Curl post requests with Spotify client id & secret return invalid client

Question

I'm following Spotify's client credentials authorization flow, but all of my curl requests are returning {"error":"invalid_client"} each time. Here are the instructions from Spotify:

The request will include parameters in the request body:

grant_type - Set to “client_credentials”.

The header of this POST request must contain the following parameter:

Authorization - A Base 64 encoded string that contains the client ID and client secret key. The field must have the format: Authorization: Basic <base64 encoded client_id:client_secret>

They also include an example of a curl request:

$ curl -H "Authorization: Basic ZjM4ZjAw...WY0MzE=" -d grant_type=client_credentials https://accounts.spotify.com/api/token

Following their example, so far I've tried curl requests with:

client_id and client_secret plain
both base64 encoded seperately
only one or the other encoded
both encoded as one string with the colon
both encoded as one string without the colon
each of the above with a regenerated client secret

I'm using Ruby's Base64#encode64 method to encode. Still no luck. Any helpful hints?

Does the curl request work for you? Can you post the exact Ruby code you're trying to use? — Xavier Shay
The curl request was not working; I was trying to get that to work before trying it in the actual Rails app. But I figured it out - you can see my answer below. — Matthew Hinea

Matthew Hinea Matthew Hinea · Accepted Answer · 2016-09-11T00:33:05

Okay, I got it working - passing my client_id and client_secret, separated by a colon, to Base64.strict_encode64 (NOT Base64.encode64) and then passing that to the above curl request gets a 200 response with an access token. Apparently encode64 was not enough.

Curl post requests with Spotify client id & secret return invalid client

2 Answers