src/login/logind-acl.c

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