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Date: Tue, 15 Jul 2014 16:30:07 +0000
From: Brent Cook <>
Subject: [PATCH] implement issetugid(2) (v4)

>From OpenBSD 2.0 and later, NetBSD, FreeBSD, OS X and Solaris

While getauxval(AT_SECURE) might have been able to provide comparable
functionality on the libc versions that support it, several Linux libc
versions implement it in a way such that the results cannot be trusted,
since there is no way to tell if it has failed. Worse, the result of '0'
returned on failures effectively causes the security mechanism to fail

There is also no simultaneously reliable and portable way for a
library to identify if the C library has a usable version of getauxval,
since the symbol is unversioned. Compile-time checks for usability are
also unfeasible, since static libraries built with a 'good' version can
be linked to a 'bad' version of getauxval.

The fix is to implement the BSD issetugid(2) interface so that a
portable library can use its presence to determine if the underlying C
library has a reliable way of determining if it is running in a secure
 include/unistd.h       | 1 +
 src/unistd/issetugid.c | 7 +++++++
 2 files changed, 8 insertions(+)
 create mode 100644 src/unistd/issetugid.c

diff --git a/include/unistd.h b/include/unistd.h
index bb19cd8..ac6055a 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -178,6 +178,7 @@ char *getusershell(void);
 int acct(const char *);
 long syscall(long, ...);
 int execvpe(const char *, char *const [], char *const []);
+int issetugid(void);
 #ifdef _GNU_SOURCE
diff --git a/src/unistd/issetugid.c b/src/unistd/issetugid.c
new file mode 100644
index 0000000..6ffd930
--- /dev/null
+++ b/src/unistd/issetugid.c
@@ -0,0 +1,7 @@
+#include <unistd.h>
+#include "libc.h"
+int issetugid(void)
+	return;

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