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