feat(files_sharing): fetch remote avatars for external shares

Signed-off-by: Kent Delante <kent@delante.me>
Assisted-by: ClaudeCode:claude-sonnet-5

Author: leftybournes

lib/private/Avatar/AvatarManager.php

@@ -13,6 +13,7 @@
 use OC\User\Manager;
 use OCP\Accounts\IAccountManager;
 use OCP\Accounts\PropertyDoesNotExistException;
+use OCP\Federation\ICloudIdManager;
 use OCP\Files\IAppData;
 use OCP\Files\NotFoundException;
 use OCP\Files\NotPermittedException;
@@ -55,6 +56,11 @@ public function __construct(
 	public function getAvatar(string $userId): IAvatar {
 		$user = $this->userManager->get($userId);
 		if ($user === null) {
+			$cloudIdManager = \OCP\Server::get(ICloudIdManager::class);
+			if ($cloudIdManager->isValidCloudId($userId)) {
+				return $this->getRemoteAvatar($userId);
+			}
+
 			throw new \Exception('user does not exist');
 		}
 
@@ -134,4 +140,13 @@ public function deleteUserAvatar(string $userId): void {
 	public function getGuestAvatar(string $name): IAvatar {
 		return new GuestAvatar($name, $this->config, $this->logger);
 	}
+
+	/**
+	 * Returns a RemoteAvatar
+	 *
+	 * @param string $userId The \OCP\Federation\ICloudId of the remote account, e.g. account@example.com
+	 */
+	private function getRemoteAvatar(string $userId): IAvatar {
+		return new RemoteAvatar($userId, $this->config, $this->logger);
+	}
 }

lib/private/Avatar/RemoteAvatar.php

@@ -0,0 +1,96 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+declare(strict_types=1);
+
+namespace OC\Avatar;
+
+use OCP\Federation\ICloudId;
+use OCP\Federation\ICloudIdManager;
+use OCP\Files\SimpleFS\InMemoryFile;
+use OCP\Files\SimpleFS\ISimpleFile;
+use OCP\Http\Client\IClientService;
+use OCP\IConfig;
+use Psr\Log\LoggerInterface;
+
+class RemoteAvatar extends Avatar {
+	private ICloudId $cloudId;
+
+	public function __construct(
+		protected string $userId,
+		protected IConfig $config,
+		protected LoggerInterface $logger,
+	) {
+		parent::__construct($config, $logger);
+
+		$cloudIdManager = \OCP\Server::get(ICloudIdManager::class);
+		$this->cloudId = $cloudIdManager->resolveCloudId($userId);
+	}
+
+	#[\Override]
+	public function exists(): bool {
+		return true;
+	}
+
+	#[\Override]
+	public function getDisplayName(): string {
+		return $this->cloudId->getDisplayId();
+	}
+
+	/**
+	 * Setting avatars isn't implemented for remote accounts
+	 */
+	public function set($data): void {
+	}
+
+	/**
+	 * Removing avatars isn't implemented for remote accounts
+	 */
+	public function remove(bool $silent = false): void {
+	}
+
+	#[\Override]
+	public function getFile(int $size, bool $darkTheme = false): ISimpleFile {
+		$url = rtrim($this->cloudId->getRemote(), '/') . '/index.php/avatar/' . rawurlencode($this->cloudId->getUser()) . '/' . $size;
+		if ($darkTheme) {
+			$url .= '/dark';
+		}
+
+		$clientService = \OCP\Server::get(IClientService::class);
+		$client = $clientService->newClient();
+		$response = $client->get($url, [
+			'verify' => !$this->config->getSystemValueBool('sharing.federation.allowSelfSignedCertificates', false)
+		]);
+
+		$contentType = $response->getHeader('Content-Type');
+		if ($contentType !== 'image/png') {
+			throw new \Exception('Unknown filetype');
+		}
+
+		$avatar = $response->getBody();
+		if (is_resource($avatar)) {
+			$avatar = stream_get_contents($avatar);
+			if ($avatar === false) {
+				throw new \Exception('Failed to fetch remote avatar');
+			}
+		}
+
+		return new InMemoryFile('avatar.png', $avatar);
+	}
+
+	/**
+	 * Handling user changes isn't implemented for remote accounts
+	 */
+	#[\Override]
+	public function userChanged(string $feature, $oldValue, $newValue): void {
+	}
+
+	#[\Override]
+	public function isCustomAvatar(): bool {
+		return true;
+	}
+}