242 lines
5.4 KiB
HTML
242 lines
5.4 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SETEUID</TITLE>
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</HEAD><BODY>
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<H1>SETEUID</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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seteuid, setegid - set effective user or group ID
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/sys/types.h">sys/types.h</A>></B>
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<BR>
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<B>#include <<A HREF="file:///usr/include/unistd.h">unistd.h</A>></B>
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<P>
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<B>int seteuid(uid_t </B><I>euid</I><B>);</B>
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<BR>
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<B>int setegid(gid_t </B><I>egid</I><B>);</B>
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>seteuid</B>(),
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<B>setegid</B>():
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<DL COMPACT><DT id="1"><DD>
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_POSIX_C_SOURCE >= 200112L
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<BR> || /* Glibc versions <= 2.19: */ _BSD_SOURCE
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>seteuid</B>()
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sets the effective user ID of the calling process.
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Unprivileged processes may only set the effective user ID to the
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real user ID, the effective user ID or the saved set-user-ID.
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<P>
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Precisely the same holds for
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<B>setegid</B>()
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with "group" instead of "user".
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success, zero is returned.
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On error, -1 is returned, and
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<I>errno</I>
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is set appropriately.
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<P>
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<I>Note</I>:
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there are cases where
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<B>seteuid</B>()
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can fail even when the caller is UID 0;
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it is a grave security error to omit checking for a failure return from
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<B>seteuid</B>().
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="2"><B>EINVAL</B>
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<DD>
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The target user or group ID is not valid in this user namespace.
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<DT id="3"><B>EPERM</B>
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<DD>
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In the case of
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<B>seteuid</B>():
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the calling process is not privileged (does not have the
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<B>CAP_SETUID</B>
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capability in its user namespace) and
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<I>euid</I>
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does not match the current real user ID, current effective user ID,
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or current saved set-user-ID.
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<DT id="4"><DD>
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In the case of
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<B>setegid</B>():
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the calling process is not privileged (does not have the
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<B>CAP_SETGID</B>
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capability in its user namespace) and
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<I>egid</I>
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does not match the current real group ID, current effective group ID,
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or current saved set-group-ID.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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POSIX.1-2001, POSIX.1-2008, 4.3BSD.
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<A NAME="lbAH"> </A>
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<H2>NOTES</H2>
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Setting the effective user (group) ID to the
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saved set-user-ID (saved set-group-ID) is
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possible since Linux 1.1.37 (1.1.38).
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On an arbitrary system one should check
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<B>_POSIX_SAVED_IDS</B>.
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<P>
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Under glibc 2.0,
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<B>seteuid(</B><I>euid</I><B>)</B>
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is equivalent to
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<B>setreuid(-1,</B><I> euid</I><B>)</B>
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and hence may change the saved set-user-ID.
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Under glibc 2.1 and later, it is equivalent to
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<B>setresuid(-1,</B><I> euid</I><B>, -1)</B>
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and hence does not change the saved set-user-ID.
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Analogous remarks hold for
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<B>setegid</B>(),
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with the difference that the change in implementation from
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<B>setregid(-1,</B><I> egid</I><B>)</B>
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to
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<B>setresgid(-1,</B><I> egid</I><B>, -1)</B>
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occurred in glibc 2.2 or 2.3 (depending on the hardware architecture).
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<P>
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According to POSIX.1,
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<B>seteuid</B>()
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(<B>setegid</B>())
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need not permit
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<I>euid</I>
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(<I>egid</I>)
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to be the same value as the current effective user (group) ID,
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and some implementations do not permit this.
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<A NAME="lbAI"> </A>
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<H3>C library/kernel differences</H3>
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On Linux,
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<B>seteuid</B>()
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and
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<B>setegid</B>()
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are implemented as library functions that call, respectively,
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<B><A HREF="/cgi-bin/man/man2html?2+setreuid">setreuid</A></B>(2)
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and
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<B><A HREF="/cgi-bin/man/man2html?2+setregid">setregid</A></B>(2).
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<A NAME="lbAJ"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+geteuid">geteuid</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setresuid">setresuid</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setreuid">setreuid</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+setuid">setuid</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?7+capabilities">capabilities</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+credentials">credentials</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+user_namespaces">user_namespaces</A></B>(7)
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<A NAME="lbAK"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="9"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="10"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="11"><A HREF="#lbAH">NOTES</A><DD>
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<DL>
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<DT id="12"><A HREF="#lbAI">C library/kernel differences</A><DD>
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</DL>
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<DT id="13"><A HREF="#lbAJ">SEE ALSO</A><DD>
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<DT id="14"><A HREF="#lbAK">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:34 GMT, March 31, 2021
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</BODY>
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</HTML>
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