liblttng-ust/getenv.c

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  */
   6
   7 #include <stdlib.h>
   8 #include <unistd.h>
   9 #include <stdbool.h>
  10 #include <stddef.h>
  11 #include <sys/types.h>
  12 #include <usterr-signal-safe.h>
  13 #include <helper.h>
  14 #include "getenv.h"
  15
  16 enum lttng_env_secure {
  17         LTTNG_ENV_SECURE,
  18         LTTNG_ENV_NOT_SECURE,
  19 };
  20
  21 struct lttng_env {
  22         const char *key;
  23         enum lttng_env_secure secure;
  24         char *value;
  25 };
  26
  27 static struct lttng_env lttng_env[] = {
  28         /*
  29          * LTTNG_UST_DEBUG is used directly by snprintf, because it
  30          * needs to be already set for ERR() used in
  31          * lttng_ust_getenv_init().
  32          */
  33         { "LTTNG_UST_DEBUG", LTTNG_ENV_NOT_SECURE, NULL, },
  34
  35         /* Env. var. which can be used in setuid/setgid executables. */
  36         { "LTTNG_UST_WITHOUT_BADDR_STATEDUMP", LTTNG_ENV_NOT_SECURE, NULL, },
  37         { "LTTNG_UST_REGISTER_TIMEOUT", LTTNG_ENV_NOT_SECURE, NULL, },
  38
  39         /* Env. var. which are not fetched in setuid/setgid executables. */
  40         { "LTTNG_UST_CLOCK_PLUGIN", LTTNG_ENV_SECURE, NULL, },
  41         { "LTTNG_UST_GETCPU_PLUGIN", LTTNG_ENV_SECURE, NULL, },
  42         { "LTTNG_UST_ALLOW_BLOCKING", LTTNG_ENV_SECURE, NULL, },
  43         { "HOME", LTTNG_ENV_SECURE, NULL, },
  44         { "LTTNG_HOME", LTTNG_ENV_SECURE, NULL, },
  45 };
  46
  47 static
  48 int lttng_is_setuid_setgid(void)
  49 {
  50         return geteuid() != getuid() || getegid() != getgid();
  51 }
  52
  53 char *lttng_getenv(const char *name)
  54 {
  55         size_t i;
  56         struct lttng_env *e;
  57         bool found = false;
  58
  59         for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
  60                 e = &lttng_env[i];
  61
  62                 if (strcmp(e->key, name) == 0) {
  63                         found = true;
  64                         break;
  65                 }
  66         }
  67         if (!found) {
  68                 return NULL;
  69         }
  70         return e->value;
  71 }
  72
  73 void lttng_ust_getenv_init(void)
  74 {
  75         size_t i;
  76
  77         for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
  78                 struct lttng_env *e = &lttng_env[i];
  79
  80                 if (e->secure == LTTNG_ENV_SECURE && lttng_is_setuid_setgid()) {
  81                         ERR("Getting environment variable '%s' from setuid/setgid binary refused for security reasons.",
  82                                 e->key);
  83                         continue;
  84                 }
  85                 e->value = getenv(e->key);
  86         }
  87 }