On systems without 'setfsuid', use 'setreuid' instead.

The patch originates from the Debian project for GNU/Hurd.
Authors: Steve Langasek <vorlon@debian.org>
Upstream status: A ticket was opened to request apply the patch,
ticket: 'https://fedorahosted.org/linux-pam/ticket/64'.

--- Linux-PAM-1.2.1/libpam/pam_modutil_priv.c	2015-03-24 06:02:32.000000000 -0600
+++ pam_modutil_priv-mod.c	2016-09-20 13:36:53.150663205 -0500
@@ -14,7 +14,9 @@
 #include <syslog.h>
 #include <pwd.h>
 #include <grp.h>
+#ifdef HAVE_SYS_FSUID_H
 #include <sys/fsuid.h>
+#endif /* HAVE_SYS_FSUID_H */
 
 /*
  * Two setfsuid() calls in a row are necessary to check
@@ -22,17 +24,55 @@
  */
 static int change_uid(uid_t uid, uid_t *save)
 {
+#ifdef HAVE_SYS_FSUID_H
 	uid_t tmp = setfsuid(uid);
 	if (save)
 		*save = tmp;
 	return (uid_t) setfsuid(uid) == uid ? 0 : -1;
+#else
+	uid_t euid = geteuid();
+	uid_t ruid = getuid();
+	if (save)
+		*save = ruid;
+	if (ruid == uid && uid != 0)
+		if (setreuid(euid, uid))
+			return -1;
+	else {
+		setreuid(0, -1);
+		if (setreuid(-1, uid)) {
+			setreuid(-1, 0);
+			setreuid(0, -1);
+			if (setreuid(-1, uid))
+				return -1;
+		}
+	}
+#endif
 }
 static int change_gid(gid_t gid, gid_t *save)
 {
+#ifdef HAVE_SYS_FSUID_H
 	gid_t tmp = setfsgid(gid);
 	if (save)
 		*save = tmp;
 	return (gid_t) setfsgid(gid) == gid ? 0 : -1;
+#else
+	gid_t egid = getegid();
+	gid_t rgid = getgid();
+	if (save)
+		*save = rgid;
+	if (rgid == gid)
+		if (setregid(egid, gid))
+			return -1;
+	else {
+		setregid(0, -1);
+		if (setregid(-1, gid)) {
+			setregid(-1, 0);
+			setregid(0, -1);
+			if (setregid(-1, gid))
+				return -1;
+		}
+	}
+#endif
 }
 
 static int cleanup(struct pam_modutil_privs *p)
u/packages/datastructures.scm'>
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<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
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</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=84dec7a0c08c66ba8434442c933e518c9c3b1508&amp;showmsg=1'>root</a>/<a href='/guix/log/gnu?id=84dec7a0c08c66ba8434442c933e518c9c3b1508&amp;showmsg=1'>gnu</a>/<a href='/guix/log/gnu/packages?id=84dec7a0c08c66ba8434442c933e518c9c3b1508&amp;showmsg=1'>packages</a>/<a href='/guix/log/gnu/packages/datastructures.scm?id=84dec7a0c08c66ba8434442c933e518c9c3b1508&amp;showmsg=1'>datastructures.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/datastructures.scm?id=84dec7a0c08c66ba8434442c933e518c9c3b1508'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2017-06-15 10:34:22 +0200'>2017-06-15</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/datastructures.scm?id=a3f8aae4a159baf2de10c1f8860d7128c89fbb0c'>gnu: liburcu: Update to 0.10.0.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/databases.scm (liburcu): Update to 0.10.0.


</td></tr>
<tr class='logheader'><td><span title='2017-04-17 02:04:08 +0200'>2017-04-17</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/datastructures.scm?id=d1e4ad1b02b2ea888557d3272c50b676faf18ca4'>gnu: Fix typos in descriptions.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/admin.scm (di)[description]: Likewise.
* gnu/packages/bioinformatics.scm (r-annotate)[description]: Likewise.
* gnu/packages/datastructures.scm (sparsehash)[description]: Likewise.
* gnu/packages/dns.scm (knot)[description]: Likewise.
* gnu/packages/emacs.scm (emacs-idle-highlight)[synopsis, description]:
Likewise.
* gnu/packages/gnome.scm (libpeas)[description]: Likewise.
* gnu/packages/gtk.scm (python2-pygtk)[description]: Likewise.
* gnu/packages/kde-frameworks.scm (kactivities)[description]: Fix typo.
* gnu/packages/libevent.scm (perl-anyevent)[description]: Likewise.
* gnu/packages/machine-learning.scm (ghmm)[description]: Likewise.
* gnu/packages/mail.scm (mlmmj)[description]: Likewise.
* gnu/packages/maths.scm (vc)[description]: Likewise.
* gnu/packages/music.scm (gx-super-fuzz-lv2)[description]: Likewise.
* gnu/packages/networking.scm (nload)[description]: Likewise.
* gnu/packages/python.scm (python-execnet)[description]: Likewise.
* gnu/packages/terminals.scm (tilda)[description]: Likewise.
* gnu/packages/python.scm (python-execnet, python-tables)
(python2-coverage-test-runner, python2-rope)[description]: Likewise.


</td></tr>
<tr class='logheader'><td><span title='2017-03-17 02:32:00 +0100'>2017-03-17</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/datastructures.scm?id=754667f0eb44491370a2ec4fa0b4705cfcf6d237'>gnu: Add liburcu.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/datastructures.scm (liburcu): New variable.


</td></tr>
<tr class='logheader'><td><span title='2016-07-19 23:03:30 +0200'>2016-07-19</span></td><td class='logsubject'><a href='/guix/commit/gnu/packages/datastructures.scm?id=592ccdd38850d581f669f834f051ee8f92d7ee31'>gnu: Add ssdeep.</a></td><td>Tobias Geerinckx-Rice</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
* gnu/packages/datastructures.scm (ssdeep): New variable.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;


</td></tr>