Server: Implement temporary links

server/build.gradle

@@ -80,5 +80,6 @@ dockerRun {
     name = 'uhabits-server'
     image "uhabits-server:$version"
     ports '8080:8080'
-    arguments '--restart=always'
+    daemonize false
+    clean true
 }

server/src/org/isoron/uhabits/sync/app/LinkModule.kt

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2016-2020 Alinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.sync.app
+
+import io.ktor.application.*
+import io.ktor.http.*
+import io.ktor.request.*
+import io.ktor.response.*
+import io.ktor.routing.*
+import org.isoron.uhabits.sync.*
+
+data class LinkRegisterRequestData(
+    val syncKey: String,
+)
+fun LinkRegisterRequestData.toJson(): String = defaultMapper.writeValueAsString(this)
+
+fun Routing.links(app: SyncApplication) {
+    post("/links") {
+        try {
+            val data = call.receive<LinkRegisterRequestData>()
+            val link = app.server.registerLink(data.syncKey)
+            call.respond(HttpStatusCode.OK, link)
+        } catch (e: ServiceUnavailable) {
+            call.respond(HttpStatusCode.ServiceUnavailable)
+        }
+    }
+    get("/links/{id}") {
+        try {
+            val id = call.parameters["id"]!!
+            val link = app.server.getLink(id)
+            call.respond(HttpStatusCode.OK, link)
+        } catch (e: ServiceUnavailable) {
+            call.respond(HttpStatusCode.ServiceUnavailable)
+        } catch (e: KeyNotFoundException) {
+            call.respond(HttpStatusCode.NotFound)
+        }
+    }
+}

server/src/org/isoron/uhabits/sync/app/SyncApplication.kt

@@ -46,6 +46,7 @@ class SyncApplication(
         routing {
             registration(this@SyncApplication)
             storage(this@SyncApplication)
+            links(this@SyncApplication)
         }
     }
 }

server/src/org/isoron/uhabits/sync/links/Link.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2016-2020 Alinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.sync.links
+
+import org.isoron.uhabits.sync.*
+import java.time.*
+
+/**
+ * A Link maps a public URL (such as https://sync.loophabits.org/links/B752A6)
+ * to a synchronization key. They are used to transfer sync keys between devices
+ * without ever exposing the original sync key. Unlike sync keys, links expire
+ * after a few minutes.
+ */
+data class Link(
+    val id: String,
+    val syncKey: String,
+    val createdAt: Long,
+)
+
+fun Link.toJson(): String = defaultMapper.writeValueAsString(this)

server/src/org/isoron/uhabits/sync/links/LinkManager.kt

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2016-2020 Alinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.sync.links
+
+import org.isoron.uhabits.sync.*
+import org.isoron.uhabits.sync.utils.*
+
+class LinkManager(
+    private val timeoutInMillis: Long = 900_000,
+) {
+    private val links = HashMap<String, Link>()
+
+    fun register(syncKey: String): Link {
+        val link = Link(
+            id = randomString(64),
+            syncKey = syncKey,
+            createdAt = System.currentTimeMillis(),
+        )
+        links[link.id] = link
+        return link
+    }
+
+    fun get(id: String): Link {
+        val link = links[id] ?: throw KeyNotFoundException()
+        val ageInMillis = System.currentTimeMillis() - link.createdAt
+        if (ageInMillis > timeoutInMillis) {
+            links.remove(id)
+            throw KeyNotFoundException()
+        }
+        return link
+    }
+}

server/src/org/isoron/uhabits/sync/server/AbstractSyncServer.kt

@@ -20,6 +20,7 @@
 package org.isoron.uhabits.sync.server
 
 import org.isoron.uhabits.sync.*
+import org.isoron.uhabits.sync.links.*
 
 interface AbstractSyncServer {
     /**
@@ -59,4 +60,22 @@ interface AbstractSyncServer {
      *      to insufficient server resources or network problems.
      */
     suspend fun getDataVersion(key: String): Long
+
+    /**
+     * Registers a new temporary link (mapping to the given sync key) and returns it.
+     *
+     * @throws ServiceUnavailable If the link cannot be generated at this time due to
+     *      insufficient server resources.
+     */
+    suspend fun registerLink(syncKey: String): Link
+
+    /**
+     * Retrieves the syncKey associated with the given link id.
+     *
+     * @throws ServiceUnavailable If the link cannot be resolved at this time due to
+     *      insufficient server resources.
+     * @throws KeyNotFoundException If the link id cannot be found, or if it has
+     *      expired.
+     */
+    suspend fun getLink(id: String): Link
 }

server/src/org/isoron/uhabits/sync/server/RepositorySyncServer.kt

@@ -20,15 +20,16 @@
 package org.isoron.uhabits.sync.server
 
 import org.isoron.uhabits.sync.*
+import org.isoron.uhabits.sync.links.*
 import org.isoron.uhabits.sync.repository.*
-import java.util.*
-import kotlin.streams.*
+import org.isoron.uhabits.sync.utils.*
 
 /**
  * An AbstractSyncServer that stores all data in a [Repository].
  */
 class RepositorySyncServer(
     private val repo: Repository,
+    private val linkManager: LinkManager = LinkManager(),
 ) : AbstractSyncServer {
 
     override suspend fun register(): String {
@@ -62,16 +63,19 @@ class RepositorySyncServer(
         return repo.get(key).version
     }
 
+    override suspend fun registerLink(syncKey: String): Link {
+        return linkManager.register(syncKey)
+    }
+
+    override suspend fun getLink(id: String): Link {
+        return linkManager.get(id)
+    }
+
     private suspend fun generateKey(): String {
-        val chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
         while (true) {
-            val key = Random().ints(64, 0, chars.length)
-                .asSequence()
-                .map(chars::get)
-                .joinToString("")
+            val key = randomString(64)
             if (!repo.contains(key))
                 return key
         }
-
     }
 }

server/src/org/isoron/uhabits/sync/utils/String.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2016-2020 Alinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.sync.utils
+
+import java.util.*
+import kotlin.streams.*
+
+fun randomString(length: Long): String {
+    val chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    return Random().ints(length, 0, chars.length)
+        .asSequence()
+        .map(chars::get)
+        .joinToString("")
+}

server/test/org/isoron/uhabits/sync/app/LinksModuleTest.kt

@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2016-2020 Alinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.sync.app
+
+import io.ktor.http.*
+import io.ktor.server.testing.*
+import kotlinx.coroutines.*
+import org.isoron.uhabits.sync.*
+import org.isoron.uhabits.sync.links.*
+import org.junit.Test
+import org.mockito.Mockito.*
+import kotlin.test.*
+
+class LinksModuleTest : BaseApplicationTest() {
+    private val link = Link(
+        id = "ABC123",
+        syncKey = "SECRET",
+        createdAt = System.currentTimeMillis(),
+    )
+
+    @Test
+    fun `when POST is successful should return link`(): Unit = runBlocking {
+        `when`(server.registerLink("SECRET")).thenReturn(link)
+        withTestApplication(app()) {
+            handlePost("/links", LinkRegisterRequestData(syncKey = "SECRET")).apply {
+                assertEquals(HttpStatusCode.OK, response.status())
+                assertEquals(link.toJson(), response.content)
+            }
+        }
+    }
+
+    @Test
+    fun `when GET is successful should return link`(): Unit = runBlocking {
+        `when`(server.getLink("ABC123")).thenReturn(link)
+        withTestApplication(app()) {
+            handleGet("/links/ABC123").apply {
+                assertEquals(HttpStatusCode.OK, response.status())
+                assertEquals(link.toJson(), response.content)
+            }
+        }
+    }
+
+    @Test
+    fun `GET with invalid link id should return 404`(): Unit = runBlocking {
+        `when`(server.getLink("ABC123")).thenThrow(KeyNotFoundException())
+        withTestApplication(app()) {
+            handleGet("/links/ABC123").apply {
+                assertEquals(HttpStatusCode.NotFound, response.status())
+            }
+        }
+    }
+
+    private fun TestApplicationEngine.handlePost(url: String, data: LinkRegisterRequestData): TestApplicationCall {
+        return handleRequest(HttpMethod.Post, url) {
+            addHeader(HttpHeaders.ContentType, ContentType.Application.Json.toString())
+            setBody(data.toJson())
+        }
+    }
+
+    private fun TestApplicationEngine.handleGet(url: String): TestApplicationCall {
+        return handleRequest(HttpMethod.Get, url)
+    }
+
+}

server/test/org/isoron/uhabits/sync/links/LinkManagerTest.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2016-2020 Alinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.sync.links
+
+import org.isoron.uhabits.sync.*
+import org.junit.Test
+import kotlin.test.*
+
+class LinkManagerTest {
+
+    @Test
+    fun testUsage() {
+        val manager = LinkManager(timeoutInMillis = 250)
+        val originalLink = manager.register(syncKey = "SECRET")
+        val retrievedLink = manager.get(originalLink.id)
+        assertEquals(originalLink, retrievedLink)
+
+        Thread.sleep(260) // wait until expiration
+        assertFailsWith<KeyNotFoundException> {
+            manager.get(originalLink.id)
+        }
+
+        assertFailsWith<KeyNotFoundException> {
+            manager.get("INVALID")
+        }
+    }
+}

server/test/org/isoron/uhabits/sync/server/RepositorySyncServerTest.kt

@@ -17,11 +17,11 @@
  * with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-package org.isoron.uhabits.sync
+package org.isoron.uhabits.sync.server
 
 import kotlinx.coroutines.*
+import org.isoron.uhabits.sync.*
 import org.isoron.uhabits.sync.repository.*
-import org.isoron.uhabits.sync.server.*
 import org.junit.Test
 import java.nio.file.*
 import kotlin.test.*