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diff --git a/src/util/open_as.c b/src/util/open_as.c
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+/*++
+/* NAME
+/* open_as 3
+/* SUMMARY
+/* open file as user
+/* SYNOPSIS
+/* #include <fcntl.h>
+/* #include <open_as.h>
+/*
+/* int open_as(path, flags, mode, euid, egid)
+/* const char *path;
+/* int mode;
+/* uid_t euid;
+/* gid_t egid;
+/* DESCRIPTION
+/* open_as() opens the named \fIpath\fR with the named \fIflags\fR
+/* and \fImode\fR, and with the effective rights specified by \fIeuid\fR
+/* and \fIegid\fR. A -1 result means the open failed.
+/* DIAGNOSTICS
+/* Fatal error: no permission to change privilege level.
+/* SEE ALSO
+/* set_eugid(3) switch effective rights
+/* 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
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+/* Utility library. */
+
+#include "msg.h"
+#include "set_eugid.h"
+#include "open_as.h"
+
+/* open_as - open file as user */
+
+int open_as(const char *path, int flags, int mode, uid_t euid, gid_t egid)
+{
+ uid_t saved_euid = geteuid();
+ gid_t saved_egid = getegid();
+ int fd;
+
+ /*
+ * Switch to the target user privileges.
+ */
+ set_eugid(euid, egid);
+
+ /*
+ * Open that file.
+ */
+ fd = open(path, flags, mode);
+
+ /*
+ * Restore saved privileges.
+ */
+ set_eugid(saved_euid, saved_egid);
+
+ return (fd);
+}