Give kyuubi.server.redaction.regex a default so REDACTED redacts on a stock install

kyuubi-common/src/main/scala/org/apache/kyuubi/Utils.scala

@@ -327,16 +327,13 @@ object Utils extends Logging {
   }
 
   def redactCommandLineArgs(conf: KyuubiConf, commands: Iterable[String]): Iterable[String] = {
-    conf.get(SERVER_SECRET_REDACTION_PATTERN) match {
-      case Some(redactionPattern) =>
-        commands.map {
-          case PATTERN_FOR_KEY_VALUE_ARG(key, value) =>
-            val (_, newValue) = redact(redactionPattern, Seq((key, value))).head
-            genKeyValuePair(key, newValue)
-          case cmd =>
-            cmd
-        }
-      case _ => commands
+    val redactionPattern = conf.get(SERVER_SECRET_REDACTION_PATTERN)
+    commands.map {
+      case PATTERN_FOR_KEY_VALUE_ARG(key, value) =>
+        val (_, newValue) = redact(redactionPattern, Seq((key, value))).head
+        genKeyValuePair(key, newValue)
+      case cmd =>
+        cmd
     }
   }
 

kyuubi-common/src/main/scala/org/apache/kyuubi/config/KyuubiConf.scala

@@ -3572,15 +3572,17 @@ object KyuubiConf {
       .booleanConf
       .createWithDefault(false)
 
-  val SERVER_SECRET_REDACTION_PATTERN: OptionalConfigEntry[Regex] =
+  val SERVER_SECRET_REDACTION_PATTERN: ConfigEntry[Regex] =
     buildConf("kyuubi.server.redaction.regex")
       .audience(SERVER)
       .immutable
       .doc("Regex to decide which Kyuubi contain sensitive information. When this regex matches " +
-        "a property key or value, the value is redacted from the various logs.")
+        "a property key or value, the value is redacted from the various logs. Defaults to " +
+        "the same pattern Spark uses for spark.redaction.regex, so common secret-bearing keys " +
+        "are redacted out of the box.")
       .version("1.6.0")
       .regexConf
-      .createOptional
+      .createWithDefault("(?i)secret|password|token|access[.]key".r)
 
   val SERVER_CONF_RETRIEVE_MODE: ConfigEntry[String] =
     buildConf("kyuubi.server.conf.retrieveMode")
@@ -3589,7 +3591,8 @@ object KyuubiConf {
       .doc("Controls how session configurations are returned in REST API responses. " +
         "Supported values: " +
         "<ul>" +
-        "<li>REDACTED: Mask values that match kyuubi.server.redaction.regex (default).</li>" +
+        "<li>REDACTED: Mask values that match kyuubi.server.redaction.regex, which has a " +
+        "default pattern (default).</li>" +
         "<li>ORIGINAL: Return the raw config values as-is.</li>" +
         "<li>NONE: Omit the conf map from responses entirely.</li>" +
         "</ul>")

kyuubi-server/src/main/scala/org/apache/kyuubi/server/api/ApiUtils.scala

@@ -42,7 +42,7 @@ object ApiUtils extends Logging {
       case ConfRetrieveMode.ORIGINAL => rawConf.asJava
       case ConfRetrieveMode.REDACTED =>
         val pattern = session.sessionManager.getConf.get(SERVER_SECRET_REDACTION_PATTERN)
-        Utils.redact(pattern, rawConf.toSeq).toMap.asJava
+        Utils.redact(Some(pattern), rawConf.toSeq).toMap.asJava
     }
   }
 

kyuubi-server/src/test/scala/org/apache/kyuubi/server/api/v1/SessionsResourceSuite.scala

@@ -439,6 +439,29 @@ class SessionsResourceSuite extends KyuubiFunSuite with RestFrontendTestHelper {
     }
   }
 
+  test("get /sessions redacts spark confs by default with no explicit redaction regex") {
+    withNoExplicitRedactionPattern {
+      val sensitiveKey = "spark.password"
+      val sensitiveValue = "shouldNeverLeak"
+      val requestObj = new SessionOpenRequest(Map(sensitiveKey -> sensitiveValue).asJava)
+
+      val r = webTarget.path("api/v1/sessions")
+        .request(MediaType.APPLICATION_JSON_TYPE)
+        .post(Entity.entity(requestObj, MediaType.APPLICATION_JSON_TYPE))
+      assert(200 == r.getStatus)
+      val sessionHandle = r.readEntity(classOf[SessionHandle]).getIdentifier
+
+      val r2 = webTarget.path("api/v1/sessions").request().get()
+      assert(200 == r2.getStatus)
+      val sessions = r2.readEntity(new GenericType[Seq[SessionData]]() {})
+      val sessionConf = sessions.find(_.getIdentifier == sessionHandle.toString).get.getConf
+      assert(sessionConf.get(sensitiveKey) != sensitiveValue)
+      assert(sessionConf.get(sensitiveKey) == "*********(redacted)")
+
+      webTarget.path(s"api/v1/sessions/$sessionHandle").request().delete()
+    }
+  }
+
   test("get /sessions returns raw conf when mode is ORIGINAL") {
     withSessionConfDisplayMode("ORIGINAL") {
       val sensitiveKey = "spark.password"
@@ -465,4 +488,10 @@ class SessionsResourceSuite extends KyuubiFunSuite with RestFrontendTestHelper {
     try f
     finally conf.set(KyuubiConf.SERVER_CONF_RETRIEVE_MODE, "REDACTED")
   }
+
+  private def withNoExplicitRedactionPattern(f: => Unit): Unit = {
+    conf.unset(KyuubiConf.SERVER_SECRET_REDACTION_PATTERN)
+    try f
+    finally conf.set(KyuubiConf.SERVER_SECRET_REDACTION_PATTERN, "(?i)password".r)
+  }
 }