// Copyright (c) 2015-2022 The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <httprpc.h>

#include <common/args.h>

#include <crypto/hmac_sha256.h>

#include <httpserver.h>

#include <logging.h>

#include <netaddress.h>

#include <rpc/protocol.h>

#include <rpc/server.h>

#include <util/fs.h>

#include <util/fs_helpers.h>

#include <util/strencodings.h>

#include <util/string.h>

#include <walletinitinterface.h>

#include <algorithm>

#include <iterator>

#include <map>

#include <memory>

#include <optional>

#include <set>

#include <string>

#include <vector>

using util::SplitString;

using util::TrimStringView;

/** WWW-Authenticate to present with 401 Unauthorized response */

static const char* WWW_AUTH_HEADER_DATA = "Basic realm=\"jsonrpc\"";

/* List of -rpcauth values */

static std::vector<std::vector<std::string>> g_rpcauth;

/* RPC Auth Whitelist */

static std::map<std::string, std::set<std::string>> g_rpc_whitelist;

static bool g_rpc_whitelist_default = false;

static void JSONErrorReply(HTTPRequest* req, UniValue objError, const JSONRPCRequest& jreq)

{

    // Sending HTTP errors is a legacy JSON-RPC behavior.

    Assume(jreq.m_json_version != JSONRPCVersion::V2);

    // Send error reply from json-rpc error object

    int nStatus = HTTP_INTERNAL_SERVER_ERROR;

    int code = objError.find_value("code").getInt<int>();

    if (code == RPC_INVALID_REQUEST)

        nStatus = HTTP_BAD_REQUEST;

    else if (code == RPC_METHOD_NOT_FOUND)

        nStatus = HTTP_NOT_FOUND;

    std::string strReply = JSONRPCReplyObj(NullUniValue, std::move(objError), jreq.id, jreq.m_json_version).write() + "\n";

    req->WriteHeader("Content-Type", "application/json");

    req->WriteReply(nStatus, strReply);

}

//This function checks username and password against -rpcauth

//entries from config file.

static bool CheckUserAuthorized(std::string_view user, std::string_view pass)

{

    for (const auto& fields : g_rpcauth) {

        if (!TimingResistantEqual(std::string_view(fields[0]), user)) {

            continue;

        }

        const std::string& salt = fields[1];

        const std::string& hash = fields[2];

        std::array<unsigned char, CHMAC_SHA256::OUTPUT_SIZE> out;

        CHMAC_SHA256(UCharCast(salt.data()), salt.size()).Write(UCharCast(pass.data()), pass.size()).Finalize(out.data());

        std::string hash_from_pass = HexStr(out);

        if (TimingResistantEqual(hash_from_pass, hash)) {

            return true;

        }

    }

    return false;

}

static bool RPCAuthorized(const std::string& strAuth, std::string& strAuthUsernameOut)

{

    if (!strAuth.starts_with("Basic "))

        return false;

    std::string_view strUserPass64 = TrimStringView(std::string_view{strAuth}.substr(6));

    auto userpass_data = DecodeBase64(strUserPass64);

    std::string strUserPass;

    if (!userpass_data) return false;

    strUserPass.assign(userpass_data->begin(), userpass_data->end());

    size_t colon_pos = strUserPass.find(':');

    if (colon_pos == std::string::npos) {

        return false; // Invalid basic auth.

    }

    std::string user = strUserPass.substr(0, colon_pos);

    std::string pass = strUserPass.substr(colon_pos + 1);

    strAuthUsernameOut = user;

    return CheckUserAuthorized(user, pass);

}

static bool HTTPReq_JSONRPC(const std::any& context, HTTPRequest* req)

{

    // JSONRPC handles only POST

    if (req->GetRequestMethod() != HTTPRequest::POST) {

        req->WriteReply(HTTP_BAD_METHOD, "JSONRPC server handles only POST requests");

        return false;

    }

    // Check authorization

    std::pair<bool, std::string> authHeader = req->GetHeader("authorization");

    if (!authHeader.first) {

        req->WriteHeader("WWW-Authenticate", WWW_AUTH_HEADER_DATA);

        req->WriteReply(HTTP_UNAUTHORIZED);

        return false;

    }

    JSONRPCRequest jreq;

    jreq.context = context;

    jreq.peerAddr = req->GetPeer().ToStringAddrPort();

    if (!RPCAuthorized(authHeader.second, jreq.authUser)) {

        LogPrintf("ThreadRPCServer incorrect password attempt from %s\n", jreq.peerAddr);

        /* Deter brute-forcing

           If this results in a DoS the user really

           shouldn't have their RPC port exposed. */

        UninterruptibleSleep(std::chrono::milliseconds{250});

        req->WriteHeader("WWW-Authenticate", WWW_AUTH_HEADER_DATA);

        req->WriteReply(HTTP_UNAUTHORIZED);

        return false;

    }

    try {

        // Parse request

        UniValue valRequest;

        if (!valRequest.read(req->ReadBody()))

            throw JSONRPCError(RPC_PARSE_ERROR, "Parse error");

        // Set the URI

        jreq.URI = req->GetURI();

        UniValue reply;

        bool user_has_whitelist = g_rpc_whitelist.count(jreq.authUser);

        if (!user_has_whitelist && g_rpc_whitelist_default) {

            LogPrintf("RPC User %s not allowed to call any methods\n", jreq.authUser);

            req->WriteReply(HTTP_FORBIDDEN);

            return false;

        // singleton request

        } else if (valRequest.isObject()) {

            jreq.parse(valRequest);

            if (user_has_whitelist && !g_rpc_whitelist[jreq.authUser].count(jreq.strMethod)) {

                LogPrintf("RPC User %s not allowed to call method %s\n", jreq.authUser, jreq.strMethod);

                req->WriteReply(HTTP_FORBIDDEN);

                return false;

            }

            // Legacy 1.0/1.1 behavior is for failed requests to throw

            // exceptions which return HTTP errors and RPC errors to the client.

            // 2.0 behavior is to catch exceptions and return HTTP success with

            // RPC errors, as long as there is not an actual HTTP server error.

            const bool catch_errors{jreq.m_json_version == JSONRPCVersion::V2};

            reply = JSONRPCExec(jreq, catch_errors);

            if (jreq.IsNotification()) {

                // Even though we do execute notifications, we do not respond to them

                req->WriteReply(HTTP_NO_CONTENT);

                return true;

            }

        // array of requests

        } else if (valRequest.isArray()) {

            // Check authorization for each request's method

            if (user_has_whitelist) {

                for (unsigned int reqIdx = 0; reqIdx < valRequest.size(); reqIdx++) {

                    if (!valRequest[reqIdx].isObject()) {

                        throw JSONRPCError(RPC_INVALID_REQUEST, "Invalid Request object");

                    } else {

                        const UniValue& request = valRequest[reqIdx].get_obj();

                        // Parse method

                        std::string strMethod = request.find_value("method").get_str();

                        if (!g_rpc_whitelist[jreq.authUser].count(strMethod)) {

                            LogPrintf("RPC User %s not allowed to call method %s\n", jreq.authUser, strMethod);

                            req->WriteReply(HTTP_FORBIDDEN);

                            return false;

                        }

                    }

                }

            }

            // Execute each request

            reply = UniValue::VARR;

            for (size_t i{0}; i < valRequest.size(); ++i) {

                // Batches never throw HTTP errors, they are always just included

                // in "HTTP OK" responses. Notifications never get any response.

                UniValue response;

                try {

                    jreq.parse(valRequest[i]);

                    response = JSONRPCExec(jreq, /*catch_errors=*/true);

                } catch (UniValue& e) {

                    response = JSONRPCReplyObj(NullUniValue, std::move(e), jreq.id, jreq.m_json_version);

                } catch (const std::exception& e) {

                    response = JSONRPCReplyObj(NullUniValue, JSONRPCError(RPC_PARSE_ERROR, e.what()), jreq.id, jreq.m_json_version);

                }

                if (!jreq.IsNotification()) {

                    reply.push_back(std::move(response));

                }

            }

            // Return no response for an all-notification batch, but only if the

            // batch request is non-empty. Technically according to the JSON-RPC

            // 2.0 spec, an empty batch request should also return no response,

            // However, if the batch request is empty, it means the request did

            // not contain any JSON-RPC version numbers, so returning an empty

            // response could break backwards compatibility with old RPC clients

            // relying on previous behavior. Return an empty array instead of an

            // empty response in this case to favor being backwards compatible

            // over complying with the JSON-RPC 2.0 spec in this case.

            if (reply.size() == 0 && valRequest.size() > 0) {

                req->WriteReply(HTTP_NO_CONTENT);

                return true;

            }

        }

        else

            throw JSONRPCError(RPC_PARSE_ERROR, "Top-level object parse error");

        req->WriteHeader("Content-Type", "application/json");

        req->WriteReply(HTTP_OK, reply.write() + "\n");

    } catch (UniValue& e) {

        JSONErrorReply(req, std::move(e), jreq);

        return false;

    } catch (const std::exception& e) {

        JSONErrorReply(req, JSONRPCError(RPC_PARSE_ERROR, e.what()), jreq);

        return false;

    }

    return true;

}

static bool InitRPCAuthentication()

{

    std::string user;

    std::string pass;

    if (gArgs.GetArg("-rpcpassword", "") == "")

    {

        std::optional<fs::perms> cookie_perms{std::nullopt};

        auto cookie_perms_arg{gArgs.GetArg("-rpccookieperms")};

        if (cookie_perms_arg) {

            auto perm_opt = InterpretPermString(*cookie_perms_arg);

            if (!perm_opt) {

                LogError("Invalid -rpccookieperms=%s; must be one of 'owner', 'group', or 'all'.", *cookie_perms_arg);

                return false;

            }

            cookie_perms = *perm_opt;

        }

        switch (GenerateAuthCookie(cookie_perms, user, pass)) {

        case GenerateAuthCookieResult::ERR:

            return false;

        case GenerateAuthCookieResult::DISABLED:

            LogInfo("RPC authentication cookie file generation is disabled.");

            break;

        case GenerateAuthCookieResult::OK:

            LogInfo("Using random cookie authentication.");

            break;

        }

    } else {

        LogInfo("Using rpcuser/rpcpassword authentication.");

        LogWarning("The use of rpcuser/rpcpassword is less secure, because credentials are configured in plain text. It is recommended that locally-run instances switch to cookie-based auth, or otherwise to use hashed rpcauth credentials. See share/rpcauth in the source directory for more information.");

        user = gArgs.GetArg("-rpcuser", "");

        pass = gArgs.GetArg("-rpcpassword", "");

    }

    // If there is a plaintext credential, hash it with a random salt before storage.

    if (!user.empty() || !pass.empty()) {

        // Generate a random 16 byte hex salt.

        std::array<unsigned char, 16> raw_salt;

        GetStrongRandBytes(raw_salt);

        std::string salt = HexStr(raw_salt);

        // Compute HMAC.

        std::array<unsigned char, CHMAC_SHA256::OUTPUT_SIZE> out;

        CHMAC_SHA256(UCharCast(salt.data()), salt.size()).Write(UCharCast(pass.data()), pass.size()).Finalize(out.data());

        std::string hash = HexStr(out);

        g_rpcauth.push_back({user, salt, hash});

    }

    if (!gArgs.GetArgs("-rpcauth").empty()) {

        LogInfo("Using rpcauth authentication.\n");

        for (const std::string& rpcauth : gArgs.GetArgs("-rpcauth")) {

            std::vector<std::string> fields{SplitString(rpcauth, ':')};

            const std::vector<std::string> salt_hmac{SplitString(fields.back(), '$')};

            if (fields.size() == 2 && salt_hmac.size() == 2) {

                fields.pop_back();

                fields.insert(fields.end(), salt_hmac.begin(), salt_hmac.end());

                g_rpcauth.push_back(fields);

            } else {

                LogPrintf("Invalid -rpcauth argument.\n");

                return false;

            }

        }

    }

    g_rpc_whitelist_default = gArgs.GetBoolArg("-rpcwhitelistdefault", !gArgs.GetArgs("-rpcwhitelist").empty());

    for (const std::string& strRPCWhitelist : gArgs.GetArgs("-rpcwhitelist")) {

        auto pos = strRPCWhitelist.find(':');

        std::string strUser = strRPCWhitelist.substr(0, pos);

        bool intersect = g_rpc_whitelist.count(strUser);

        std::set<std::string>& whitelist = g_rpc_whitelist[strUser];

        if (pos != std::string::npos) {

            std::string strWhitelist = strRPCWhitelist.substr(pos + 1);

            std::vector<std::string> whitelist_split = SplitString(strWhitelist, ", ");

            std::set<std::string> new_whitelist{

                std::make_move_iterator(whitelist_split.begin()),

                std::make_move_iterator(whitelist_split.end())};

            if (intersect) {

                std::set<std::string> tmp_whitelist;

                std::set_intersection(new_whitelist.begin(), new_whitelist.end(),

                       whitelist.begin(), whitelist.end(), std::inserter(tmp_whitelist, tmp_whitelist.end()));

                new_whitelist = std::move(tmp_whitelist);

            }

            whitelist = std::move(new_whitelist);

        }

    }

    return true;

}

bool StartHTTPRPC(const std::any& context)

{

    LogDebug(BCLog::RPC, "Starting HTTP RPC server\n");

    if (!InitRPCAuthentication())

        return false;

    auto handle_rpc = [context](HTTPRequest* req, const std::string&) { return HTTPReq_JSONRPC(context, req); };

    RegisterHTTPHandler("/", true, handle_rpc);

    if (g_wallet_init_interface.HasWalletSupport()) {

        RegisterHTTPHandler("/wallet/", false, handle_rpc);

    }

    struct event_base* eventBase = EventBase();

    assert(eventBase);

    return true;

}

void InterruptHTTPRPC()

{

    LogDebug(BCLog::RPC, "Interrupting HTTP RPC server\n");

}

void StopHTTPRPC()

{

    LogDebug(BCLog::RPC, "Stopping HTTP RPC server\n");

    UnregisterHTTPHandler("/", true);

    if (g_wallet_init_interface.HasWalletSupport()) {

        UnregisterHTTPHandler("/wallet/", false);

    }

}