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 "lib/queue.h"
  28
  29 #ifdef __cplusplus
  30 extern "C" {
  31 #endif
  32
  33 /* list of zebra capabilities */
  34 typedef enum {
  35         ZCAP_SETID,
  36         ZCAP_BIND,
  37         ZCAP_NET_ADMIN,
  38         ZCAP_SYS_ADMIN,
  39         ZCAP_NET_RAW,
  40         ZCAP_CHROOT,
  41         ZCAP_NICE,
  42         ZCAP_PTRACE,
  43         ZCAP_DAC_OVERRIDE,
  44         ZCAP_READ_SEARCH,
  45         ZCAP_FOWNER,
  46         ZCAP_MAX
  47 } zebra_capabilities_t;
  48
  49 typedef enum {
  50         ZPRIVS_LOWERED,
  51         ZPRIVS_RAISED,
  52         ZPRIVS_UNKNOWN,
  53 } zebra_privs_current_t;
  54
  55 typedef enum {
  56         ZPRIVS_RAISE,
  57         ZPRIVS_LOWER,
  58 } zebra_privs_ops_t;
  59
  60 struct zebra_privs_refs_t {
  61         STAILQ_ENTRY(zebra_privs_refs_t) entry;
  62         pthread_t tid;
  63         uint32_t refcount;
  64         const char *raised_in_funcname;
  65 };
  66
  67 struct zebra_privs_t {
  68         zebra_capabilities_t *caps_p; /* caps required for operation */
  69         zebra_capabilities_t *caps_i; /* caps to allow inheritance of */
  70         int cap_num_p;                /* number of caps in arrays */
  71         int cap_num_i;
  72
  73         /* Mutex and counter used to avoid race conditions in multi-threaded
  74          * processes. If privs status is process-wide, we need to
  75          * control changes to the privilege status among threads.
  76          * If privs changes are per-thread, we need to be able to
  77          * manage that too.
  78          */
  79         pthread_mutex_t mutex;
  80         struct zebra_privs_refs_t process_refs;
  81
  82         STAILQ_HEAD(thread_refs_q, zebra_privs_refs_t) thread_refs;
  83
  84         const char *user; /* user and group to run as */
  85         const char *group;
  86         const char *vty_group; /* group to chown vty socket to */
  87         /* methods */
  88         int (*change)(zebra_privs_ops_t); /* change privileges, 0 on success */
  89         zebra_privs_current_t (*current_state)(
  90                 void); /* current privilege state */
  91 };
  92
  93 struct zprivs_ids_t {
  94         /* -1 is undefined */
  95         uid_t uid_priv;   /* privileged uid */
  96         uid_t uid_normal; /* normal uid */
  97         gid_t gid_priv;   /* privileged uid */
  98         gid_t gid_normal; /* normal uid */
  99         gid_t gid_vty;    /* vty gid */
 100 };
 101
 102 /* initialise zebra privileges */
 103 extern void zprivs_preinit(struct zebra_privs_t *zprivs);
 104 extern void zprivs_init(struct zebra_privs_t *zprivs);
 105 /* drop all and terminate privileges */
 106 extern void zprivs_terminate(struct zebra_privs_t *);
 107 /* query for runtime uid's and gid's, eg vty needs this */
 108 extern void zprivs_get_ids(struct zprivs_ids_t *);
 109
 110 /*
 111  * Wrapper around zprivs, to be used as:
 112  *   frr_with_privs(&privs) {
 113  *     ... code ...
 114  *     if (error)
 115  *       break;         -- break can be used to get out of the block
 116  *     ... code ...
 117  *   }
 118  *
 119  * The argument to frr_with_privs() can be NULL to leave privileges as-is
 120  * (mostly useful for conditional privilege-raising, i.e.:)
 121  *   frr_with_privs(cond ? &privs : NULL) {}
 122  *
 123  * NB: The code block is always executed, regardless of whether privileges
 124  * could be raised or not, or whether NULL was given or not.  This is fully
 125  * intentional;  the user may have configured some RBAC or similar that we
 126  * are not aware of, but that allows our code to proceed without privileges.
 127  *
 128  * The point of this wrapper is to prevent accidental bugs where privileges
 129  * are elevated but then not dropped.  This can happen when, for example, a
 130  * "return", "goto" or "break" in the middle of the elevated-privilege code
 131  * skips past the privilege dropping call.
 132  *
 133  * The macro below uses variable cleanup to drop privileges as soon as the
 134  * code block is left in any way (and thus the _privs variable goes out of
 135  * scope.)  _once is just a trick to run the loop exactly once.
 136  */
 137 extern struct zebra_privs_t *_zprivs_raise(struct zebra_privs_t *privs,
 138                                            const char *funcname);
 139 extern void _zprivs_lower(struct zebra_privs_t **privs);
 140
 141 #define frr_with_privs(privs)                                               \
 142         for (struct zebra_privs_t *_once = NULL,                               \
 143                                   *_privs __attribute__(                       \
 144                                           (unused, cleanup(_zprivs_lower))) =  \
 145                                           _zprivs_raise(privs, __func__);      \
 146              _once == NULL; _once = (void *)1)
 147
 148 #ifdef __cplusplus
 149 }
 150 #endif
 151
 152 #endif /* _ZEBRA_PRIVS_H */