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/security/transport/auth_filters.h"
  
  #include <string.h>
  
  #include <grpc/support/alloc.h>
  #include <grpc/support/log.h>
  #include <grpc/support/string_util.h>
  
  #include "src/core/lib/channel/channel_stack.h"
  #include "src/core/lib/profiling/timers.h"
  #include "src/core/lib/security/context/security_context.h"
  #include "src/core/lib/security/credentials/credentials.h"
  #include "src/core/lib/security/transport/security_connector.h"
  #include "src/core/lib/slice/slice_internal.h"
  #include "src/core/lib/support/string.h"
  #include "src/core/lib/surface/call.h"
  #include "src/core/lib/transport/static_metadata.h"
  
  #define MAX_CREDENTIALS_METADATA_COUNT 4
  
  /* We can have a per-call credentials. */
  typedef struct {
    grpc_call_credentials *creds;
    grpc_mdstr *host;
    grpc_mdstr *method;
    /* pollset{_set} bound to this call; if we need to make external
       network requests, they should be done under a pollset added to this
       pollset_set so that work can progress when this call wants work to progress
    */
    grpc_polling_entity *pollent;
    grpc_transport_stream_op op;
    uint8_t security_context_set;
    grpc_linked_mdelem md_links[MAX_CREDENTIALS_METADATA_COUNT];
    grpc_auth_metadata_context auth_md_context;
  } call_data;
  
  /* We can have a per-channel credentials. */
  typedef struct {
    grpc_channel_security_connector *security_connector;
    grpc_auth_context *auth_context;
  } channel_data;
  
  static void reset_auth_metadata_context(
      grpc_auth_metadata_context *auth_md_context) {
    if (auth_md_context->service_url != NULL) {
      gpr_free((char *)auth_md_context->service_url);
      auth_md_context->service_url = NULL;
    }
    if (auth_md_context->method_name != NULL) {
      gpr_free((char *)auth_md_context->method_name);
      auth_md_context->method_name = NULL;
    }
    GRPC_AUTH_CONTEXT_UNREF(
        (grpc_auth_context *)auth_md_context->channel_auth_context,
        "grpc_auth_metadata_context");
    auth_md_context->channel_auth_context = NULL;
  }
  
  static void bubble_up_error(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                              grpc_status_code status, const char *error_msg) {
    call_data *calld = elem->call_data;
    gpr_log(GPR_ERROR, "Client side authentication failure: %s", error_msg);
    grpc_slice error_slice = grpc_slice_from_copied_string(error_msg);
    grpc_transport_stream_op_add_close(exec_ctx, &calld->op, status,
                                       &error_slice);
    grpc_call_next_op(exec_ctx, elem, &calld->op);
  }
  
  static void on_credentials_metadata(grpc_exec_ctx *exec_ctx, void *user_data,
                                      grpc_credentials_md *md_elems,
                                      size_t num_md,
                                      grpc_credentials_status status,
                                      const char *error_details) {
    grpc_call_element *elem = (grpc_call_element *)user_data;
    call_data *calld = elem->call_data;
    grpc_transport_stream_op *op = &calld->op;
    grpc_metadata_batch *mdb;
    size_t i;
    reset_auth_metadata_context(&calld->auth_md_context);
    if (status != GRPC_CREDENTIALS_OK) {
      bubble_up_error(exec_ctx, elem, GRPC_STATUS_UNAUTHENTICATED,
                      (error_details != NULL && strlen(error_details) > 0)
                          ? error_details
                          : "Credentials failed to get metadata.");
      return;
    }
    GPR_ASSERT(num_md <= MAX_CREDENTIALS_METADATA_COUNT);
    GPR_ASSERT(op->send_initial_metadata != NULL);
    mdb = op->send_initial_metadata;
    for (i = 0; i < num_md; i++) {
      grpc_metadata_batch_add_tail(
          mdb, &calld->md_links[i],
          grpc_mdelem_from_slices(exec_ctx,
                                  grpc_slice_ref_internal(md_elems[i].key),
                                  grpc_slice_ref_internal(md_elems[i].value)));
    }
    grpc_call_next_op(exec_ctx, elem, op);
  }
  
  void build_auth_metadata_context(grpc_security_connector *sc,
                                   grpc_auth_context *auth_context,
                                   call_data *calld) {
    char *service = gpr_strdup(grpc_mdstr_as_c_string(calld->method));
    char *last_slash = strrchr(service, '/');
    char *method_name = NULL;
    char *service_url = NULL;
    reset_auth_metadata_context(&calld->auth_md_context);
    if (last_slash == NULL) {
      gpr_log(GPR_ERROR, "No '/' found in fully qualified method name");
      service[0] = '\0';
    } else if (last_slash == service) {
      /* No service part in fully qualified method name: will just be "/". */
      service[1] = '\0';
    } else {
      *last_slash = '\0';
      method_name = gpr_strdup(last_slash + 1);
    }
    if (method_name == NULL) method_name = gpr_strdup("");
    gpr_asprintf(&service_url, "%s://%s%s",
                 sc->url_scheme == NULL ? "" : sc->url_scheme,
                 grpc_mdstr_as_c_string(calld->host), service);
    calld->auth_md_context.service_url = service_url;
    calld->auth_md_context.method_name = method_name;
    calld->auth_md_context.channel_auth_context =
        GRPC_AUTH_CONTEXT_REF(auth_context, "grpc_auth_metadata_context");
    gpr_free(service);
  }
  
  static void send_security_metadata(grpc_exec_ctx *exec_ctx,
                                     grpc_call_element *elem,
                                     grpc_transport_stream_op *op) {
    call_data *calld = elem->call_data;
    channel_data *chand = elem->channel_data;
    grpc_client_security_context *ctx =
        (grpc_client_security_context *)op->context[GRPC_CONTEXT_SECURITY].value;
    grpc_call_credentials *channel_call_creds =
        chand->security_connector->request_metadata_creds;
    int call_creds_has_md = (ctx != NULL) && (ctx->creds != NULL);
  
    if (channel_call_creds == NULL && !call_creds_has_md) {
      /* Skip sending metadata altogether. */
      grpc_call_next_op(exec_ctx, elem, op);
      return;
    }
  
    if (channel_call_creds != NULL && call_creds_has_md) {
      calld->creds = grpc_composite_call_credentials_create(channel_call_creds,
                                                            ctx->creds, NULL);
      if (calld->creds == NULL) {
        bubble_up_error(exec_ctx, elem, GRPC_STATUS_UNAUTHENTICATED,
                        "Incompatible credentials set on channel and call.");
        return;
      }
    } else {
      calld->creds = grpc_call_credentials_ref(
          call_creds_has_md ? ctx->creds : channel_call_creds);
    }
  
    build_auth_metadata_context(&chand->security_connector->base,
                                chand->auth_context, calld);
    calld->op = *op; /* Copy op (originates from the caller's stack). */
    GPR_ASSERT(calld->pollent != NULL);
    grpc_call_credentials_get_request_metadata(
        exec_ctx, calld->creds, calld->pollent, calld->auth_md_context,
        on_credentials_metadata, elem);
  }
  
  static void on_host_checked(grpc_exec_ctx *exec_ctx, void *user_data,
                              grpc_security_status status) {
    grpc_call_element *elem = (grpc_call_element *)user_data;
    call_data *calld = elem->call_data;
  
    if (status == GRPC_SECURITY_OK) {
      send_security_metadata(exec_ctx, elem, &calld->op);
    } else {
      char *error_msg;
      gpr_asprintf(&error_msg, "Invalid host %s set in :authority metadata.",
                   grpc_mdstr_as_c_string(calld->host));
      bubble_up_error(exec_ctx, elem, GRPC_STATUS_UNAUTHENTICATED, error_msg);
      gpr_free(error_msg);
    }
  }
  
  /* 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) {
    GPR_TIMER_BEGIN("auth_start_transport_op", 0);
  
    /* grab pointers to our data from the call element */
    call_data *calld = elem->call_data;
    channel_data *chand = elem->channel_data;
    grpc_linked_mdelem *l;
    grpc_client_security_context *sec_ctx = NULL;
  
    if (calld->security_context_set == 0 && op->cancel_error == GRPC_ERROR_NONE) {
      calld->security_context_set = 1;
      GPR_ASSERT(op->context);
      if (op->context[GRPC_CONTEXT_SECURITY].value == NULL) {
        op->context[GRPC_CONTEXT_SECURITY].value =
            grpc_client_security_context_create();
        op->context[GRPC_CONTEXT_SECURITY].destroy =
            grpc_client_security_context_destroy;
      }
      sec_ctx = op->context[GRPC_CONTEXT_SECURITY].value;
      GRPC_AUTH_CONTEXT_UNREF(sec_ctx->auth_context, "client auth filter");
      sec_ctx->auth_context =
          GRPC_AUTH_CONTEXT_REF(chand->auth_context, "client_auth_filter");
    }
  
    if (op->send_initial_metadata != NULL) {
      for (l = op->send_initial_metadata->list.head; l != NULL; l = l->next) {
        grpc_mdelem *md = l->md;
        /* Pointer comparison is OK for md_elems created from the same context.
         */
        if (md->key == GRPC_MDSTR_AUTHORITY) {
          if (calld->host != NULL) GRPC_MDSTR_UNREF(exec_ctx, calld->host);
          calld->host = GRPC_MDSTR_REF(md->value);
        } else if (md->key == GRPC_MDSTR_PATH) {
          if (calld->method != NULL) GRPC_MDSTR_UNREF(exec_ctx, calld->method);
          calld->method = GRPC_MDSTR_REF(md->value);
        }
      }
      if (calld->host != NULL) {
        const char *call_host = grpc_mdstr_as_c_string(calld->host);
        calld->op = *op; /* Copy op (originates from the caller's stack). */
        grpc_channel_security_connector_check_call_host(
            exec_ctx, chand->security_connector, call_host, chand->auth_context,
            on_host_checked, elem);
        GPR_TIMER_END("auth_start_transport_op", 0);
        return; /* early exit */
      }
    }
  
    /* pass control down the stack */
    grpc_call_next_op(exec_ctx, elem, op);
    GPR_TIMER_END("auth_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) {
    call_data *calld = elem->call_data;
    memset(calld, 0, sizeof(*calld));
    return GRPC_ERROR_NONE;
  }
  
  static void set_pollset_or_pollset_set(grpc_exec_ctx *exec_ctx,
                                         grpc_call_element *elem,
                                         grpc_polling_entity *pollent) {
    call_data *calld = elem->call_data;
    calld->pollent = pollent;
  }
  
  /* 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) {
    call_data *calld = elem->call_data;
    grpc_call_credentials_unref(exec_ctx, calld->creds);
    if (calld->host != NULL) {
      GRPC_MDSTR_UNREF(exec_ctx, calld->host);
    }
    if (calld->method != NULL) {
      GRPC_MDSTR_UNREF(exec_ctx, calld->method);
    }
    reset_auth_metadata_context(&calld->auth_md_context);
  }
  
  /* Constructor for channel_data */
  static grpc_error *init_channel_elem(grpc_exec_ctx *exec_ctx,
                                       grpc_channel_element *elem,
                                       grpc_channel_element_args *args) {
    grpc_security_connector *sc =
        grpc_find_security_connector_in_args(args->channel_args);
    grpc_auth_context *auth_context =
        grpc_find_auth_context_in_args(args->channel_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(!args->is_last);
    GPR_ASSERT(sc != NULL);
    GPR_ASSERT(auth_context != NULL);
  
    /* initialize members */
    chand->security_connector =
        (grpc_channel_security_connector *)GRPC_SECURITY_CONNECTOR_REF(
            sc, "client_auth_filter");
    chand->auth_context =
        GRPC_AUTH_CONTEXT_REF(auth_context, "client_auth_filter");
    return GRPC_ERROR_NONE;
  }
  
  /* 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_channel_security_connector *sc = chand->security_connector;
    if (sc != NULL) {
      GRPC_SECURITY_CONNECTOR_UNREF(exec_ctx, &sc->base, "client_auth_filter");
    }
    GRPC_AUTH_CONTEXT_UNREF(chand->auth_context, "client_auth_filter");
  }
  
  const grpc_channel_filter grpc_client_auth_filter = {
      auth_start_transport_op, grpc_channel_next_op,       sizeof(call_data),
      init_call_elem,          set_pollset_or_pollset_set, destroy_call_elem,
      sizeof(channel_data),    init_channel_elem,          destroy_channel_elem,
      grpc_call_next_get_peer, grpc_channel_next_get_info, "client-auth"};
  