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setreuid(3p) — Linux manual page

PROLOG \|NAME \|SYNOPSIS \|DESCRIPTION \|RETURN VALUE \|ERRORS \|EXAMPLES \|APPLICATION USAGE \|RATIONALE \|FUTURE DIRECTIONS \|SEE ALSO \|COPYRIGHT

SETREUID(3P)            POSIX Programmer's ManualSETREUID(3P)

PROLOG top

       This manual page is part of the POSIX Programmer's Manual.  The       Linux implementation of this interface may differ (consult the       corresponding Linux manual page for details of Linux behavior), or       the interface may not be implemented on Linux.

NAME top

       setreuid — set real and effective user IDs

SYNOPSIS top

       #include <unistd.h>       int setreuid(uid_truid, uid_teuid);

DESCRIPTION top

       Thesetreuid() function shall set the real and effective user IDs       of the current process to the values specified by theruid andeuid arguments. Ifruid oreuid is -1, the corresponding effective       or real user ID of the current process shall be left unchanged.       A process with appropriate privileges can set either ID to any       value.  An unprivileged process can only set the effective user ID       if theeuid argument is equal to either the real, effective, or       saved user ID of the process.       If the real user ID is being set (ruid is not -1), or the       effective user ID is being set to a value not equal to the real       user ID, then the saved set-user-ID of the current process shall       be set equal to the new effective user ID.       It is unspecified whether a process without appropriate privileges       is permitted to change the real user ID to match the current       effective user ID or saved set-user-ID of the process.

RETURN VALUE top

       Upon successful completion, 0 shall be returned. Otherwise, -1       shall be returned anderrno set to indicate the error.

ERRORS top

       Thesetreuid() function shall fail if:EINVALThe value of theruid oreuid argument is invalid or out-              of-range.EPERMThe current process does not have appropriate privileges,              and either an attempt was made to change the effective user              ID to a value other than the real user ID or the saved set-              user-ID or an attempt was made to change the real user ID              to a value not permitted by the implementation.The following sections are informative.

EXAMPLES top

Setting the Effective User ID to the Real User ID       The following example sets the effective user ID of the calling       process to the real user ID, so that files created later will be       owned by the current user. It also sets the saved set-user-ID to       the real user ID, so any future attempt to set the effective user       ID back to its previous value will fail.           #include <unistd.h>           #include <sys/types.h>           ...           setreuid(getuid(), getuid());           ...

APPLICATION USAGE top

       None.

RATIONALE top

       Earlier versions of this standard did not specify whether the       saved set-user-ID was affected bysetreuid() calls. This version       specifies common existing practice that constitutes an important       security feature. The ability to set both the effective user ID       and saved set-user-ID to be the same as the real user ID means       that any security weakness in code that is executed after that       point cannot result in malicious code being executed with the       previous effective user ID. Privileged applications could already       do this using justsetuid(), but for non-privileged applications       the only standard method available is to use this feature ofsetreuid().

FUTURE DIRECTIONS top

       None.

COPYRIGHT top

       Portions of this text are reprinted and reproduced in electronic       form from IEEE Std 1003.1-2017, Standard for Information       Technology -- Portable Operating System Interface (POSIX), The       Open Group Base Specifications Issue 7, 2018 Edition, Copyright       (C) 2018 by the Institute of Electrical and Electronics Engineers,       Inc and The Open Group.  In the event of any discrepancy between       this version and the original IEEE and The Open Group Standard,       the original IEEE and The Open Group Standard is the referee       document. The original Standard can be obtained online athttp://www.opengroup.org/unix/online.html .       Any typographical or formatting errors that appear in this page       are most likely to have been introduced during the conversion of       the source files to man page format. To report such errors, seehttps://www.kernel.org/doc/man-pages/reporting_bugs.html .IEEE/The Open Group                2017SETREUID(3P)

Pages that refer to this page:unistd.h(0p), getegid(3p), geteuid(3p), getgid(3p), getuid(3p), setegid(3p), seteuid(3p), setgid(3p), setregid(3p), setuid(3p)