diff --git a/packages/hydrooj/src/error.ts b/packages/hydrooj/src/error.ts
index 96945e63b5..aa63a519a7 100644
--- a/packages/hydrooj/src/error.ts
+++ b/packages/hydrooj/src/error.ts
@@ -109,6 +109,7 @@ export const ProblemAlreadyExistError = Err('ProblemAlreadyExistError', Forbidde
 export const ProblemAlreadyUsedByContestError = Err('ProblemAlreadyUsedByContestError', ForbiddenError, 'Problem {0} is already used by contest {1}.');
 export const ProblemNotAllowPretestError = Err('ProblemNotAllowPretestError', ForbiddenError, 'This {0} is not allow run pretest.');
 export const ProblemNotAllowLanguageError = Err('ProblemNotAllowSubmitError', ForbiddenError, 'This language is not allow to submit.');
+export const ProblemLockError = Err('ProblemLockError', ForbiddenError, 'Lock Error: {0}');
 
 export const HackRejudgeFailedError = Err('HackRejudgeFailedError', BadRequestError, 'Cannot rejudge a hack record.');
 export const CannotDeleteSystemDomainError = Err('CannotDeleteSystemDomainError', BadRequestError, 'You are not allowed to delete system domain.');
diff --git a/packages/hydrooj/src/handler/contest.ts b/packages/hydrooj/src/handler/contest.ts
index 6d633b95b6..88109587c7 100644
--- a/packages/hydrooj/src/handler/contest.ts
+++ b/packages/hydrooj/src/handler/contest.ts
@@ -9,7 +9,8 @@ import {
 import {
     BadRequestError, ContestNotAttendedError, ContestNotEndedError, ContestNotFoundError, ContestNotLiveError,
     ContestScoreboardHiddenError, FileLimitExceededError, FileUploadError,
-    InvalidTokenError, NotAssignedError, PermissionError, ValidationError,
+    InvalidTokenError, NotAssignedError, PermissionError, ProblemLockError,
+    ValidationError,
 } from '../error';
 import { ScoreboardConfig, Tdoc } from '../interface';
 import paginate from '../lib/paginate';
@@ -640,6 +641,20 @@ export class ContestUserHandler extends ContestManagementBaseHandler {
         this.back();
     }
 }
+
+export class ContestProblemLockHandler extends Handler {
+    @param('tid', Types.ObjectId)
+    @param('pid', Types.UnsignedInt)
+    async post(domainId: string, tid: ObjectId, pid: number) {
+        const lockList = await contest.getLockedList(domainId, tid);
+        if (!lockList) throw new ProblemLockError('This contest is not lockable.');
+        if (lockList[pid].includes(this.user._id)) throw new ProblemLockError('This problem has Locked before.');
+        lockList[pid].push(this.user._id);
+        await contest.updateLockedList(domainId, tid, lockList);
+        this.back();
+    }
+}
+
 export async function apply(ctx) {
     ctx.Route('contest_create', '/contest/create', ContestEditHandler);
     ctx.Route('contest_main', '/contest', ContestListHandler, PERM.PERM_VIEW_CONTEST);
@@ -652,4 +667,5 @@ export async function apply(ctx) {
     ctx.Route('contest_code', '/contest/:tid/code', ContestCodeHandler, PERM.PERM_VIEW_CONTEST);
     ctx.Route('contest_file_download', '/contest/:tid/file/:filename', ContestFileDownloadHandler, PERM.PERM_VIEW_CONTEST);
     ctx.Route('contest_user', '/contest/:tid/user', ContestUserHandler, PERM.PERM_VIEW_CONTEST);
+    ctx.Route('contest_lock_problem', '/contest/:tid/lock', ContestProblemLockHandler, PERM.PERM_VIEW_CONTEST);
 }
diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index b47f00c838..8a0dd23aca 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -10,7 +10,8 @@ import {
     BadRequestError, ContestNotAttendedError, ContestNotEndedError, ContestNotFoundError, ContestNotLiveError,
     FileLimitExceededError, HackFailedError, NoProblemError, NotFoundError,
     PermissionError, ProblemAlreadyExistError, ProblemAlreadyUsedByContestError, ProblemConfigError,
-    ProblemIsReferencedError, ProblemNotAllowLanguageError, ProblemNotAllowPretestError, ProblemNotFoundError,
+    ProblemIsReferencedError, ProblemLockError,
+    ProblemNotAllowLanguageError, ProblemNotAllowPretestError, ProblemNotFoundError,
     RecordNotFoundError, SolutionNotFoundError, ValidationError,
 } from '../error';
 import {
@@ -479,7 +480,7 @@ export class ProblemSubmitHandler extends ProblemDetailHandler {
         if (typeof this.pdoc.config === 'string') throw new ProblemConfigError();
     }
 
-    async get() {
+    async get(domainId: string, tid?: ObjectId) {
         this.response.template = 'problem_submit.html';
         const langRange = (typeof this.pdoc.config === 'object' && this.pdoc.config.langs)
             ? Object.fromEntries(this.pdoc.config.langs.map((i) => [i, setting.langs[i]?.display || i]))
@@ -488,6 +489,7 @@ export class ProblemSubmitHandler extends ProblemDetailHandler {
             langRange,
             pdoc: this.pdoc,
             udoc: this.udoc,
+            tdoc: this.tdoc,
             title: this.pdoc.title,
             page_name: this.tdoc
                 ? this.tdoc.rule === 'homework'
@@ -503,6 +505,12 @@ export class ProblemSubmitHandler extends ProblemDetailHandler {
     @param('input', Types.String, true)
     @param('tid', Types.ObjectId, true)
     async post(domainId: string, lang: string, code: string, pretest = false, input = '', tid?: ObjectId) {
+        if (tid) {
+            const tdoc = await contest.get(domainId, tid);
+            if (tdoc.rule === 'cf' && tdoc.lockedList[this.pdoc.docId].includes(this.user._id)) {
+                throw new ProblemLockError('You have locked this problem.');
+            }
+        }
         const config = this.pdoc.config;
         if (typeof config === 'string' || config === null) throw new ProblemConfigError();
         if (['submit_answer', 'objective'].includes(config.type)) {
@@ -570,7 +578,7 @@ export class ProblemHackHandler extends ProblemDetailHandler {
         if (!this.rdoc || this.rdoc.pid !== this.pdoc.docId
             || this.rdoc.contest?.toString() !== tid?.toString()) throw new RecordNotFoundError(domainId, rid);
         if (tid) {
-            if (this.tdoc.rule !== 'codeforces') throw new HackFailedError('This contest is not hackable.');
+            if (this.tdoc.rule !== 'cf') throw new HackFailedError('This contest is not hackable.');
             if (!contest.isOngoing(this.tdoc, this.tsdoc)) throw new ContestNotLiveError(this.tdoc.docId);
         }
         if (this.rdoc.uid === this.user._id) throw new HackFailedError('You cannot hack your own submission');
diff --git a/packages/hydrooj/src/handler/record.ts b/packages/hydrooj/src/handler/record.ts
index 9eae08f921..ba0bcce508 100644
--- a/packages/hydrooj/src/handler/record.ts
+++ b/packages/hydrooj/src/handler/record.ts
@@ -58,7 +58,7 @@ class RecordListHandler extends ContestDetailBaseHandler {
             this.tdoc = tdoc;
             if (!tdoc) throw new ContestNotFoundError(domainId, pid);
             if (!contest.canShowScoreboard.call(this, tdoc, true)) throw new PermissionError(PERM.PERM_VIEW_CONTEST_HIDDEN_SCOREBOARD);
-            if (!contest[q.uid === this.user._id ? 'canShowSelfRecord' : 'canShowRecord'].call(this, tdoc, true)) {
+            if (!contest[q.uid === this.user._id ? 'canShowSelfRecord' : 'canShowRecord'].call(this, tdoc, true, pid ? await problem.get(domainId, pid) : null)) {
                 throw new PermissionError(PERM.PERM_VIEW_CONTEST_HIDDEN_SCOREBOARD);
             }
             if (!(await contest.getStatus(domainId, tid, this.user._id))?.attend) {
@@ -152,7 +152,7 @@ class RecordDetailHandler extends ContestDetailBaseHandler {
         } else if (rdoc.contest) {
             this.tdoc = await contest.get(domainId, rdoc.contest);
             let canView = this.user.own(this.tdoc);
-            canView ||= contest.canShowRecord.call(this, this.tdoc);
+            canView ||= contest.canShowRecord.call(this, this.tdoc, true, await problem.get(domainId, rdoc.pid));
             canView ||= contest.canShowSelfRecord.call(this, this.tdoc, true) && rdoc.uid === this.user._id;
             if (!canView && rdoc.uid !== this.user._id) throw new PermissionError(rid);
             canViewDetail = canView;
diff --git a/packages/hydrooj/src/interface.ts b/packages/hydrooj/src/interface.ts
index 9d0f77c689..2bd243c1bf 100644
--- a/packages/hydrooj/src/interface.ts
+++ b/packages/hydrooj/src/interface.ts
@@ -407,6 +407,9 @@ export interface Tdoc<docType = document['TYPE_CONTEST'] | document['TYPE_TRAINI
     // For training
     description?: string;
     dag?: TrainingNode[];
+
+    // For codeforces
+    lockedList?: {};
 }
 
 export interface TrainingDoc extends Tdoc {
@@ -525,7 +528,7 @@ export interface ContestRule<T = any> {
     submitAfterAccept: boolean;
     showScoreboard: (tdoc: Tdoc<30>, now: Date) => boolean;
     showSelfRecord: (tdoc: Tdoc<30>, now: Date) => boolean;
-    showRecord: (tdoc: Tdoc<30>, now: Date) => boolean;
+    showRecord: (tdoc: Tdoc<30>, now: Date, user?: User, pdoc?: ProblemDoc) => boolean;
     stat: (this: ContestRule<T>, tdoc: Tdoc<30>, journal: any[]) => ContestStat & T;
     scoreboardHeader: (
         this: ContestRule<T>, config: ScoreboardConfig, _: (s: string) => string,
diff --git a/packages/hydrooj/src/model/contest.ts b/packages/hydrooj/src/model/contest.ts
index 0d60214e21..d955a865c1 100644
--- a/packages/hydrooj/src/model/contest.ts
+++ b/packages/hydrooj/src/model/contest.ts
@@ -14,7 +14,7 @@ import * as bus from '../service/bus';
 import type { Handler } from '../service/server';
 import { PERM, STATUS, STATUS_SHORT_TEXTS } from './builtin';
 import * as document from './document';
-import problem from './problem';
+import problem, { ProblemDoc } from './problem';
 import user, { User } from './user';
 
 interface AcmJournal {
@@ -502,6 +502,98 @@ const ledo = buildContestRule({
     },
 }, oi);
 
+const cf = buildContestRule({
+    TEXT: 'Codeforces',
+    check: () => { },
+    submitAfterAccept: false,
+    showScoreboard: (tdoc, now) => now > tdoc.beginAt,
+    showSelfRecord: () => true,
+    showRecord: (tdoc, now, user, pdoc) => {
+        if (now > tdoc.endAt) return true;
+        if (pdoc && tdoc.lockedList[pdoc.docId].includes(user._id)) return true;
+        return false;
+    },
+    stat(tdoc, journal) {
+        const ntry = Counter<number>();
+        const hackSucc = Counter<number>();
+        const hackFail = Counter<number>();
+        const detail = {};
+        for (const j of journal) {
+            if ([STATUS.STATUS_COMPILE_ERROR, STATUS.STATUS_FORMAT_ERROR].includes(j.status)) continue;
+            // if (this.submitAfterAccept) continue;
+            if (STATUS.STATUS_ACCEPTED !== j.status) ntry[j.pid]++;
+            if ([STATUS.STATUS_HACK_SUCCESSFUL, STATUS.STATUS_HACK_UNSUCCESSFUL].includes(j.status)) {
+                if (j.status === STATUS.STATUS_HACK_SUCCESSFUL) detail[j.pid].hackSucc++;
+                else detail[j.pid].hackFail++;
+                continue;
+            }
+            const timePenaltyScore = Math.round(Math.max(j.score * 100
+                                                - ((j.rid.getTimestamp().getTime() - tdoc.beginAt.getTime()) * (j.score * 100)) / (250 * 60000),
+                                                j.score * 100 * 0.3));
+            const penaltyScore = Math.max(timePenaltyScore - 50 * (ntry[j.pid]), 0);
+            if (!detail[j.pid] || detail[j.pid].penaltyScore < penaltyScore) {
+                detail[j.pid] = {
+                    ...j,
+                    penaltyScore,
+                    timePenaltyScore,
+                    ntry: ntry[j.pid],
+                    hackFail: hackFail[j.pid],
+                    hackSucc: hackSucc[j.pid],
+                };
+            }
+        }
+        let score = 0;
+        let originalScore = 0;
+        for (const pid of tdoc.pids) {
+            if (!detail[pid]) continue;
+            detail[pid].penaltyScore -= 50 * detail[pid].hackFail;
+            detail[pid].penaltyScore += 100 * detail[pid].hackSucc;
+            score += detail[pid].penaltyScore;
+            originalScore += detail[pid].score;
+        }
+        return {
+            score, originalScore, detail,
+        };
+    },
+    async scoreboardRow(config, _, tdoc, pdict, udoc, rank, tsdoc, meta) {
+        const tsddict = tsdoc.detail || {};
+        const row: ScoreboardRow = [
+            { type: 'rank', value: rank.toString() },
+            { type: 'user', value: udoc.uname, raw: tsdoc.uid },
+        ];
+        if (config.isExport) {
+            row.push({ type: 'email', value: udoc.mail });
+            row.push({ type: 'string', value: udoc.school || '' });
+            row.push({ type: 'string', value: udoc.displayName || '' });
+            row.push({ type: 'string', value: udoc.studentId || '' });
+        }
+        row.push({
+            type: 'total_score',
+            value: tsdoc.score || 0,
+            hover: tsdoc.score !== tsdoc.originalScore ? _('Original score: {0}').format(tsdoc.originalScore) : '',
+        });
+        for (const s of tsdoc.journal || []) {
+            if (!pdict[s.pid]) continue;
+            pdict[s.pid].nSubmit++;
+            if (s.status === STATUS.STATUS_ACCEPTED) pdict[s.pid].nAccept++;
+        }
+        for (const pid of tdoc.pids) {
+            row.push({
+                type: 'record',
+                value: tsddict[pid]?.penaltyScore || '',
+                hover: tsddict[pid]?.penaltyScore
+                    ? `${tsddict[pid].timePenaltyScore}, -${tsddict[pid].ntry}, +${tsddict[pid].hackSucc} , -${tsddict[pid].hackFail}`
+                    : '',
+                raw: tsddict[pid]?.rid,
+                style: tsddict[pid]?.status === STATUS.STATUS_ACCEPTED && tsddict[pid]?.rid.getTimestamp().getTime() === meta?.first?.[pid]
+                    ? 'background-color: rgb(217, 240, 199);'
+                    : undefined,
+            });
+        }
+        return row;
+    },
+}, oi);
+
 const homework = buildContestRule({
     TEXT: 'Assignment',
     hidden: true,
@@ -652,7 +744,7 @@ const homework = buildContestRule({
 });
 
 export const RULES: ContestRules = {
-    acm, oi, homework, ioi, ledo, strictioi,
+    acm, oi, homework, ioi, ledo, strictioi, cf,
 };
 
 function _getStatusJournal(tsdoc) {
@@ -672,7 +764,7 @@ export async function add(
     RULES[rule].check(data);
     await bus.parallel('contest/before-add', data);
     const res = await document.add(domainId, content, owner, document.TYPE_CONTEST, null, null, null, {
-        ...data, title, rule, beginAt, endAt, pids, attend: 0, rated,
+        ...data, title, rule, beginAt, endAt, pids, attend: 0, rated, lockedList: pids.reduce((acc, curr) => ({ ...acc, [curr]: [] }), {}),
     });
     await bus.parallel('contest/add', data, res);
     return res;
@@ -848,8 +940,8 @@ export function canViewHiddenScoreboard(this: { user: User }, tdoc: Tdoc<30>) {
     return this.user.hasPerm(PERM.PERM_VIEW_CONTEST_HIDDEN_SCOREBOARD);
 }
 
-export function canShowRecord(this: { user: User }, tdoc: Tdoc<30>, allowPermOverride = true) {
-    if (RULES[tdoc.rule].showRecord(tdoc, new Date())) return true;
+export function canShowRecord(this: { user: User }, tdoc: Tdoc<30>, allowPermOverride = true, pdoc?: ProblemDoc) {
+    if (RULES[tdoc.rule].showRecord(tdoc, new Date(), this.user, pdoc)) return true;
     if (allowPermOverride && canViewHiddenScoreboard.call(this, tdoc)) return true;
     return false;
 }
@@ -890,6 +982,18 @@ export const statusText = (tdoc: Tdoc, tsdoc?: any) => (
                 ? 'Live...'
                 : 'Done');
 
+export async function getLockedList(domainId: string, tid: ObjectId) {
+    const tdoc = await document.get(domainId, document.TYPE_CONTEST, tid);
+    if (tdoc.rule !== 'cf') return null;
+    return tdoc.lockedList;
+}
+
+export async function updateLockedList(domainId: string, tid: ObjectId, $lockList: any) {
+    const tdoc = await document.get(domainId, document.TYPE_CONTEST, tid);
+    tdoc.lockedList = $lockList;
+    edit(domainId, tid, tdoc);
+}
+
 global.Hydro.model.contest = {
     RULES,
     add,
@@ -922,4 +1026,6 @@ global.Hydro.model.contest = {
     isLocked,
     isExtended,
     statusText,
+    getLockedList,
+    updateLockedList,
 };
diff --git a/packages/ui-default/components/scratchpad/ScratchpadToolbarContainer.jsx b/packages/ui-default/components/scratchpad/ScratchpadToolbarContainer.jsx
index 0efbc32a95..2c3671274f 100644
--- a/packages/ui-default/components/scratchpad/ScratchpadToolbarContainer.jsx
+++ b/packages/ui-default/components/scratchpad/ScratchpadToolbarContainer.jsx
@@ -123,7 +123,8 @@ export default connect(mapStateToProps, mapDispatchToProps)(class ScratchpadTool
           </ToolbarButton>
         )}
         <ToolbarButton
-          disabled={this.props.isPosting || !!this.props.submitWaitSec}
+          disabled={this.props.isPosting || !!this.props.submitWaitSec || 
+            (UiContext.tdoc && UiContext.tdoc.lockedList[UiContext.pdoc.docId].includes(UserContext._id))}
           className="scratchpad__toolbar__submit"
           onClick={() => this.props.postSubmit(this.props)}
           data-global-hotkey="f10"
diff --git a/packages/ui-default/templates/contest_problemlist.html b/packages/ui-default/templates/contest_problemlist.html
index 84374a0c37..79148e80fe 100644
--- a/packages/ui-default/templates/contest_problemlist.html
+++ b/packages/ui-default/templates/contest_problemlist.html
@@ -49,6 +49,19 @@ <h1 class="section__title">{{ _('Problems') }}</h1>
                 <a href="{{ url('problem_detail', pid=pid, query={tid:tdoc.docId}) }}">
                   <b>{{ String.fromCharCode(65+loop.index0) }}</b>&nbsp;&nbsp;{{ pdict[pid].title }}
                 </a>
+                {% if tdoc.rule === "cf" %}
+                  <a style="float: right; margin-left: 10px;" href="{{ url('record_main', query={tid:tdoc.docId, pid:pid, status:1}) }}" target="_blank">Hack</a>
+                    <form style="float: right; margin-left: 10px;" action="{{ url('contest_lock_problem', tid=tdoc.docId) }}" method="POST">
+                      <input type="hidden" name="pid" value="{{ pid }}">
+                        <button class="btn--lock" type="submit">
+                          {% if not tdoc.lockedList[pid].includes(handler.user._id) %}
+                            Lock
+                          {% else %}
+                            Locked
+                          {% endif %}
+                        </button>
+                    </form>
+                {% endif %}
               </td>
             </tr>
           {%- endfor -%}
diff --git a/packages/ui-default/templates/problem_submit.html b/packages/ui-default/templates/problem_submit.html
index 8fad7ceb44..f9d6d4e590 100644
--- a/packages/ui-default/templates/problem_submit.html
+++ b/packages/ui-default/templates/problem_submit.html
@@ -1,6 +1,9 @@
 {% extends "layout/basic.html" %}
 {% block content %}
 {{ set(UiContext, 'pdoc', pdoc) }}
+{% if tdoc %}
+  {{ set(UiContext, 'tdoc', tdoc) }}
+{% endif %}
 <div class="row">
   <div class="medium-9 columns">
     <div class="section">
@@ -26,7 +29,11 @@ <h1 class="section__title">{{ _('Submit to Judge') }}</h1>
             </div>
           </div>
           <div class="row"><div class="columns">
-            <input type="submit" class="rounded primary button" value="{{ _('Submit') }}">
+            {% if not tdoc or not tdoc.lockedList[pdoc.docId].includes(handler.user._id) %}
+              <input type="submit" class="rounded primary button" value="{{ _('Submit') }}">
+            {% else %}
+              <input disabled type="submit" class="rounded primary button" value="{{ _('Locked') }}">
+            {% endif %}
           </div></div>
         </form>
       </div>
diff --git a/packages/ui-default/templates/record_detail.html b/packages/ui-default/templates/record_detail.html
index 2c5c24693b..d6fee3c7e5 100644
--- a/packages/ui-default/templates/record_detail.html
+++ b/packages/ui-default/templates/record_detail.html
@@ -52,9 +52,15 @@ <h1 class="section__title">{{ _('Information') }}</h1>
       <div class="section__body no-padding">
         <ol class="menu">
           <li class="menu__item">
-            <a class="menu__link" href="{{ url('problem_hack', pid=pdoc.pid|default(pdoc.docId), rid=rdoc._id) }}">
-              <span class="icon icon-debug"></span> {{ _('Hack') }}
-            </a>
+            {% if rdoc.contest %}
+              <a class="menu__link" href="{{ url('problem_hack', pid=pdoc.pid|default(pdoc.docId), rid=rdoc._id, query={tid:rdoc.contest}) }}">
+                <span class="icon icon-debug"></span> {{ _('Hack') }}
+              </a>
+            {% else %}
+              <a class="menu__link" href="{{ url('problem_hack', pid=pdoc.pid|default(pdoc.docId), rid=rdoc._id) }}">
+                <span class="icon icon-debug"></span> {{ _('Hack') }}
+              </a>
+            {% endif %}
           </li>
         </ol>
       </div>