1PKEXEC(1) pkexec PKEXEC(1)
2
6 pkexec - Execute a command as another user
7
9 pkexec [--version] [--help]
10 pkexec [--user username] PROGRAM [ARGUMENTS...]
12
14 pkexec allows an authorized user to execute PROGRAM as another user. If
15 username is not specified, then the program will be executed as the
16 administrative super user, root.
17
19 Upon successful completion, the return value is the return value of
20 PROGRAM. If the calling process is not authorized or an authorization
21 could not be obtained through authentication or an error occured,
22 pkexec exits with a return value of 127.
23
25 Executing a program as another user is a privileged operation. By
26 default the required authorization (See the section called “REQUIRED
27 AUTHORIZATIONS”) requires administrator authentication. In addition,
28 the authentication dialog presented to the user will display the full
29 path to the program to be executed so the user is aware of what will
30 happen:
31 [IMAGE][1]
33 +----------------------------------------------------------+
35 | Authenticate [X] |
36 +----------------------------------------------------------+
37 | |
38 | [Icon] Authentication is needed to run `/bin/bash´ |
39 | as the super user |
40 | |
41 | An application is attempting to perform an |
42 | action that requires privileges. Authentication |
43 | as the super user is required to perform this |
44 | action. |
45 | |
46 | Password for root: [_________________________] |
47 | |
48 | [V] Details: |
49 | Command: /bin/bash |
50 | Run As: Super User (root) |
51 | Action: org.freedesktop.policykit.exec |
52 | Vendor: The PolicyKit Project |
53 | |
54 | [Cancel] [Authenticate] |
55 +----------------------------------------------------------+
56 The environment that PROGRAM will run it, will be set to a minimal
58 known and safe environment in order to avoid injecting code through
59 LD_LIBRARY_PATH or similar mechanisms. In addition the PKEXEC_UID
60 environment variable is set to the user id of the process invoking
61 pkexec. As a result, pkexec will not allow you to run e.g. X11
62 applications as another user since the $DISPLAY environment variable is
63 not set.
64
66 By default, the org.freedesktop.policykit.exec authorization is
67 required unless an action definition file is present for the program in
68 question. To require another authorization, it can be specified using
69 the org.freedesktop.policykit.exec.path annotation on an action (See
70 the section called “EXAMPLE” for details).
71
73 To specify what kind of authorization is needed to execute the program
74 /usr/bin/pk-example-frobnicate as another user, simply write an action
75 definition file like this
76 <?xml version="1.0" encoding="UTF-8"?>
78 <!DOCTYPE policyconfig PUBLIC
79 "-//freedesktop//DTD PolicyKit Policy Configuration 1.0//EN"
80 "http://www.freedesktop.org/standards/PolicyKit/1/policyconfig.dtd">
81 <policyconfig>
82 <vendor>Examples for the PolicyKit Project</vendor>
84 <vendor_url>http://hal.freedesktop.org/docs/PolicyKit/</vendor_url>
85 <action id="org.freedesktop.policykit.example.pkexec.run-frobnicate">
87 <description>Run the PolicyKit example program Frobnicate</description>
88 <description xml:lang="da">Kør PolicyKit eksemplet Frobnicate</description>
89 <message>Authentication is required to run the PolicyKit example program Frobnicate</message>
90 <message xml:lang="da">Autorisering er påkrævet for at afvikle PolicyKit eksemplet Frobnicate</message>
91 <icon_name>audio-x-generic</icon_name>
92 <defaults>
93 <allow_any>no</allow_any>
94 <allow_inactive>no</allow_inactive>
95 <allow_active>auth_self_keep</allow_active>
96 </defaults>
97 <annotate key="org.freedesktop.policykit.exec.path">/usr/bin/pk-example-frobnicate</annotate>
98 </action>
99 </policyconfig>
101 and drop it in the /usr/share/polkit-1/actions directory under a
103 suitable name (e.g. matching the namespace of the action). Note that in
104 addition to specifying the program, the authentication message,
105 description, icon and defaults can be specified. For example, for the
106 action defined above, the following authentication dialog will be
107 shown:
108 [IMAGE][2]
110 +----------------------------------------------------------+
112 | Authenticate [X] |
113 +----------------------------------------------------------+
114 | |
115 | [Icon] Authentication is required to run the PolicyKit |
116 | example program Frobnicate |
117 | |
118 | An application is attempting to perform an |
119 | action that requires privileges. Authentication |
120 | is required to perform this action. |
121 | |
122 | Password: [__________________________________] |
123 | |
124 | [V] Details: |
125 | Command: /usr/bin/pk-example-frobnicate |
126 | Run As: Super User (root) |
127 | Action: org.fd.pk.example.pkexec.run-frobnicate |
128 | Vendor: Examples for the PolicyKit Project |
129 | |
130 | [Cancel] [Authenticate] |
131 +----------------------------------------------------------+
132 If the user is using the da_DK locale, the dialog looks like this:
134 [IMAGE][3]
136 +----------------------------------------------------------+
138 | Autorisering [X] |
139 +----------------------------------------------------------+
140 | |
141 | [Icon] Autorisering er påkrævet for at afvikle |
142 | PolicyKit eksemplet Frobnicate |
143 | |
144 | Et program forsøger at udføre en handling der |
145 | kræver privilegier. Autorisering er påkrævet. |
146 | |
147 | Kodeord: [___________________________________] |
148 | |
149 | [V] Detaljer: |
150 | Bruger: Super User (root) |
151 | Program: /usr/bin/pk-example-frobnicate |
152 | Handling: org.fd.pk.example.pkexec.run-frobnicate |
153 | Vendor: Examples for the PolicyKit Project |
154 | |
155 | [Annullér] [Autorisering] |
156 +----------------------------------------------------------+
157 Note that pkexec does no validation of the ARGUMENTS passed to PROGRAM.
159 In the normal case (where administrator authentication is required
160 every time pkexec is used), this is not a problem since if the user is
161 an administrator he might as well just run pkexec bash to get root.
162 However, if an action is used for which the user can retain
164 authorization (or if the user is implicitly authorized), such as with
165 pk-example-frobnicate above, this could be a security hole. Therefore,
166 as a rule of thumb, programs for which the default required
167 authorization is changed, should never implicitly trust user input
168 (e.g. like any other well-written suid program).
169
171 Written by David Zeuthen davidz@redhat.com with a lot of help from many
172 others.
173
175 Please send bug reports to either the distribution or the polkit-devel
176 mailing list, see the link
177 http://lists.freedesktop.org/mailman/listinfo/polkit-devel on how to
178 subscribe.
179
181 polkit(8), pkaction(1), pkcheck(1)
182
184 1. /usr/share/gtk-doc/html/polkit-1/pkexec-bash.png
185 2. /usr/share/gtk-doc/html/polkit-1/pkexec-frobnicate.png
187 3. /usr/share/gtk-doc/html/polkit-1/pkexec-frobnicate-da.png
189polkit May 2009 PKEXEC(1)