lstat_as.c

[詳解]

/*++
/* NAME
/*  lstat_as 3
/* SUMMARY
/*  lstat file as user
/* SYNOPSIS
/*  #include <sys/stat.h>
/*  #include <lstat_as.h>
/*
/*  int lstat_as(path, st, euid, egid)
/*  const char *path;
/*  struct stat *st;
/*  uid_t   euid;
/*  gid_t   egid;
/* DESCRIPTION
/*  lstat_as() looks up the file status of the named \fIpath\fR,
/*  using the effective rights specified by \fIeuid\fR
/*  and \fIegid\fR, and stores the result into the structure pointed
/*  to by \fIst\fR.  A -1 result means the lookup failed.
/*  This call does not follow symbolic links.
/* 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 <sys/stat.h>
#include <unistd.h>

/* Utility library. */

#include "msg.h"
#include "set_eugid.h"
#include "lstat_as.h"
#include "warn_stat.h"

/* lstat_as - lstat file as user */

int     lstat_as(const char *path, struct stat * st, uid_t euid, gid_t egid)
{
    uid_t   saved_euid = geteuid();
    gid_t   saved_egid = getegid();
    int     status;

    /*
     * Switch to the target user privileges.
     */
    set_eugid(euid, egid);

    /*
     * Lstat that file.
     */
    status = lstat(path, st);

    /*
     * Restore saved privileges.
     */
    set_eugid(saved_euid, saved_egid);

    return (status);
}