text: /*
   *
   * Copyright 2015 gRPC authors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *
   */
  
  #include <grpc/support/port_platform.h>
  
  #include <string.h>
  
  #include <grpc/support/alloc.h>
  #include <grpc/support/log.h>
  
  #include "src/core/lib/security/context/security_context.h"
  #include "src/core/lib/security/credentials/credentials.h"
  #include "src/core/lib/security/transport/auth_filters.h"
  #include "src/core/lib/slice/slice_internal.h"
  
  namespace {
  enum async_state {
    STATE_INIT = 0,
    STATE_DONE,
    STATE_CANCELLED,
  };
  
  struct call_data {
    grpc_call_combiner* call_combiner;
    grpc_call_stack* owning_call;
    grpc_transport_stream_op_batch* recv_initial_metadata_batch;
    grpc_closure* original_recv_initial_metadata_ready;
    grpc_closure recv_initial_metadata_ready;
    grpc_metadata_array md;
    const grpc_metadata* consumed_md;
    size_t num_consumed_md;
    grpc_closure cancel_closure;
    gpr_atm state;  // async_state
  };
  
  struct channel_data {
    grpc_auth_context* auth_context;
    grpc_server_credentials* creds;
  };
  }  // namespace
  
  static grpc_metadata_array metadata_batch_to_md_array(
      const grpc_metadata_batch* batch) {
    grpc_linked_mdelem* l;
    grpc_metadata_array result;
    grpc_metadata_array_init(&result);
    for (l = batch->list.head; l != nullptr; l = l->next) {
      grpc_metadata* usr_md = nullptr;
      grpc_mdelem md = l->md;
      grpc_slice key = GRPC_MDKEY(md);
      grpc_slice value = GRPC_MDVALUE(md);
      if (result.count == result.capacity) {
        result.capacity = GPR_MAX(result.capacity + 8, result.capacity * 2);
        result.metadata = static_cast<grpc_metadata*>(gpr_realloc(
            result.metadata, result.capacity * sizeof(grpc_metadata)));
      }
      usr_md = &result.metadata[result.count++];
      usr_md->key = grpc_slice_ref_internal(key);
      usr_md->value = grpc_slice_ref_internal(value);
    }
    return result;
  }
  
  static grpc_filtered_mdelem remove_consumed_md(void* user_data,
                                                 grpc_mdelem md) {
    grpc_call_element* elem = static_cast<grpc_call_element*>(user_data);
    call_data* calld = static_cast<call_data*>(elem->call_data);
    size_t i;
    for (i = 0; i < calld->num_consumed_md; i++) {
      const grpc_metadata* consumed_md = &calld->consumed_md[i];
      if (grpc_slice_eq(GRPC_MDKEY(md), consumed_md->key) &&
          grpc_slice_eq(GRPC_MDVALUE(md), consumed_md->value))
        return GRPC_FILTERED_REMOVE();
    }
    return GRPC_FILTERED_MDELEM(md);
  }
  
  static void on_md_processing_done_inner(grpc_call_element* elem,
                                          const grpc_metadata* consumed_md,
                                          size_t num_consumed_md,
                                          const grpc_metadata* response_md,
                                          size_t num_response_md,
                                          grpc_error* error) {
    call_data* calld = static_cast<call_data*>(elem->call_data);
    grpc_transport_stream_op_batch* batch = calld->recv_initial_metadata_batch;
    /* TODO(jboeuf): Implement support for response_md. */
    if (response_md != nullptr && num_response_md > 0) {
      gpr_log(GPR_INFO,
              "response_md in auth metadata processing not supported for now. "
              "Ignoring...");
    }
    if (error == GRPC_ERROR_NONE) {
      calld->consumed_md = consumed_md;
      calld->num_consumed_md = num_consumed_md;
      error = grpc_metadata_batch_filter(
          batch->payload->recv_initial_metadata.recv_initial_metadata,
          remove_consumed_md, elem, "Response metadata filtering error");
    }
    GRPC_CLOSURE_SCHED(calld->original_recv_initial_metadata_ready, error);
  }
  
  // Called from application code.
  static void on_md_processing_done(
      void* user_data, const grpc_metadata* consumed_md, size_t num_consumed_md,
      const grpc_metadata* response_md, size_t num_response_md,
      grpc_status_code status, const char* error_details) {
    grpc_call_element* elem = static_cast<grpc_call_element*>(user_data);
    call_data* calld = static_cast<call_data*>(elem->call_data);
    grpc_core::ExecCtx exec_ctx;
    // If the call was not cancelled while we were in flight, process the result.
    if (gpr_atm_full_cas(&calld->state, static_cast<gpr_atm>(STATE_INIT),
                         static_cast<gpr_atm>(STATE_DONE))) {
      grpc_error* error = GRPC_ERROR_NONE;
      if (status != GRPC_STATUS_OK) {
        if (error_details == nullptr) {
          error_details = "Authentication metadata processing failed.";
        }
        error = grpc_error_set_int(
            GRPC_ERROR_CREATE_FROM_COPIED_STRING(error_details),
            GRPC_ERROR_INT_GRPC_STATUS, status);
      }
      on_md_processing_done_inner(elem, consumed_md, num_consumed_md, response_md,
                                  num_response_md, error);
    }
    // Clean up.
    for (size_t i = 0; i < calld->md.count; i++) {
      grpc_slice_unref_internal(calld->md.metadata[i].key);
      grpc_slice_unref_internal(calld->md.metadata[i].value);
    }
    grpc_metadata_array_destroy(&calld->md);
    GRPC_CALL_STACK_UNREF(calld->owning_call, "server_auth_metadata");
  }
  
  static void cancel_call(void* arg, grpc_error* error) {
    grpc_call_element* elem = static_cast<grpc_call_element*>(arg);
    call_data* calld = static_cast<call_data*>(elem->call_data);
    // If the result was not already processed, invoke the callback now.
    if (error != GRPC_ERROR_NONE &&
        gpr_atm_full_cas(&calld->state, static_cast<gpr_atm>(STATE_INIT),
                         static_cast<gpr_atm>(STATE_CANCELLED))) {
      on_md_processing_done_inner(elem, nullptr, 0, nullptr, 0,
                                  GRPC_ERROR_REF(error));
    }
    GRPC_CALL_STACK_UNREF(calld->owning_call, "cancel_call");
  }
  
  static void recv_initial_metadata_ready(void* arg, grpc_error* error) {
    grpc_call_element* elem = static_cast<grpc_call_element*>(arg);
    channel_data* chand = static_cast<channel_data*>(elem->channel_data);
    call_data* calld = static_cast<call_data*>(elem->call_data);
    grpc_transport_stream_op_batch* batch = calld->recv_initial_metadata_batch;
    if (error == GRPC_ERROR_NONE) {
      if (chand->creds != nullptr && chand->creds->processor.process != nullptr) {
        // We're calling out to the application, so we need to make sure
        // to drop the call combiner early if we get cancelled.
        GRPC_CALL_STACK_REF(calld->owning_call, "cancel_call");
        GRPC_CLOSURE_INIT(&calld->cancel_closure, cancel_call, elem,
                          grpc_schedule_on_exec_ctx);
        grpc_call_combiner_set_notify_on_cancel(calld->call_combiner,
                                                &calld->cancel_closure);
        GRPC_CALL_STACK_REF(calld->owning_call, "server_auth_metadata");
        calld->md = metadata_batch_to_md_array(
            batch->payload->recv_initial_metadata.recv_initial_metadata);
        chand->creds->processor.process(
            chand->creds->processor.state, chand->auth_context,
            calld->md.metadata, calld->md.count, on_md_processing_done, elem);
        return;
      }
    }
    GRPC_CLOSURE_RUN(calld->original_recv_initial_metadata_ready,
                     GRPC_ERROR_REF(error));
  }
  
  static void auth_start_transport_stream_op_batch(
      grpc_call_element* elem, grpc_transport_stream_op_batch* batch) {
    call_data* calld = static_cast<call_data*>(elem->call_data);
    if (batch->recv_initial_metadata) {
      // Inject our callback.
      calld->recv_initial_metadata_batch = batch;
      calld->original_recv_initial_metadata_ready =
          batch->payload->recv_initial_metadata.recv_initial_metadata_ready;
      batch->payload->recv_initial_metadata.recv_initial_metadata_ready =
          &calld->recv_initial_metadata_ready;
    }
    grpc_call_next_op(elem, batch);
  }
  
  /* Constructor for call_data */
  static grpc_error* init_call_elem(grpc_call_element* elem,
                                    const grpc_call_element_args* args) {
    call_data* calld = static_cast<call_data*>(elem->call_data);
    channel_data* chand = static_cast<channel_data*>(elem->channel_data);
    calld->call_combiner = args->call_combiner;
    calld->owning_call = args->call_stack;
    GRPC_CLOSURE_INIT(&calld->recv_initial_metadata_ready,
                      recv_initial_metadata_ready, elem,
                      grpc_schedule_on_exec_ctx);
    // Create server security context.  Set its auth context from channel
    // data and save it in the call context.
    grpc_server_security_context* server_ctx =
        grpc_server_security_context_create(args->arena);
    server_ctx->auth_context =
        GRPC_AUTH_CONTEXT_REF(chand->auth_context, "server_auth_filter");
    if (args->context[GRPC_CONTEXT_SECURITY].value != nullptr) {
      args->context[GRPC_CONTEXT_SECURITY].destroy(
          args->context[GRPC_CONTEXT_SECURITY].value);
    }
    args->context[GRPC_CONTEXT_SECURITY].value = server_ctx;
    args->context[GRPC_CONTEXT_SECURITY].destroy =
        grpc_server_security_context_destroy;
    return GRPC_ERROR_NONE;
  }
  
  /* Destructor for call_data */
  static void destroy_call_elem(grpc_call_element* elem,
                                const grpc_call_final_info* final_info,
                                grpc_closure* ignored) {}
  
  /* Constructor for channel_data */
  static grpc_error* init_channel_elem(grpc_channel_element* elem,
                                       grpc_channel_element_args* args) {
    GPR_ASSERT(!args->is_last);
    channel_data* chand = static_cast<channel_data*>(elem->channel_data);
    grpc_auth_context* auth_context =
        grpc_find_auth_context_in_args(args->channel_args);
    GPR_ASSERT(auth_context != nullptr);
    chand->auth_context =
        GRPC_AUTH_CONTEXT_REF(auth_context, "server_auth_filter");
    grpc_server_credentials* creds =
        grpc_find_server_credentials_in_args(args->channel_args);
    chand->creds = grpc_server_credentials_ref(creds);
    return GRPC_ERROR_NONE;
  }
  
  /* Destructor for channel data */
  static void destroy_channel_elem(grpc_channel_element* elem) {
    channel_data* chand = static_cast<channel_data*>(elem->channel_data);
    GRPC_AUTH_CONTEXT_UNREF(chand->auth_context, "server_auth_filter");
    grpc_server_credentials_unref(chand->creds);
  }
  
  const grpc_channel_filter grpc_server_auth_filter = {
      auth_start_transport_stream_op_batch,
      grpc_channel_next_op,
      sizeof(call_data),
      init_call_elem,
      grpc_call_stack_ignore_set_pollset_or_pollset_set,
      destroy_call_elem,
      sizeof(channel_data),
      init_channel_elem,
      destroy_channel_elem,
      grpc_channel_next_get_info,
      "server-auth"};
  