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[gnome-software] Rewrite the external appstream helper in C

commit cd9dfee83127cb2618a2367849bbe51768385f67
Author: Richard Hughes <richard hughsie com>
Date:   Wed Nov 23 09:57:28 2016 +0000

    Rewrite the external appstream helper in C
    
    Doing this in C is several orders of magnitude safer than trying to to it
    with bash. When we read the file, check the content type, then check it's a
    valid AppStream file and then install it with a hardcoded path and a specific
    prefix. Also write it with specific permissions.
    
    Many thanks go to the SUSE security team for spotting all the issues.

 po/POTFILES.in                                  |    1 +
 src/plugins/Makefile.am                         |   17 +--
 src/plugins/gnome-software-install-appstream.in |    9 --
 src/plugins/gs-install-appstream.c              |  155 +++++++++++++++++++++++
 src/plugins/gs-plugin-external-appstream.c      |    8 +-
 5 files changed, 166 insertions(+), 24 deletions(-)
---
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 4048c0a..80f4397 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -68,3 +68,4 @@ src/org.gnome.Software.desktop.in
 src/gs-shell-loading.c
 [type: gettext/glade]src/gs-shell-loading.ui
 src/plugins/gs-desktop-common.c
+src/plugins/gs-install-appstream.c
diff --git a/src/plugins/Makefile.am b/src/plugins/Makefile.am
index b8aefa3..20e8b12 100644
--- a/src/plugins/Makefile.am
+++ b/src/plugins/Makefile.am
@@ -26,6 +26,7 @@ AM_CPPFLAGS =                                         \
        -DLIBDIR=\""$(libdir)"\"                        \
        -DLIBEXECDIR=\""$(libexecdir)"\"                \
        -DLOCALSTATEDIR=\""$(localstatedir)"\"          \
+       -DLOCALEDIR=\""$(localedir)"\"                  \
        -DSBINDIR=\"$(sbindir)\"                        \
        -DSYSCONFDIR=\""$(sysconfdir)"\"                \
        -DTESTDATADIR=\""$(top_srcdir)/data/tests"\"    \
@@ -53,8 +54,8 @@ plugin_LTLIBRARIES =                                  \
 if HAVE_EXTERNAL_APPSTREAM
 plugin_LTLIBRARIES += libgs_plugin_external-appstream.la
 
-libexec_SCRIPTS =                      \
-       gnome-software-install-appstream
+libexec_PROGRAMS = gnome-software-install-appstream
+
 endif
 
 if HAVE_SNAP
@@ -137,16 +138,12 @@ libgs_plugin_external_appstream_la_LIBADD = $(GS_PLUGIN_LIBS) $(SOUP_LIBS)
 libgs_plugin_external_appstream_la_LDFLAGS = -module -avoid-version
 libgs_plugin_external_appstream_la_CFLAGS = $(GS_PLUGIN_CFLAGS) $(WARN_CFLAGS) $(SOUP_CFLAGS)
 
-gnome-software-install-appstream: gnome-software-install-appstream.in Makefile
-       $(AM_V_GEN) sed -e "s|@localstatedir[@]|$(localstatedir)|g" $< > $@
+gnome_software_install_appstream_SOURCES = gs-install-appstream.c
+gnome_software_install_appstream_LDADD = $(GLIB_LIBS) $(APPSTREAM_LIBS)
+gnome_software_install_appstream_CFLAGS = $(WARN_CFLAGS)
+gnome_software_install_appstream_LDFLAGS = $(PIE_LDFLAGS) $(RELRO_LDFLAGS)
 endif
 
-EXTRA_DIST =                                           \
-       gnome-software-install-appstream.in
-
-CLEANFILES =                                           \
-       gnome-software-install-appstream
-
 libgs_plugin_key_colors_la_SOURCES = gs-plugin-key-colors.c
 libgs_plugin_key_colors_la_LIBADD = $(GS_PLUGIN_LIBS)
 libgs_plugin_key_colors_la_LDFLAGS = -module -avoid-version
diff --git a/src/plugins/gs-install-appstream.c b/src/plugins/gs-install-appstream.c
new file mode 100644
index 0000000..fb697da
--- /dev/null
+++ b/src/plugins/gs-install-appstream.c
@@ -0,0 +1,155 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
+ *
+ * Copyright (C) 2009-2016 Richard Hughes <richard hughsie com>
+ *
+ * Licensed under the GNU General Public License Version 2
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include <locale.h>
+#include <stdlib.h>
+
+#include <appstream-glib.h>
+#include <gio/gio.h>
+#include <glib/gi18n.h>
+#include <glib-object.h>
+
+static gboolean
+gs_install_appstream_copy_file (GFile *file, GError **error)
+{
+       g_autofree gchar *basename = NULL;
+       g_autofree gchar *basename_prefixed = NULL;
+       g_autofree gchar *cachedir = NULL;
+       g_autofree gchar *cachefn = NULL;
+       g_autoptr(GFile) cachedir_file = NULL;
+       g_autoptr(GFile) cachefn_file = NULL;
+
+       /* make sure the parent directory exists, but if not then create with
+        * the ownership and permissions of the current process */
+       cachedir = g_build_filename (LOCALSTATEDIR, "cache", "app-info", "xmls", NULL);
+       cachedir_file = g_file_new_for_path (cachedir);
+       if (!g_file_query_exists (cachedir_file, NULL)) {
+               if (!g_file_make_directory_with_parents (cachedir_file, NULL, error))
+                       return FALSE;
+       }
+
+       /* do the copy, overwriting existing files and setting the permissions
+        * of the current process (so that should be -rw-r--r--) */
+       basename = g_file_get_basename (file);
+       basename_prefixed = g_strdup_printf ("org.gnome.Software-%s", basename);
+       cachefn = g_build_filename (cachedir, basename_prefixed, NULL);
+       cachefn_file = g_file_new_for_path (cachefn);
+       return g_file_copy (file, cachefn_file,
+                           G_FILE_COPY_OVERWRITE |
+                           G_FILE_COPY_NOFOLLOW_SYMLINKS |
+                           G_FILE_COPY_TARGET_DEFAULT_PERMS,
+                           NULL, NULL, NULL, error);
+}
+
+static gboolean
+gs_install_appstream_check_content_type (GFile *file, GError **error)
+{
+       const gchar *type;
+       g_autoptr(AsStore) store = NULL;
+       g_autoptr(GFileInfo) info = NULL;
+
+       /* check is correct type */
+       info = g_file_query_info (file,
+                                 G_FILE_ATTRIBUTE_STANDARD_CONTENT_TYPE,
+                                 G_FILE_QUERY_INFO_NONE,
+                                 NULL, error);
+       if (info == NULL)
+               return FALSE;
+       type = g_file_info_get_attribute_string (info, G_FILE_ATTRIBUTE_STANDARD_CONTENT_TYPE);
+       if (g_strcmp0 (type, "application/gzip") != 0 &&
+           g_strcmp0 (type, "application/xml") != 0) {
+               g_set_error (error,
+                            G_IO_ERROR,
+                            G_IO_ERROR_INVALID_DATA,
+                            "Invalid type %s: ", type);
+               return FALSE;
+       }
+
+       /* check is an AppStream file */
+       store = as_store_new ();
+       if (!as_store_from_file (store, file, NULL, NULL, error))
+               return FALSE;
+       if (as_store_get_size (store) == 0) {
+               g_set_error_literal (error,
+                                    G_IO_ERROR,
+                                    G_IO_ERROR_INVALID_DATA,
+                                    "No applications found in the AppStream XML");
+               return FALSE;
+       }
+
+       return TRUE;
+}
+
+int
+main (int argc, char *argv[])
+{
+       g_autoptr(GError) error = NULL;
+       g_autoptr(GFile) file = NULL;
+       g_autoptr(GOptionContext) context = NULL;
+
+       /* setup translations */
+       setlocale (LC_ALL, "");
+       bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);
+       bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
+       textdomain (GETTEXT_PACKAGE);
+
+       context = g_option_context_new (NULL);
+       /* TRANSLATORS: tool that is used when copying profiles system-wide */
+       g_option_context_set_summary (context, _("GNOME Software AppStream system-wide installer"));
+       if (!g_option_context_parse (context, &argc, &argv, &error)) {
+               g_print ("%s\n", _("Failed to parse command line arguments"));
+               return EXIT_FAILURE;
+       }
+
+       /* check input */
+       if (g_strv_length (argv) != 2) {
+               /* TRANSLATORS: user did not specify a valid filename */
+               g_print ("%s\n", _("You need to specify exactly one filename"));
+               return EXIT_FAILURE;
+       }
+
+       /* check calling process */
+       if (getuid () != 0 || geteuid () != 0) {
+               /* TRANSLATORS: only able to install files as root */
+               g_print ("%s\n", _("This program can only be used by the root user"));
+               return EXIT_FAILURE;
+       }
+
+       /* check content type for file */
+       file = g_file_new_for_path (argv[1]);
+       if (!gs_install_appstream_check_content_type (file, &error)) {
+               /* TRANSLATORS: error details */
+               g_print ("%s: %s\n", _("Failed to validate content type"), error->message);
+               return EXIT_FAILURE;
+       }
+
+       /* do the copy */
+       if (!gs_install_appstream_copy_file (file, &error)) {
+               /* TRANSLATORS: error details */
+               g_print ("%s: %s\n", _("Failed to copy"), error->message);
+               return EXIT_FAILURE;
+       }
+
+       /* success */
+       return EXIT_SUCCESS;
+}
diff --git a/src/plugins/gs-plugin-external-appstream.c b/src/plugins/gs-plugin-external-appstream.c
index e56b5bf..5827a98 100644
--- a/src/plugins/gs-plugin-external-appstream.c
+++ b/src/plugins/gs-plugin-external-appstream.c
@@ -62,14 +62,13 @@ gs_plugin_external_appstream_check (const gchar *appstream_path,
 
 static gboolean
 gs_plugin_external_appstream_install (const gchar *appstream_file,
-                                     const gchar *target_file_name,
                                      GCancellable *cancellable,
                                      GError **error)
 {
        g_autoptr(GSubprocess) subprocess = NULL;
        const gchar *argv[] = { "pkexec",
                                LIBEXECDIR "/gnome-software-install-appstream",
-                               appstream_file, target_file_name, NULL};
+                               appstream_file, NULL};
        g_debug ("Installing the appstream file %s in the system",
                 appstream_file);
        subprocess = g_subprocess_newv (argv,
@@ -163,7 +162,7 @@ gs_plugin_external_appstream_refresh_url (GsPlugin *plugin,
        }
 
        /* write the download contents into a temporary file that will be
-        * moved into the system */
+        * copied into the system */
        tmp_file_tmpl = g_strdup_printf ("XXXXXX_%s", file_name);
        tmp_file = g_file_new_tmp (tmp_file_tmpl, &iostream, error);
        if (tmp_file == NULL)
@@ -191,11 +190,10 @@ gs_plugin_external_appstream_refresh_url (GsPlugin *plugin,
 
        /* install file systemwide */
        if (!gs_plugin_external_appstream_install (tmp_file_path,
-                                                  file_name,
                                                   cancellable,
                                                   error))
                return FALSE;
-       g_debug ("Installed appstream file %s as %s", tmp_file_path, file_name);
+       g_debug ("Installed appstream file %s", tmp_file_path);
 
        return TRUE;
 }
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