lib/privs.h

   1 /*
   2  * Zebra privileges header.
   3  *
   4  * Copyright (C) 2003 Paul Jakma.
   5  *
   6  * This file is part of GNU Zebra.
   7  *
   8  * GNU Zebra is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the
  10  * Free Software Foundation; either version 2, or (at your option) any
  11  * later version.
  12  *
  13  * GNU Zebra is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; see the file COPYING; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #ifndef _ZEBRA_PRIVS_H
  24 #define _ZEBRA_PRIVS_H
  25
  26 #include <pthread.h>
  27 #include <stdint.h>
  28 #include "lib/queue.h"
  29
  30 #ifdef __cplusplus
  31 extern "C" {
  32 #endif
  33
  34 /* list of zebra capabilities */
  35 typedef enum {
  36         ZCAP_SETID,
  37         ZCAP_BIND,
  38         ZCAP_NET_ADMIN,
  39         ZCAP_SYS_ADMIN,
  40         ZCAP_NET_RAW,
  41         ZCAP_CHROOT,
  42         ZCAP_NICE,
  43         ZCAP_PTRACE,
  44         ZCAP_DAC_OVERRIDE,
  45         ZCAP_READ_SEARCH,
  46         ZCAP_FOWNER,
  47         ZCAP_MAX
  48 } zebra_capabilities_t;
  49
  50 typedef enum {
  51         ZPRIVS_LOWERED,
  52         ZPRIVS_RAISED,
  53         ZPRIVS_UNKNOWN,
  54 } zebra_privs_current_t;
  55
  56 typedef enum {
  57         ZPRIVS_RAISE,
  58         ZPRIVS_LOWER,
  59 } zebra_privs_ops_t;
  60
  61 struct zebra_privs_refs_t {
  62         STAILQ_ENTRY(zebra_privs_refs_t) entry;
  63         pthread_t tid;
  64         uint32_t refcount;
  65         const char *raised_in_funcname;
  66 };
  67
  68 struct zebra_privs_t {
  69         zebra_capabilities_t *caps_p; /* caps required for operation */
  70         zebra_capabilities_t *caps_i; /* caps to allow inheritance of */
  71         int cap_num_p;                /* number of caps in arrays */
  72         int cap_num_i;
  73
  74         /* Mutex and counter used to avoid race conditions in multi-threaded
  75          * processes. If privs status is process-wide, we need to
  76          * control changes to the privilege status among threads.
  77          * If privs changes are per-thread, we need to be able to
  78          * manage that too.
  79          */
  80         pthread_mutex_t mutex;
  81         struct zebra_privs_refs_t process_refs;
  82
  83         STAILQ_HEAD(thread_refs_q, zebra_privs_refs_t) thread_refs;
  84
  85         const char *user; /* user and group to run as */
  86         const char *group;
  87         const char *vty_group; /* group to chown vty socket to */
  88         /* methods */
  89         int (*change)(zebra_privs_ops_t); /* change privileges, 0 on success */
  90         zebra_privs_current_t (*current_state)(
  91                 void); /* current privilege state */
  92 };
  93
  94 struct zprivs_ids_t {
  95         /* -1 is undefined */
  96         uid_t uid_priv;   /* privileged uid */
  97         uid_t uid_normal; /* normal uid */
  98         gid_t gid_priv;   /* privileged uid */
  99         gid_t gid_normal; /* normal uid */
 100         gid_t gid_vty;    /* vty gid */
 101 };
 102
 103 extern struct zebra_privs_t *lib_privs;
 104
 105 /* initialise zebra privileges */
 106 extern void zprivs_preinit(struct zebra_privs_t *zprivs);
 107 extern void zprivs_init(struct zebra_privs_t *zprivs);
 108 /* drop all and terminate privileges */
 109 extern void zprivs_terminate(struct zebra_privs_t *);
 110 /* query for runtime uid's and gid's, eg vty needs this */
 111 extern void zprivs_get_ids(struct zprivs_ids_t *);
 112
 113 /*
 114  * Wrapper around zprivs, to be used as:
 115  *   frr_with_privs(&privs) {
 116  *     ... code ...
 117  *     if (error)
 118  *       break;         -- break can be used to get out of the block
 119  *     ... code ...
 120  *   }
 121  *
 122  * The argument to frr_with_privs() can be NULL to leave privileges as-is
 123  * (mostly useful for conditional privilege-raising, i.e.:)
 124  *   frr_with_privs(cond ? &privs : NULL) {}
 125  *
 126  * NB: The code block is always executed, regardless of whether privileges
 127  * could be raised or not, or whether NULL was given or not.  This is fully
 128  * intentional;  the user may have configured some RBAC or similar that we
 129  * are not aware of, but that allows our code to proceed without privileges.
 130  *
 131  * The point of this wrapper is to prevent accidental bugs where privileges
 132  * are elevated but then not dropped.  This can happen when, for example, a
 133  * "return", "goto" or "break" in the middle of the elevated-privilege code
 134  * skips past the privilege dropping call.
 135  *
 136  * The macro below uses variable cleanup to drop privileges as soon as the
 137  * code block is left in any way (and thus the _privs variable goes out of
 138  * scope.)  _once is just a trick to run the loop exactly once.
 139  */
 140 extern struct zebra_privs_t *_zprivs_raise(struct zebra_privs_t *privs,
 141                                            const char *funcname);
 142 extern void _zprivs_lower(struct zebra_privs_t **privs);
 143
 144 #define frr_with_privs(privs)                                               \
 145         for (struct zebra_privs_t *_once = NULL,                               \
 146                                   *_privs __attribute__(                       \
 147                                           (unused, cleanup(_zprivs_lower))) =  \
 148                                           _zprivs_raise(privs, __func__);      \
 149              _once == NULL; _once = (void *)1)
 150
 151 #ifdef __cplusplus
 152 }
 153 #endif
 154
 155 #endif /* _ZEBRA_PRIVS_H */