Add experimental AIX support.

This includes a WIP failsafe issetugid for now, while research continues
on the proper way to do this in a race-free fashion in AIX.

configure.ac

@@ -18,6 +18,10 @@ LT_INIT
 CFLAGS="$CFLAGS -Wall -std=gnu99"
 
 case $host_os in
+	*aix*)
+		HOST_OS=aix
+		AC_SUBST([PLATFORM_LDADD], ['-lperfstat -lpthread'])
+		;;
 	*cygwin*)
 		HOST_OS=cygwin
 		;;
@@ -68,6 +72,7 @@ case $host_os in
 	*) ;;
 esac
 
+AM_CONDITIONAL([HOST_AIX],     [test x$HOST_OS = xaix])
 AM_CONDITIONAL([HOST_CYGWIN],  [test x$HOST_OS = xcygwin])
 AM_CONDITIONAL([HOST_DARWIN],  [test x$HOST_OS = xdarwin])
 AM_CONDITIONAL([HOST_FREEBSD], [test x$HOST_OS = xfreebsd])

crypto/Makefile.am

@@ -69,6 +69,9 @@ if !HAVE_ARC4RANDOM_BUF
 libcompat_la_SOURCES += compat/arc4random.c
 
 if !HAVE_GETENTROPY
+if HOST_AIX
+libcompat_la_SOURCES += compat/getentropy_aix.c
+endif
 if HOST_FREEBSD
 libcompat_la_SOURCES += compat/getentropy_freebsd.c
 endif
@@ -95,6 +98,9 @@ endif
 endif
 
 if !HAVE_ISSETUGID
+if HOST_AIX
+libcompat_la_SOURCES += compat/issetugid_aix.c
+endif
 if HOST_LINUX
 libcompat_la_SOURCES += compat/issetugid_linux.c
 endif
@@ -111,6 +117,7 @@ endif
 
 noinst_HEADERS =
 noinst_HEADERS += compat/arc4random.h
+noinst_HEADERS += compat/arc4random_aix.h
 noinst_HEADERS += compat/arc4random_freebsd.h
 noinst_HEADERS += compat/arc4random_hpux.h
 noinst_HEADERS += compat/arc4random_linux.h

crypto/compat/arc4random.h

@@ -3,7 +3,10 @@
 
 #include <sys/param.h>
 
-#if defined(__FreeBSD__)
+#if defined(_AIX)
+#include "arc4random_aix.h"
+
+#elif defined(__FreeBSD__)
 #include "arc4random_freebsd.h"
 
 #elif defined(__hpux)

crypto/compat/issetugid_aix.c

@@ -0,0 +1,107 @@
+/*	  $OpenBSD: $	 */
+
+/*
+ * Copyright (c) 2015 Michael Felt <aixtools@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include <sys/id.h>
+#include <sys/priv.h>
+
+#include <stdio.h>
+#include <unistd.h>
+
+/*
+ * AIX does not have issetugid().
+ * This experimental implementation uses getpriv() and get*id().
+ * First, try getpriv() and check equality of pv_priv values
+ * When these values are equal, using get*id() including login uid.
+ *
+ */
+int issetugid(void)
+{
+	/*
+	 * Return fail-safe while we evaluate primitives in AIX. There does
+	 * not yet appear to be a single atomic test to tell if privileges of
+	 * the process changed from that of the user who is in control of the
+	 * environment.
+	 */
+	return (1);
+
+#define PEPRIV(a,b) a.pv_priv[b]
+	/*
+	 * effective priv is what I can do now
+	 * inherited priv is what the caller gave or could have given
+	 * basically when inherited == 0 and effective != 0 then
+	 * some kind of priv escalation has occurred
+	 * when 'demoted' -- inherited != 0 but effective == 0
+	 * there is also a change, so, will report 1 as well - to be safe
+	 * PROBABLY there needs more study re: how RBAC subtley affects
+	 * the priv_t values - for now, they are either zero - nothing added
+	 * or non-zero - something added
+	 */
+	priv_t effective,inherited;
+	int luid;
+	int euid, ruid;
+
+	getpriv(PRIV_EFFECTIVE, &effective, sizeof(priv_t));
+	getpriv(PRIV_INHERITED, &inherited, sizeof(priv_t));
+
+	if (PEPRIV(effective,0) | PEPRIV(effective,1)) { /* have something */
+		if ((PEPRIV(inherited,0) | PEPRIV(inherited,1)) == 0) /* had nothing - classic u+s  bit */
+			return (1);
+	} else {
+		/*
+		 * effective priv elevation is NULL/NONE
+		 * was there something and removed via setuid()?
+		 */
+		if (PEPRIV(inherited,0) | PEPRIV(inherited,1))
+			return (1);
+	}
+
+	/*
+	 * if we get this far, then "no" differences in process priv noted
+	 * compare the different uid
+	 * the comparision of login id with effective says "TRUE" when different.
+	 * this may not work as expected when using sudo for elevation
+	 * again, looking at RBAC affects on priv may be more truthful
+	 *
+	 * ruid - real uid
+	 * euid - effictive uid
+	 * luid - login uid
+	 */
+
+	/*
+	 * if these differ (not common on AIX), return changed
+	 */
+	ruid = getuid();
+	euid = geteuid();
+	if (euid != ruid)
+		return (1);
+
+	if (getgid() != getegid())
+		return (1);
+
+	/*
+	 * luid == login id, su/sudo do not/cannot change this afaik
+	 * perhaps this is "too strict", but same as in
+	 * issetugid_win.c - err on the safe side for now
+	 */
+	luid = getuidx(ID_LOGIN);
+	if (euid != luid)
+		return (1);
+
+	return (0);
+}