src/login/logind-acl.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2011 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd 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   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <errno.h>
  23 #include <string.h>
  24
  25 #include "acl-util.h"
  26 #include "escape.h"
  27 #include "formats-util.h"
  28 #include "set.h"
  29 #include "string-util.h"
  30 #include "udev-util.h"
  31 #include "util.h"
  32 #include "logind-acl.h"
  33
  34 static int flush_acl(acl_t acl) {
  35         acl_entry_t i;
  36         int found;
  37         bool changed = false;
  38
  39         assert(acl);
  40
  41         for (found = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
  42              found > 0;
  43              found = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
  44
  45                 acl_tag_t tag;
  46
  47                 if (acl_get_tag_type(i, &tag) < 0)
  48                         return -errno;
  49
  50                 if (tag != ACL_USER)
  51                         continue;
  52
  53                 if (acl_delete_entry(acl, i) < 0)
  54                         return -errno;
  55
  56                 changed = true;
  57         }
  58
  59         if (found < 0)
  60                 return -errno;
  61
  62         return changed;
  63 }
  64
  65 int devnode_acl(const char *path,
  66                 bool flush,
  67                 bool del, uid_t old_uid,
  68                 bool add, uid_t new_uid) {
  69
  70         acl_t acl;
  71         int r = 0;
  72         bool changed = false;
  73
  74         assert(path);
  75
  76         acl = acl_get_file(path, ACL_TYPE_ACCESS);
  77         if (!acl)
  78                 return -errno;
  79
  80         if (flush) {
  81
  82                 r = flush_acl(acl);
  83                 if (r < 0)
  84                         goto finish;
  85                 if (r > 0)
  86                         changed = true;
  87
  88         } else if (del && old_uid > 0) {
  89                 acl_entry_t entry;
  90
  91                 r = acl_find_uid(acl, old_uid, &entry);
  92                 if (r < 0)
  93                         goto finish;
  94
  95                 if (r > 0) {
  96                         if (acl_delete_entry(acl, entry) < 0) {
  97                                 r = -errno;
  98                                 goto finish;
  99                         }
 100
 101                         changed = true;
 102                 }
 103         }
 104
 105         if (add && new_uid > 0) {
 106                 acl_entry_t entry;
 107                 acl_permset_t permset;
 108                 int rd, wt;
 109
 110                 r = acl_find_uid(acl, new_uid, &entry);
 111                 if (r < 0)
 112                         goto finish;
 113
 114                 if (r == 0) {
 115                         if (acl_create_entry(&acl, &entry) < 0) {
 116                                 r = -errno;
 117                                 goto finish;
 118                         }
 119
 120                         if (acl_set_tag_type(entry, ACL_USER) < 0 ||
 121                             acl_set_qualifier(entry, &new_uid) < 0) {
 122                                 r = -errno;
 123                                 goto finish;
 124                         }
 125                 }
 126
 127                 if (acl_get_permset(entry, &permset) < 0) {
 128                         r = -errno;
 129                         goto finish;
 130                 }
 131
 132                 rd = acl_get_perm(permset, ACL_READ);
 133                 if (rd < 0) {
 134                         r = -errno;
 135                         goto finish;
 136                 }
 137
 138                 wt = acl_get_perm(permset, ACL_WRITE);
 139                 if (wt < 0) {
 140                         r = -errno;
 141                         goto finish;
 142                 }
 143
 144                 if (!rd || !wt) {
 145
 146                         if (acl_add_perm(permset, ACL_READ|ACL_WRITE) < 0) {
 147                                 r = -errno;
 148                                 goto finish;
 149                         }
 150
 151                         changed = true;
 152                 }
 153         }
 154
 155         if (!changed)
 156                 goto finish;
 157
 158         if (acl_calc_mask(&acl) < 0) {
 159                 r = -errno;
 160                 goto finish;
 161         }
 162
 163         if (acl_set_file(path, ACL_TYPE_ACCESS, acl) < 0) {
 164                 r = -errno;
 165                 goto finish;
 166         }
 167
 168         r = 0;
 169
 170 finish:
 171         acl_free(acl);
 172
 173         return r;
 174 }
 175
 176 int devnode_acl_all(struct udev *udev,
 177                     const char *seat,
 178                     bool flush,
 179                     bool del, uid_t old_uid,
 180                     bool add, uid_t new_uid) {
 181
 182         _cleanup_udev_enumerate_unref_ struct udev_enumerate *e = NULL;
 183         struct udev_list_entry *item = NULL, *first = NULL;
 184         _cleanup_set_free_free_ Set *nodes = NULL;
 185         _cleanup_closedir_ DIR *dir = NULL;
 186         struct dirent *dent;
 187         Iterator i;
 188         char *n;
 189         int r;
 190
 191         assert(udev);
 192
 193         nodes = set_new(&string_hash_ops);
 194         if (!nodes)
 195                 return -ENOMEM;
 196
 197         e = udev_enumerate_new(udev);
 198         if (!e)
 199                 return -ENOMEM;
 200
 201         if (isempty(seat))
 202                 seat = "seat0";
 203
 204         /* We can only match by one tag in libudev. We choose
 205          * "uaccess" for that. If we could match for two tags here we
 206          * could add the seat name as second match tag, but this would
 207          * be hardly optimizable in libudev, and hence checking the
 208          * second tag manually in our loop is a good solution. */
 209         r = udev_enumerate_add_match_tag(e, "uaccess");
 210         if (r < 0)
 211                 return r;
 212
 213         r = udev_enumerate_add_match_is_initialized(e);
 214         if (r < 0)
 215                 return r;
 216
 217         r = udev_enumerate_scan_devices(e);
 218         if (r < 0)
 219                 return r;
 220
 221         first = udev_enumerate_get_list_entry(e);
 222         udev_list_entry_foreach(item, first) {
 223                 _cleanup_udev_device_unref_ struct udev_device *d = NULL;
 224                 const char *node, *sn;
 225
 226                 d = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
 227                 if (!d)
 228                         return -ENOMEM;
 229
 230                 sn = udev_device_get_property_value(d, "ID_SEAT");
 231                 if (isempty(sn))
 232                         sn = "seat0";
 233
 234                 if (!streq(seat, sn))
 235                         continue;
 236
 237                 node = udev_device_get_devnode(d);
 238                 /* In case people mistag devices with nodes, we need to ignore this */
 239                 if (!node)
 240                         continue;
 241
 242                 n = strdup(node);
 243                 if (!n)
 244                         return -ENOMEM;
 245
 246                 log_debug("Found udev node %s for seat %s", n, seat);
 247                 r = set_consume(nodes, n);
 248                 if (r < 0)
 249                         return r;
 250         }
 251
 252         /* udev exports "dead" device nodes to allow module on-demand loading,
 253          * these devices are not known to the kernel at this moment */
 254         dir = opendir("/run/udev/static_node-tags/uaccess");
 255         if (dir) {
 256                 FOREACH_DIRENT(dent, dir, return -errno) {
 257                         _cleanup_free_ char *unescaped_devname = NULL;
 258
 259                         if (cunescape(dent->d_name, UNESCAPE_RELAX, &unescaped_devname) < 0)
 260                                 return -ENOMEM;
 261
 262                         n = strappend("/dev/", unescaped_devname);
 263                         if (!n)
 264                                 return -ENOMEM;
 265
 266                         log_debug("Found static node %s for seat %s", n, seat);
 267                         r = set_consume(nodes, n);
 268                         if (r == -EEXIST)
 269                                 continue;
 270                         if (r < 0)
 271                                 return r;
 272                 }
 273         }
 274
 275         r = 0;
 276         SET_FOREACH(n, nodes, i) {
 277                 int k;
 278
 279                 log_debug("Changing ACLs at %s for seat %s (uid "UID_FMT"→"UID_FMT"%s%s)",
 280                           n, seat, old_uid, new_uid,
 281                           del ? " del" : "", add ? " add" : "");
 282
 283                 k = devnode_acl(n, flush, del, old_uid, add, new_uid);
 284                 if (k == -ENOENT)
 285                         log_debug("Device %s disappeared while setting ACLs", n);
 286                 else if (k < 0 && r == 0)
 287                         r = k;
 288         }
 289
 290         return r;
 291 }