/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <string.h>

#include "src/core/security/auth_filters.h"
#include "src/core/security/security_connector.h"
#include "src/core/security/security_context.h"

#include <grpc/support/alloc.h>
#include <grpc/support/log.h>

typedef struct call_data
{
  gpr_uint8 got_client_metadata;
  grpc_stream_op_buffer *recv_ops;
  /* Closure to call when finished with the auth_on_recv hook. */
  grpc_closure *on_done_recv;
  /* Receive closures are chained: we inject this closure as the on_done_recv
     up-call on transport_op, and remember to call our on_done_recv member after
     handling it. */
  grpc_closure auth_on_recv;
  grpc_transport_stream_op transport_op;
  grpc_metadata_array md;
  const grpc_metadata *consumed_md;
  size_t num_consumed_md;
  grpc_stream_op *md_op;
  grpc_auth_context *auth_context;
} call_data;

typedef struct channel_data
{
  grpc_security_connector *security_connector;
  grpc_auth_metadata_processor processor;
  grpc_mdctx *mdctx;
} channel_data;

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 != NULL; l = l->next)
    {
      grpc_metadata *usr_md = NULL;
      grpc_mdelem *md = l->md;
      grpc_mdstr *key = md->key;
      grpc_mdstr *value = md->value;
      if (result.count == result.capacity)
	{
	  result.capacity = GPR_MAX (result.capacity + 8, result.capacity * 2);
	  result.metadata = gpr_realloc (result.metadata, result.capacity * sizeof (grpc_metadata));
	}
      usr_md = &result.metadata[result.count++];
      usr_md->key = grpc_mdstr_as_c_string (key);
      usr_md->value = grpc_mdstr_as_c_string (value);
      usr_md->value_length = GPR_SLICE_LENGTH (value->slice);
    }
  return result;
}

static grpc_mdelem *
remove_consumed_md (void *user_data, grpc_mdelem * md)
{
  grpc_call_element *elem = user_data;
  call_data *calld = elem->call_data;
  size_t i;
  for (i = 0; i < calld->num_consumed_md; i++)
    {
      const grpc_metadata *consumed_md = &calld->consumed_md[i];
      /* Maybe we could do a pointer comparison but we do not have any guarantee
         that the metadata processor used the same pointers for consumed_md in the
         callback. */
      if (GPR_SLICE_LENGTH (md->key->slice) != strlen (consumed_md->key) || GPR_SLICE_LENGTH (md->value->slice) != consumed_md->value_length)
	{
	  continue;
	}
      if (memcmp (GPR_SLICE_START_PTR (md->key->slice), consumed_md->key, GPR_SLICE_LENGTH (md->key->slice)) == 0 && memcmp (GPR_SLICE_START_PTR (md->value->slice), consumed_md->value, GPR_SLICE_LENGTH (md->value->slice)) == 0)
	{
	  return NULL;		/* Delete. */
	}
    }
  return md;
}

/* 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 = user_data;
  call_data *calld = elem->call_data;
  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;

  /* TODO(jboeuf): Implement support for response_md. */
  if (response_md != NULL && num_response_md > 0)
    {
      gpr_log (GPR_INFO, "response_md in auth metadata processing not supported for now. " "Ignoring...");
    }

  if (status == GRPC_STATUS_OK)
    {
      calld->consumed_md = consumed_md;
      calld->num_consumed_md = num_consumed_md;
      grpc_metadata_batch_filter (&calld->md_op->data.metadata, remove_consumed_md, elem);
      grpc_metadata_array_destroy (&calld->md);
      calld->on_done_recv->cb (&exec_ctx, calld->on_done_recv->cb_arg, 1);
    }
  else
    {
      gpr_slice message;
      grpc_metadata_array_destroy (&calld->md);
      error_details = error_details != NULL ? error_details : "Authentication metadata processing failed.";
      message = gpr_slice_from_copied_string (error_details);
      grpc_sopb_reset (calld->recv_ops);
      grpc_transport_stream_op_add_close (&calld->transport_op, status, &message);
      grpc_call_next_op (&exec_ctx, elem, &calld->transport_op);
    }

  grpc_exec_ctx_finish (&exec_ctx);
}

static void
auth_on_recv (grpc_exec_ctx * exec_ctx, void *user_data, int success)
{
  grpc_call_element *elem = user_data;
  call_data *calld = elem->call_data;
  channel_data *chand = elem->channel_data;
  if (success)
    {
      size_t i;
      size_t nops = calld->recv_ops->nops;
      grpc_stream_op *ops = calld->recv_ops->ops;
      for (i = 0; i < nops; i++)
	{
	  grpc_stream_op *op = &ops[i];
	  if (op->type != GRPC_OP_METADATA || calld->got_client_metadata)
	    continue;
	  calld->got_client_metadata = 1;
	  if (chand->processor.process == NULL)
	    continue;
	  calld->md_op = op;
	  calld->md = metadata_batch_to_md_array (&op->data.metadata);
	  chand->processor.process (chand->processor.state, calld->auth_context, calld->md.metadata, calld->md.count, on_md_processing_done, elem);
	  return;
	}
    }
  calld->on_done_recv->cb (exec_ctx, calld->on_done_recv->cb_arg, success);
}

static void
set_recv_ops_md_callbacks (grpc_call_element * elem, grpc_transport_stream_op * op)
{
  call_data *calld = elem->call_data;

  if (op->recv_ops && !calld->got_client_metadata)
    {
      /* substitute our callback for the higher callback */
      calld->recv_ops = op->recv_ops;
      calld->on_done_recv = op->on_done_recv;
      op->on_done_recv = &calld->auth_on_recv;
      calld->transport_op = *op;
    }
}

/* Called either:
     - in response to an API call (or similar) from above, to send something
     - a network event (or similar) from below, to receive something
   op contains type and call direction information, in addition to the data
   that is being sent or received. */
static void
auth_start_transport_op (grpc_exec_ctx * exec_ctx, grpc_call_element * elem, grpc_transport_stream_op * op)
{
  set_recv_ops_md_callbacks (elem, op);
  grpc_call_next_op (exec_ctx, elem, op);
}

/* Constructor for call_data */
static void
init_call_elem (grpc_exec_ctx * exec_ctx, grpc_call_element * elem, const void *server_transport_data, grpc_transport_stream_op * initial_op)
{
  /* grab pointers to our data from the call element */
  call_data *calld = elem->call_data;
  channel_data *chand = elem->channel_data;
  grpc_server_security_context *server_ctx = NULL;

  /* initialize members */
  memset (calld, 0, sizeof (*calld));
  grpc_closure_init (&calld->auth_on_recv, auth_on_recv, elem);

  GPR_ASSERT (initial_op && initial_op->context != NULL && initial_op->context[GRPC_CONTEXT_SECURITY].value == NULL);

  /* Create a security context for the call and reference the auth context from
     the channel. */
  if (initial_op->context[GRPC_CONTEXT_SECURITY].value != NULL)
    {
      initial_op->context[GRPC_CONTEXT_SECURITY].destroy (initial_op->context[GRPC_CONTEXT_SECURITY].value);
    }
  server_ctx = grpc_server_security_context_create ();
  server_ctx->auth_context = grpc_auth_context_create (chand->security_connector->auth_context);
  server_ctx->auth_context->pollset = initial_op->bind_pollset;
  initial_op->context[GRPC_CONTEXT_SECURITY].value = server_ctx;
  initial_op->context[GRPC_CONTEXT_SECURITY].destroy = grpc_server_security_context_destroy;
  calld->auth_context = server_ctx->auth_context;

  /* Set the metadata callbacks. */
  set_recv_ops_md_callbacks (elem, initial_op);
}

/* Destructor for call_data */
static void
destroy_call_elem (grpc_exec_ctx * exec_ctx, grpc_call_element * elem)
{
}

/* Constructor for channel_data */
static void
init_channel_elem (grpc_exec_ctx * exec_ctx, grpc_channel_element * elem, grpc_channel * master, const grpc_channel_args * args, grpc_mdctx * mdctx, int is_first, int is_last)
{
  grpc_security_connector *sc = grpc_find_security_connector_in_args (args);
  grpc_auth_metadata_processor *processor = grpc_find_auth_metadata_processor_in_args (args);
  /* grab pointers to our data from the channel element */
  channel_data *chand = elem->channel_data;

  /* The first and the last filters tend to be implemented differently to
     handle the case that there's no 'next' filter to call on the up or down
     path */
  GPR_ASSERT (!is_first);
  GPR_ASSERT (!is_last);
  GPR_ASSERT (sc != NULL);
  GPR_ASSERT (processor != NULL);

  /* initialize members */
  GPR_ASSERT (!sc->is_client_side);
  chand->security_connector = GRPC_SECURITY_CONNECTOR_REF (sc, "server_auth_filter");
  chand->mdctx = mdctx;
  chand->processor = *processor;
}

/* Destructor for channel data */
static void
destroy_channel_elem (grpc_exec_ctx * exec_ctx, grpc_channel_element * elem)
{
  /* grab pointers to our data from the channel element */
  channel_data *chand = elem->channel_data;
  GRPC_SECURITY_CONNECTOR_UNREF (chand->security_connector, "server_auth_filter");
}

const grpc_channel_filter grpc_server_auth_filter = {
  auth_start_transport_op, grpc_channel_next_op,
  sizeof (call_data), init_call_elem,
  destroy_call_elem, sizeof (channel_data),
  init_channel_elem, destroy_channel_elem,
  grpc_call_next_get_peer, "server-auth"
};