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/*
* Copyright © 2016 Canonical Limited
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the licence, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
* Author: Allison Lortie <desrt@desrt.ca>
*/
#define _GNU_SOURCE
#include "confinement.h"
#include <linux/magic.h>
#include <sys/stat.h>
#include <sys/vfs.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
static gboolean
verify_tmpfs (gint fd,
gboolean *out_is_tmpfs)
{
struct statfs buf;
if (fstatfs (fd, &buf) != 0)
return FALSE;
*out_is_tmpfs = (buf.f_type == TMPFS_MAGIC);
return TRUE;
}
static gboolean
verify_regular (gint fd,
gboolean *out_is_regular,
gsize *out_size)
{
struct stat buf;
if (fstat (fd, &buf) != 0)
return FALSE;
*out_is_regular = S_ISREG (buf.st_mode);
*out_size = buf.st_size;
return TRUE;
}
static void
fd_clear (gint *fd)
{
if (*fd != -1)
close (*fd);
}
typedef gint fd;
G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(fd, fd_clear)
static gboolean
get_flatpak_info_keyfile (guint pid,
GKeyFile **out_keyfile)
{
g_autoptr(GKeyFile) keyfile = NULL;
g_autofree gchar *contents = NULL;
g_autoptr(GError) error = NULL;
g_auto(fd) root_fd = -1;
g_auto(fd) info_fd = -1;
gboolean is_regular;
gboolean is_tmpfs;
gchar rootdir[40];
gsize size;
snprintf (rootdir, sizeof rootdir, "/proc/%u/root", pid);
root_fd = open (rootdir, O_DIRECTORY | O_PATH);
if (root_fd == -1)
{
g_warning ("pid %u: cannot access root filesystem: %s", pid, g_strerror (errno));
return FALSE;
}
/* <desrt> do you guarantee for always and forever that the root fs of a flatpak app is tmpfs?
* <alexlarsson> yes
*/
if (!verify_tmpfs (root_fd, &is_tmpfs))
{
g_warning ("pid %u: fstatfs() on root filesystem failed: %s", pid, g_strerror (errno));
return FALSE;
}
if (!is_tmpfs)
{
/* Unconfined */
*out_keyfile = NULL;
return TRUE;
}
info_fd = openat (root_fd, ".flatpak-info", O_RDONLY | O_NOCTTY);
if (info_fd == -1 && errno == ENOENT)
{
/* Unconfined */
*out_keyfile = NULL;
return TRUE;
}
/* This is now surely a flatpak-confined application. We only have two
* options past this point: failure, or returning a non-NULL GKeyFile.
*/
if (info_fd == -1)
{
g_warning ("pid %u: failed to open .flatpak-info file: %s", pid, g_strerror (errno));
return FALSE;
}
if (!verify_regular (info_fd, &is_regular, &size))
{
g_warning ("pid %u: fstat() on .flatpak-info file failed: %s", pid, g_strerror (errno));
return FALSE;
}
if (!is_regular)
{
g_warning ("pid %u: .flatpak-info is not regular file", pid);
return FALSE;
}
if (size > 1000000)
{
g_warning ("pid %u: .flatpak-info file is unreasonably large", pid);
return FALSE;
}
contents = g_malloc (size);
if (read (info_fd, contents, size) != size)
{
/* "No error" in this case means that the size changed */
g_warning ("pid %u: failed to read entire .flatpak-info file: %s", pid, g_strerror (errno));
return FALSE;
}
keyfile = g_key_file_new ();
if (!g_key_file_load_from_data (keyfile, contents, size, G_KEY_FILE_NONE, &error))
{
g_warning ("pid %u: cannot parse .flatpak-info contents: %s", pid, error->message);
return FALSE;
}
*out_keyfile = g_steal_pointer (&keyfile);
return TRUE;
}
gboolean
confinement_check_flatpak (GVariant *credentials,
gboolean *out_is_confined,
Permissions *out_permissions)
{
g_autoptr(GKeyFile) keyfile = NULL;
g_autoptr(GError) error = NULL;
gchar *appid;
guint pid;
if (!g_variant_lookup (credentials, "ProcessID", "u", &pid))
{
g_warning ("Caller credentials are missing ProcessID field");
return FALSE;
}
if (!get_flatpak_info_keyfile (pid, &keyfile))
/* this will throw its own g_warning() */
return FALSE;
if (keyfile == NULL)
{
/* Everything went OK, but we didn't find a keyfile there. As far
* as flatpak is concerned, this app is unconfined.
*/
*out_is_confined = FALSE;
return TRUE;
}
appid = g_key_file_get_string (keyfile, "Application", "name", &error);
if (appid == NULL)
{
g_warning ("pid %u: .flatpak-info: %s", pid, error->message);
return FALSE;
}
/* We will have success now, even if we don't find the dconf keys (in
* which case there is simply no permissions to access dconf and we
* share an empty database).
*/
permission_list_init (&out_permissions->readable,
g_key_file_get_string_list (keyfile, "Policy dconf", "readable", NULL, NULL));
permission_list_init (&out_permissions->writable,
g_key_file_get_string_list (keyfile, "Policy dconf", "writable", NULL, NULL));
out_permissions->ipc_dir = g_build_filename (g_get_user_runtime_dir (), "app", appid, "dconf", NULL);
out_permissions->app_id = appid;
*out_is_confined = TRUE;
return TRUE;
}
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