使用policykit 的程序一般都有一个dbus daemon程序来完成相关操作,这个dbus daemon 会在系统注册一个system bus 服务名,用于响应要求root privileged的操作,当dbus请求到达时会先验证请求程序是否有相应的权限来调用这个操作(方法),而这是在.conf文件中定义的(后面说明)。
首先定义个System Dbus daemon,写一个.service文件来启动我们的daemon
org.example.foo.service
文件放置目录:/usr/share/dbus-1/system-services
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-->1 [D-BUS Service]
2 Name=org.example.foo
3 Exec=/usr/local/libexec/policykit_dbus_foo_daemon.py
4 User=root
其中Name是注册的SystemBus 服务名
Exec 是daemon 程序所在路径
我们以root权限启动
当有程序请求org.example.foo服务时,系统会自动以root启动我们的daemon。
相关信息看这里D-Bus system bus activation
注: SessionBus 的 ‘org.freedesktop.PolicyKit.AuthenticationAgent‘ 的服务,只有在请求认证的时候才自动启动,打开过一段时间会自动关闭。
再看我们的daemon程序
policykit_dbus_foo_daemon.py
文件放置目录:/usr/local/libexec
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--> 1 #!/usr/bin/python
2 # -*- coding: UTF-8 -*-
3 """
4 Author: joe.zhou
5 """
6 import os
7 import sys
8 import gobject
9 import dbus
10 import dbus.service
11 import dbus.mainloop.glib
12
13 class NotPrivilegedException (dbus.DBusException):
14 _dbus_error_name = "org.example.foo.dbus.service.PolKit.NotPrivilegedException"
15 def __init__ (self, action_id, *p, **k):
16 self._dbus_error_name = self.__class__._dbus_error_name + "." + action_id
17 super (NotPrivilegedException, self).__init__ (*p, **k)
18
19 def require_auth (action_id):
20 def require_auth_decorator(func):
21 def _func(*args,**kwds):
22 revoke_if_one_shot = True
23 system_bus = dbus.SystemBus()
24 auth_obj = system_bus.get_object(‘org.freedesktop.PolicyKit‘,‘/‘)
25 auth_interface = dbus.Interface(auth_obj,‘org.freedesktop.PolicyKit‘)
26 try:
27 dbus_name = kwds[‘sender_keyword‘]
28 except:
29 raise NotPrivilegedException (action_id)
30 granted = auth_interface.IsSystemBusNameAuthorized(action_id,dbus_name,revoke_if_one_shot)
31 if granted != ‘yes‘:
32 raise NotPrivilegedException (action_id)
33
34 return func(*args,**kwds)
35
36 _func.func_name = func.func_name
37 _func.__name__ = func.__name__
38 _func.__doc__ = func.__doc__
39 return _func
40 return require_auth_decorator
41
42 ‘‘‘
43 A D-Bus service that PolicyKit controls access to.
44 ‘‘‘
45 class PolicyKitFooMechanism(dbus.service.Object):
46 SERVICE_NAME = ‘org.example.foo‘
47 SERVICE_PATH = ‘/org/example/foo‘
48 INTERFACE_NAME = ‘org.example.foo‘
49
50 def __init__(self, conn, object_path=SERVICE_PATH):
51 dbus.service.Object.__init__(self, conn, object_path)
52
53 @dbus.service.method(dbus_interface=INTERFACE_NAME, in_signature=‘ss‘,out_signature=‘s‘,sender_keyword=‘sender‘)
54 def WriteFile(self, filepath, contents,sender=None):
55 ‘‘‘
56 Write the contents to a file that requires sudo/root access to do so.
57 PolicyKit will not allow this function to be called without sudo/root
58 access, and will ask the user to authenticate if necessary, when
59 the application calls PolicyKit‘s ObtainAuthentication().
60 ‘‘‘
61 @require_auth(‘org.example.foo.modify‘)
62 def _write_file(filepath,contents,sender_keyword = None):
63 f = open(filepath, ‘w‘)
64 f.write(contents)
65 f.close()
66 return ‘done‘
67 return _write_file(filepath,contents,sender_keyword = sender)
68
69 @dbus.service.method(dbus_interface=INTERFACE_NAME, in_signature=‘s‘,out_signature=‘as‘,sender_keyword=‘sender‘)
70 def RunCmd(self, cmdStr, sender=None):
71 @require_auth(‘org.example.foo.sys‘)
72 def _run_cmd(cmdStr,sender_keyword = None):
73 f = os.popen(cmdStr)
74 output = f.readlines()
75 f.close()
76 return output
77 return _run_cmd(cmdStr,sender_keyword = sender)
78
79 @dbus.service.method(dbus_interface=INTERFACE_NAME,in_signature=‘‘, out_signature=‘‘,sender_keyword=‘sender‘)
80 def Exit(self, sender=None):
81 @require_auth(‘org.example.foo.sys‘)
82 def _exit(sender_keyword = None):
83 loop.quit()
84 return _exit(sender_keyword = sender)
85
86 @dbus.service.method(dbus_interface=INTERFACE_NAME,in_signature=‘‘, out_signature=‘s‘)
87 def hello(self):
88 return ‘hello‘
89
90 if __name__ == ‘__main__‘:
91 dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
92 bus = dbus.SystemBus()
93 name = dbus.service.BusName(PolicyKitFooMechanism.SERVICE_NAME, bus)
94 the_object = PolicyKitFooMechanism(bus)
95 loop = gobject.MainLoop()
96 loop.run()
97
98
在daemon程序中定义了三个需要权限的操作,一个不需要权限的操作,也定义了操作(方法)要求验证的action id,程序請求写文件操作时需先向org.freedesktop.PolicyKit.AuthenticationAgent 请求对应的 action id权限才能再进行调用,
否则会提示没有权限,hello操作不需要操作权限,两者区别在于来请求时是否先向 org.freedesktop.Policykit 检测这个 dbus 請求是否有 previleged。
具体是调用 IsSystemBusNameAuthorized 方法来验证,通过则返回‘yes‘,否则 返回其它字符串
使用命令以下命令查看方法的 IsSystemBusNameAuthorized 详细 introspec
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-->dbus-send --system --print-reply --dest=org.freedesktop.PolicyKit / org.freedesktop.DBus.Introspectable.Introspect
在这里值得注意的是如果你定义了一系列的系统级调用操作(以root方式启动前面的程序,但去除了前面的@require_auth 部分),你必须保证每个操作要进行权限验证,即加上这个东西@require_auth(‘org.example.foo.sys‘)
如果你定义了写文件的dbus操作,但是没有进行权限验证的话,一个普通用户的dbus 调用請求也会调用通过,即普通用户可以随意改写任何文件,这是很危险的
你也可以尝试把前面的@require_auth部分去掉,再启动服务,用d-feet 就可以调用WriteFile方法随意地在根目录上写入文件
--题外话——
本想将程序写成这种形式的
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-->1 @require_auth(‘org.example.foo.sys‘)
2 @dbus.service.method(dbus_interface=INTERFACE_NAME,in_signature=‘‘, out_signature=‘‘,sender_keyword=‘sender‘)
3 def Exit(self, sender=None):
4 loop.quit()
这样写,用d-feet 看了下,服务起不来,调了很久也找不出原因,无奈写成这种冗余的方式 --!,看能否有高手指点下,不尽感激!!
接着定义谁可以调用这些操作(方法),在.conf 文件定义
org.example.foo.conf
文件放置目录:/etc/dbus-1/system.d
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--> 1 <?xml version="1.0" encoding="UTF-8"?> <!-- -*- XML -*- -->
2
3 <!DOCTYPE busconfig PUBLIC
4 "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
5 "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
6 <busconfig>
7
8 <!-- Only root can own the service -->
9 <policy user="root">
10 <allow own="org.example.foo"/>
11 <allow send_interface="org.example.foo"/>
12 </policy>
13
14 <!-- allow Introspectable --><!-- 任何人都可以调用,在后面使用.policy进行約束-->
15 <policy context="default">
16 <allow send_interface="org.example.foo"/>
17 <allow send_interface="org.freedesktop.DBus.Introspectable"/>
18 </policy>
19
20 </busconfig>
21
再跟着是定义相关的 action id了,在.policy 文件定义
其中定义授权认证的方式和时效可以有以下几种
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-->no
auth_self$$
auth_admin$$
yes
其中加$$的可以附加后缀 _one_shot,_keep_session,_keep_always
其意义字面已经很清楚了
另外也可以看看 man policykit.conf
不会写?参照/usr/share/PolicyKit/policy 目录下一堆 .policy文件总会了吧
写好后可以用工具 polkit-policy-file-validate 验证下是否有效
org.example.foo.policy
文件放置目录:/usr/share/PolicyKit/policy
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--> 1 <?xml version="1.0" encoding="UTF-8"?>
2 <!DOCTYPE policyconfig PUBLIC
3 "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN"
4 "http://www.freedesktop.org/standards/PolicyKit/1.0/policyconfig.dtd">
5 <policyconfig>
6
7 <vendor>Example Application</vendor>
8 <vendor_url>http://fedoraproject.org/example</vendor_url>
9
10 <action id="org.example.foo.modify">
11 <description>Example Write Access</description>
12 <message>System policy prevents write access to the Example service</message>
13 <defaults>
14 <allow_inactive>no</allow_inactive>
15 <allow_active>auth_admin</allow_active>
16 </defaults>
17 </action>
18
19 <action id="org.example.foo.sys">
20 <description>Example system action</description>
21 <message>System policy prevents do system action to the Example service</message>
22 <defaults>
23 <allow_inactive>no</allow_inactive>
24 <allow_active>auth_admin</allow_active>
25 </defaults>
26 </action>
27
28
29 </policyconfig>
做好以上工作,我们可以写我们的调用端程序了
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--> 1 #!/usr/bin/python
2 # -*- coding: UTF-8 -*-
3 import os
4 import sys
5 import gobject
6 import dbus
7 import dbus.service
8 import dbus.mainloop.glib
9 import traceback
10
11 def auth_proxy (func):
12 DBUSNAME = ‘org.freedesktop.PolicyKit.AuthenticationAgent‘
13 DBUSPATH = ‘/‘
14 DBUSINTERFACE = ‘org.freedesktop.PolicyKit.AuthenticationAgent‘
15 EXC_NAME = "org.example.foo.dbus.service.PolKit.NotPrivilegedException"
16 def auth_proxy_wrapper (*args, **kwds):
17 try:
18 return func (*args, **kwds)
19 except dbus.DBusException, e:
20 exc_name = e.get_dbus_name ()
21 if exc_name.startswith (EXC_NAME + "."):
22 session_bus = dbus.SessionBus ()
23 auth_obj = session_bus.get_object (DBUSNAME, DBUSPATH)
24 auth_interface = dbus.Interface(auth_obj,DBUSINTERFACE)
25 action_id = exc_name[len (EXC_NAME)+1:]
26 granted = auth_interface.ObtainAuthorization (action_id, dbus.UInt32 (0),dbus.UInt32 (os.getpid ()))
27 if not granted:
28 raise
29 else:
30 raise
31
32 return func(*args, **kwds)
33 return auth_proxy_wrapper
34
35 class DbusTestProxy:
36 SERVICE_NAME = ‘org.example.foo‘
37 SERVICE_PATH = ‘/org/example/foo‘
38 INTERFACE_NAME = ‘org.example.foo‘
39 def __init__(self):
40 self.bus = dbus.SystemBus()
41 self.o = self.bus.get_object(self.SERVICE_NAME,self.SERVICE_PATH)
42 self.i = dbus.Interface(self.o,self.INTERFACE_NAME)
43
44 @auth_proxy
45 def WriteFileWithAuth(self,filePath,contents):
46 return self.i.WriteFile(filePath,contents)
47
48 def WriteFileWithoutAuth(self,filePath,contents):
49 return self.i.WriteFile(filePath,contents)
50
51 @auth_proxy
52 def RunCmd(self,cmdStr):
53 return self.i.RunCmd(cmdStr)
54
55 @auth_proxy
56 def Exit(self):
57 return self.i.Exit()
58
59 #do not need to auth
60 def hello(self):
61 return self.i.hello()
62
63
64 if __name__ == "__main__":
65 p = DbusTestProxy()
66 #print p.RunCmd(‘ls -al‘)
67 print p.WriteFileWithAuth(‘/text‘,‘test\n‘)
68 #print p.WriteFileWithoutAuth(‘/text‘,‘test\n‘)
69 #p.Exit()
70 print p.hello()
运行上面的程序尝试WriteFileWithAuth 方法会弹出验证的对话框,口令正确的话会在根目录写入文件,调用WriteFileWithoutAuth会因为没有调用权限验证
而返回没有privileged的 异常,因为WriteFile操作是需要权限的。
以上程序相当的简单,因为我也是python新手,相信你也看得明白。
最后打个包,点击下载 policykit_dbus_foo.7z
#install
sudo ./install.sh install
#remove
sudo ./install.sh uninstall
#test
./policykit_dbus_foo_client.py
以上系统环境为ubuntu 8.04
Reference:
http://hal.freedesktop.org/docs/PolicyKit
Policy, Mechanism and Time zones
http://dbus.freedesktop.org/doc/dbus-specification.html
http://dbus.freedesktop.org/doc/dbus-python/doc/tutorial.html
python Decorator for functions and methods
最后发现了个开源项目 python-slip
其中 slip.dbus.polkit 部分,封装了policykit, 能使你在项目中使用policykit 更容易些.(我觉得python已经够简单的了Orz)
注:转载注明出处
http://www.cnblogs.com/joe2k8/archive/2009/05/24/1488074.html