hotplug-dispatch.c

   1 /*
   2  * Copyright (C) 2021 Daniel Golle <daniel@makrotopia.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #define _GNU_SOURCE
  15
  16 #include <sys/inotify.h>
  17 #include <sys/types.h>
  18
  19 #include <dirent.h>
  20 #include <errno.h>
  21 #include <glob.h>
  22 #include <limits.h>
  23 #include <stdbool.h>
  24 #include <stdlib.h>
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28
  29 #include <libubox/avl.h>
  30 #include <libubox/avl-cmp.h>
  31 #include <libubox/list.h>
  32 #include <libubox/uloop.h>
  33 #include <libubus.h>
  34
  35 #include "procd.h"
  36
  37 #define HOTPLUG_BASEDIR "/etc/hotplug.d"
  38 #define HOTPLUG_OBJECT_PREFIX "hotplug."
  39
  40 #define INOTIFY_SZ (sizeof(struct inotify_event) + PATH_MAX + 1)
  41
  42 struct ubus_context *ctx;
  43 static char *inotify_buffer;
  44 static struct uloop_fd fd_inotify_read;
  45
  46 static LIST_HEAD(subsystems);
  47
  48 extern char **environ;
  49
  50 struct hotplug_subsys {
  51         struct list_head list;
  52         struct ubus_object ubus;
  53 };
  54
  55 struct envlist {
  56         struct avl_node avl;
  57         char *env;
  58 };
  59
  60 struct hotplug_process {
  61         struct ubus_object *ubus;
  62         char **envp;
  63         struct uloop_timeout timeout;
  64         struct uloop_process process;
  65         glob_t globbuf;
  66         unsigned int cnt;
  67         int ret;
  68 };
  69
  70 static void env_free(char **envp)
  71 {
  72         char **tmp;
  73
  74         tmp = envp;
  75         while (*tmp)
  76                 free(*(tmp++));
  77         free(envp);
  78 }
  79
  80 static void hotplug_free(struct hotplug_process *pc)
  81 {
  82         env_free(pc->envp);
  83         globfree(&pc->globbuf);
  84         free(pc);
  85 }
  86
  87 static void hotplug_done(struct uloop_process *c, int ret)
  88 {
  89         struct hotplug_process *pc = container_of(c, struct hotplug_process, process);
  90
  91         pc->ret = ret;
  92
  93         uloop_timeout_set(&pc->timeout, 50);
  94 }
  95
  96 static void hotplug_exec(struct uloop_timeout *t)
  97 {
  98         struct hotplug_process *pc = container_of(t, struct hotplug_process, timeout);
  99         char *script;
 100         char *exec_argv[4];
 101         /* we have reached the last entry in the globbuf */
 102         if (pc->cnt == pc->globbuf.gl_pathc) {
 103                 hotplug_free(pc);
 104                 return;
 105         }
 106
 107         if (asprintf(&script, ". /lib/functions.sh\n. %s\n", pc->globbuf.gl_pathv[pc->cnt++]) == -1) {
 108                 pc->ret = ENOMEM;
 109                 return;
 110         }
 111
 112         /* prepare for execve() */
 113         exec_argv[0] = "/bin/sh";
 114         exec_argv[1] = "-c";
 115         exec_argv[2] = script;
 116         exec_argv[3] = NULL;
 117
 118         /* set callback in uloop_process */
 119         pc->process.cb = hotplug_done;
 120         pc->process.pid = fork();
 121         if (pc->process.pid == 0) {
 122                 /* child */
 123                 exit(execve(exec_argv[0], exec_argv, pc->envp));
 124         } else if (pc->process.pid < 0) {
 125                 /* fork error */
 126                 free(script);
 127                 hotplug_free(pc);
 128                 return;
 129         }
 130         /* parent */
 131         free(script);
 132         uloop_process_add(&pc->process);
 133 }
 134
 135 static int avl_envcmp(const void *k1, const void *k2, void *ptr)
 136 {
 137         const char *tmp;
 138
 139         tmp = strchr(k1, '=');
 140         if (!tmp)
 141                 return -1;
 142
 143         /*
 144          * compare the variable name only, ie. limit strncmp to check
 145          * only up to and including the '=' sign
 146          */
 147         return strncmp(k1, k2, (tmp - (char *)k1) + 1);
 148 }
 149
 150 /* validate NULL-terminated environment variable name */
 151 static int validate_envvarname(const char *envvarname)
 152 {
 153         const char *tmp = envvarname;
 154
 155         /* check for illegal characters in env variable name */
 156         while (tmp[0] != '\0') {
 157                 if (!((tmp[0] >= 'a' && tmp[0] <= 'z') ||
 158                       (tmp[0] >= 'A' && tmp[0] <= 'Z') ||
 159                       (tmp[0] == '_') ||
 160                       /* allow numbers unless they are at the first character */
 161                       ((tmp != envvarname) && tmp[0] >= '0' && tmp[0] <= '9')))
 162                         return EINVAL;
 163                 ++tmp;
 164         }
 165
 166         return 0;
 167 }
 168
 169 enum {
 170         HOTPLUG_ENV,
 171         __HOTPLUG_MAX
 172 };
 173
 174 static const struct blobmsg_policy hotplug_policy[__HOTPLUG_MAX] = {
 175         [HOTPLUG_ENV] = { .name = "env", .type = BLOBMSG_TYPE_ARRAY },
 176 };
 177
 178 static int hotplug_call(struct ubus_context *ctx, struct ubus_object *obj,
 179                         struct ubus_request_data *req, const char *method,
 180                         struct blob_attr *msg)
 181 {
 182         const char *subsys = &obj->name[strlen(HOTPLUG_OBJECT_PREFIX)];
 183         struct blob_attr *tb[__HOTPLUG_MAX], *cur;
 184         AVL_TREE(env, avl_envcmp, false, NULL);
 185         struct envlist *envle, *p;
 186         int rem;
 187         char **envp, *globstr, *tmp, **tmpenv;
 188         size_t envz = 0;
 189         struct hotplug_process *pc;
 190         bool async = true;
 191         int err = UBUS_STATUS_UNKNOWN_ERROR;
 192
 193         blobmsg_parse(hotplug_policy, __HOTPLUG_MAX, tb, blobmsg_data(msg), blobmsg_len(msg));
 194
 195         if (!tb[HOTPLUG_ENV])
 196                 return UBUS_STATUS_INVALID_ARGUMENT;
 197
 198         tmpenv = environ;
 199
 200         /* first adding existing environment to avl_tree */
 201         while (*tmpenv) {
 202                 envle = calloc(1, sizeof(struct envlist));
 203                 if (!envle)
 204                         goto err_envle;
 205
 206                 envle->env = strdup(*tmpenv);
 207                 if (!envle->env) {
 208                         free(envle);
 209                         goto err_envle;
 210                 }
 211                 envle->avl.key = envle->env;
 212                 if (avl_insert(&env, &envle->avl) == -1) {
 213                         free(envle->env);
 214                         free(envle);
 215                         goto err_envle;
 216                 }
 217
 218                 ++tmpenv;
 219         }
 220
 221         /* then adding additional variables from ubus call */
 222         blobmsg_for_each_attr(cur, tb[HOTPLUG_ENV], rem) {
 223                 char *enve = blobmsg_get_string(cur);
 224                 if (!enve)
 225                         continue;
 226
 227                 if (!strncmp(enve, "LD_", 3))
 228                         continue;
 229
 230                 if (!strcmp(enve, "PATH"))
 231                         continue;
 232
 233                 if (strlen(enve) < 3)
 234                         continue;
 235
 236                 if (!(tmp = strchr(enve, '=')))
 237                         continue;
 238
 239                 *tmp = '\0';
 240                 if (validate_envvarname(enve))
 241                         continue;
 242                 *tmp = '=';
 243
 244                 if (!strcmp(enve, "ASYNC=0"))
 245                         async = false;
 246
 247                 envle = calloc(1, sizeof(struct envlist));
 248                 if (!envle)
 249                         goto err_envle;
 250
 251                 envle->env = strdup(enve);
 252                 if (!envle->env) {
 253                         free(envle);
 254                         goto err_envle;
 255                 }
 256                 envle->avl.key = envle->env;
 257                 if (avl_insert(&env, &envle->avl)) {
 258                         /* do not override existing env values, just skip */
 259                         free((void*)envle->env);
 260                         free(envle);
 261                 }
 262         }
 263
 264         /* synchronous calls are unsupported for now */
 265         if (!async) {
 266                 err = UBUS_STATUS_NOT_SUPPORTED;
 267                 goto err_envle;
 268         }
 269
 270         /* allocating new environment */
 271         avl_for_each_element(&env, envle, avl)
 272                 ++envz;
 273
 274         envp = calloc(envz + 1, sizeof(char *));
 275         if (!envp)
 276                 goto err_envle;
 277
 278         /* populating new environment */
 279         envz = 0;
 280         avl_for_each_element_safe(&env, envle, avl, p) {
 281                 envp[envz++] = envle->env;
 282                 avl_delete(&env, &envle->avl);
 283                 free(envle);
 284         }
 285
 286         pc = calloc(1, sizeof(struct hotplug_process));
 287         if (!pc) {
 288                 env_free(envp);
 289                 return UBUS_STATUS_UNKNOWN_ERROR;
 290         }
 291         pc->timeout.cb = hotplug_exec;
 292         pc->envp = envp;
 293         pc->cnt = 0;
 294         pc->ubus = obj;
 295
 296         /* glob'ing for hotplug scripts */
 297         if (asprintf(&globstr, "%s/%s/*", HOTPLUG_BASEDIR, subsys) == -1) {
 298                 hotplug_free(pc);
 299                 return UBUS_STATUS_UNKNOWN_ERROR;
 300         }
 301
 302         if (glob(globstr, GLOB_DOOFFS, NULL, &pc->globbuf)) {
 303                 free(globstr);
 304                 hotplug_free(pc);
 305                 return UBUS_STATUS_OK;
 306         }
 307
 308         free(globstr);
 309
 310         /* asynchronous call to hotplug_exec() */
 311         uloop_timeout_set(&pc->timeout, 50);
 312
 313         return UBUS_STATUS_OK;
 314
 315 err_envle:
 316         avl_for_each_element_safe(&env, envle, avl, p) {
 317                 if (envle->env)
 318                         free(envle->env);
 319
 320                 avl_delete(&env, &envle->avl);
 321                 free(envle);
 322         }
 323
 324         return err;
 325 }
 326
 327 static const struct ubus_method hotplug_methods[] = {
 328         UBUS_METHOD("call", hotplug_call, hotplug_policy),
 329 };
 330
 331 static struct ubus_object_type hotplug_object_type =
 332         UBUS_OBJECT_TYPE("hotplug", hotplug_methods);
 333
 334 static void add_subsystem(int nlen, char *newname)
 335 {
 336         struct hotplug_subsys *nh = calloc(1, sizeof(struct hotplug_subsys));
 337         char *name;
 338
 339         if (asprintf(&name, "%s%.*s", HOTPLUG_OBJECT_PREFIX, nlen, newname) == -1)
 340                 exit(ENOMEM);
 341
 342         /* prepare and add ubus object */
 343         nh->ubus.name = name;
 344         nh->ubus.type = &hotplug_object_type;
 345         nh->ubus.methods = hotplug_object_type.methods;
 346         nh->ubus.n_methods = hotplug_object_type.n_methods;
 347         list_add(&nh->list, &subsystems);
 348         ubus_add_object(ctx, &nh->ubus);
 349 }
 350
 351 static void remove_subsystem(int nlen, char *name)
 352 {
 353         struct hotplug_subsys *n, *h;
 354
 355         /* find match subsystem object by name or any if not given */
 356         list_for_each_entry_safe(h, n, &subsystems, list) {
 357                 if (nlen && (strlen(h->ubus.name) != strnlen(name, nlen) + strlen(HOTPLUG_OBJECT_PREFIX)))
 358                         continue;
 359                 if (nlen && (strncmp(name, &h->ubus.name[strlen(HOTPLUG_OBJECT_PREFIX)], nlen)))
 360                         continue;
 361
 362                 list_del(&h->list);
 363                 ubus_remove_object(ctx, &h->ubus);
 364                 free((void*)h->ubus.name);
 365                 free(h);
 366         }
 367 }
 368
 369 static int init_subsystems(void)
 370 {
 371         DIR *dir;
 372         struct dirent *dirent;
 373
 374         dir = opendir(HOTPLUG_BASEDIR);
 375         if (dir == NULL)
 376                 return ENOENT;
 377
 378         while ((dirent = readdir(dir))) {
 379                 /* skip everything but directories */
 380                 if (dirent->d_type != DT_DIR)
 381                         continue;
 382
 383                 /* skip '.' and '..' as well as hidden files */
 384                 if (dirent->d_name[0] == '.')
 385                         continue;
 386
 387                 add_subsystem(strlen(dirent->d_name), dirent->d_name);
 388         }
 389         closedir(dir);
 390
 391         return 0;
 392 }
 393
 394 static void inotify_read_handler(struct uloop_fd *u, unsigned int events)
 395 {
 396         int rc;
 397         char *p;
 398         struct inotify_event *in;
 399
 400         /* read inotify events */
 401         while ((rc = read(u->fd, inotify_buffer, INOTIFY_SZ)) == -1 && errno == EINTR);
 402
 403         if (rc <= 0)
 404                 return;
 405
 406         /* process events from buffer */
 407         for (p = inotify_buffer;
 408              rc - (p - inotify_buffer) >= (int)sizeof(struct inotify_event);
 409              p += sizeof(struct inotify_event) + in->len) {
 410                 in = (struct inotify_event*)p;
 411
 412                 /* skip everything but directories */
 413                 if (!(in->mask & IN_ISDIR))
 414                         continue;
 415
 416                 if (in->len < 1)
 417                         continue;
 418
 419                 /* skip hidden files */
 420                 if (in->name[0] == '.')
 421                         continue;
 422
 423                 /* add/remove subsystem objects */
 424                 if (in->mask & (IN_CREATE | IN_MOVED_TO))
 425                         add_subsystem(in->len, in->name);
 426                 else if (in->mask & (IN_DELETE | IN_MOVED_FROM))
 427                         remove_subsystem(in->len, in->name);
 428         }
 429 }
 430
 431 void ubus_init_hotplug(struct ubus_context *newctx)
 432 {
 433         ctx = newctx;
 434         remove_subsystem(0, NULL);
 435         if (init_subsystems()) {
 436                 printf("failed to initialize hotplug subsystems from %s\n", HOTPLUG_BASEDIR);
 437                 return;
 438         }
 439         fd_inotify_read.fd = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
 440         fd_inotify_read.cb = inotify_read_handler;
 441         if (fd_inotify_read.fd == -1) {
 442                 printf("failed to initialize inotify handler for %s\n", HOTPLUG_BASEDIR);
 443                 return;
 444         }
 445
 446         inotify_buffer = calloc(1, INOTIFY_SZ);
 447         if (!inotify_buffer)
 448                 return;
 449
 450         if (inotify_add_watch(fd_inotify_read.fd, HOTPLUG_BASEDIR,
 451                 IN_CREATE | IN_MOVED_TO | IN_DELETE | IN_MOVED_FROM | IN_ONLYDIR) == -1)
 452                 return;
 453
 454         uloop_fd_add(&fd_inotify_read, ULOOP_READ);
 455 }