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/*
* privs.h - header for privileged operations
* Copyright (C) 1993 Thomas Koenig
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _PRIVS_H
#define _PRIVS_H
#ifndef _USE_BSD
#define _USE_BSD 1
#include <unistd.h>
#undef _USE_BSD
#else
#include <unistd.h>
#endif
/* Relinquish privileges temporarily for a setuid or setgid program
* with the option of getting them back later. This is done by swapping
* the real and effective userid BSD style. Call RELINQUISH_PRIVS once
* at the beginning of the main program. This will cause all operations
* to be executed with the real userid. When you need the privileges
* of the setuid/setgid invocation, call PRIV_START; when you no longer
* need it, call PRIV_END. Note that it is an error to call PRIV_START
* and not PRIV_END within the same function.
*
* Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
* as root, and you want to drop back the effective userid to a
* and the effective group id to b, with the option to get them back
* later.
*
* If you no longer need root privileges, but those of some other
* userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
* is the user's.
*
* Problems: Do not use return between PRIV_START and PRIV_END; this
* will cause the program to continue running in an unprivileged
* state.
*
* It is NOT safe to call exec(), system() or popen() with a user-
* supplied program (i.e. without carefully checking PATH and any
* library load paths) with relinquished privileges; the called program
* can aquire them just as easily. Set both effective and real userid
* to the real userid before calling any of them.
*/
extern uid_t real_uid, effective_uid, daemon_uid;
extern gid_t real_gid, effective_gid, daemon_gid;
#ifdef HAVE_SETREUID
#define RELINQUISH_PRIVS { \
real_uid = getuid(); \
effective_uid = geteuid(); \
real_gid = getgid(); \
effective_gid = getegid(); \
setreuid(effective_uid, real_uid); \
setregid(effective_gid, real_gid); \
}
#define RELINQUISH_PRIVS_ROOT(a,b) { \
real_uid = (a); \
effective_uid = geteuid(); \
real_gid = (b); \
effective_gid = getegid(); \
setregid(effective_gid, real_gid); \
setreuid(effective_uid, real_uid); \
}
#define PRIV_START {\
setreuid(real_uid, effective_uid); \
setregid(real_gid, effective_gid);
#define PRIV_END \
setregid(effective_gid, real_gid); \
setreuid(effective_uid, real_uid); \
}
#define REDUCE_PRIV(a,b) {\
setreuid(real_uid, effective_uid); \
setregid(real_gid, effective_gid); \
effective_uid = (a); \
effective_gid = (b); \
setregid(effective_gid, real_gid); \
setreuid(effective_uid, real_uid); \
}
#elif HAVE_SETRESUID
#define RELINQUISH_PRIVS { \
real_uid = getuid(); \
effective_uid = geteuid(); \
real_gid = getgid(); \
effective_gid = getegid(); \
setresuid(effective_uid, real_uid, -1); \
setresgid(effective_gid, real_gid, -1); \
}
/*
* HP-UX kill(2) requires that the real or effective user ID of the
* sender match the real or _saved_ user ID of the recipient. In order
* for "at" (with random real ID and effective ID "daemon") to signal
* "atd" (with real ID "root" and effective ID "daemon"), we must make
* "atd"'s saved ID "daemon".
*/
#define RELINQUISH_PRIVS_ROOT(a,b) { \
real_uid = (a); \
effective_uid = geteuid(); \
real_gid = (b); \
effective_gid = getegid(); \
setresgid(effective_gid, real_gid, real_gid); \
setresuid(effective_uid, real_uid, real_uid); \
}
#define PRIV_START {\
setresuid(real_uid, effective_uid, -1); \
setresgid(real_gid, effective_gid, -1);
#define PRIV_END \
setresgid(effective_gid, real_gid, -1); \
setresuid(effective_uid, real_uid, -1); \
}
#define REDUCE_PRIV(a,b) {\
setresuid(real_uid, effective_uid, -1); \
setresgid(real_gid, effective_gid, -1); \
effective_uid = (a); \
effective_gid = (b); \
setresgid(effective_gid, real_gid, -1); \
setresuid(effective_uid, real_uid, -1); \
}
#else
#error "Cannot implement user ID swapping without setreuid or setresuid"
#endif
#endif
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