Add a null provider which implements no algorithms.

By loading the null provider into the default context, it is possible
to verify that it is not accidentally being used.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11488)

1 files changed, 106 insertions, 0 deletions

diff --git a/providers/nullprov.c b/providers/nullprov.c
new file mode 100644
index 0000000000..a1a2681173
--- /dev/null
+++ b/providers/nullprov.c
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <string.h>
+#include <stdio.h>
+#include <openssl/core.h>
+#include <openssl/core_numbers.h>
+#include <openssl/core_names.h>
+#include <openssl/params.h>
+#include "prov/implementations.h"
+
+OSSL_provider_init_fn ossl_null_provider_init;
+
+/* Functions provided by the core */
+static OSSL_core_gettable_params_fn *c_gettable_params = NULL;
+static OSSL_core_get_params_fn *c_get_params = NULL;
+
+/* Parameters we provide to the core */
+static const OSSL_ITEM null_param_types[] = {
+    { OSSL_PARAM_UTF8_PTR, OSSL_PROV_PARAM_NAME },
+    { OSSL_PARAM_UTF8_PTR, OSSL_PROV_PARAM_VERSION },
+    { OSSL_PARAM_UTF8_PTR, OSSL_PROV_PARAM_BUILDINFO },
+    { 0, NULL }
+};
+
+static const OSSL_ITEM *null_gettable_params(const OSSL_PROVIDER *prov)
+{
+    return null_param_types;
+}
+
+static int null_get_params(const OSSL_PROVIDER *prov, OSSL_PARAM params[])
+{
+    OSSL_PARAM *p;
+
+    p = OSSL_PARAM_locate(params, OSSL_PROV_PARAM_NAME);
+    if (p != NULL && !OSSL_PARAM_set_utf8_ptr(p, "OpenSSL Null Provider"))
+        return 0;
+    p = OSSL_PARAM_locate(params, OSSL_PROV_PARAM_VERSION);
+    if (p != NULL && !OSSL_PARAM_set_utf8_ptr(p, OPENSSL_VERSION_STR))
+        return 0;
+    p = OSSL_PARAM_locate(params, OSSL_PROV_PARAM_BUILDINFO);
+    if (p != NULL && !OSSL_PARAM_set_utf8_ptr(p, OPENSSL_FULL_VERSION_STR))
+        return 0;
+
+    return 1;
+}
+
+static const OSSL_ALGORITHM *null_query(OSSL_PROVIDER *prov,
+                                          int operation_id,
+                                          int *no_cache)
+{
+    *no_cache = 0;
+    return NULL;
+}
+
+/* Functions we provide to the core */
+static const OSSL_DISPATCH null_dispatch_table[] = {
+    { OSSL_FUNC_PROVIDER_GETTABLE_PARAMS, (void (*)(void))null_gettable_params },
+    { OSSL_FUNC_PROVIDER_GET_PARAMS, (void (*)(void))null_get_params },
+    { OSSL_FUNC_PROVIDER_QUERY_OPERATION, (void (*)(void))null_query },
+    { 0, NULL }
+};
+
+int ossl_null_provider_init(const OSSL_PROVIDER *provider,
+                            const OSSL_DISPATCH *in,
+                            const OSSL_DISPATCH **out,
+                            void **provctx)
+{
+    OSSL_core_get_library_context_fn *c_get_libctx = NULL;
+
+    for (; in->function_id != 0; in++) {
+        switch (in->function_id) {
+        case OSSL_FUNC_CORE_GETTABLE_PARAMS:
+            c_gettable_params = OSSL_get_core_gettable_params(in);
+            break;
+        case OSSL_FUNC_CORE_GET_PARAMS:
+            c_get_params = OSSL_get_core_get_params(in);
+            break;
+        case OSSL_FUNC_CORE_GET_LIBRARY_CONTEXT:
+            c_get_libctx = OSSL_get_core_get_library_context(in);
+            break;
+        /* Just ignore anything we don't understand */
+        default:
+            break;
+        }
+    }
+
+    if (c_get_libctx == NULL)
+        return 0;
+
+    *out = null_dispatch_table;
+
+    /*
+     * We want to make sure that all calls from this provider that requires
+     * a library context use the same context as the one used to call our
+     * functions.  We do that by passing it along as the provider context.
+     */
+    *provctx = c_get_libctx(provider);
+    return 1;
+}