luci-mod-admin-full: check backup.tar.gz on apply

If an uploaded backup.tar.gz is not valid we will not get a respond from
LuCI. The system will perform a reboot without applying the "tar.gz"
even though the backup import failed.

To fix this check if the backup archive is valid with the command
"gunzip -t <archive>" and if the validation fails render the flashops page
with a hint. On the other hand apply the backup archive and perform a
reboot as before.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>

modules/luci-mod-admin-full/luasrc/controller/admin/system.lua

@@ -341,9 +341,17 @@ function action_restore()
 
 	local upload = http.formvalue("archive")
 	if upload and #upload > 0 then
+		if os.execute("gunzip -t %q >/dev/null 2>&1" % archive_tmp) == 0 then
 			luci.template.render("admin_system/applyreboot")
 			os.execute("tar -C / -xzf %q >/dev/null 2>&1" % archive_tmp)
 			luci.sys.reboot()
+		else
+			luci.template.render("admin_system/flashops", {
+				reset_avail   = supports_reset(),
+				upgrade_avail = supports_sysupgrade(),
+				backup_invalid = true
+			})
+		end
 		return
 	end
 

modules/luci-mod-admin-full/luasrc/view/admin_system/flashops.htm

@@ -50,6 +50,9 @@
 				</div>
 			</div>
 		</form>
+		<% if backup_invalid then %>
+			<div class="cbi-section-error"><%:The backup archive does not appear to be a valid gzip file.%></div>
+		<% end %>
 	</div>
 	<% if reset_avail then %>
 		<div class="alert-message warning"><%:Custom files (certificates, scripts) may remain on the system. To prevent this, perform a factory-reset first.%></div>