| 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 <pthread.h> |
| 13 | #include <urcu/system.h> |
| 14 | #include "common/logging.h" |
| 15 | #include "common/macros.h" |
| 16 | #include "common/getenv.h" |
| 17 | |
| 18 | enum lttng_env_secure { |
| 19 | LTTNG_ENV_SECURE, |
| 20 | LTTNG_ENV_NOT_SECURE, |
| 21 | }; |
| 22 | |
| 23 | struct lttng_env { |
| 24 | const char *key; |
| 25 | enum lttng_env_secure secure; |
| 26 | char *value; |
| 27 | }; |
| 28 | |
| 29 | /* lttng_ust_getenv_init_mutex provides mutual exclusion for initialization. */ |
| 30 | static pthread_mutex_t lttng_ust_getenv_init_mutex = PTHREAD_MUTEX_INITIALIZER; |
| 31 | static int lttng_ust_getenv_is_init = 0; |
| 32 | |
| 33 | static struct lttng_env lttng_env[] = { |
| 34 | /* |
| 35 | * LTTNG_UST_DEBUG and LTTNG_UST_ABORT_ON_CRITICAL are used directly by |
| 36 | * the internal logging, because they need to be already set for ERR() |
| 37 | * used in lttng_ust_getenv_init(). |
| 38 | */ |
| 39 | { "LTTNG_UST_DEBUG", LTTNG_ENV_NOT_SECURE, NULL, }, |
| 40 | { "LTTNG_UST_ABORT_ON_CRITICAL", LTTNG_ENV_NOT_SECURE, NULL, }, |
| 41 | |
| 42 | /* Env. var. which can be used in setuid/setgid executables. */ |
| 43 | { "LTTNG_UST_WITHOUT_BADDR_STATEDUMP", LTTNG_ENV_NOT_SECURE, NULL, }, |
| 44 | { "LTTNG_UST_REGISTER_TIMEOUT", LTTNG_ENV_NOT_SECURE, NULL, }, |
| 45 | { "LTTNG_UST_MAP_POPULATE_POLICY", LTTNG_ENV_NOT_SECURE, NULL, }, |
| 46 | |
| 47 | /* Env. var. which are not fetched in setuid/setgid executables. */ |
| 48 | { "LTTNG_UST_CLOCK_PLUGIN", LTTNG_ENV_SECURE, NULL, }, |
| 49 | { "LTTNG_UST_GETCPU_PLUGIN", LTTNG_ENV_SECURE, NULL, }, |
| 50 | { "LTTNG_UST_ALLOW_BLOCKING", LTTNG_ENV_SECURE, NULL, }, |
| 51 | { "HOME", LTTNG_ENV_SECURE, NULL, }, |
| 52 | { "LTTNG_HOME", LTTNG_ENV_SECURE, NULL, }, |
| 53 | { "LTTNG_UST_APP_PATH", LTTNG_ENV_SECURE, NULL, }, |
| 54 | }; |
| 55 | |
| 56 | static |
| 57 | int lttng_is_setuid_setgid(void) |
| 58 | { |
| 59 | return geteuid() != getuid() || getegid() != getgid(); |
| 60 | } |
| 61 | |
| 62 | /* |
| 63 | * Wrapper over getenv that will only return the values of whitelisted |
| 64 | * environment variables when the current process is setuid and/or setgid. |
| 65 | */ |
| 66 | char *lttng_ust_getenv(const char *name) |
| 67 | { |
| 68 | size_t i; |
| 69 | struct lttng_env *e; |
| 70 | bool found = false; |
| 71 | |
| 72 | /* |
| 73 | * Perform lazy initialization of lttng_ust_getenv for early use |
| 74 | * by library constructors. |
| 75 | */ |
| 76 | lttng_ust_getenv_init(); |
| 77 | |
| 78 | for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) { |
| 79 | e = <tng_env[i]; |
| 80 | |
| 81 | if (strcmp(e->key, name) == 0) { |
| 82 | found = true; |
| 83 | break; |
| 84 | } |
| 85 | } |
| 86 | if (!found) { |
| 87 | return NULL; |
| 88 | } |
| 89 | return e->value; |
| 90 | } |
| 91 | |
| 92 | void lttng_ust_getenv_init(void) |
| 93 | { |
| 94 | size_t i; |
| 95 | |
| 96 | /* |
| 97 | * Return early if the init has already completed. |
| 98 | */ |
| 99 | if (CMM_LOAD_SHARED(lttng_ust_getenv_is_init)) { |
| 100 | /* |
| 101 | * Load lttng_ust_getenv_is_init before reading environment cache. |
| 102 | */ |
| 103 | cmm_smp_rmb(); |
| 104 | return; |
| 105 | } |
| 106 | |
| 107 | pthread_mutex_lock(<tng_ust_getenv_init_mutex); |
| 108 | |
| 109 | /* |
| 110 | * Check again if the init has completed in another thread now that we |
| 111 | * have acquired the mutex. |
| 112 | */ |
| 113 | if (lttng_ust_getenv_is_init) |
| 114 | goto end_init; |
| 115 | |
| 116 | for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) { |
| 117 | struct lttng_env *e = <tng_env[i]; |
| 118 | |
| 119 | if (e->secure == LTTNG_ENV_SECURE && lttng_is_setuid_setgid()) { |
| 120 | ERR("Getting environment variable '%s' from setuid/setgid binary refused for security reasons.", |
| 121 | e->key); |
| 122 | continue; |
| 123 | } |
| 124 | e->value = getenv(e->key); |
| 125 | } |
| 126 | |
| 127 | /* |
| 128 | * Store environment cache before setting lttng_ust_getenv_is_init to 1. |
| 129 | */ |
| 130 | cmm_smp_wmb(); |
| 131 | CMM_STORE_SHARED(lttng_ust_getenv_is_init, 1); |
| 132 | end_init: |
| 133 | pthread_mutex_unlock(<tng_ust_getenv_init_mutex); |
| 134 | } |