Add a list of exempted path prefixes for https redirection.

binary-compatibility-validator/reference-public-api/ktor-server-core.txt

@@ -620,14 +620,17 @@ public final class io/ktor/features/HSTS$Feature : io/ktor/application/Applicati
 public final class io/ktor/features/HttpsRedirect {
 	public static final field Feature Lio/ktor/features/HttpsRedirect$Feature;
 	public fun <init> (Lio/ktor/features/HttpsRedirect$Configuration;)V
+	public final fun getExemptions ()Ljava/util/List;
 	public final fun getPermanent ()Z
 	public final fun getRedirectPort ()I
 }
 
 public final class io/ktor/features/HttpsRedirect$Configuration {
 	public fun <init> ()V
+	public final fun getExemptions ()Ljava/util/List;
 	public final fun getPermanentRedirect ()Z
 	public final fun getSslPort ()I
+	public final fun setExemptions (Ljava/util/List;)V
 	public final fun setPermanentRedirect (Z)V
 	public final fun setSslPort (I)V
 }

ktor-server/ktor-server-core/jvm/src/io/ktor/features/HttpsRedirect.kt

@@ -23,6 +23,12 @@ class HttpsRedirect(config: Configuration) {
      */
     val permanent: Boolean = config.permanentRedirect
 
+    /**
+     * Exempted paths
+     */
+
+    val exemptions: List<String> = config.exemptions
+
     /**
      * Redirect feature configuration
      */
@@ -36,6 +42,12 @@ class HttpsRedirect(config: Configuration) {
          * Use permanent redirect or temporary
          */
         var permanentRedirect: Boolean = true
+
+        /**
+         * Exempted path prefixes. Any request for a path starting with these prefixes will not be redirected.
+         */
+
+        var exemptions: List<String> = listOf()
     }
 
     /**
@@ -46,7 +58,8 @@ class HttpsRedirect(config: Configuration) {
         override fun install(pipeline: ApplicationCallPipeline, configure: Configuration.() -> Unit): HttpsRedirect {
             val feature = HttpsRedirect(Configuration().apply(configure))
             pipeline.intercept(ApplicationCallPipeline.Features) {
-                if (call.request.origin.scheme == "http") {
+                if (call.request.origin.scheme == "http" &&
+                        !feature.exemptions.any { call.request.origin.uri.startsWith(it) }) { 
                     val redirectUrl = call.url { protocol = URLProtocol.HTTPS; port = feature.redirectPort }
                     call.respondRedirect(redirectUrl, feature.permanent)
                     finish()

ktor-server/ktor-server-tests/jvm/test/io/ktor/tests/server/features/HttpsRedirectFeatureTest.kt

@@ -83,4 +83,24 @@ class HttpsRedirectFeatureTest {
             }
         }
     }
+
+    @Test
+    fun testRedirectHttpsExemption() {
+        withTestApplication {
+            application.install(HttpsRedirect) {
+                exemptions = listOf("/exempted")
+            }
+            application.intercept(ApplicationCallPipeline.Fallback) {
+                call.respond("ok")
+            }
+
+            handleRequest(HttpMethod.Get, "/nonexempted").let { call ->
+                assertEquals(HttpStatusCode.MovedPermanently, call.response.status())
+            }
+
+            handleRequest(HttpMethod.Get, "/exempted/path").let { call ->
+                assertEquals(HttpStatusCode.OK, call.response.status())
+            }
+        }
+    }
 }