+/*
+ * SPDX-License-Identifier: LGPL-2.1-only
+ *
+ * Copyright (C) 2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ */
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <sys/types.h>
+#include <urcu/system.h>
+#include "common/logging.h"
+#include "common/macros.h"
+#include "common/getenv.h"
+
+enum lttng_env_secure {
+ LTTNG_ENV_SECURE,
+ LTTNG_ENV_NOT_SECURE,
+};
+
+struct lttng_env {
+ const char *key;
+ enum lttng_env_secure secure;
+ char *value;
+};
+
+static
+int lttng_ust_getenv_is_init = 0;
+
+static struct lttng_env lttng_env[] = {
+ /*
+ * LTTNG_UST_DEBUG is used directly by snprintf, because it
+ * needs to be already set for ERR() used in
+ * lttng_ust_getenv_init().
+ */
+ { "LTTNG_UST_DEBUG", LTTNG_ENV_NOT_SECURE, NULL, },
+
+ /* Env. var. which can be used in setuid/setgid executables. */
+ { "LTTNG_UST_WITHOUT_BADDR_STATEDUMP", LTTNG_ENV_NOT_SECURE, NULL, },
+ { "LTTNG_UST_REGISTER_TIMEOUT", LTTNG_ENV_NOT_SECURE, NULL, },
+
+ /* Env. var. which are not fetched in setuid/setgid executables. */
+ { "LTTNG_UST_CLOCK_PLUGIN", LTTNG_ENV_SECURE, NULL, },
+ { "LTTNG_UST_GETCPU_PLUGIN", LTTNG_ENV_SECURE, NULL, },
+ { "LTTNG_UST_ALLOW_BLOCKING", LTTNG_ENV_SECURE, NULL, },
+ { "HOME", LTTNG_ENV_SECURE, NULL, },
+ { "LTTNG_HOME", LTTNG_ENV_SECURE, NULL, },
+};
+
+static
+int lttng_is_setuid_setgid(void)
+{
+ return geteuid() != getuid() || getegid() != getgid();
+}
+
+/*
+ * Wrapper over getenv that will only return the values of whitelisted
+ * environment variables when the current process is setuid and/or setgid.
+ */
+char *lttng_ust_getenv(const char *name)
+{
+ size_t i;
+ struct lttng_env *e;
+ bool found = false;
+
+ if (!CMM_LOAD_SHARED(lttng_ust_getenv_is_init))
+ abort();
+
+ for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
+ e = <tng_env[i];
+
+ if (strcmp(e->key, name) == 0) {
+ found = true;
+ break;
+ }
+ }
+ if (!found) {
+ return NULL;
+ }
+ return e->value;
+}
+
+void lttng_ust_getenv_init(void)
+{
+ size_t i;
+
+ if (CMM_LOAD_SHARED(lttng_ust_getenv_is_init))
+ return;
+
+ for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
+ struct lttng_env *e = <tng_env[i];
+
+ if (e->secure == LTTNG_ENV_SECURE && lttng_is_setuid_setgid()) {
+ ERR("Getting environment variable '%s' from setuid/setgid binary refused for security reasons.",
+ e->key);
+ continue;
+ }
+ e->value = getenv(e->key);
+ }
+ CMM_STORE_SHARED(lttng_ust_getenv_is_init, 1);
+}