Fix #272: run c_obj_create under a lock.

See #272.

This commit adds a lock to run `c_obj_create` and `OBJ_create` thread-safely in
`OQS_PROVIDER_ENTRYPOINT_NAME`,

oqsprov/oqsprov.c

@@ -900,6 +900,23 @@ static const OSSL_DISPATCH oqsprovider_dispatch_table[]
 #    define OQS_PROVIDER_ENTRYPOINT_NAME OSSL_provider_init
 #endif // ifdef OQS_PROVIDER_STATIC
 
+static CRYPTO_ONCE once_obj_create = CRYPTO_ONCE_STATIC_INIT;
+static CRYPTO_RWLOCK *lock_obj_create;
+
+/* Initializes a lock for `OBJ_create`. */
+static void init_obj_create_lock(void)
+{
+    lock_obj_create = CRYPTO_THREAD_lock_new();
+}
+
+#ifndef _WIN32
+__attribute__((destructor)) static void exit_obj_create_lock(void)
+{
+    CRYPTO_THREAD_lock_free(lock_obj_create);
+    lock_obj_create = NULL;
+}
+#endif
+
 int OQS_PROVIDER_ENTRYPOINT_NAME(const OSSL_CORE_HANDLE *handle,
                                  const OSSL_DISPATCH *in,
                                  const OSSL_DISPATCH **out, void **provctx)
@@ -963,14 +980,21 @@ int OQS_PROVIDER_ENTRYPOINT_NAME(const OSSL_CORE_HANDLE *handle,
         ossl_versionp = *(void **)version_request[0].data;
     }
 
+    // initialize lock for `OBJ_create`.
+    if (!CRYPTO_THREAD_run_once(&once_obj_create, init_obj_create_lock)
+        || lock_obj_create == NULL) {
+        goto end_init;
+    }
+    CRYPTO_THREAD_write_lock(lock_obj_create);
+
     // insert all OIDs to the global objects list
     for (i = 0; i < OQS_OID_CNT; i += 2) {
         if (!c_obj_create(handle, oqs_oid_alg_list[i], oqs_oid_alg_list[i + 1],
                           oqs_oid_alg_list[i + 1])) {
             ERR_raise(ERR_LIB_USER, OQSPROV_R_OBJ_CREATE_ERR);
             fprintf(stderr, "error registering NID for %s\n",
                     oqs_oid_alg_list[i + 1]);
-            goto end_init;
+            goto unlock_obj_create_lock;
         }
 
         /* create object (NID) again to avoid setup corner case problems
@@ -986,15 +1010,15 @@ int OQS_PROVIDER_ENTRYPOINT_NAME(const OSSL_CORE_HANDLE *handle,
         if (!oqs_set_nid((char *)oqs_oid_alg_list[i + 1],
                          OBJ_sn2nid(oqs_oid_alg_list[i + 1]))) {
             ERR_raise(ERR_LIB_USER, OQSPROV_R_OBJ_CREATE_ERR);
-            goto end_init;
+            goto unlock_obj_create_lock;
         }
 
         if (!c_obj_add_sigid(handle, oqs_oid_alg_list[i + 1], "",
                              oqs_oid_alg_list[i + 1])) {
             fprintf(stderr, "error registering %s with no hash\n",
                     oqs_oid_alg_list[i + 1]);
             ERR_raise(ERR_LIB_USER, OQSPROV_R_OBJ_CREATE_ERR);
-            goto end_init;
+            goto unlock_obj_create_lock;
         }
 
         if (OBJ_sn2nid(oqs_oid_alg_list[i + 1]) != 0) {
@@ -1006,7 +1030,7 @@ int OQS_PROVIDER_ENTRYPOINT_NAME(const OSSL_CORE_HANDLE *handle,
                     "OQS PROV: Impossible error: NID unregistered for %s.\n",
                     oqs_oid_alg_list[i + 1]);
             ERR_raise(ERR_LIB_USER, OQSPROV_R_OBJ_CREATE_ERR);
-            goto end_init;
+            goto unlock_obj_create_lock;
         }
     }
 
@@ -1017,7 +1041,7 @@ int OQS_PROVIDER_ENTRYPOINT_NAME(const OSSL_CORE_HANDLE *handle,
             == NULL)) {
         OQS_PROV_PRINTF("OQS PROV: error creating new provider context\n");
         ERR_raise(ERR_LIB_USER, OQSPROV_R_LIB_CREATE_ERR);
-        goto end_init;
+        goto unlock_obj_create_lock;
     }
 
     *out = oqsprovider_dispatch_table;
@@ -1032,6 +1056,9 @@ int OQS_PROVIDER_ENTRYPOINT_NAME(const OSSL_CORE_HANDLE *handle,
     }
     rc = 1;
 
+unlock_obj_create_lock:
+    CRYPTO_THREAD_unlock(lock_obj_create);
+
 end_init:
     if (!rc) {
         if (ossl_versionp)

test/CMakeLists.txt

@@ -110,11 +110,32 @@ set_tests_properties(oqs_endecode
 )
 endif()
 
+add_executable(oqs_test_multi_thread oqs_test_multi_thread.c)
+target_link_libraries(oqs_test_multi_thread PRIVATE ${OPENSSL_CRYPTO_LIBRARY})
+add_test(
+  NAME oqs_multi_thread
+  COMMAND oqs_test_multi_thread
+          "oqsprovider"
+          "${CMAKE_CURRENT_SOURCE_DIR}/openssl-ca.cnf"
+)
+# openssl under MSVC seems to have a bug registering NIDs:
+# It only works when setting OPENSSL_CONF, not when loading the same cnf file:
+if (MSVC)
+set_tests_properties(oqs_multi_thread
+    PROPERTIES ENVIRONMENT "OPENSSL_MODULES=${OQS_PROV_BINARY_DIR};OPENSSL_CONF=${CMAKE_CURRENT_SOURCE_DIR}/openssl-ca.cnf"
+)
+else()
+set_tests_properties(oqs_multi_thread
+    PROPERTIES ENVIRONMENT "OPENSSL_MODULES=${OQS_PROV_BINARY_DIR}"
+)
+endif()
+
 if (OQS_PROVIDER_BUILD_STATIC)
   targets_set_static_provider(oqs_test_signatures
     oqs_test_kems
     oqs_test_groups
     oqs_test_tlssig
     oqs_test_endecode
+    oqs_multi_thread
   )
 endif()

test/oqs_test_multi_thread.c

@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: Apache-2.0 AND MIT
+
+#ifdef _WIN32
+
+#    include <Windows.h>
+
+#else
+
+#    include <pthread.h>
+
+#endif // ifdef _WIN32
+
+#include <openssl/crypto.h>
+#include <openssl/provider.h>
+
+#include "test_common.h"
+
+static const size_t N_THREADS = 6;
+
+static const char *kModuleName = NULL;
+static const char *kConfigFile = NULL;
+
+/** \brief Loads the oqs-provider in an `OSSL_LIB_CTX` object. */
+static int load_oqs_provider_thread(OSSL_LIB_CTX *libctx)
+{
+    OSSL_PROVIDER *default_provider = NULL;
+    OSSL_PROVIDER *oqs_provider = NULL;
+    int ret = -1;
+
+#ifdef OQS_PROVIDER_STATIC
+    if ((default_provider = OSSL_PROVIDER_load(libctx, "default")) == NULL) {
+        goto end;
+    }
+    if (OSSL_PROVIDER_add_builtin(libctx, "oqsprovider",
+                                  OQS_PROVIDER_ENTRYPOINT_NAME)
+        != 1) {
+        goto unload_default_provider;
+    }
+    if ((oqs_provider = OSSL_PROVIDER_load(libctx, "oqsprovider")) == NULL) {
+        goto unload_default_provider;
+    }
+    ret = 0;
+    OSS_PROVIDER_unload(oqs_provider);
+
+#else
+
+    if (OSSL_LIB_CTX_load_config(libctx, kConfigFile) == 1
+        && OSSL_PROVIDER_available(libctx, kModuleName)) {
+        ret = 0;
+    }
+    goto end;
+
+#endif // ifdef OQS_PROVIDER_STATIC
+
+unload_default_provider:
+    OSSL_PROVIDER_unload(default_provider);
+
+end:
+    return ret;
+}
+
+/** \brief Creates an OSSL_LIB_CTX object and loads oqs-provider. */
+static void *thread_create_ossl_libctx(void *arg)
+{
+    OSSL_LIB_CTX *libctx = NULL;
+    int ret = -1;
+
+    (void)arg;
+
+    if ((libctx = OSSL_LIB_CTX_new()) == NULL) {
+        goto end;
+    }
+    ret = load_oqs_provider_thread(libctx);
+    OSSL_LIB_CTX_free(libctx);
+
+end:
+    return (void *)(size_t)ret;
+}
+
+int main(int argc, char **argv)
+{
+#ifdef _WIN32
+    HANDLE threads[N_THREADS];
+#else
+    pthread_t threads[N_THREADS];
+#endif // ifdef _WIN32
+    size_t i;
+    void *result;
+    int ret = 0;
+
+    T(argc == 3);
+
+    kModuleName = argv[1];
+    kConfigFile = argv[2];
+
+    for (i = 0; i < N_THREADS; ++i) {
+#ifdef _WIN32
+        threads[i]
+            = CreateThread(NULL, 0, thread_create_ossl_libctx, NULL, 0, NULL);
+#else
+        pthread_create(threads + i, NULL, thread_create_ossl_libctx, NULL);
+#endif // ifdef _WIN32
+    }
+
+#ifdef _WIN32
+    WaitForMultipleObjects(N_THREADS, threads, TRUE, INFINITE);
+#endif // ifdef _WIN32
+
+    for (i = 0; i < N_THREADS; ++i) {
+        result = NULL;
+#ifdef _WIN32
+        ret |= CloseHandle(threads[i]);
+#else
+        pthread_join(threads[i], &result);
+        ret |= (int)(size_t)result;
+#endif // ifdef _WIN32
+    }
+
+    return ret;
+}