fix(dav): Public WebDAV endpoint should allow GET requests

`GET` should be allowed even without Ajax header to allow downloading files,
or show files in the viewer. All other requests could be guarded, but this should not.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

apps/dav/appinfo/v2/publicremote.php

@@ -96,11 +96,15 @@
 $baseuri = $baseuri . $match[0];
 
 $server = $serverFactory->createServer($baseuri, $requestUri, $authPlugin, function (\Sabre\DAV\Server $server) use ($authBackend, $linkCheckPlugin, $filesDropPlugin) {
-	$isAjax = in_array('XMLHttpRequest', explode(',', $_SERVER['HTTP_X_REQUESTED_WITH'] ?? ''));
-	$federatedShareProvider = \OCP\Server::get(FederatedShareProvider::class);
-	if ($federatedShareProvider->isOutgoingServer2serverShareEnabled() === false && !$isAjax) {
-		// this is what is thrown when trying to access a non-existing share
-		throw new NotAuthenticated();
+	// GET must be allowed for e.g. showing images and allowing Zip downloads
+	if ($server->httpRequest->getMethod() !== 'GET') {
+		// If this is *not* a GET request we only allow access to public DAV from AJAX or when Server2Server is allowed
+		$isAjax = in_array('XMLHttpRequest', explode(',', $_SERVER['HTTP_X_REQUESTED_WITH'] ?? ''));
+		$federatedShareProvider = \OCP\Server::get(FederatedShareProvider::class);
+		if ($federatedShareProvider->isOutgoingServer2serverShareEnabled() === false && $isAjax === false) {
+			// this is what is thrown when trying to access a non-existing share
+			throw new NotAuthenticated();
+		}
 	}
 
 	$share = $authBackend->getShare();
@@ -152,4 +156,4 @@
 $server->addPlugin($filesDropPlugin);
 
 // And off we go!
-$server->exec();
+$server->start();

build/integration/config/behat.yml

@@ -58,7 +58,7 @@ default:
       paths:
         - "%paths.base%/../dav_features"
       contexts:
-        - FeatureContext:
+        - DavFeatureContext:
             baseUrl:  http://localhost:8080/ocs/
             admin:
               - admin

build/integration/dav_features/dav-v2-public.feature

@@ -0,0 +1,41 @@
+# SPDX-FileCopyrightText: 2023 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+Feature: dav-v2-public
+	Background:
+		Given using api version "1"
+
+	Scenario: Downloading a file from public share with Ajax header
+		Given using new dav path
+		And As an "admin"
+		And user "user0" exists
+		And user "user1" exists
+		And As an "user1"
+		And user "user1" created a folder "/testshare"
+		When User "user1" uploads file "data/green-square-256.png" to "/testshare/image.png"
+		And as "user1" creating a share with
+		  | path | testshare |
+		  | shareType | 3 |
+		  | permissions | 1 |
+		And As an "user0"
+		Given using new public dav path
+		When Downloading public file "/image.png"
+		Then the downloaded file has the content of "/testshare/image.png" from "user1" data
+
+	# Test that downloading files work to ensure e.g. the viewer works or files can be downloaded
+	Scenario: Downloading a file from public share without Ajax header and disabled s2s share
+		Given using new dav path
+		And As an "admin"
+		And user "user0" exists
+		And user "user1" exists
+		And As an "user1"
+		And user "user1" created a folder "/testshare"
+		When User "user1" uploads file "data/green-square-256.png" to "/testshare/image.png"
+		And as "user1" creating a share with
+		  | path | testshare |
+		  | shareType | 3 |
+		  | permissions | 1 |
+		And As an "user0"
+		Given parameter "outgoing_server2server_share_enabled" of app "files_sharing" is set to "no"
+		Given using new public dav path
+		When Downloading public file "/image.png" without ajax header
+		Then the downloaded file has the content of "/testshare/image.png" from "user1" data

build/integration/features/bootstrap/CommandLineContext.php

@@ -26,6 +26,7 @@
  */
 require __DIR__ . '/../../vendor/autoload.php';
 
+use Behat\Behat\Context\Exception\ContextNotFoundException;
 use Behat\Behat\Hook\Scope\BeforeScenarioScope;
 use PHPUnit\Framework\Assert;
 
@@ -61,8 +62,12 @@ public function maintenanceModeIsDisabled() {
 	/** @BeforeScenario */
 	public function gatherContexts(BeforeScenarioScope $scope) {
 		$environment = $scope->getEnvironment();
-		// this should really be "WebDavContext" ...
-		$this->featureContext = $environment->getContext('FeatureContext');
+		// this should really be "WebDavContext"
+		try {
+			$this->featureContext = $environment->getContext('FeatureContext');
+		} catch (ContextNotFoundException) {
+			$this->featureContext = $environment->getContext('DavFeatureContext');
+		}
 	}
 
 	private function findLastTransferFolderForUser($sourceUser, $targetUser) {

build/integration/features/bootstrap/CommentsContext.php

@@ -49,8 +49,6 @@ public function __construct($baseUrl) {
 		}
 	}
 
-
-
 	/**
 	 * get a named entry from response instead of picking a random entry from values
 	 *

build/integration/features/bootstrap/DavFeatureContext.php

@@ -0,0 +1,23 @@
+<?php
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+use Behat\Behat\Context\Context;
+use Behat\Behat\Context\SnippetAcceptingContext;
+
+require __DIR__ . '/../../vendor/autoload.php';
+
+class DavFeatureContext implements Context, SnippetAcceptingContext {
+	use AppConfiguration;
+	use ContactsMenu;
+	use ExternalStorage;
+	use Search;
+	use WebDav;
+	use Trashbin;
+
+	protected function resetAppConfigs() {
+		$this->deleteServerConfig('files_sharing', 'outgoing_server2server_share_enabled');
+	}
+}

build/integration/features/bootstrap/Download.php

@@ -138,4 +138,18 @@ public function theDownloadedZipFileContainsAFolderNamed($folderName) {
 			"Local header for folder did not appear once in zip file"
 		);
 	}
+
+	/**
+	 * @Then the downloaded file has the content of :sourceFilename from :user data
+	 */
+	public function theDownloadedFileHasContentOfUserFile($sourceFilename, $user) {
+		$this->getDownloadedFile();
+		$expectedFileContents = file_get_contents($this->getDataDirectory() . "/$user/files" . $sourceFilename);
+
+		// prevent the whole file from being printed in case of error.
+		Assert::assertEquals(
+			0, strcmp($expectedFileContents, $this->downloadedFile),
+			'Downloaded file content does not match local file content'
+		);
+	}
 }

build/integration/features/bootstrap/FeatureContext.php

@@ -28,7 +28,6 @@
 
 require __DIR__ . '/../../vendor/autoload.php';
 
-
 /**
  * Features context.
  */

build/integration/features/bootstrap/WebDav.php

@@ -80,6 +80,14 @@ public function usingNewDavPath() {
 		$this->usingOldDavPath = false;
 	}
 
+	/**
+	 * @Given /^using new public dav path$/
+	 */
+	public function usingNewPublicDavPath() {
+		$this->davPath = 'public.php/dav';
+		$this->usingOldDavPath = false;
+	}
+
 	public function getDavFilesPath($user) {
 		if ($this->usingOldDavPath === true) {
 			return $this->davPath;
@@ -270,6 +278,42 @@ public function downloadingFile($fileName) {
 		}
 	}
 
+	/**
+	 * @When Downloading public file :filename
+	 */
+	public function downloadingPublicFile(string $filename) {
+		$token = $this->lastShareData->data->token;
+		$fullUrl = substr($this->baseUrl, 0, -4) . "public.php/dav/files/$token/$filename";
+
+		$client = new GClient();
+		$options = [
+			'headers' => [
+				'X-Requested-With' => 'XMLHttpRequest',
+			]
+		];
+
+		try {
+			$this->response = $client->request('GET', $fullUrl, $options);
+		} catch (\GuzzleHttp\Exception\ClientException $e) {
+			$this->response = $e->getResponse();
+		}
+	}
+
+	/**
+	 * @When Downloading public file :filename without ajax header
+	 */
+	public function downloadingPublicFileWithoutHeader(string $filename) {
+		$token = $this->lastShareData->data->token;
+		$fullUrl = substr($this->baseUrl, 0, -4) . "public.php/dav/files/$token/$filename";
+
+		$client = new GClient();
+		try {
+			$this->response = $client->request('GET', $fullUrl);
+		} catch (\GuzzleHttp\Exception\ClientException $e) {
+			$this->response = $e->getResponse();
+		}
+	}
+
 	/**
 	 * @Then Downloaded content should start with :start
 	 * @param int $start