# Server-to-Server OAuth returns 400 when requesting access token - Powershell **URL:** \ **Category:** API and Webhooks\ **Tags:** oauth, api\ **Created:** [October 5, 2022, 11:47pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999 "2022-10-05T23:47:17Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![zoom123](https://avatars.discourse-cdn.com/v4/letter/z/85e7bf/32.png) [@zoom123](https://devforum.zoom.us/u/zoom123)\ **Post date:** [October 5, 2022, 11:47pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/1 "2022-10-05T23:47:17Z")
**API Endpoint** _[https://zoom.us/oauth/token?grant\_type=account\_credentials&account\_id=a12b3c4d5e6f](https://zoom.us/oauth/token?grant_type=account_credentials&account_id=a12b3c4d5e6f)_ **Description** I read the docs, cannot figure this out. Using Powershell, when I send a POST containing the header “Authorization: Basic {Base64 Encoded client\_id:client\_secret}” and to the endpoint above (using the account\_id on the same page from the App Credentials), I always get a 400 Bad Request. I know I can call REST APIs using this same/similar code, because in the same script I’m making successful calls to the Microsoft Graph API. I tried disabling and re-enabling the app, regenerating the client secret, passing ContentType as _application/json_ and _application/x-www-form-urlencoded_, even used curl _exactly_ as it’s shown in the docs - no dice. `` **Example Code** `$zoomAuthSecret = "client_id:client_secret" $zasBytes = [System.Text.Encoding]::Unicode.GetBytes($zoomAuthSecret) $EncodedZas = [Convert]::ToBase64String($zasBytes)` `Invoke-RestMethod -Headers @{Authorization = "Basic $EncodedZas"} -Uri "https://zoom.us/oauth/token?grant_type=account_credentials&account_id={account_id}" -Method Post` ---
**Author:** ![donte.zoom](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/donte.zoom/32/24412_2.png) [@donte.zoom](https://devforum.zoom.us/u/donte.zoom)\ **Post date:** [October 6, 2022, 12:15am UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/2 "2022-10-06T00:15:54Z")
Hi, @zoom123, Thank you for posting in the Developer Forum – I am happy to help. Sorry to hear that you getting 400 bad request. Can you try to make the request with the following curl command : ```auto curl --location --request POST 'https://zoom.us/oauth/token?grant_type=account_credentials&account_id={accountId}' \ --header 'Authorization: Basic Base64Encoder(clientId:clientSecret)' \ --data-raw '' ``` Also, there is a helpful utility script to generate a Zoom Server-to-Server Oauth Token and copy it to the clipboard on our GitHub as well: > **[GitHub - zoom/Server-to-Server-Oauth-Token: Utility script to generate a Zoom...](https://github.com/zoom/Server-to-Server-Oauth-Token)** > > Utility script to generate a Zoom Server-to-Server Oauth Token and copy to clipboard - GitHub - zoom/Server-to-Server-Oauth-Token: Utility script to generate a Zoom Server-to-Server Oauth Token and... ---
**Author:** ![zoom123](https://avatars.discourse-cdn.com/v4/letter/z/85e7bf/32.png) [@zoom123](https://devforum.zoom.us/u/zoom123)\ **Post date:** [October 6, 2022, 12:39am UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/3 "2022-10-06T00:39:55Z")
That worked on curl! But that begs the question, why does that not work in powershell? ---
**Author:** ![donte.zoom](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/donte.zoom/32/24412_2.png) [@donte.zoom](https://devforum.zoom.us/u/donte.zoom)\ **Post date:** [October 6, 2022, 12:44am UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/4 "2022-10-06T00:44:51Z")
@zoom123, Can you try this Powershell RestMethod and share the result: ```auto $headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]" $headers.Add("Authorization", "Basic Base64Encoder(clientId:clientSecret)") $body = "" $response = Invoke-RestMethod 'https://zoom.us/oauth/token?grant_type=account_credentials&account_id={accountId}' -Method 'POST' -Headers $headers -Body $body $response | ConvertTo-Json ``` ---
**Author:** ![zoom123](https://avatars.discourse-cdn.com/v4/letter/z/85e7bf/32.png) [@zoom123](https://devforum.zoom.us/u/zoom123)\ **Post date:** [October 6, 2022, 1:05pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/5 "2022-10-06T13:05:13Z")
```auto $zoomAuthSecret = "client_id:client_secret" $zasBytes = [System.Text.Encoding]::Unicode.GetBytes($zoomAuthSecret) $EncodedZas =[Convert]::ToBase64String($zasBytes) $zoomheaders = New-Object "System.Collections.Generic.Dictionary[[String],[String]]" $zoomheaders.Add("Authorization", "Basic $EncodedZas") $body = "" $response = Invoke-RestMethod 'https://zoom.us/oauth/token?grant_type=account_credentials&account_id={account_id}' -Method 'POST' -Headers $zoomheaders -Body $body $response | ConvertTo-Json ``` This unfortunately still returns a 400. ---
**Author:** ![MultiplayerSession](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/multiplayersession/32/66446_2.png) [@MultiplayerSession](https://devforum.zoom.us/u/MultiplayerSession)\ **Post date:** [October 6, 2022, 3:12pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/6 "2022-10-06T15:12:51Z")
Some potential areas you may want to check: - Use a single-byte encoding like ASCII or UTF-8. - ~~Encode using base64url encoding, which replaces certain characters and discards padding.~~ Actually, my current Server-to-Server OAuth implementation is using base64 encoding; it was JWT that used base64url encoding. ~~A .NET Framework / PowerShell compatible implementation for both of the above might be available via [Microsoft.IdentityModel.Tokens.Base64UrlEncoder.Encode](https://learn.microsoft.com/en-us/dotnet/api/microsoft.identitymodel.tokens.base64urlencoder.encode).~~ ---
**Author:** ![zoom123](https://avatars.discourse-cdn.com/v4/letter/z/85e7bf/32.png) [@zoom123](https://devforum.zoom.us/u/zoom123)\ **Post date:** [October 6, 2022, 4:18pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/7 "2022-10-06T16:18:45Z")
Looks like encoding was the issue! When converting the string above to bytes, I was converting it using Unicode: ```auto $zasBytes = [System.Text.Encoding]::Unicode.GetBytes($zoomAuthSecret) ``` But if I change it to **UTF8** : ```auto $zasBytes = [System.Text.Encoding]::UTF8.GetBytes($zoomAuthSecret) ``` Success! Thank you so much ---
**Author:** ![donte.zoom](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/donte.zoom/32/24412_2.png) [@donte.zoom](https://devforum.zoom.us/u/donte.zoom)\ **Post date:** [October 6, 2022, 4:48pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/8 "2022-10-06T16:48:44Z")
> [@zoom123](#): > > Looks like encoding was the issue! When converting the string above to bytes, I was converting it using Unicode: Awesome, glad to hear you were able to solve the issue. Can you share a snippet of both the failed and successful requests? It will be a great benefit to the community. ---
**Author:** ![zoom123](https://avatars.discourse-cdn.com/v4/letter/z/85e7bf/32.png) [@zoom123](https://devforum.zoom.us/u/zoom123)\ **Post date:** [October 6, 2022, 5:34pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/9 "2022-10-06T17:34:05Z")
**Failed response using unicode encoding for Base64 Credentials** ```auto Invoke-RestMethod : The remote server returned an error: (400) Bad Request. At line:10 char:13 + $response = Invoke-RestMethod 'https://zoom.us/oauth/token?grant_type ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand ``` **Successful response using UTF8 encoding for Base64 Credentials** _access\_token and scope redacted_ \* ```auto { "access_token": "", "token_type": "bearer", "expires_in": 3599, "scope": "" } ``` ---
**Author:** ![donte.zoom](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/donte.zoom/32/24412_2.png) [@donte.zoom](https://devforum.zoom.us/u/donte.zoom)\ **Post date:** [October 6, 2022, 5:59pm UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/10 "2022-10-06T17:59:50Z")
Thanks for taking the time to share your solution with the community, @zoom123 ! ```auto $zoomAuthSecret = "client_id:client_secret" $zasBytes = [System.Text.Encoding]::UTF8.GetBytes($zoomAuthSecret) $EncodedZas =[Convert]::ToBase64String($zasBytes) $zoomheaders = New-Object "System.Collections.Generic.Dictionary[[String],[String]]" $zoomheaders.Add("Authorization", "Basic $EncodedZas") $body = "" $response = Invoke-RestMethod 'https://zoom.us/oauth/token?grant_type=account_credentials&account_id={account_id}' -Method 'POST' -Headers $zoomheaders -Body $body $response | ConvertTo-Json ``` ---
**Author:** ![system](https://us1.discourse-cdn.com/flex016/uploads/zoomdeveloper/original/3X/6/1/614bdd549b610bbaa46ff934617683a02bdaa03c.png) [@system](https://devforum.zoom.us/u/system)\ **Post date:** [October 10, 2023, 9:36am UTC](https://devforum.zoom.us/t/server-to-server-oauth-returns-400-when-requesting-access-token-powershell/76999/11 "2023-10-10T09:36:28Z")
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