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From a3fa3b86f0015e42a534526ed800bcde5b3f2a15 Mon Sep 17 00:00:00 2001
From: Colin Walters <walters@verbum.org>
Date: Mon, 19 Aug 2013 12:16:11 -0400
Subject: [PATCH] pkcheck: Support --process=pid,start-time,uid syntax too
The uid is a new addition; this allows callers such as libvirt to
close a race condition in reading the uid of the process talking to
them. They can read it via getsockopt(SO_PEERCRED) or equivalent,
rather than having pkcheck look at /proc later after the fact.
Programs which invoke pkcheck but need to know beforehand (i.e. at
compile time) whether or not it supports passing the uid can
use:
pkcheck_supports_uid=$($PKG_CONFIG --variable pkcheck_supports_uid polkit-gobject-1)
test x$pkcheck_supports_uid = xyes
Conflicts:
docs/man/pkcheck.xml
src/programs/pkcheck.c
---
data/polkit-gobject-1.pc.in | 3 +++
docs/man/pkcheck.xml | 33 +++++++++++++++++++++------------
src/programs/pkcheck.c | 7 ++++++-
3 files changed, 30 insertions(+), 13 deletions(-)
diff --git a/data/polkit-gobject-1.pc.in b/data/polkit-gobject-1.pc.in
index c39677d..5c4c620 100644
--- a/data/polkit-gobject-1.pc.in
+++ b/data/polkit-gobject-1.pc.in
@@ -11,3 +11,6 @@ Version: @VERSION@
Libs: -L${libdir} -lpolkit-gobject-1
Cflags: -I${includedir}/polkit-1
Requires: gio-2.0 >= 2.18 glib-2.0 >= 2.18
+# Programs using pkcheck can use this to determine
+# whether or not it can be passed a uid.
+pkcheck_supports_uid=true
diff --git a/docs/man/pkcheck.xml b/docs/man/pkcheck.xml
index 6b8a874..9f2faef 100644
--- a/docs/man/pkcheck.xml
+++ b/docs/man/pkcheck.xml
@@ -55,6 +55,9 @@
<arg choice="plain">
<replaceable>pid,pid-start-time</replaceable>
</arg>
+ <arg choice="plain">
+ <replaceable>pid,pid-start-time,uid</replaceable>
+ </arg>
</group>
</arg>
<arg choice="plain">
@@ -90,7 +93,7 @@
<title>DESCRIPTION</title>
<para>
<command>pkcheck</command> is used to check whether a process, specified by
- either <option>--process</option> or <option>--system-bus-name</option>,
+ either <option>--process</option> (see below) or <option>--system-bus-name</option>,
is authorized for <replaceable>action</replaceable>. The <option>--detail</option>
option can be used zero or more times to pass details about <replaceable>action</replaceable>.
If <option>--allow-user-interaction</option> is passed, <command>pkcheck</command> blocks
@@ -160,17 +163,23 @@ KEY3=VALUE3
<refsect1 id="pkcheck-notes">
<title>NOTES</title>
<para>
- Since process identifiers can be recycled, the caller should always use
- <replaceable>pid,pid-start-time</replaceable> to specify the process
- to check for authorization when using the <option>--process</option> option.
- The value of <replaceable>pid-start-time</replaceable>
- can be determined by consulting e.g. the
- <citerefentry>
- <refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum>
- </citerefentry>
- file system depending on the operating system. If only <replaceable>pid</replaceable>
- is passed to the <option>--process</option> option, then <command>pkcheck</command>
- will look up the start time itself but note that this may be racy.
+ Do not use either the bare <replaceable>pid</replaceable> or
+ <replaceable>pid,start-time</replaceable> syntax forms for
+ <option>--process</option>. There are race conditions in both.
+ New code should always use
+ <replaceable>pid,pid-start-time,uid</replaceable>. The value of
+ <replaceable>start-time</replaceable> can be determined by
+ consulting e.g. the
+ <citerefentry><refentrytitle>proc</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ file system depending on the operating system. If fewer than 3
+ arguments are passed, <command>pkcheck</command> will attempt to
+ look up them up internally, but note that this may be racy.
+ </para>
+ <para>
+ If your program is a daemon with e.g. a custom Unix domain
+ socket, you should determine the <replaceable>uid</replaceable>
+ parameter via operating system mechanisms such as
+ <literal>PEERCRED</literal>.
</para>
</refsect1>
diff --git a/src/programs/pkcheck.c b/src/programs/pkcheck.c
index 719a36c..057e926 100644
--- a/src/programs/pkcheck.c
+++ b/src/programs/pkcheck.c
@@ -372,6 +372,7 @@ main (int argc, char *argv[])
else if (g_strcmp0 (argv[n], "--process") == 0 || g_strcmp0 (argv[n], "-p") == 0)
{
gint pid;
+ guint uid;
guint64 pid_start_time;
n++;
@@ -381,7 +382,11 @@ main (int argc, char *argv[])
goto out;
}
- if (sscanf (argv[n], "%i,%" G_GUINT64_FORMAT, &pid, &pid_start_time) == 2)
+ if (sscanf (argv[n], "%i,%" G_GUINT64_FORMAT ",%u", &pid, &pid_start_time, &uid) == 3)
+ {
+ subject = polkit_unix_process_new_for_owner (pid, pid_start_time, uid);
+ }
+ else if (sscanf (argv[n], "%i,%" G_GUINT64_FORMAT, &pid, &pid_start_time) == 2)
{
subject = polkit_unix_process_new_full (pid, pid_start_time);
}
--
1.8.5.1
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