src/login/logind-acl.c

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