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 <assert.h>
  20 #include <dirent.h>
  21 #include <errno.h>
  22 #include <glob.h>
  23 #include <limits.h>
  24 #include <stdbool.h>
  25 #include <stdlib.h>
  26 #include <stdio.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29
  30 #include <libubox/avl.h>
  31 #include <libubox/avl-cmp.h>
  32 #include <libubox/list.h>
  33 #include <libubox/uloop.h>
  34 #include <libubus.h>
  35
  36 #include "procd.h"
  37
  38 #define HOTPLUG_BASEDIR "/etc/hotplug.d"
  39 #define HOTPLUG_OBJECT_PREFIX "hotplug."
  40
  41 #define INOTIFY_SZ (sizeof(struct inotify_event) + PATH_MAX + 1)
  42
  43 struct ubus_context *ctx;
  44 static char *inotify_buffer;
  45 static struct uloop_fd fd_inotify_read;
  46
  47 static LIST_HEAD(subsystems);
  48
  49 extern char **environ;
  50
  51 struct hotplug_subsys {
  52         struct list_head list;
  53         struct ubus_object ubus;
  54 };
  55
  56 struct envlist {
  57         struct avl_node avl;
  58         char *env;
  59 };
  60
  61 struct hotplug_process {
  62         struct ubus_object *ubus;
  63         char **envp;
  64         struct uloop_timeout timeout;
  65         struct uloop_process process;
  66         glob_t globbuf;
  67         unsigned int cnt;
  68         int ret;
  69 };
  70
  71 static void env_free(char **envp)
  72 {
  73         char **tmp;
  74
  75         tmp = envp;
  76         while (*tmp)
  77                 free(*(tmp++));
  78         free(envp);
  79 }
  80
  81 static void hotplug_free(struct hotplug_process *pc)
  82 {
  83         env_free(pc->envp);
  84         globfree(&pc->globbuf);
  85         free(pc);
  86 }
  87
  88 static void hotplug_done(struct uloop_process *c, int ret)
  89 {
  90         struct hotplug_process *pc = container_of(c, struct hotplug_process, process);
  91
  92         pc->ret = ret;
  93
  94         uloop_timeout_set(&pc->timeout, 50);
  95 }
  96
  97 static void hotplug_exec(struct uloop_timeout *t)
  98 {
  99         struct hotplug_process *pc = container_of(t, struct hotplug_process, timeout);
 100         char *script;
 101         char *exec_argv[4];
 102         /* we have reached the last entry in the globbuf */
 103         if (pc->cnt == pc->globbuf.gl_pathc) {
 104                 hotplug_free(pc);
 105                 return;
 106         }
 107
 108         if (asprintf(&script, ". /lib/functions.sh\n. %s\n", pc->globbuf.gl_pathv[pc->cnt++]) == -1) {
 109                 pc->ret = ENOMEM;
 110                 return;
 111         }
 112
 113         /* prepare for execve() */
 114         exec_argv[0] = "/bin/sh";
 115         exec_argv[1] = "-c";
 116         exec_argv[2] = script;
 117         exec_argv[3] = NULL;
 118
 119         /* set callback in uloop_process */
 120         pc->process.cb = hotplug_done;
 121         pc->process.pid = fork();
 122         if (pc->process.pid == 0) {
 123                 /* child */
 124                 exit(execve(exec_argv[0], exec_argv, pc->envp));
 125         } else if (pc->process.pid < 0) {
 126                 /* fork error */
 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
 192         blobmsg_parse(hotplug_policy, __HOTPLUG_MAX, tb, blobmsg_data(msg), blobmsg_len(msg));
 193
 194         if (!tb[HOTPLUG_ENV])
 195                 return UBUS_STATUS_INVALID_ARGUMENT;
 196
 197         tmpenv = environ;
 198
 199         /* first adding existing environment to avl_tree */
 200         while (*tmpenv) {
 201                 envle = calloc(1, sizeof(struct envlist));
 202                 assert(envle != NULL);
 203                 envle->env = strdup(*tmpenv);
 204                 envle->avl.key = envle->env;
 205                 avl_insert(&env, &envle->avl);
 206                 ++tmpenv;
 207         }
 208
 209         /* then adding additional variables from ubus call */
 210         blobmsg_for_each_attr(cur, tb[HOTPLUG_ENV], rem) {
 211                 char *enve = blobmsg_get_string(cur);
 212                 if (!enve)
 213                         continue;
 214
 215                 if (!strncmp(enve, "LD_", 3))
 216                         continue;
 217
 218                 if (!strcmp(enve, "PATH"))
 219                         continue;
 220
 221                 if (strlen(enve) < 3)
 222                         continue;
 223
 224                 if (!(tmp = strchr(enve, '=')))
 225                         continue;
 226
 227                 *tmp = '\0';
 228                 if (validate_envvarname(enve))
 229                         continue;
 230                 *tmp = '=';
 231
 232                 if (!strlen(++tmp))
 233                         continue;
 234
 235                 if (!strcmp(enve, "ASYNC=0"))
 236                         async = false;
 237
 238                 envle = calloc(1, sizeof(struct envlist));
 239                 assert(envle != NULL);
 240                 envle->env = strdup(enve);
 241                 envle->avl.key = envle->env;
 242                 if (avl_insert(&env, &envle->avl)) {
 243                         free((void*)envle->env);
 244                         free(envle);
 245                 }
 246                 ++tmpenv;
 247         }
 248
 249         /* allocating new environment */
 250         avl_for_each_element(&env, envle, avl)
 251                 ++envz;
 252
 253         envp = calloc(envz + 1, sizeof(char *));
 254         assert(envp != NULL);
 255
 256         /* populating new environment */
 257         envz = 0;
 258         avl_for_each_element_safe(&env, envle, avl, p) {
 259                 envp[envz++] = envle->env;
 260                 avl_delete(&env, &envle->avl);
 261                 free(envle);
 262         }
 263
 264         /* glob'ing for hotplug scripts */
 265         if (asprintf(&globstr, "%s/%s/*", HOTPLUG_BASEDIR, subsys) == -1) {
 266                 env_free(envp);
 267                 return UBUS_STATUS_UNKNOWN_ERROR;
 268         }
 269
 270         /* synchronous calls are unsupported for now */
 271         if (!async) {
 272                 env_free(envp);
 273                 return UBUS_STATUS_NOT_SUPPORTED;
 274         }
 275
 276         pc = calloc(1, sizeof(struct hotplug_process));
 277         assert(pc != NULL);
 278         pc->timeout.cb = hotplug_exec;
 279         pc->envp = envp;
 280         pc->cnt = 0;
 281         pc->ubus = obj;
 282
 283         if (glob(globstr, GLOB_DOOFFS, NULL, &pc->globbuf)) {
 284                 free(globstr);
 285                 hotplug_free(pc);
 286                 return UBUS_STATUS_OK;
 287         }
 288
 289         free(globstr);
 290
 291         /* asynchronous call to hotplug_exec() */
 292         uloop_timeout_set(&pc->timeout, 50);
 293
 294         return UBUS_STATUS_OK;
 295 }
 296
 297 static const struct ubus_method hotplug_methods[] = {
 298         UBUS_METHOD("call", hotplug_call, hotplug_policy),
 299 };
 300
 301 static struct ubus_object_type hotplug_object_type =
 302         UBUS_OBJECT_TYPE("hotplug", hotplug_methods);
 303
 304 static void add_subsystem(int nlen, char *newname)
 305 {
 306         struct hotplug_subsys *nh = calloc(1, sizeof(struct hotplug_subsys));
 307         char *name;
 308
 309         if (asprintf(&name, "%s%.*s", HOTPLUG_OBJECT_PREFIX, nlen, newname) == -1)
 310                 exit(ENOMEM);
 311
 312         /* prepare and add ubus object */
 313         nh->ubus.name = name;
 314         nh->ubus.type = &hotplug_object_type;
 315         nh->ubus.methods = hotplug_object_type.methods;
 316         nh->ubus.n_methods = hotplug_object_type.n_methods;
 317         list_add(&nh->list, &subsystems);
 318         ubus_add_object(ctx, &nh->ubus);
 319 }
 320
 321 static void remove_subsystem(int nlen, char *name)
 322 {
 323         struct hotplug_subsys *n, *h;
 324
 325         /* find match subsystem object by name or any if not given */
 326         list_for_each_entry_safe(h, n, &subsystems, list) {
 327                 if (nlen && (strlen(h->ubus.name) != strnlen(name, nlen) + strlen(HOTPLUG_OBJECT_PREFIX)))
 328                         continue;
 329                 if (nlen && (strncmp(name, &h->ubus.name[strlen(HOTPLUG_OBJECT_PREFIX)], nlen)))
 330                         continue;
 331
 332                 list_del(&h->list);
 333                 ubus_remove_object(ctx, &h->ubus);
 334                 free((void*)h->ubus.name);
 335                 free(h);
 336         }
 337 }
 338
 339 static int init_subsystems(void)
 340 {
 341         DIR *dir;
 342         struct dirent *dirent;
 343
 344         dir = opendir(HOTPLUG_BASEDIR);
 345         if (dir == NULL)
 346                 return ENOENT;
 347
 348         while ((dirent = readdir(dir))) {
 349                 /* skip everything but directories */
 350                 if (dirent->d_type != DT_DIR)
 351                         continue;
 352
 353                 /* skip '.' and '..' as well as hidden files */
 354                 if (dirent->d_name[0] == '.')
 355                         continue;
 356
 357                 add_subsystem(strlen(dirent->d_name), dirent->d_name);
 358         }
 359         closedir(dir);
 360
 361         return 0;
 362 }
 363
 364 static void inotify_read_handler(struct uloop_fd *u, unsigned int events)
 365 {
 366         int rc;
 367         char *p;
 368         struct inotify_event *in;
 369
 370         /* read inotify events */
 371         while ((rc = read(u->fd, inotify_buffer, INOTIFY_SZ)) == -1 && errno == EINTR);
 372
 373         if (rc <= 0)
 374                 return;
 375
 376         /* process events from buffer */
 377         for (p = inotify_buffer;
 378              rc - (p - inotify_buffer) >= (int)sizeof(struct inotify_event);
 379              p += sizeof(struct inotify_event) + in->len) {
 380                 in = (struct inotify_event*)p;
 381
 382                 /* skip everything but directories */
 383                 if (!(in->mask & IN_ISDIR))
 384                         continue;
 385
 386                 if (in->len < 1)
 387                         continue;
 388
 389                 /* skip hidden files */
 390                 if (in->name[0] == '.')
 391                         continue;
 392
 393                 /* add/remove subsystem objects */
 394                 if (in->mask & (IN_CREATE | IN_MOVED_TO))
 395                         add_subsystem(in->len, in->name);
 396                 else if (in->mask & (IN_DELETE | IN_MOVED_FROM))
 397                         remove_subsystem(in->len, in->name);
 398         }
 399 }
 400
 401 void ubus_init_hotplug(struct ubus_context *newctx)
 402 {
 403         ctx = newctx;
 404         remove_subsystem(0, NULL);
 405         if (init_subsystems()) {
 406                 printf("failed to initialize hotplug subsystems from %s\n", HOTPLUG_BASEDIR);
 407                 return;
 408         }
 409         fd_inotify_read.fd = inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
 410         fd_inotify_read.cb = inotify_read_handler;
 411         assert(fd_inotify_read.fd != -1);
 412
 413         inotify_buffer = calloc(1, INOTIFY_SZ);
 414         assert(inotify_buffer != NULL);
 415         inotify_add_watch(fd_inotify_read.fd, HOTPLUG_BASEDIR, IN_CREATE | IN_MOVED_TO | IN_DELETE | IN_MOVED_FROM | IN_ONLYDIR);
 416         uloop_fd_add(&fd_inotify_read, ULOOP_READ);
 417 }