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 <sys/types.h>
  23 #include <usterr-signal-safe.h>
  24 #include <helper.h>
  25 #include "getenv.h"
  26
  27 enum lttng_env_secure {
  28         LTTNG_ENV_SECURE,
  29         LTTNG_ENV_NOT_SECURE,
  30 };
  31
  32 struct lttng_env {
  33         const char *key;
  34         enum lttng_env_secure secure;
  35         char *value;
  36 };
  37
  38 static struct lttng_env lttng_env[] = {
  39         /*
  40          * LTTNG_UST_DEBUG is used directly by snprintf, because it
  41          * needs to be already set for ERR() used in
  42          * lttng_ust_getenv_init().
  43          */
  44         { "LTTNG_UST_DEBUG", LTTNG_ENV_NOT_SECURE, NULL, },
  45
  46         /* Env. var. which can be used in setuid/setgid executables. */
  47         { "LTTNG_UST_WITHOUT_BADDR_STATEDUMP", LTTNG_ENV_NOT_SECURE, NULL, },
  48         { "LTTNG_UST_REGISTER_TIMEOUT", LTTNG_ENV_NOT_SECURE, NULL, },
  49
  50         /* Env. var. which are not fetched in setuid/setgid executables. */
  51         { "LTTNG_UST_CLOCK_PLUGIN", LTTNG_ENV_SECURE, NULL, },
  52         { "LTTNG_UST_GETCPU_PLUGIN", LTTNG_ENV_SECURE, NULL, },
  53         { "LTTNG_UST_ALLOW_BLOCKING", LTTNG_ENV_SECURE, NULL, },
  54         { "HOME", LTTNG_ENV_SECURE, NULL, },
  55         { "LTTNG_HOME", LTTNG_ENV_SECURE, NULL, },
  56 };
  57
  58 static
  59 int lttng_is_setuid_setgid(void)
  60 {
  61         return geteuid() != getuid() || getegid() != getgid();
  62 }
  63
  64 char *lttng_getenv(const char *name)
  65 {
  66         size_t i;
  67         struct lttng_env *e;
  68         bool found = false;
  69
  70         for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
  71                 e = &lttng_env[i];
  72
  73                 if (strcmp(e->key, name) == 0) {
  74                         found = true;
  75                         break;
  76                 }
  77         }
  78         if (!found) {
  79                 return NULL;
  80         }
  81         return e->value;
  82 }
  83
  84 void lttng_ust_getenv_init(void)
  85 {
  86         size_t i;
  87
  88         for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
  89                 struct lttng_env *e = &lttng_env[i];
  90
  91                 if (e->secure == LTTNG_ENV_SECURE && lttng_is_setuid_setgid()) {
  92                         ERR("Getting environment variable '%s' from setuid/setgid binary refused for security reasons.",
  93                                 e->key);
  94                         continue;
  95                 }
  96                 e->value = getenv(e->key);
  97         }
  98 }