA certificate), but the hostname is
+ *     not checked against the certificate.</li>
+ *     <li>{@link #STRICT} - full verification (default): certificate chain is validated and the
+ *     hostname must match the certificate.</li>
+ * </ul>
+ */
+public enum SSLMode {
+
+    /**
+     * SSL is not used. Connection is not encrypted. Doesn't work with HTTPS.
+     * Reserved for TCP where protocol doesn't define encryption.
+     */
+    DISABLED,
+
+    /**
+     * The hostname is not verified and any server certificate is accepted. A configured trust store or
+     * CA certificate has no effect in this mode and is ignored (a warning is logged). A configured
+     * client certificate/key is still applied for mTLS.
+     */
+    TRUST,
+
+    /**
+     * Server certificate chain is validated, but the hostname is not verified.
+     */
+    VERIFY_CA,
+
+    /**
+     * Full verification: certificate chain is validated and the hostname must match
+     * the certificate. Default mode for HTTPs.
+     */
+    STRICT;
+
+    /**
+     * Case-insensitive variant of {@link #valueOf(String)}.
+     *
+     * @param value mode name in any case
+     * @return matching mode
+     * @throws IllegalArgumentException when the value does not match any mode
+     */
+    public static SSLMode fromValue(String value) {
+        for (SSLMode mode : values()) {
+            if (mode.name().equalsIgnoreCase(value)) {
+                return mode;
+            }
+        }
+        throw new IllegalArgumentException("Unknown SSL mode '" + value + "'");
+    }
+}

client-v2/src/main/java/com/clickhouse/client/api/internal/HttpAPIClientHelper.java

@@ -11,9 +11,9 @@
 import com.clickhouse.client.api.DataTransferException;
 import com.clickhouse.client.api.ServerException;
 import com.clickhouse.client.api.enums.ProxyType;
+import com.clickhouse.client.api.enums.SSLMode;
 import com.clickhouse.client.api.http.ClickHouseHttpProto;
 import com.clickhouse.client.api.transport.Endpoint;
-import com.clickhouse.client.config.ClickHouseDefaultSslContextProvider;
 import com.clickhouse.data.ClickHouseFormat;
 import net.jpountz.lz4.LZ4Factory;
 import org.apache.commons.compress.compressors.CompressorStreamFactory;
@@ -85,7 +85,6 @@
 import java.net.URLEncoder;
 import java.net.UnknownHostException;
 import java.nio.charset.StandardCharsets;
-import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
 import java.util.Base64;
 import java.util.Collection;
@@ -131,7 +130,7 @@ public class HttpAPIClientHelper {
 
     LZ4Factory lz4Factory;
 
-    private final ClickHouseDefaultSslContextProvider sslContextProvider = new ClickHouseDefaultSslContextProvider();
+    private final SslContextProvider sslContextProvider = new SslContextProvider();
 
     public HttpAPIClientHelper(Map<String, Object> configuration, Object metricsRegistry, boolean initSslContext, LZ4Factory lz4Factory) {
         this.metricsRegistry = metricsRegistry;
@@ -159,34 +158,46 @@ public HttpAPIClientHelper(Map<String, Object> configuration, Object metricsRegi
      * @return SSLContext
      */
     public SSLContext createSSLContext(Map<String, Object> configuration) {
-        SSLContext sslContext;
-        try {
-            sslContext = SSLContext.getDefault();
-        } catch (NoSuchAlgorithmException e) {
-            throw new ClientException("Failed to create default SSL context", e);
-        }
+        final SSLMode sslMode = ClientConfigProperties.SSL_MODE.getOrDefault(configuration);
         final String trustStorePath = (String) configuration.get(ClientConfigProperties.SSL_TRUST_STORE.getKey());
         final String caCertificate = (String) configuration.get(ClientConfigProperties.CA_CERTIFICATE.getKey());
         final String sslCertificate = (String) configuration.get(ClientConfigProperties.SSL_CERTIFICATE.getKey());
         final String sslKey = (String) configuration.get(ClientConfigProperties.SSL_KEY.getKey());
-        if (trustStorePath != null) {
-            try {
-                sslContext = sslContextProvider.getSslContextFromKeyStore(
-                        trustStorePath,
-                        (String) configuration.get(ClientConfigProperties.SSL_KEY_STORE_PASSWORD.getKey()),
-                        (String) configuration.get(ClientConfigProperties.SSL_KEYSTORE_TYPE.getKey())
-                );
-            } catch (SSLException e) {
-                throw new ClientMisconfigurationException("Failed to create SSL context from a keystore", e);
+
+        SslContextProvider.Builder builder = sslContextProvider.builder();
+
+        // The client certificate/key (mTLS) are independent of how the server certificate is verified,
+        // so they are applied whenever configured, regardless of the SSL mode.
+        if (sslCertificate != null && !sslCertificate.isEmpty()) {
+            builder.clientCertificate(sslCertificate, sslKey);
+        }
+
+        if (sslMode == SSLMode.TRUST) {
+            // TRUST accepts any server certificate and skips the hostname check (the latter is applied
+            // where the connection socket factory is created). A configured trust store or CA
+            // certificate has no effect in this mode and is ignored with a warning.
+            if (trustStorePath != null || caCertificate != null) {
+                LOG.warn("SSL mode '{}' trusts any server certificate; the configured {} is ignored.",
+                        SSLMode.TRUST, trustStorePath != null ? "trust store" : "CA certificate");
             }
-        } else if (caCertificate != null || sslCertificate != null|| sslKey != null) {
-            try {
-                sslContext = sslContextProvider.getSslContextFromCerts(sslCertificate, sslKey, caCertificate);
-            } catch (SSLException e) {
-                throw new ClientMisconfigurationException("Failed to create SSL context from certificates", e);
+            builder.trustAllCertificates();
+        } else if (trustStorePath != null) {
+            // VERIFY_CA / STRICT: validate against the trust store. A trust store and a CA certificate
+            // cannot both take effect, so the CA certificate is ignored with a warning.
+            if (caCertificate != null) {
+                LOG.warn("Both a trust store and a CA certificate are configured; using the trust store and"
+                        + " ignoring the CA certificate. Import the CA certificate into the trust store instead.");
             }
+            builder.trustStore(trustStorePath,
+                    (String) configuration.get(ClientConfigProperties.SSL_KEY_STORE_PASSWORD.getKey()),
+                    (String) configuration.get(ClientConfigProperties.SSL_KEYSTORE_TYPE.getKey()));
+        } else if (caCertificate != null) {
+            // VERIFY_CA / STRICT: validate against the CA certificate.
+            builder.rootCertificate(caCertificate);
         }
-        return sslContext;
+        // else VERIFY_CA / STRICT with no trust material: the JVM default trust store is used.
+
+        return builder.build();
     }
 
     private static final long CONNECTION_INACTIVITY_CHECK = 5000L;
@@ -272,7 +283,11 @@ public CloseableHttpClient createHttpClient(boolean initSslContext, Map<String,
         LayeredConnectionSocketFactory sslConnectionSocketFactory;
         if (sslContext != null) {
             String socketSNI = (String)configuration.get(ClientConfigProperties.SSL_SOCKET_SNI.getKey());
-            if (socketSNI != null && !socketSNI.trim().isEmpty()) {
+            SSLMode sslMode = ClientConfigProperties.SSL_MODE.getOrDefault(configuration);
+            // Trust and VerifyCa skip hostname verification. The same applies when a custom SNI is
+            // set because the connection hostname will not match the certificate.
+            boolean trustAllHostnames = sslMode == SSLMode.TRUST || sslMode == SSLMode.VERIFY_CA;
+            if (socketSNI != null && !socketSNI.trim().isEmpty() || trustAllHostnames) {
                 sslConnectionSocketFactory = new CustomSSLConnectionFactory(socketSNI, sslContext, (hostname, session) -> true);
             } else {
                 sslConnectionSocketFactory = new SSLConnectionSocketFactory(sslContext);
@@ -880,6 +895,10 @@ public RuntimeException wrapException(String message, Exception cause, String qu
             return (RuntimeException) cause;
         }
 
+        if (cause instanceof SSLException) {
+            return new ClickHouseException("SSL Problem", cause, queryId);
+        }
+
         if (cause instanceof ConnectionRequestTimeoutException ||
                 cause instanceof NoHttpResponseException ||
                 cause instanceof ConnectTimeoutException ||