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+/*++
+/* NAME
+/* unsafe 3
+/* SUMMARY
+/* are we running at non-user privileges
+/* SYNOPSIS
+/* #include <safe.h>
+/*
+/* int unsafe()
+/* DESCRIPTION
+/* The \fBunsafe()\fR routine attempts to determine if the process
+/* (runs with privileges or has access to information) that the
+/* controlling user has no access to. The purpose is to prevent
+/* misuse of privileges, including access to protected information.
+/*
+/* The result is always false when both of the following conditions
+/* are true:
+/* .IP \(bu
+/* The real UID is zero.
+/* .IP \(bu
+/* The effective UID is zero.
+/* .PP
+/* Otherwise, the result is true if any of the following conditions
+/* is true:
+/* .IP \(bu
+/* The issetuid kernel flag is non-zero (on systems that support
+/* this concept).
+/* .IP \(bu
+/* The real and effective user id differ.
+/* .IP \(bu
+/* The real and effective group id differ.
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*
+/* Wietse Venema
+/* Google, Inc.
+/* 111 8th Avenue
+/* New York, NY 10011, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <unistd.h>
+
+/* Utility library. */
+
+#include "safe.h"
+
+/* unsafe - can we trust user-provided environment, working directory, etc. */
+
+int unsafe(void)
+{
+
+ /*
+ * The super-user is trusted.
+ */
+ if (getuid() == 0 && geteuid() == 0)
+ return (0);
+
+ /*
+ * Danger: don't trust inherited process attributes, and don't leak
+ * privileged info that the parent has no access to.
+ */
+ return (geteuid() != getuid()
+#ifdef HAS_ISSETUGID
+ || issetugid()
+#endif
+ || getgid() != getegid());
+}