delegate credential provider (#117)

include/aws/auth/auth.h

@@ -25,6 +25,7 @@ enum aws_auth_errors {
     AWS_AUTH_SIGNING_ILLEGAL_REQUEST_HEADER,
     AWS_AUTH_SIGNING_INVALID_CONFIGURATION,
     AWS_AUTH_CREDENTIALS_PROVIDER_INVALID_ENVIRONMENT,
+    AWS_AUTH_CREDENTIALS_PROVIDER_INVALID_DELEGATE,
     AWS_AUTH_CREDENTIALS_PROVIDER_PROFILE_SOURCE_FAILURE,
     AWS_AUTH_CREDENTIALS_PROVIDER_IMDS_SOURCE_FAILURE,
     AWS_AUTH_CREDENTIALS_PROVIDER_STS_SOURCE_FAILURE,

include/aws/auth/credentials.h

@@ -406,6 +406,23 @@ struct aws_credentials_provider_chain_default_options {
     struct aws_client_bootstrap *bootstrap;
 };
 
+/**
+ * Configuration options for the delegate credentials provider.
+ */
+struct aws_credentials_provider_delegate_options {
+    struct aws_credentials_provider_shutdown_options shutdown_options;
+
+    /**
+     * Provide the vtable of functions to get credentials.
+     */
+    struct aws_credentials_provider_vtable *provider_vtable;
+
+    /**
+     * Optional implementation.
+     */
+    void *impl;
+};
+
 AWS_EXTERN_C_BEGIN
 
 /*
@@ -705,6 +722,19 @@ struct aws_credentials_provider *aws_credentials_provider_new_process(
     struct aws_allocator *allocator,
     const struct aws_credentials_provider_process_options *options);
 
+/**
+ * Create a credentials provider depends on provided vtable to fetch the credentials.
+ *
+ * @param allocator memory allocator to use for all memory allocation
+ * @param options provider-specific configuration options
+ *
+ * @return the newly-constructed credentials provider, or NULL if an error occurred.
+ */
+AWS_AUTH_API
+struct aws_credentials_provider *aws_credentials_provider_new_delegate(
+    struct aws_allocator *allocator,
+    struct aws_credentials_provider_delegate_options *options);
+
 /**
  * Creates the default provider chain used by most AWS SDKs.
  *

source/auth.c

@@ -44,6 +44,9 @@ static struct aws_error_info s_errors[] = {
     AWS_DEFINE_ERROR_INFO_AUTH(
         AWS_AUTH_CREDENTIALS_PROVIDER_INVALID_ENVIRONMENT,
         "Valid credentials could not be sourced from process environment"),
+    AWS_DEFINE_ERROR_INFO_AUTH(
+        AWS_AUTH_CREDENTIALS_PROVIDER_INVALID_DELEGATE,
+        "Valid credentials could not be sourced from the provided vtable"),
     AWS_DEFINE_ERROR_INFO_AUTH(
         AWS_AUTH_CREDENTIALS_PROVIDER_PROFILE_SOURCE_FAILURE,
         "Valid credentials could not be sourced by a profile provider"),

source/crdential_provider_delegate.c

@@ -0,0 +1,25 @@
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+#include <aws/auth/credentials.h>
+
+#include <aws/auth/private/credentials_utils.h>
+#include <aws/common/environment.h>
+#include <aws/common/string.h>
+
+struct aws_credentials_provider *aws_credentials_provider_new_delegate(
+    struct aws_allocator *allocator,
+    struct aws_credentials_provider_delegate_options *options) {
+    struct aws_credentials_provider *provider = aws_mem_calloc(allocator, 1, sizeof(struct aws_credentials_provider));
+    if (provider == NULL) {
+        return NULL;
+    }
+
+    aws_credentials_provider_init_base(provider, allocator, options->provider_vtable, options->impl);
+
+    provider->shutdown_options = options->shutdown_options;
+
+    return provider;
+}