liblttng-ust/getenv.c

   1 /*
   2  * Copyright (C) 2017 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; only
   7  * version 2.1 of the License.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #include <stdlib.h>
  20 #include <unistd.h>
  21 #include <stdbool.h>
  22 #include <stddef.h>
  23 #include <sys/types.h>
  24 #include <usterr-signal-safe.h>
  25 #include <helper.h>
  26 #include "getenv.h"
  27
  28 enum lttng_env_secure {
  29         LTTNG_ENV_SECURE,
  30         LTTNG_ENV_NOT_SECURE,
  31 };
  32
  33 struct lttng_env {
  34         const char *key;
  35         enum lttng_env_secure secure;
  36         char *value;
  37 };
  38
  39 static struct lttng_env lttng_env[] = {
  40         /*
  41          * LTTNG_UST_DEBUG is used directly by snprintf, because it
  42          * needs to be already set for ERR() used in
  43          * lttng_ust_getenv_init().
  44          */
  45         { "LTTNG_UST_DEBUG", LTTNG_ENV_NOT_SECURE, NULL, },
  46
  47         /* Env. var. which can be used in setuid/setgid executables. */
  48         { "LTTNG_UST_WITHOUT_BADDR_STATEDUMP", LTTNG_ENV_NOT_SECURE, NULL, },
  49         { "LTTNG_UST_REGISTER_TIMEOUT", LTTNG_ENV_NOT_SECURE, NULL, },
  50
  51         /* Env. var. which are not fetched in setuid/setgid executables. */
  52         { "LTTNG_UST_CLOCK_PLUGIN", LTTNG_ENV_SECURE, NULL, },
  53         { "LTTNG_UST_GETCPU_PLUGIN", LTTNG_ENV_SECURE, NULL, },
  54         { "LTTNG_UST_ALLOW_BLOCKING", LTTNG_ENV_SECURE, NULL, },
  55         { "HOME", LTTNG_ENV_SECURE, NULL, },
  56         { "LTTNG_HOME", LTTNG_ENV_SECURE, NULL, },
  57 };
  58
  59 static
  60 int lttng_is_setuid_setgid(void)
  61 {
  62         return geteuid() != getuid() || getegid() != getgid();
  63 }
  64
  65 char *lttng_getenv(const char *name)
  66 {
  67         size_t i;
  68         struct lttng_env *e;
  69         bool found = false;
  70
  71         for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
  72                 e = &lttng_env[i];
  73
  74                 if (strcmp(e->key, name) == 0) {
  75                         found = true;
  76                         break;
  77                 }
  78         }
  79         if (!found) {
  80                 return NULL;
  81         }
  82         return e->value;
  83 }
  84
  85 void lttng_ust_getenv_init(void)
  86 {
  87         size_t i;
  88
  89         for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
  90                 struct lttng_env *e = &lttng_env[i];
  91
  92                 if (e->secure == LTTNG_ENV_SECURE && lttng_is_setuid_setgid()) {
  93                         ERR("Getting environment variable '%s' from setuid/setgid binary refused for security reasons.",
  94                                 e->key);
  95                         continue;
  96                 }
  97                 e->value = getenv(e->key);
  98         }
  99 }