text: /*
   *
   * 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 "src/core/lib/channel/http_server_filter.h"
  
  #include <grpc/support/alloc.h>
  #include <grpc/support/log.h>
  #include <string.h>
  #include "src/core/lib/profiling/timers.h"
  #include "src/core/lib/transport/static_metadata.h"
  
  #define EXPECTED_CONTENT_TYPE "application/grpc"
  #define EXPECTED_CONTENT_TYPE_LENGTH sizeof(EXPECTED_CONTENT_TYPE) - 1
  
  typedef struct call_data {
    uint8_t seen_path;
    uint8_t seen_method;
    uint8_t sent_status;
    uint8_t seen_scheme;
    uint8_t seen_te_trailers;
    uint8_t seen_authority;
    uint8_t seen_payload_bin;
    grpc_linked_mdelem status;
    grpc_linked_mdelem content_type;
  
    /* flag to ensure payload_bin is delivered only once */
    uint8_t payload_bin_delivered;
  
    grpc_metadata_batch *recv_initial_metadata;
    bool *recv_idempotent_request;
    bool *recv_cacheable_request;
    /** Closure to call when finished with the hs_on_recv hook */
    grpc_closure *on_done_recv;
    /** Closure to call when we retrieve read message from the payload-bin header
     */
    grpc_closure *recv_message_ready;
    grpc_closure *on_complete;
    grpc_byte_stream **pp_recv_message;
    gpr_slice_buffer read_slice_buffer;
    grpc_slice_buffer_stream read_stream;
  
    /** 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 hs_on_recv;
    grpc_closure hs_on_complete;
    grpc_closure hs_recv_message_ready;
  } call_data;
  
  typedef struct channel_data { uint8_t unused; } channel_data;
  
  typedef struct {
    grpc_call_element *elem;
    grpc_exec_ctx *exec_ctx;
  } server_filter_args;
  
  static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
    server_filter_args *a = user_data;
    grpc_call_element *elem = a->elem;
    call_data *calld = elem->call_data;
  
    /* Check if it is one of the headers we care about. */
    if (md == GRPC_MDELEM_TE_TRAILERS || md == GRPC_MDELEM_METHOD_POST ||
        md == GRPC_MDELEM_METHOD_PUT || md == GRPC_MDELEM_METHOD_GET ||
        md == GRPC_MDELEM_SCHEME_HTTP || md == GRPC_MDELEM_SCHEME_HTTPS ||
        md == GRPC_MDELEM_CONTENT_TYPE_APPLICATION_SLASH_GRPC) {
      /* swallow it */
      if (md == GRPC_MDELEM_METHOD_POST) {
        calld->seen_method = 1;
        *calld->recv_idempotent_request = false;
        *calld->recv_cacheable_request = false;
      } else if (md == GRPC_MDELEM_METHOD_PUT) {
        calld->seen_method = 1;
        *calld->recv_idempotent_request = true;
      } else if (md == GRPC_MDELEM_METHOD_GET) {
        calld->seen_method = 1;
        *calld->recv_cacheable_request = true;
      } else if (md->key == GRPC_MDSTR_SCHEME) {
        calld->seen_scheme = 1;
      } else if (md == GRPC_MDELEM_TE_TRAILERS) {
        calld->seen_te_trailers = 1;
      }
      /* TODO(klempner): Track that we've seen all the headers we should
         require */
      return NULL;
    } else if (md->key == GRPC_MDSTR_CONTENT_TYPE) {
      const char *value_str = grpc_mdstr_as_c_string(md->value);
      if (strncmp(value_str, EXPECTED_CONTENT_TYPE,
                  EXPECTED_CONTENT_TYPE_LENGTH) == 0 &&
          (value_str[EXPECTED_CONTENT_TYPE_LENGTH] == '+' ||
           value_str[EXPECTED_CONTENT_TYPE_LENGTH] == ';')) {
        /* Although the C implementation doesn't (currently) generate them,
           any custom +-suffix is explicitly valid. */
        /* TODO(klempner): We should consider preallocating common values such
           as +proto or +json, or at least stashing them if we see them. */
        /* TODO(klempner): Should we be surfacing this to application code? */
      } else {
        /* TODO(klempner): We're currently allowing this, but we shouldn't
           see it without a proxy so log for now. */
        gpr_log(GPR_INFO, "Unexpected content-type '%s'", value_str);
      }
      return NULL;
    } else if (md->key == GRPC_MDSTR_TE || md->key == GRPC_MDSTR_METHOD ||
               md->key == GRPC_MDSTR_SCHEME) {
      gpr_log(GPR_ERROR, "Invalid %s: header: '%s'",
              grpc_mdstr_as_c_string(md->key), grpc_mdstr_as_c_string(md->value));
      /* swallow it and error everything out. */
      /* TODO(klempner): We ought to generate more descriptive error messages
         on the wire here. */
      grpc_call_element_send_cancel(a->exec_ctx, elem);
      return NULL;
    } else if (md->key == GRPC_MDSTR_PATH) {
      if (calld->seen_path) {
        gpr_log(GPR_ERROR, "Received :path twice");
        return NULL;
      }
      calld->seen_path = 1;
      return md;
    } else if (md->key == GRPC_MDSTR_AUTHORITY) {
      calld->seen_authority = 1;
      return md;
    } else if (md->key == GRPC_MDSTR_HOST) {
      /* translate host to :authority since :authority may be
         omitted */
      grpc_mdelem *authority = grpc_mdelem_from_metadata_strings(
          GRPC_MDSTR_AUTHORITY, GRPC_MDSTR_REF(md->value));
      calld->seen_authority = 1;
      return authority;
    } else if (md->key == GRPC_MDSTR_GRPC_PAYLOAD_BIN) {
      /* Retrieve the payload from the value of the 'grpc-internal-payload-bin'
         header field */
      calld->seen_payload_bin = 1;
      gpr_slice_buffer_init(&calld->read_slice_buffer);
      gpr_slice_buffer_add(&calld->read_slice_buffer,
                           gpr_slice_ref(md->value->slice));
      grpc_slice_buffer_stream_init(&calld->read_stream,
                                    &calld->read_slice_buffer, 0);
      return NULL;
    } else {
      return md;
    }
  }
  
  static void hs_on_recv(grpc_exec_ctx *exec_ctx, void *user_data,
                         grpc_error *err) {
    grpc_call_element *elem = user_data;
    call_data *calld = elem->call_data;
    if (err == GRPC_ERROR_NONE) {
      server_filter_args a;
      a.elem = elem;
      a.exec_ctx = exec_ctx;
      grpc_metadata_batch_filter(calld->recv_initial_metadata, server_filter, &a);
      /* Have we seen the required http2 transport headers?
         (:method, :scheme, content-type, with :path and :authority covered
         at the channel level right now) */
      if (calld->seen_method && calld->seen_scheme && calld->seen_te_trailers &&
          calld->seen_path && calld->seen_authority) {
        /* do nothing */
      } else {
        err = GRPC_ERROR_CREATE("Bad incoming HTTP headers");
        if (!calld->seen_path) {
          err = grpc_error_add_child(err,
                                     GRPC_ERROR_CREATE("Missing :path header"));
        }
        if (!calld->seen_authority) {
          err = grpc_error_add_child(
              err, GRPC_ERROR_CREATE("Missing :authority header"));
        }
        if (!calld->seen_method) {
          err = grpc_error_add_child(err,
                                     GRPC_ERROR_CREATE("Missing :method header"));
        }
        if (!calld->seen_scheme) {
          err = grpc_error_add_child(err,
                                     GRPC_ERROR_CREATE("Missing :scheme header"));
        }
        if (!calld->seen_te_trailers) {
          err = grpc_error_add_child(
              err, GRPC_ERROR_CREATE("Missing te: trailers header"));
        }
        /* Error this call out */
        grpc_call_element_send_cancel(exec_ctx, elem);
      }
    } else {
      GRPC_ERROR_REF(err);
    }
    calld->on_done_recv->cb(exec_ctx, calld->on_done_recv->cb_arg, err);
    GRPC_ERROR_UNREF(err);
  }
  
  static void hs_on_complete(grpc_exec_ctx *exec_ctx, void *user_data,
                             grpc_error *err) {
    grpc_call_element *elem = user_data;
    call_data *calld = elem->call_data;
    /* Call recv_message_ready if we got the payload via the header field */
    if (calld->seen_payload_bin && calld->recv_message_ready != NULL) {
      *calld->pp_recv_message = calld->payload_bin_delivered
                                    ? NULL
                                    : (grpc_byte_stream *)&calld->read_stream;
      calld->recv_message_ready->cb(exec_ctx, calld->recv_message_ready->cb_arg,
                                    err);
      calld->recv_message_ready = NULL;
      calld->payload_bin_delivered = true;
    }
    calld->on_complete->cb(exec_ctx, calld->on_complete->cb_arg, err);
  }
  
  static void hs_recv_message_ready(grpc_exec_ctx *exec_ctx, void *user_data,
                                    grpc_error *err) {
    grpc_call_element *elem = user_data;
    call_data *calld = elem->call_data;
    if (calld->seen_payload_bin) {
      /* do nothing. This is probably a GET request, and payload will be returned
      in hs_on_complete callback. */
    } else {
      calld->recv_message_ready->cb(exec_ctx, calld->recv_message_ready->cb_arg,
                                    err);
    }
  }
  
  static void hs_mutate_op(grpc_call_element *elem,
                           grpc_transport_stream_op *op) {
    /* grab pointers to our data from the call element */
    call_data *calld = elem->call_data;
  
    if (op->send_initial_metadata != NULL && !calld->sent_status) {
      calld->sent_status = 1;
      grpc_metadata_batch_add_head(op->send_initial_metadata, &calld->status,
                                   GRPC_MDELEM_STATUS_200);
      grpc_metadata_batch_add_tail(
          op->send_initial_metadata, &calld->content_type,
          GRPC_MDELEM_CONTENT_TYPE_APPLICATION_SLASH_GRPC);
    }
  
    if (op->recv_initial_metadata) {
      /* substitute our callback for the higher callback */
      GPR_ASSERT(op->recv_idempotent_request != NULL);
      GPR_ASSERT(op->recv_cacheable_request != NULL);
      calld->recv_initial_metadata = op->recv_initial_metadata;
      calld->recv_idempotent_request = op->recv_idempotent_request;
      calld->recv_cacheable_request = op->recv_cacheable_request;
      calld->on_done_recv = op->recv_initial_metadata_ready;
      op->recv_initial_metadata_ready = &calld->hs_on_recv;
    }
  
    if (op->recv_message) {
      calld->recv_message_ready = op->recv_message_ready;
      calld->pp_recv_message = op->recv_message;
      if (op->recv_message_ready) {
        op->recv_message_ready = &calld->hs_recv_message_ready;
      }
      if (op->on_complete) {
        calld->on_complete = op->on_complete;
        op->on_complete = &calld->hs_on_complete;
      }
    }
  }
  
  static void hs_start_transport_op(grpc_exec_ctx *exec_ctx,
                                    grpc_call_element *elem,
                                    grpc_transport_stream_op *op) {
    GRPC_CALL_LOG_OP(GPR_INFO, elem, op);
    GPR_TIMER_BEGIN("hs_start_transport_op", 0);
    hs_mutate_op(elem, op);
    grpc_call_next_op(exec_ctx, elem, op);
    GPR_TIMER_END("hs_start_transport_op", 0);
  }
  
  /* Constructor for call_data */
  static grpc_error *init_call_elem(grpc_exec_ctx *exec_ctx,
                                    grpc_call_element *elem,
                                    grpc_call_element_args *args) {
    /* grab pointers to our data from the call element */
    call_data *calld = elem->call_data;
    /* initialize members */
    memset(calld, 0, sizeof(*calld));
    grpc_closure_init(&calld->hs_on_recv, hs_on_recv, elem);
    grpc_closure_init(&calld->hs_on_complete, hs_on_complete, elem);
    grpc_closure_init(&calld->hs_recv_message_ready, hs_recv_message_ready, elem);
    return GRPC_ERROR_NONE;
  }
  
  /* Destructor for call_data */
  static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                                const grpc_call_final_info *final_info,
                                void *ignored) {}
  
  /* Constructor for channel_data */
  static void init_channel_elem(grpc_exec_ctx *exec_ctx,
                                grpc_channel_element *elem,
                                grpc_channel_element_args *args) {
    GPR_ASSERT(!args->is_last);
  }
  
  /* Destructor for channel data */
  static void destroy_channel_elem(grpc_exec_ctx *exec_ctx,
                                   grpc_channel_element *elem) {}
  
  const grpc_channel_filter grpc_http_server_filter = {
      hs_start_transport_op,
      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_call_next_get_peer,
      "http-server"};
  