http/routing.hpp

// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: Copyright OpenBMC Authors
#pragma once

#include "async_resp.hpp"
#include "dbus_privileges.hpp"
#include "http_request.hpp"
#include "http_response.hpp"
#include "logging.hpp"
#include "routing/baserule.hpp"
#include "routing/dynamicrule.hpp"
#include "routing/taggedrule.hpp"
#include "routing/trie.hpp"
#include "verb.hpp"

#include <boost/beast/http/field.hpp>
#include <boost/beast/http/status.hpp>

#include <algorithm>
#include <array>
#include <cerrno>
#include <cstdint>
#include <cstdlib>
#include <format>
#include <functional>
#include <memory>
#include <optional>
#include <stdexcept>
#include <string>
#include <string_view>
#include <tuple>
#include <utility>
#include <vector>

namespace crow
{

class Router
{
  public:
    Router() = default;

    DynamicRule& newRuleDynamic(const std::string& rule)
    {
        std::unique_ptr<DynamicRule> ruleObject =
            std::make_unique<DynamicRule>(rule);
        DynamicRule* ptr = ruleObject.get();
        allRules.emplace_back(std::move(ruleObject));

        return *ptr;
    }

    template <uint64_t NumArgs>
    auto& newRuleTagged(const std::string& rule)
    {
        if constexpr (NumArgs == 0)
        {
            using RuleT = TaggedRule<>;
            std::unique_ptr<RuleT> ruleObject = std::make_unique<RuleT>(rule);
            RuleT* ptr = ruleObject.get();
            allRules.emplace_back(std::move(ruleObject));
            return *ptr;
        }
        else if constexpr (NumArgs == 1)
        {
            using RuleT = TaggedRule<std::string>;
            std::unique_ptr<RuleT> ruleObject = std::make_unique<RuleT>(rule);
            RuleT* ptr = ruleObject.get();
            allRules.emplace_back(std::move(ruleObject));
            return *ptr;
        }
        else if constexpr (NumArgs == 2)
        {
            using RuleT = TaggedRule<std::string, std::string>;
            std::unique_ptr<RuleT> ruleObject = std::make_unique<RuleT>(rule);
            RuleT* ptr = ruleObject.get();
            allRules.emplace_back(std::move(ruleObject));
            return *ptr;
        }
        else if constexpr (NumArgs == 3)
        {
            using RuleT = TaggedRule<std::string, std::string, std::string>;
            std::unique_ptr<RuleT> ruleObject = std::make_unique<RuleT>(rule);
            RuleT* ptr = ruleObject.get();
            allRules.emplace_back(std::move(ruleObject));
            return *ptr;
        }
        else if constexpr (NumArgs == 4)
        {
            using RuleT =
                TaggedRule<std::string, std::string, std::string, std::string>;
            std::unique_ptr<RuleT> ruleObject = std::make_unique<RuleT>(rule);
            RuleT* ptr = ruleObject.get();
            allRules.emplace_back(std::move(ruleObject));
            return *ptr;
        }
        else
        {
            using RuleT = TaggedRule<std::string, std::string, std::string,
                                     std::string, std::string>;
            std::unique_ptr<RuleT> ruleObject = std::make_unique<RuleT>(rule);
            RuleT* ptr = ruleObject.get();
            allRules.emplace_back(std::move(ruleObject));
            return *ptr;
        }
        static_assert(NumArgs <= 5, "Max number of args supported is 5");
    }

    struct PerMethod
    {
        std::vector<BaseRule*> rules;
        Trie<crow::Node> trie;
        // rule index 0 has special meaning; preallocate it to avoid
        // duplication.
        PerMethod() : rules(1) {}

        void internalAdd(std::string_view rule, BaseRule* ruleObject)
        {
            rules.emplace_back(ruleObject);
            trie.add(rule, static_cast<unsigned>(rules.size() - 1U));
            // directory case:
            //   request to `/about' url matches `/about/' rule
            if (rule.size() > 2 && rule.back() == '/')
            {
                trie.add(rule.substr(0, rule.size() - 1),
                         static_cast<unsigned>(rules.size() - 1));
            }
        }
    };

    void internalAddRuleObject(const std::string& rule, BaseRule* ruleObject)
    {
        if (ruleObject == nullptr)
        {
            return;
        }
        for (size_t method = 0; method <= maxVerbIndex; method++)
        {
            size_t methodBit = 1 << method;
            if ((ruleObject->methodsBitfield & methodBit) > 0U)
            {
                perMethods[method].internalAdd(rule, ruleObject);
            }
        }

        if (ruleObject->isNotFound)
        {
            notFoundRoutes.internalAdd(rule, ruleObject);
        }

        if (ruleObject->isMethodNotAllowed)
        {
            methodNotAllowedRoutes.internalAdd(rule, ruleObject);
        }

        if (ruleObject->isUpgrade)
        {
            upgradeRoutes.internalAdd(rule, ruleObject);
        }
    }

    void validate()
    {
        for (std::unique_ptr<BaseRule>& rule : allRules)
        {
            if (rule)
            {
                std::unique_ptr<BaseRule> upgraded = rule->upgrade();
                if (upgraded)
                {
                    rule = std::move(upgraded);
                }
                rule->validate();
                internalAddRuleObject(rule->rule, rule.get());
            }
        }
        for (PerMethod& perMethod : perMethods)
        {
            perMethod.trie.validate();
        }
    }

    struct FindRoute
    {
        BaseRule* rule = nullptr;
        std::vector<std::string> params;
    };

    struct FindRouteResponse
    {
        std::string allowHeader;
        FindRoute route;
    };

    static FindRoute findRouteByPerMethod(std::string_view url,
                                          const PerMethod& perMethod)
    {
        FindRoute route;

        Trie<crow::Node>::FindResult found = perMethod.trie.find(url);
        if (found.ruleIndex >= perMethod.rules.size())
        {
            throw std::runtime_error("Trie internal structure corrupted!");
        }
        // Found a 404 route, switch that in
        if (found.ruleIndex != 0U)
        {
            route.rule = perMethod.rules[found.ruleIndex];
            route.params = std::move(found.params);
        }
        return route;
    }

    FindRouteResponse findRoute(const Request& req) const
    {
        FindRouteResponse findRoute;

        // Check to see if this url exists at any verb
        for (size_t perMethodIndex = 0; perMethodIndex <= maxVerbIndex;
             perMethodIndex++)
        {
            // Make sure it's safe to deference the array at that index
            static_assert(
                maxVerbIndex < std::tuple_size_v<decltype(perMethods)>);
            FindRoute route = findRouteByPerMethod(req.url().encoded_path(),
                                                   perMethods[perMethodIndex]);
            if (route.rule == nullptr)
            {
                continue;
            }
            if (!findRoute.allowHeader.empty())
            {
                findRoute.allowHeader += ", ";
            }
            HttpVerb thisVerb = static_cast<HttpVerb>(perMethodIndex);
            findRoute.allowHeader += httpVerbToString(thisVerb);
        }

        std::optional<HttpVerb> verb = httpVerbFromBoost(req.method());
        if (!verb)
        {
            return findRoute;
        }
        size_t reqMethodIndex = static_cast<size_t>(*verb);
        if (reqMethodIndex >= perMethods.size())
        {
            return findRoute;
        }

        FindRoute route = findRouteByPerMethod(req.url().encoded_path(),
                                               perMethods[reqMethodIndex]);
        if (route.rule != nullptr)
        {
            findRoute.route = route;
        }

        return findRoute;
    }

    template <typename Adaptor>
    void handleUpgrade(const std::shared_ptr<Request>& req,
                       const std::shared_ptr<bmcweb::AsyncResp>& asyncResp,
                       Adaptor&& adaptor)
    {
        PerMethod& perMethod = upgradeRoutes;
        Trie<crow::Node>& trie = perMethod.trie;
        std::vector<BaseRule*>& rules = perMethod.rules;

        Trie<crow::Node>::FindResult found =
            trie.find(req->url().encoded_path());
        unsigned ruleIndex = found.ruleIndex;
        if (ruleIndex == 0U)
        {
            BMCWEB_LOG_DEBUG("Cannot match rules {}",
                             req->url().encoded_path());
            asyncResp->res.result(boost::beast::http::status::not_found);
            return;
        }

        if (ruleIndex >= rules.size())
        {
            throw std::runtime_error("Trie internal structure corrupted!");
        }

        BaseRule& rule = *rules[ruleIndex];

        BMCWEB_LOG_DEBUG("Matched rule (upgrade) '{}'", rule.rule);

        // TODO(ed) This should be able to use std::bind_front, but it doesn't
        // appear to work with the std::move on adaptor.
        validatePrivilege(
            req, asyncResp, rule,
            [req, &rule, asyncResp,
             adaptor = std::forward<Adaptor>(adaptor)]() mutable {
                rule.handleUpgrade(*req, asyncResp, std::move(adaptor));
            });
    }

    void handle(const std::shared_ptr<Request>& req,
                const std::shared_ptr<bmcweb::AsyncResp>& asyncResp)
    {
        FindRouteResponse foundRoute = findRoute(*req);

        if (foundRoute.route.rule == nullptr)
        {
            // Couldn't find a normal route with any verb, try looking for a 404
            // route
            if (foundRoute.allowHeader.empty())
            {
                foundRoute.route = findRouteByPerMethod(
                    req->url().encoded_path(), notFoundRoutes);
            }
            else
            {
                // See if we have a method not allowed (405) handler
                foundRoute.route = findRouteByPerMethod(
                    req->url().encoded_path(), methodNotAllowedRoutes);
            }
        }

        // Fill in the allow header if it's valid
        if (!foundRoute.allowHeader.empty())
        {
            asyncResp->res.addHeader(boost::beast::http::field::allow,
                                     foundRoute.allowHeader);
        }

        // If we couldn't find a real route or a 404 route, return a generic
        // response
        if (foundRoute.route.rule == nullptr)
        {
            if (foundRoute.allowHeader.empty())
            {
                asyncResp->res.result(boost::beast::http::status::not_found);
            }
            else
            {
                asyncResp->res.result(
                    boost::beast::http::status::method_not_allowed);
            }
            return;
        }

        BaseRule& rule = *foundRoute.route.rule;
        std::vector<std::string> params = std::move(foundRoute.route.params);

        BMCWEB_LOG_DEBUG("Matched rule '{}' {} / {}", rule.rule,
                         req->methodString(), rule.getMethods());

        if (req->session == nullptr)
        {
            rule.handle(*req, asyncResp, params);
            return;
        }
        validatePrivilege(
            req, asyncResp, rule,
            [req, asyncResp, &rule, params = std::move(params)]() {
                rule.handle(*req, asyncResp, params);
            });
    }

    void debugPrint()
    {
        for (size_t i = 0; i < perMethods.size(); i++)
        {
            BMCWEB_LOG_DEBUG("{}", httpVerbToString(static_cast<HttpVerb>(i)));
            perMethods[i].trie.debugPrint();
        }
    }

    std::vector<const std::string*> getRoutes(const std::string& parent)
    {
        std::vector<const std::string*> ret;

        for (const PerMethod& pm : perMethods)
        {
            std::vector<unsigned> x;
            pm.trie.findRouteIndexes(parent, x);
            for (unsigned index : x)
            {
                ret.push_back(&pm.rules[index]->rule);
            }
        }
        return ret;
    }

  private:
    std::array<PerMethod, static_cast<size_t>(HttpVerb::Max)> perMethods;

    PerMethod notFoundRoutes;
    PerMethod upgradeRoutes;
    PerMethod methodNotAllowedRoutes;

    std::vector<std::unique_ptr<BaseRule>> allRules;
};
} // namespace crow