diff --git a/client/src/api/auth.js b/client/src/api/auth.js
index 661fa6f58..f206a4522 100644
--- a/client/src/api/auth.js
+++ b/client/src/api/auth.js
@@ -1,19 +1,25 @@
 import { request } from './util'
 import { route } from 'preact-router'
 
-export const login = ({ teamToken }) => {
+export const login = ({ teamToken, ctftimeToken }) => {
   return request('POST', '/auth/login', {
-    teamToken
+    teamToken,
+    ctftimeToken
   })
     .then(resp => {
       switch (resp.kind) {
         case 'goodLogin':
           localStorage.setItem('token', resp.data.authToken)
-          return route('/challs')
+          route('/challs')
+          return
         case 'badTokenVerification':
           return {
             teamToken: resp.message
           }
+        case 'badUnknownUser':
+          return {
+            badUnknownUser: true
+          }
         default:
           return {
             teamToken: 'Unknown response from server, please contact ctf administrator'
@@ -53,11 +59,12 @@ export const verify = ({ verifyToken }) => {
     })
 }
 
-export const register = ({ email, name, division }) => {
+export const register = ({ email, name, division, ctftimeToken }) => {
   return request('POST', '/auth/register', {
     email,
     name,
-    division: Number.parseInt(division)
+    division: Number.parseInt(division),
+    ctftimeToken
   })
     .then(resp => {
       switch (resp.kind) {
@@ -80,3 +87,9 @@ export const register = ({ email, name, division }) => {
       }
     })
 }
+
+export const ctftimeCallback = ({ ctftimeCode }) => {
+  return request('POST', '/integrations/ctftime/callback', {
+    ctftimeCode
+  })
+}
diff --git a/client/src/components/ctftime-additional.js b/client/src/components/ctftime-additional.js
new file mode 100644
index 000000000..b1e51dd76
--- /dev/null
+++ b/client/src/components/ctftime-additional.js
@@ -0,0 +1,77 @@
+import { Component } from 'preact'
+import Form from '../components/form'
+import config from '../../../config/client'
+import 'linkstate/polyfill'
+import withStyles from '../components/jss'
+import { register } from '../api/auth'
+import UserCircle from '../icons/user-circle.svg'
+
+export default withStyles({
+  root: {
+    padding: '1.5em'
+  },
+  submit: {
+    marginTop: '1.5em'
+  },
+  title: {
+    textAlign: 'center'
+  }
+}, class CtftimeAdditional extends Component {
+  state = {
+    showName: false,
+    disabledButton: false,
+    division: '',
+    name: '',
+    errors: {}
+  }
+
+  render ({ classes }, { showName, disabledButton, division, name, errors }) {
+    return (
+      <div class='row u-center'>
+        <h4 class={`col-12 ${classes.title}`}>Finish registration</h4>
+        <Form class={`${classes.root} col-6`} onSubmit={this.handleSubmit} disabled={disabledButton} errors={errors} buttonText='Register'>
+          <select required class='select' name='division' value={division} onChange={this.linkState('division')}>
+            <option value='' disabled selected>Division</option>
+            {
+              Object.entries(config.divisions).map(([name, code]) => {
+                return <option key={code} value={code}>{name}</option>
+              })
+            }
+          </select>
+          {showName && (
+            <input autofocus required icon={<UserCircle />} name='name' placeholder='Team Name' type='text' value={name} onChange={this.linkState('name')} />
+          )}
+        </Form>
+      </div>
+    )
+  }
+
+  handleSubmit = (e) => {
+    e.preventDefault()
+
+    this.setState({
+      disabledButton: true
+    })
+
+    register({
+      ctftimeToken: this.props.ctftimeToken,
+      division: this.state.division,
+      name: this.state.name || undefined
+    })
+      .then(errors => {
+        if (!errors) {
+          return
+        }
+        if (errors.name) {
+          this.setState({
+            showName: true
+          })
+        }
+
+        this.setState({
+          errors,
+          disabledButton: false
+        })
+      })
+  }
+})
diff --git a/client/src/components/ctftime-button.js b/client/src/components/ctftime-button.js
new file mode 100644
index 000000000..b3306ff44
--- /dev/null
+++ b/client/src/components/ctftime-button.js
@@ -0,0 +1,72 @@
+import { Component } from 'preact'
+import Ctftime from '../icons/ctftime.svg'
+import openPopup from '../util/ctftime'
+import withStyles from '../components/jss'
+import { ctftimeCallback } from '../api/auth'
+import { withToast } from '../components/toast'
+
+export default withStyles({
+  ctftimeButton: {
+    margin: 'auto',
+    lineHeight: '0',
+    padding: '10px',
+    '& svg': {
+      width: '150px'
+    }
+  },
+  or: {
+    textAlign: 'center',
+    display: 'block',
+    margin: '15px auto'
+  }
+}, withToast(class CtftimeButton extends Component {
+  componentDidMount () {
+    window.addEventListener('message', this.handlePostMessage)
+  }
+
+  componentWillUnmount () {
+    window.removeEventListener('message', this.handlePostMessage)
+  }
+
+  oauthState = null
+
+  handlePostMessage = async (evt) => {
+    if (evt.origin !== location.origin) {
+      return
+    }
+    if (evt.data.kind !== 'ctftimeCallback') {
+      return
+    }
+    if (this.oauthState === null || evt.data.state !== this.oauthState) {
+      return
+    }
+    const { kind, message, data } = await ctftimeCallback({
+      ctftimeCode: evt.data.ctftimeCode
+    })
+    if (kind !== 'goodCtftimeToken') {
+      this.props.toast({
+        body: message,
+        type: 'error'
+      })
+      return
+    }
+    this.props.onCtftimeDone(data.ctftimeToken)
+  }
+
+  handleClick = () => {
+    this.oauthState = openPopup()
+  }
+
+  render ({ classes, ...props }) {
+    return (
+      <div {...props} >
+        <div class={classes.or}>
+          <h5>or</h5>
+        </div>
+        <button class={classes.ctftimeButton} onClick={this.handleClick}>
+          <Ctftime />
+        </button>
+      </div>
+    )
+  }
+}))
diff --git a/client/src/components/form.js b/client/src/components/form.js
index 7878bb7b8..5c322564d 100644
--- a/client/src/components/form.js
+++ b/client/src/components/form.js
@@ -21,6 +21,9 @@ export default withStyles({
     <form onSubmit={onSubmit} class={props.class}>
       {
         [].concat(children).map(input => {
+          if (input.props === undefined) {
+            return
+          }
           let { icon, error, name } = input.props
 
           if (errors !== undefined && name !== undefined) error = error || errors[name]
diff --git a/client/src/icons/ctftime.svg b/client/src/icons/ctftime.svg
new file mode 100644
index 000000000..0aec8653b
--- /dev/null
+++ b/client/src/icons/ctftime.svg
@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 283 80"><path fill="#e3000b" d="M0 80h283V0H0l33 40z"/><path fill="#fff" d="M62 58h18v-6H69V28h11v-7H62zm24-30h6v30h7V28h5v-7H86zm24 30h8V43h9v-6h-9v-9h11v-7h-19zm73-33h5v33h5V25h5v-4h-15zm20-4h4v37h-4zm21 14l-5-14h-4v37h4V32l5 13 5-13v26h5V21h-5zm21 19V42h7v-5h-7V25h12l1-4h-18v37h18l-1-4zM136 21v37h39V21zm34 32h-29V26h29v27m-16-14l-6 6 4 4 9-9-16-16h-7z"/></svg>
diff --git a/client/src/index.js b/client/src/index.js
index 2c325a6f2..fe80fbd08 100644
--- a/client/src/index.js
+++ b/client/src/index.js
@@ -15,6 +15,7 @@ import Scoreboard from './routes/scoreboard'
 import Error from './routes/error'
 import Sponsors from './routes/sponsors'
 import Verify from './routes/verify'
+import CtftimeCallback from './routes/ctftime-callback'
 
 import { ToastProvider } from './components/toast'
 
@@ -48,6 +49,7 @@ function App () {
   let allPaths = [
     <Profile key='multiProfile' path='/profile/:uuid' />,
     <Verify key='verify' path='/verify' />,
+    <CtftimeCallback key='ctftimeCallback' path='/integrations/ctftime/callback' />,
     <Error key='error' error='404' default />
   ]
   allPaths = allPaths.concat(loggedInPaths).concat(loggedOutPaths)
diff --git a/client/src/routes/ctftime-callback.js b/client/src/routes/ctftime-callback.js
new file mode 100644
index 000000000..534b3c7e4
--- /dev/null
+++ b/client/src/routes/ctftime-callback.js
@@ -0,0 +1,16 @@
+import { Component } from 'preact'
+
+export default class CtftimeCallback extends Component {
+  componentDidMount () {
+    window.opener.postMessage({
+      kind: 'ctftimeCallback',
+      state: this.props.state,
+      ctftimeCode: this.props.code
+    })
+    window.close()
+  }
+
+  render () {
+    return null
+  }
+}
diff --git a/client/src/routes/login.js b/client/src/routes/login.js
index c2ceb8cd4..d3317f677 100644
--- a/client/src/routes/login.js
+++ b/client/src/routes/login.js
@@ -7,6 +7,8 @@ import withStyles from '../components/jss'
 import { login } from '../api/auth'
 import IdCard from '../icons/id-card.svg'
 import { route } from 'preact-router'
+import CtftimeButton from '../components/ctftime-button'
+import CtftimeAdditional from '../components/ctftime-additional'
 
 export default withStyles({
   root: {
@@ -20,7 +22,8 @@ export default withStyles({
   state = {
     teamToken: '',
     errors: {},
-    disabledButton: false
+    disabledButton: false,
+    ctftimeToken: undefined
   }
 
   componentDidMount () {
@@ -42,17 +45,34 @@ export default withStyles({
     }
   }
 
-  render (props, { teamToken, errors, disabledButton }) {
-    const { classes } = props
+  render ({ classes }, { teamToken, errors, disabledButton, ctftimeToken }) {
+    if (ctftimeToken) {
+      return <CtftimeAdditional ctftimeToken={ctftimeToken} />
+    }
     return (
       <div class='row u-center'>
         <Form class={`${classes.root} col-6`} onSubmit={this.handleSubmit} disabled={disabledButton} buttonText='Login' errors={errors}>
           <input autofocus name='teamToken' icon={<IdCard />} placeholder='Team Token' type='text' value={teamToken} onChange={this.linkState('teamToken')} />
         </Form>
+        <CtftimeButton class='col-12' onCtftimeDone={this.handleCtftimeDone} />
       </div>
     )
   }
 
+  handleCtftimeDone = async (ctftimeToken) => {
+    this.setState({
+      disabledButton: true
+    })
+    const loginRes = await login({
+      ctftimeToken
+    })
+    if (loginRes && loginRes.badUnknownUser) {
+      this.setState({
+        ctftimeToken
+      })
+    }
+  }
+
   handleSubmit = e => {
     e.preventDefault()
 
diff --git a/client/src/routes/registration.js b/client/src/routes/registration.js
index 812a7c18c..cb84de829 100644
--- a/client/src/routes/registration.js
+++ b/client/src/routes/registration.js
@@ -4,9 +4,11 @@ import config from '../../../config/client'
 import 'linkstate/polyfill'
 import withStyles from '../components/jss'
 
-import { register } from '../api/auth'
+import { register, login } from '../api/auth'
 import UserCircle from '../icons/user-circle.svg'
 import EnvelopeOpen from '../icons/envelope-open.svg'
+import CtftimeButton from '../components/ctftime-button'
+import CtftimeAdditional from '../components/ctftime-additional'
 
 export default withStyles({
   root: {
@@ -15,12 +17,16 @@ export default withStyles({
   },
   submit: {
     marginTop: '1.5em'
+  },
+  or: {
+    textAlign: 'center'
   }
 }, class Register extends Component {
   state = {
     name: '',
     email: '',
     division: '',
+    ctftimeToken: undefined,
     disabledButton: false,
     errors: {}
   }
@@ -29,7 +35,10 @@ export default withStyles({
     document.title = `Registration${config.ctfTitle}`
   }
 
-  render ({ classes }, { name, email, division, disabledButton, errors }) {
+  render ({ classes }, { name, email, division, disabledButton, errors, ctftimeToken }) {
+    if (ctftimeToken) {
+      return <CtftimeAdditional ctftimeToken={ctftimeToken} />
+    }
     return (
       <div class='row u-center'>
         <Form class={`${classes.root} col-6`} onSubmit={this.handleSubmit} disabled={disabledButton} errors={errors} buttonText='Register'>
@@ -44,10 +53,25 @@ export default withStyles({
             }
           </select>
         </Form>
+        <CtftimeButton class='col-12' onCtftimeDone={this.handleCtftimeDone} />
       </div>
     )
   }
 
+  handleCtftimeDone = async (ctftimeToken) => {
+    this.setState({
+      disabledButton: true
+    })
+    const loginRes = await login({
+      ctftimeToken
+    })
+    if (loginRes && loginRes.badUnknownUser) {
+      this.setState({
+        ctftimeToken
+      })
+    }
+  }
+
   handleSubmit = e => {
     e.preventDefault()
 
@@ -57,6 +81,10 @@ export default withStyles({
 
     register(this.state)
       .then(errors => {
+        if (!errors) {
+          return
+        }
+
         this.setState({
           errors,
           disabledButton: false
diff --git a/client/src/util/ctftime.js b/client/src/util/ctftime.js
new file mode 100644
index 000000000..7425b59c2
--- /dev/null
+++ b/client/src/util/ctftime.js
@@ -0,0 +1,34 @@
+import config from '../../../config/client'
+
+const openPopup = ({ url, title, w, h }) => {
+  const systemZoom = window.innerWidth / window.screen.availWidth
+  const left = (window.innerWidth - w) / 2 / systemZoom + window.screenLeft
+  const top = (window.innerHeight - h) / 2 / systemZoom + window.screenTop
+  const popup = window.open(url, title, [
+    'scrollbars',
+    'resizable',
+    `width=${w / systemZoom}`,
+    `height=${h / systemZoom}`,
+    `top=${top}`,
+    `left=${left}`
+  ].join(','))
+  popup.focus()
+}
+
+const getState = () => Array.from(crypto.getRandomValues(new Uint8Array(16)))
+  .map(v => v.toString(16).padStart(2, '0')).join('')
+
+export default () => {
+  const state = getState()
+  openPopup({
+    url: 'https://oauth.ctftime.org/authorize' +
+    `?scope=${encodeURIComponent('team:read')}` +
+    `&client_id=${encodeURIComponent(config.ctftimeClientId)}` +
+    `&redirect_uri=${encodeURIComponent(`${location.origin}/integrations/ctftime/callback`)}` +
+    `&state=${encodeURIComponent(state)}`,
+    title: 'CTFtime',
+    w: 500,
+    h: 500
+  })
+  return state
+}
diff --git a/server/api/auth/register.js b/server/api/auth/register.js
index d9d48f2c7..73305b045 100644
--- a/server/api/auth/register.js
+++ b/server/api/auth/register.js
@@ -67,11 +67,6 @@ module.exports = {
       })
     }
 
-    const conflictError = await util.auth.getRegisterConflict({ name, email, ctftimeId })
-    if (conflictError !== undefined) {
-      return conflictError
-    }
-
     if (req.body.ctftimeToken !== undefined) {
       return auth.register.register({
         division: req.body.division,
diff --git a/server/util/auth.js b/server/util/auth.js
deleted file mode 100644
index e86e831e3..000000000
--- a/server/util/auth.js
+++ /dev/null
@@ -1,23 +0,0 @@
-const { responses } = require('../responses')
-const database = require('../database')
-
-module.exports = {
-  getRegisterConflict: async ({ name, email, ctftimeId }) => {
-    let dbResult
-    if (ctftimeId === undefined) {
-      dbResult = await database.auth.getUserByNameOrEmail({ name, email })
-    } else {
-      dbResult = await database.auth.getUserByNameOrCtftimeId({ name, ctftimeId })
-    }
-    if (dbResult === undefined) {
-      return
-    }
-    if (ctftimeId !== undefined && dbResult.ctftime_id === ctftimeId) {
-      return responses.badKnownCtftimeId
-    }
-    if (ctftimeId !== undefined && dbResult.email === email) {
-      return responses.badKnownEmail
-    }
-    return responses.badKnownName
-  }
-}
diff --git a/server/util/index.js b/server/util/index.js
index 49cb03080..27cab0c3b 100644
--- a/server/util/index.js
+++ b/server/util/index.js
@@ -8,7 +8,6 @@ const normalize = require('./normalize')
 module.exports = {
   scores: require('./scores'),
   email: require('./email'),
-  auth: require('./auth'),
   normalize,
   notStarted: () => {
     return [