CODEWITHSUNDEEP
slackslack-api
Tom
Tom

Reputation: 2944

Uploading and attaching images to private messages from bots in Slack

I have a node service that's using WebClient from @slack/client.

I am using the access token of a bot to upload an image using the web.files.upload API method. I then want to send the uploaded image to a user as an attachment to a private message (i.e. a channel that starts with D). I want access to this image to be limited to the Slack users in this team (much like when you share a document or other file).

I tried doing this with the response from the files.upload function, but there doesn't seem to be any property of res.file that gives me a URL that's accessible to all members of this Slack team:

conversationId = 'Dxxxxxxxx'; // ID of private channel between bot and user

web.chat
  .postMessage({
    channel: conversationId,
    text: 'Hello there',
    attachments: [
      {
        fallback: 'Required plain-text summary of the attachment.',
        color: '#36a64f',
        title: 'Slack API Documentation',
        title_link: 'https://api.slack.com/',
        text: 'Optional text that appears within the attachment',
        image_url: res.file.permalink_public,
        ts: 123456789
      }
    ]
  });

From the docs, it sounds like this file is private to the bot until it is sent to a public channel.

An alternative I considered was uploading the file to the private message channel between the user and the bot, however that gives me the following error:

{ Error: An API error occurred: invalid_channel
  code: 'slackclient_platform_error',
  data:
  { ok: false,
    error: 'invalid_channel',
    channel: '["Dxxxxxxxx"]',
    scopes: [ 'identify', 'bot:basic' ],
    acceptedScopes: [ 'files:write:user', 'post' ] } }

Is there no way to achieve what I'm after?

Upvotes: 1

Views: 2421

Answers (2)

Tom
Tom

Reputation: 2944

My mistake came from misreading the docs - the files.upload API expects a comma-separated string for the channels property and I was passing an array.

Once I had corrected this I could successfully upload files and share them with a user privately (channel IDs starting with 'D') and in public channels (channel IDs starting with 'C').

Copying the image URL and pasting it in a browser brought me to a login page, so by default they are private to the Slack team as I had hoped.

Upvotes: 1

Erik Kalkoken
Erik Kalkoken

Reputation: 32737

To use an image URL in a message attachment that image must have a public URL or it will not work. Uploaded files have access restrictions and are not public by default (e.g. you need to provide authentication along with your URL).

If you want to use that image in an attachment you need to first get a public URL. However, sharing it "in a public channel" is not sufficient. You need to make the file public with the API method files.sharedPublicUrl.

Alternatively you can use an external image service for uploading the image file and getting a public URL, e.g. imgur has an API for uploading and sharing image files.

Upvotes: 1

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