Parser.cpp

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/*
 * SNode.C - A Slim Toolkit for Network Communication
 * Copyright (C) Volker Christian <me@vchrist.at>
 *               2020, 2021, 2022, 2023, 2024, 2025
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
 
/*
 * MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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 */
 
#include "web/http/Parser.h"
 
#include "core/socket/stream/SocketContext.h"
#include "web/http/decoder/Chunked.h"
#include "web/http/decoder/HTTP10Response.h"
#include "web/http/decoder/Identity.h"
 
#ifndef DOXYGEN_SHOULD_SKIP_THIS
 
#include "web/http/http_utils.h"
 
#include <charconv>
#include <limits>
#include <system_error>
#include <tuple>
#include <utility>
 
#endif /* DOXYGEN_SHOULD_SKIP_THIS */
 
namespace web::http {
 
    static bool parseContentLengthStrict(const std::string& s, std::size_t& out) {
        bool success = false;
 
        unsigned long long value = 0;
 
        if (!s.empty()) {
            const char* first = s.data();
            const char* last = s.data() + s.size();
 
            const auto [ptr, ec] = std::from_chars(first, last, value, 10);
 
            if (ec == std::errc{} && ptr == last && value <= static_cast<unsigned long long>(std::numeric_limits<std::size_t>::max())) {
                out = static_cast<std::size_t>(value);
                success = true;
            }
        }
 
        return success;
    }
 
    static bool transferEncodingHasChunked(CiStringMap<std::string>& headers) {
        bool hasChunked = false;
 
        if (headers.contains("Transfer-Encoding")) {
            const std::string& encoding = headers["Transfer-Encoding"];
            hasChunked = web::http::ciContains(encoding, "chunked");
        }
 
        return hasChunked;
    }
 
    // HTTP/1.0 and HTTP/1.1
    const std::regex Parser::httpVersionRegex("^HTTP/([1])[.]([0-1])$");
 
    Parser::Parser(core::socket::stream::SocketContext* socketContext, const enum Parser::HTTPCompliance& compliance)
        : hTTPCompliance(compliance)
        , socketContext(socketContext)
        , headerDecoder(socketContext)
        , trailerDecoder(socketContext) {
    }
 
    Parser::~Parser() {
        reset();
    }
 
    void Parser::reset() {
        parserState = ParserState::BEGIN;
        headers.clear();
        content.clear();
        httpMinor = 0;
        httpMajor = 0;
        line.clear();
        contentLength = 0;
        contentLengthRead = 0;
 
        for (const ContentDecoder* contentDecoder : decoderQueue) {
            delete contentDecoder;
        }
        decoderQueue.clear();
 
        trailerFieldsExpected.clear();
    }
 
    std::size_t Parser::parse() {
        std::size_t ret = 0;
        std::size_t consumed = 0;
 
        do {
            switch (parserState) {
                case ParserState::BEGIN:
                    begin();
                    parserState = ParserState::FIRSTLINE;
                    [[fallthrough]];
                case ParserState::FIRSTLINE:
                    ret = readStartLine();
                    break;
                case ParserState::HEADER:
                    ret = readHeader();
                    break;
                case ParserState::BODY:
                    ret = readContent();
                    break;
                case ParserState::TRAILER:
                    ret = readTrailer();
                    break;
                case ParserState::ERROR:
                    break;
            }
            consumed += ret;
        } while (ret > 0 && parserState != ParserState::BEGIN && parserState != ParserState::ERROR);
 
        return consumed;
    }
 
    std::size_t Parser::readStartLine() {
        std::size_t consumed = 0;
        std::size_t ret = 0;
 
        do {
            char ch = 0;
            ret = socketContext->readFromPeer(&ch, 1);
 
            if (ret > 0) {
                consumed += ret;
                if (ch == '\r' || ch == '\n') {
                    if (ch == '\n') {
                        parseStartLine(line);
                        line.clear();
                    }
                } else {
                    line += ch;
                }
            }
        } while (ret > 0 && parserState == ParserState::FIRSTLINE);
 
        return consumed;
    }
 
    std::size_t Parser::readHeader() {
        const std::size_t consumed = headerDecoder.read();
 
        if (headerDecoder.isError()) {
            parseError(headerDecoder.getErrorCode(), headerDecoder.getErrorReason());
        } else if (headerDecoder.isComplete()) {
            headers = std::move(headerDecoder.getHeader());
            analyzeHeader();
        }
 
        return consumed;
    }
 
    void Parser::analyzeHeader() {
        bool success = true;
 
        // Determine message framing.
        // RFC 9112 §6.3: Transfer-Encoding (chunked) overrides Content-Length.
        const bool hasChunked = transferEncodingHasChunked(headers);
 
        if (hasChunked) {
            transferEncoding = TransferEncoding::Chunked;
            decoderQueue.emplace_back(new web::http::decoder::Chunked(socketContext));
 
            if (headers.contains("Trailer")) {
                std::string trailers = headers["Trailer"];
 
                while (!trailers.empty()) {
                    std::string trailerField;
                    std::tie(trailerField, trailers) = httputils::str_split(trailers, ',');
                    httputils::str_trimm(trailerField);
                    trailerFieldsExpected.insert(trailerField);
                    trailerField.clear();
                }
                trailerDecoder.setFieldsExpected(trailerFieldsExpected);
            }
        } else if (headers.contains("Content-Length")) {
            std::size_t length = 0;
 
            if (!parseContentLengthStrict(headers["Content-Length"], length)) {
                parseError(400, "Invalid Content-Length");
                success = false;
            } else {
                contentLength = length;
                decoderQueue.emplace_back(new web::http::decoder::Identity(socketContext, contentLength));
            }
        }
 
        if (success) {
            // Transfer-Encoding (other than chunked) is currently not implemented, but we keep the
            // existing behavior of not altering the decoder queue here.
            if (headers.contains("Transfer-Encoding")) {
                const std::string& encoding = headers["Transfer-Encoding"];
                if (web::http::ciContains(encoding, "compressed")) {
                    //  decoderQueue.emplace_back(new web::http::decoder::Compress(socketContext));
                }
                if (web::http::ciContains(encoding, "deflate")) {
                    //  decoderQueue.emplace_back(new web::http::decoder::Deflate(socketContext));
                }
                if (web::http::ciContains(encoding, "gzip")) {
                    //  decoderQueue.emplace_back(new web::http::decoder::GZip(socketContext));
                }
            }
 
            if (decoderQueue.empty()) {
                decoderQueue.emplace_back(new web::http::decoder::HTTP10Response(socketContext));
            }
 
            if (headers.contains("Content-Encoding")) {
                const std::string& encoding = headers["Content-Encoding"];
 
                if (web::http::ciContains(encoding, "compressed")) {
                    //  decoderQueue.emplace_back(new web::http::decoder::Compress(socketContext));
                }
                if (web::http::ciContains(encoding, "deflate")) {
                    //  decoderQueue.emplace_back(new web::http::decoder::Deflate(socketContext));
                }
                if (web::http::ciContains(encoding, "gzip")) {
                    //  decoderQueue.emplace_back(new web::http::decoder::GZip(socketContext));
                }
                if (web::http::ciContains(encoding, "br")) {
                    //  decoderQueue.emplace_back(new web::http::decoder::Br(socketContext));
                }
            }
        }
    }
 
    std::size_t Parser::readContent() {
        ContentDecoder* contentDecoder = decoderQueue.front();
 
        const std::size_t consumed = contentDecoder->read();
 
        if (contentDecoder->isComplete()) {
            contentDecoder = decoderQueue.back();
 
            std::vector<char> chunk = contentDecoder->getContent();
            content.insert(content.end(), chunk.begin(), chunk.end());
 
            if (transferEncoding == TransferEncoding::Chunked && headers.contains("Trailer")) {
                parserState = Parser::ParserState::TRAILER;
            } else {
                parsingFinished();
            }
        } else if (contentDecoder->isError()) {
            parseError(501, "Wrong content encoding");
        }
 
        return consumed;
    }
 
    std::size_t Parser::readTrailer() {
        const std::size_t consumed = trailerDecoder.read();
 
        if (trailerDecoder.isError()) {
            parseError(trailerDecoder.getErrorCode(), trailerDecoder.getErrorReason());
        } else if (trailerDecoder.isComplete()) {
            web::http::CiStringMap<std::string>&& trailer = trailerDecoder.getHeader();
            headers.insert(trailer.begin(), trailer.end());
            parsingFinished();
        }
 
        return consumed;
    }
 
    enum Parser::HTTPCompliance operator|(const enum Parser::HTTPCompliance& c1, const enum Parser::HTTPCompliance& c2) {
        return static_cast<enum Parser::HTTPCompliance>(static_cast<unsigned short>(c1) | static_cast<unsigned short>(c2));
    }
 
    enum Parser::HTTPCompliance operator&(const enum Parser::HTTPCompliance& c1, const enum Parser::HTTPCompliance& c2) {
        return static_cast<enum Parser::HTTPCompliance>(static_cast<unsigned short>(c1) & static_cast<unsigned short>(c2));
    }
 
} // namespace web::http