http_parser.h

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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the Apache 2.0 License.
#pragma once
 
#include "ccf/ds/hex.h"
#include "ccf/http_configuration.h"
#include "enclave/tls_session.h"
#include "http/http_exceptions.h"
#include "http_builder.h"
#include "http_proc.h"
 
#include <algorithm>
#include <cctype>
#include <llhttp/llhttp.h>
#include <map>
#include <queue>
#include <regex>
#include <string>
#include <string_view>
 
namespace http
{
  inline auto split_url_path(const std::string_view& url)
  {
    LOG_TRACE_FMT("Received url to parse: {}", std::string_view(url));
 
    const auto path_end = url.find('?');
    const auto query_start =
      path_end == std::string::npos ? url.size() : path_end + 1;
 
    const auto query_end = url.find('#', query_start);
    const auto fragment_start =
      query_end == std::string::npos ? url.size() : query_end + 1;
 
    return std::make_tuple(
      url.substr(0, path_end),
      url.substr(query_start, query_end - query_start),
      url.substr(fragment_start));
  }
 
  static std::string url_decode(const std::string_view& s_)
  {
    std::string s(s_);
    char const* src = s.c_str();
    char const* end = s.c_str() + s.size();
    char* dst = s.data();
 
    while (src < end)
    {
      char const c = *src++;
      if (
        c == '%' && (src + 1) < end && (isxdigit(src[0]) != 0) &&
        (isxdigit(src[1]) != 0))
      {
        const auto a = ccf::ds::hex_char_to_int(*src++);
        const auto b = ccf::ds::hex_char_to_int(*src++);
        *dst++ = (a << 4) | b;
      }
      else if (c == '+')
      {
        *dst++ = ' ';
      }
      else
      {
        *dst++ = c;
      }
    }
 
    s.resize(dst - s.data());
    return s;
  }
 
  inline bool status_success(ccf::http_status status)
  {
    return status >= 200 && status < 300;
  }
 
  struct SimpleRequestProcessor : public http::RequestProcessor
  {
  public:
    ~SimpleRequestProcessor() override = default;
 
    struct Request
    {
      llhttp_method method;
      std::string url;
      ccf::http::HeaderMap headers;
      std::vector<uint8_t> body;
    };
 
    std::queue<Request> received;
 
    void handle_request(
      llhttp_method method,
      const std::string_view& url,
      ccf::http::HeaderMap&& headers,
      std::vector<uint8_t>&& body,
      int32_t /*stream_id*/) override
    {
      received.emplace(Request{method, std::string(url), headers, body});
    }
  };
 
  struct SimpleResponseProcessor : public ::http::ResponseProcessor
  {
  public:
    ~SimpleResponseProcessor() override = default;
 
    struct Response
    {
      ccf::http_status status;
      ccf::http::HeaderMap headers;
      std::vector<uint8_t> body;
    };
 
    std::queue<Response> received;
 
    void handle_response(
      ccf::http_status status,
      ccf::http::HeaderMap&& headers,
      std::vector<uint8_t>&& body) override
    {
      received.emplace(Response{status, headers, body});
    }
  };
 
  enum State : uint8_t
  {
    DONE,
    IN_MESSAGE
  };
 
  static int on_msg_begin(llhttp_t* parser);
  static int on_url(llhttp_t* parser, const char* at, size_t length);
  static int on_header_field(llhttp_t* parser, const char* at, size_t length);
  static int on_header_value(llhttp_t* parser, const char* at, size_t length);
  static int on_headers_complete(llhttp_t* parser);
  static int on_body(llhttp_t* parser, const char* at, size_t length);
  static int on_msg_end(llhttp_t* parser);
 
  struct URL
  {
    std::string scheme;
    std::string host;
    std::string port;
    std::string path;
    std::string query;
    std::string fragment;
  };
 
  inline URL parse_url_full(const std::string& url)
  {
    LOG_TRACE_FMT("Received url to parse: {}", url);
 
    // From https://tools.ietf.org/html/rfc3986#appendix-B
    std::regex url_regex(
      "^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\\?([^#]*))?(#(.*))?");
 
    std::smatch match;
    if (!std::regex_match(url, match, url_regex))
    {
      throw std::invalid_argument(fmt::format("Unable to parse url: {}", url));
    }
 
    const auto host_port = match[4].str();
 
    // IPv6 hosts may contain colons, so only search for port after the closing
    // square bracket
    const auto closing_bracket = host_port.rfind(']');
    const auto port_delim_start =
      closing_bracket == std::string::npos ? 0 : closing_bracket;
    const auto port_delim = host_port.find(':', port_delim_start);
 
    URL u;
    u.scheme = match[2].str();
    u.host = host_port.substr(0, port_delim);
    if (port_delim != std::string::npos)
    {
      u.port = host_port.substr(port_delim + 1);
    }
    u.path = match[5].str();
    u.query = match[7].str();
    u.fragment = match[9].str();
    return u;
  }
 
  class Parser
  {
  public:
    virtual ~Parser() = default;
 
  protected:
    llhttp_t parser;
    llhttp_settings_t settings;
    ccf::http::ParserConfiguration configuration;
    State state = DONE;
 
    std::vector<uint8_t> body_buf;
    ccf::http::HeaderMap headers;
 
    std::pair<std::string, std::string> partial_parsed_header;
 
    void complete_header()
    {
      headers.emplace(partial_parsed_header);
      partial_parsed_header.first.clear();
      partial_parsed_header.second.clear();
    }
 
    Parser(
      llhttp_type_t type,
      ccf::http::ParserConfiguration config =
        ccf::http::ParserConfiguration{}) :
      parser{},
      settings{},
      configuration(std::move(config))
    {
      llhttp_settings_init(&settings);
 
      settings.on_message_begin = on_msg_begin;
      settings.on_header_field = on_header_field;
      settings.on_header_value = on_header_value;
      settings.on_headers_complete = on_headers_complete;
      settings.on_body = on_body;
      settings.on_message_complete = on_msg_end;
 
      llhttp_init(&parser, type, &settings);
      parser.data = this;
    }
 
  public:
    void execute(const uint8_t* data, size_t size)
    {
      // NOLINTNEXTLINE(cppcoreguidelines-pro-type-reinterpret-cast)
      const auto* const data_char = reinterpret_cast<const char*>(data);
      auto err_no = llhttp_execute(&parser, data_char, size);
 
      if (err_no == HPE_PAUSED_UPGRADE)
      {
        // Assume Upgrade requests will be handled by caller inspecting headers,
        // so we can instantly resume the parser.
        llhttp_resume_after_upgrade(&parser);
      }
      else if (err_no != HPE_OK)
      {
        throw std::runtime_error(fmt::format(
          "HTTP parsing failed ({}: {}) around byte {}",
          llhttp_errno_name(err_no),
          llhttp_get_error_reason(&parser),
          llhttp_get_error_pos(&parser) - data_char));
      }
    }
 
    void append_body(const char* at, size_t length)
    {
      if (state == IN_MESSAGE)
      {
        LOG_TRACE_FMT("Appending chunk [{} bytes]", length);
        std::copy(at, at + length, std::back_inserter(body_buf));
 
        auto const& max_body_size = configuration.max_body_size.value_or(
          ccf::http::default_max_body_size);
        if (body_buf.size() > max_body_size)
        {
          throw RequestPayloadTooLargeException(fmt::format(
            "HTTP request body is too large (max size allowed: {})",
            max_body_size));
        }
      }
      else
      {
        throw std::runtime_error("Receiving content outside of message");
      }
    }
 
    virtual void new_message()
    {
      if (state == DONE)
      {
        LOG_TRACE_FMT("Entering new message");
        state = IN_MESSAGE;
        body_buf.clear();
        headers.clear();
      }
      else
      {
        throw std::runtime_error(
          "Entering new message when previous message isn't complete");
      }
    }
 
    virtual void handle_completed_message() = 0;
 
    void end_message()
    {
      if (state == IN_MESSAGE)
      {
        LOG_TRACE_FMT("Done with message");
        handle_completed_message();
        state = DONE;
      }
      else
      {
        throw std::runtime_error("Ending message, but not in a message");
      }
    }
 
    void header_field(const char* at, size_t length)
    {
      if (!partial_parsed_header.second.empty())
      {
        complete_header();
      }
 
      const auto max_headers_count = configuration.max_headers_count.value_or(
        ccf::http::default_max_headers_count);
      if (headers.size() >= max_headers_count)
      {
        throw RequestHeaderTooLargeException(fmt::format(
          "Too many headers (max number allowed: {})", max_headers_count));
      }
 
      // HTTP headers are stored lowercase as it is easier to verify HTTP
      // signatures later on
      auto f = std::string(at, length);
      ccf::nonstd::to_lower(f);
      auto& partial_header_key = partial_parsed_header.first;
      partial_header_key.append(f);
 
      auto const& max_header_size = configuration.max_header_size.value_or(
        ccf::http::default_max_header_size);
      if (partial_header_key.size() > max_header_size)
      {
        throw RequestHeaderTooLargeException(fmt::format(
          "Header key for '{}' is too large (max size allowed: {})",
          partial_parsed_header.first,
          max_header_size));
      }
    }
 
    void header_value(const char* at, size_t length)
    {
      auto& partial_header_value = partial_parsed_header.second;
      partial_header_value.append(at, length);
      auto const& max_header_size = configuration.max_header_size.value_or(
        ccf::http::default_max_header_size);
      if (partial_header_value.size() > max_header_size)
      {
        throw RequestHeaderTooLargeException(fmt::format(
          "Header value for '{}' is too large (max size allowed: {})",
          partial_parsed_header.first,
          max_header_size));
      }
    }
 
    void headers_complete()
    {
      complete_header();
    }
  };
 
  static int on_msg_begin(llhttp_t* parser)
  {
    auto* p = reinterpret_cast<Parser*>(parser->data);
    p->new_message();
    return HPE_OK;
  }
 
  static int on_header_field(llhttp_t* parser, const char* at, size_t length)
  {
    auto* p = reinterpret_cast<Parser*>(parser->data);
    p->header_field(at, length);
    return HPE_OK;
  }
 
  static int on_header_value(llhttp_t* parser, const char* at, size_t length)
  {
    auto* p = reinterpret_cast<Parser*>(parser->data);
    p->header_value(at, length);
    return HPE_OK;
  }
 
  static int on_headers_complete(llhttp_t* parser)
  {
    auto* p = reinterpret_cast<Parser*>(parser->data);
    p->headers_complete();
    return HPE_OK;
  }
 
  static int on_body(llhttp_t* parser, const char* at, size_t length)
  {
    auto* p = reinterpret_cast<Parser*>(parser->data);
    p->append_body(at, length);
    return HPE_OK;
  }
 
  static int on_msg_end(llhttp_t* parser)
  {
    auto* p = reinterpret_cast<Parser*>(parser->data);
    p->end_message();
    return HPE_OK;
  }
 
  // Request-specific
  class RequestParser : public Parser
  {
  private:
    RequestProcessor& proc;
 
    std::string url;
 
  public:
    ~RequestParser() override = default;
 
    RequestParser(
      RequestProcessor& proc_,
      const ccf::http::ParserConfiguration& config =
        ccf::http::ParserConfiguration{}) :
      Parser(HTTP_REQUEST, config),
      proc(proc_)
    {
      settings.on_url = on_url;
    }
 
    void append_url(const char* at, size_t length)
    {
      url.append(at, length);
    }
 
    void new_message() override
    {
      Parser::new_message();
      url.clear();
    }
 
    void handle_completed_message() override
    {
      if (url.empty())
      {
        proc.handle_request(
          llhttp_method(parser.method),
          {},
          std::move(headers),
          std::move(body_buf));
      }
      else
      {
        proc.handle_request(
          llhttp_method(parser.method),
          url,
          std::move(headers),
          std::move(body_buf));
      }
    }
  };
 
  static int on_url(llhttp_t* parser, const char* at, size_t length)
  {
    auto* p = reinterpret_cast<RequestParser*>(parser->data);
    p->append_url(at, length);
    return HPE_OK;
  }
 
  // Response-specific
  class ResponseParser : public Parser
  {
  private:
    ResponseProcessor& proc;
 
  public:
    ~ResponseParser() override = default;
 
    ResponseParser(ResponseProcessor& proc_) :
      Parser(HTTP_RESPONSE, ccf::http::ParserConfiguration{}),
      proc(proc_)
    {}
 
    void handle_completed_message() override
    {
      proc.handle_response(
        ccf::http_status(parser.status_code),
        std::move(headers),
        std::move(body_buf));
    }
  };
}