modules: refactor check_flatpak to a common place

Move check_flatpak used by module-access and module-protocol-pulse
to a common flatpak-utils.h

src/modules/flatpak-utils.h

@@ -0,0 +1,88 @@
+/* PipeWire
+ *
+ * Copyright © 2018 Wim Taymans
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef FLATPAK_UTILS_H
+#define FLATPAK_UTILS_H
+
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/vfs.h>
+
+#include <spa/include/spa/utils/result.h>
+#include <pipewire/log.h>
+
+
+static int pw_check_flatpak(pid_t pid)
+{
+#if defined(__linux__)
+	char root_path[2048];
+	int root_fd, info_fd, res;
+	struct stat stat_buf;
+
+	snprintf(root_path, sizeof(root_path), "/proc/%d/root", (int)pid);
+	root_fd = openat (AT_FDCWD, root_path, O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC | O_NOCTTY);
+	if (root_fd == -1) {
+		res = -errno;
+		if (res == -EACCES) {
+			struct statfs buf;
+			/* Access to the root dir isn't allowed. This can happen if the root is on a fuse
+			 * filesystem, such as in a toolbox container. We will never have a fuse rootfs
+			 * in the flatpak case, so in that case its safe to ignore this and
+			 * continue to detect other types of apps. */
+			if (statfs(root_path, &buf) == 0 &&
+			    buf.f_type == 0x65735546) /* FUSE_SUPER_MAGIC */
+				return 0;
+		}
+		/* Not able to open the root dir shouldn't happen. Probably the app died and
+		 * we're failing due to /proc/$pid not existing. In that case fail instead
+		 * of treating this as privileged. */
+		pw_log_info("failed to open \"%s\": %s", root_path, spa_strerror(res));
+		return res;
+	}
+	info_fd = openat (root_fd, ".flatpak-info", O_RDONLY | O_CLOEXEC | O_NOCTTY);
+	close (root_fd);
+	if (info_fd == -1) {
+		if (errno == ENOENT) {
+			pw_log_debug("no .flatpak-info, client on the host");
+			/* No file => on the host */
+			return 0;
+		}
+		res = -errno;
+		pw_log_error("error opening .flatpak-info: %m");
+		return res;
+        }
+	if (fstat (info_fd, &stat_buf) != 0 || !S_ISREG (stat_buf.st_mode)) {
+		/* Some weird fd => failure, assume sandboxed */
+		pw_log_error("error fstat .flatpak-info: %m");
+	}
+	close(info_fd);
+	return 1;
+#else
+	return 0;
+#endif
+}
+
+#endif /* FLATPAK_UTILS_H */