src/shared/devnode-acl.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4
   5 #include "sd-device.h"
   6
   7 #include "acl-util.h"
   8 #include "alloc-util.h"
   9 #include "device-util.h"
  10 #include "devnode-acl.h"
  11 #include "dirent-util.h"
  12 #include "fd-util.h"
  13 #include "format-util.h"
  14 #include "fs-util.h"
  15 #include "glyph-util.h"
  16 #include "set.h"
  17 #include "string-util.h"
  18
  19 static int flush_acl(acl_t acl) {
  20         acl_entry_t i;
  21         int found;
  22         bool changed = false;
  23
  24         assert(acl);
  25
  26         for (found = acl_get_entry(acl, ACL_FIRST_ENTRY, &i);
  27              found > 0;
  28              found = acl_get_entry(acl, ACL_NEXT_ENTRY, &i)) {
  29
  30                 acl_tag_t tag;
  31
  32                 if (acl_get_tag_type(i, &tag) < 0)
  33                         return -errno;
  34
  35                 if (tag != ACL_USER)
  36                         continue;
  37
  38                 if (acl_delete_entry(acl, i) < 0)
  39                         return -errno;
  40
  41                 changed = true;
  42         }
  43
  44         if (found < 0)
  45                 return -errno;
  46
  47         return changed;
  48 }
  49
  50 int devnode_acl(const char *path,
  51                 bool flush,
  52                 bool del, uid_t old_uid,
  53                 bool add, uid_t new_uid) {
  54
  55         _cleanup_(acl_freep) acl_t acl = NULL;
  56         int r;
  57         bool changed = false;
  58
  59         assert(path);
  60
  61         acl = acl_get_file(path, ACL_TYPE_ACCESS);
  62         if (!acl)
  63                 return -errno;
  64
  65         if (flush) {
  66
  67                 r = flush_acl(acl);
  68                 if (r < 0)
  69                         return r;
  70                 if (r > 0)
  71                         changed = true;
  72
  73         } else if (del && old_uid > 0) {
  74                 acl_entry_t entry;
  75
  76                 r = acl_find_uid(acl, old_uid, &entry);
  77                 if (r < 0)
  78                         return r;
  79
  80                 if (r > 0) {
  81                         if (acl_delete_entry(acl, entry) < 0)
  82                                 return -errno;
  83
  84                         changed = true;
  85                 }
  86         }
  87
  88         if (add && new_uid > 0) {
  89                 acl_entry_t entry;
  90                 acl_permset_t permset;
  91                 int rd, wt;
  92
  93                 r = acl_find_uid(acl, new_uid, &entry);
  94                 if (r < 0)
  95                         return r;
  96
  97                 if (r == 0) {
  98                         if (acl_create_entry(&acl, &entry) < 0)
  99                                 return -errno;
 100
 101                         if (acl_set_tag_type(entry, ACL_USER) < 0 ||
 102                             acl_set_qualifier(entry, &new_uid) < 0)
 103                                 return -errno;
 104                 }
 105
 106                 if (acl_get_permset(entry, &permset) < 0)
 107                         return -errno;
 108
 109                 rd = acl_get_perm(permset, ACL_READ);
 110                 if (rd < 0)
 111                         return -errno;
 112
 113                 wt = acl_get_perm(permset, ACL_WRITE);
 114                 if (wt < 0)
 115                         return -errno;
 116
 117                 if (!rd || !wt) {
 118
 119                         if (acl_add_perm(permset, ACL_READ|ACL_WRITE) < 0)
 120                                 return -errno;
 121
 122                         changed = true;
 123                 }
 124         }
 125
 126         if (!changed)
 127                 return 0;
 128
 129         if (acl_calc_mask(&acl) < 0)
 130                 return -errno;
 131
 132         if (acl_set_file(path, ACL_TYPE_ACCESS, acl) < 0)
 133                 return -errno;
 134
 135         return 0;
 136 }
 137
 138 int devnode_acl_all(const char *seat,
 139                     bool flush,
 140                     bool del, uid_t old_uid,
 141                     bool add, uid_t new_uid) {
 142
 143         _cleanup_(sd_device_enumerator_unrefp) sd_device_enumerator *e = NULL;
 144         _cleanup_set_free_ Set *nodes = NULL;
 145         _cleanup_closedir_ DIR *dir = NULL;
 146         char *n;
 147         int r;
 148
 149         r = sd_device_enumerator_new(&e);
 150         if (r < 0)
 151                 return r;
 152
 153         if (isempty(seat))
 154                 seat = "seat0";
 155
 156         /* We can only match by one tag in libudev. We choose
 157          * "uaccess" for that. If we could match for two tags here we
 158          * could add the seat name as second match tag, but this would
 159          * be hardly optimizable in libudev, and hence checking the
 160          * second tag manually in our loop is a good solution. */
 161         r = sd_device_enumerator_add_match_tag(e, "uaccess");
 162         if (r < 0)
 163                 return r;
 164
 165         FOREACH_DEVICE(e, d) {
 166                 const char *node, *sn;
 167
 168                 /* Make sure the tag is still in place */
 169                 if (sd_device_has_current_tag(d, "uaccess") <= 0)
 170                         continue;
 171
 172                 if (sd_device_get_property_value(d, "ID_SEAT", &sn) < 0 || isempty(sn))
 173                         sn = "seat0";
 174
 175                 if (!streq(seat, sn))
 176                         continue;
 177
 178                 /* In case people mistag devices with nodes, we need to ignore this */
 179                 if (sd_device_get_devname(d, &node) < 0)
 180                         continue;
 181
 182                 log_device_debug(d, "Found udev node %s for seat %s", node, seat);
 183                 r = set_put_strdup_full(&nodes, &path_hash_ops_free, node);
 184                 if (r < 0)
 185                         return r;
 186         }
 187
 188         /* udev exports "dead" device nodes to allow module on-demand loading,
 189          * these devices are not known to the kernel at this moment */
 190         dir = opendir("/run/udev/static_node-tags/uaccess");
 191         if (dir) {
 192                 FOREACH_DIRENT(de, dir, return -errno) {
 193                         r = readlinkat_malloc(dirfd(dir), de->d_name, &n);
 194                         if (r == -ENOENT)
 195                                 continue;
 196                         if (r < 0) {
 197                                 log_debug_errno(r,
 198                                                 "Unable to read symlink '/run/udev/static_node-tags/uaccess/%s', ignoring: %m",
 199                                                 de->d_name);
 200                                 continue;
 201                         }
 202
 203                         log_debug("Found static node %s for seat %s", n, seat);
 204                         r = set_ensure_consume(&nodes, &path_hash_ops_free, n);
 205                         if (r < 0)
 206                                 return r;
 207                 }
 208         }
 209
 210         r = 0;
 211         SET_FOREACH(n, nodes) {
 212                 int k;
 213
 214                 log_debug("Changing ACLs at %s for seat %s (uid "UID_FMT"%s"UID_FMT"%s%s)",
 215                           n, seat, old_uid, special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), new_uid,
 216                           del ? " del" : "", add ? " add" : "");
 217
 218                 k = devnode_acl(n, flush, del, old_uid, add, new_uid);
 219                 if (k == -ENOENT)
 220                         log_debug("Device %s disappeared while setting ACLs", n);
 221                 else
 222                         RET_GATHER(r, k);
 223         }
 224
 225         return r;
 226 }