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.

4 files changed, 123 insertions, 1 deletions

diff --git a/configure.ac b/configure.ac
index 67266cb..75a1ec2 100644
--- a/configure.ac
+++ b/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])
diff --git a/crypto/Makefile.am b/crypto/Makefile.am
index e350cda..83bf0c6 100644
--- a/crypto/Makefile.am
+++ b/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
diff --git a/crypto/compat/arc4random.h b/crypto/compat/arc4random.h
index ce1bbea..762aec2 100644
--- a/crypto/compat/arc4random.h
+++ b/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)
diff --git a/crypto/compat/issetugid_aix.c b/crypto/compat/issetugid_aix.c
new file mode 100644
index 0000000..16f0a6d
--- /dev/null
+++ b/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);
+}