set_eugid.c

[詳解]

/*++
/* NAME
/*  set_eugid 3
/* SUMMARY
/*  set effective user and group attributes
/* SYNOPSIS
/*  #include <set_eugid.h>
/*
/*  void    set_eugid(euid, egid)
/*  uid_t   euid;
/*  gid_t   egid;
/*
/*  void    SAVE_AND_SET_EUGID(uid, gid)
/*  uid_t   uid;
/*  gid_t gid;
/*
/*  void    RESTORE_SAVED_EUGID()
/* DESCRIPTION
/*  set_eugid() sets the effective user and group process attributes
/*  and updates the process group access list to be just the specified
/*  effective group id.
/*
/*  SAVE_AND_SET_EUGID() opens a block that executes with the
/*  specified privilege. RESTORE_SAVED_EUGID() closes the block. 
/* DIAGNOSTICS
/*  All system call errors are fatal.
/* SEE ALSO
/*  seteuid(2), setegid(2), setgroups(2)
/* 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 <unistd.h>
#include <grp.h>
#include <errno.h>

/* Utility library. */

#include "msg.h"
#include "set_eugid.h"

/* set_eugid - set effective user and group attributes */

void    set_eugid(uid_t euid, gid_t egid)
{
    int     saved_errno = errno;

    if (geteuid() != 0)
    if (seteuid(0))
        msg_fatal("set_eugid: seteuid(0): %m");
    if (setegid(egid) < 0)
    msg_fatal("set_eugid: setegid(%ld): %m", (long) egid);
    if (setgroups(1, &egid) < 0)
    msg_fatal("set_eugid: setgroups(%ld): %m", (long) egid);
    if (euid != 0 && seteuid(euid) < 0)
    msg_fatal("set_eugid: seteuid(%ld): %m", (long) euid);
    if (msg_verbose)
    msg_info("set_eugid: euid %ld egid %ld", (long) euid, (long) egid);
    errno = saved_errno;
}