Merge pull request #56341 from nextcloud/backport/55648/stable32

[stable32] fix(ocm): align discovery process with OCM spec

Author: AndyScherzinger

lib/private/OCM/OCMDiscoveryService.php

@@ -103,22 +103,46 @@ public function discover(string $remote, bool $skipCache = false): ICapabilityAw
 			if ($this->config->getSystemValueBool('sharing.federation.allowSelfSignedCertificates') === true) {
 				$options['verify'] = false;
 			}
-			$response = $client->get($remote . '/ocm-provider/', $options);
-
-			$body = null;
-			if ($response->getStatusCode() === Http::STATUS_OK) {
-				$body = $response->getBody();
-				// update provider with data returned by the request
-				$provider->import(json_decode($body, true, 8, JSON_THROW_ON_ERROR) ?? []);
-				$this->cache->set($remote, $body, 60 * 60 * 24);
-				$this->remoteProviders[$remote] = $provider;
-				return $provider;
+			$urls = [
+				$remote . '/.well-known/ocm',
+				$remote . '/ocm-provider',
+			];
+
+
+			foreach ($urls as $url) {
+				$exception = null;
+				$body = null;
+				$status = null;
+				try {
+					$response = $client->get($url, $options);
+					if ($response->getStatusCode() === Http::STATUS_OK) {
+						$body = $response->getBody();
+						$status = $response->getStatusCode();
+						// update provider with data returned by the request
+						$provider->import(json_decode($body, true, 8, JSON_THROW_ON_ERROR) ?? []);
+						$this->cache->set($remote, $body, 60 * 60 * 24);
+						$this->remoteProviders[$remote] = $provider;
+						return $provider;
+					}
+				} catch (\Exception $e) {
+					$this->logger->debug("Tried unsuccesfully to do discovery at: {$url}", [
+						'exception' => $e,
+						'remote' => $remote
+					]);
+					// We want to throw only the last exception
+					$exception = $e;
+					continue;
+				}
+			}
+			if ($exception) {
+				throw $exception;
 			}
 
+
 			throw new OCMProviderException('invalid remote ocm endpoint');
 		} catch (JsonException|OCMProviderException) {
 			$this->cache->set($remote, false, 5 * 60);
-			throw new OCMProviderException('data returned by remote seems invalid - status:' . $response->getStatusCode() . ' - ' . ($body ?? ''));
+			throw new OCMProviderException('data returned by remote seems invalid - status: ' . ($status ?? '') . ' - body: ' . ($body ?? ''));
 		} catch (\Exception $e) {
 			$this->cache->set($remote, false, 5 * 60);
 			$this->logger->warning('error while discovering ocm provider', [