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I use social authentication in my ASP.NET Core application, one of which is LinkedIn authentication.

Looks like there's been some changes in LinkedIn API and now we seem to get some parameters with user images.

Here's a dummy full/original image URL I'd get from LinkedIn API. Any idea what these parameters mean? In particular, the one that begins with t?

https://media.licdn.com/dms/image/A1205CPGrwDzHZS_Apr/profile-originalphoto-shrink_900_1200/0?e=1525989600&v=beta&t=PNuO2bh5rNrIJv19PN1OXOjzDWcQgKdYCl1-ZVzgPOw

The reason why this is important is that when the user logs in, I compare the data that's already in the database with the new data coming from LinkedIn -- in my case, it's limited to user profile images i.e. both the smaller size image and the original one the user uploaded.

I've noticed that the image is always showing different. In closer analysis, I could see that these parameters, in particular the one that begins with t is where the difference is. This small change triggers an event in my code to update the user's images which could be a completely wasted database call. I could confirm this with my own LinkedIn login. Even though my image hasn't changed, the image URL for the original image is always different due to this difference in the t component.

The t parameter could be some type of time stamp which means it may always be different. I don't want to make that assumption, hence this questions.

Sam
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  • How often did it change for you? I have tried it several times across sessions, even over different VPN connections but it did not change for me. The size of the value of the `t` parameter is suggesting a SHA256 encoded to base64. So it is most likely just for cache busting and indeed like a timestamp. If it changes, I think you should bite the bullet and make that database call. – Sawrub May 17 '18 at 16:36

1 Answers1

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I tried the below LinkedIn endpoint 'https://api.linkedin.com/v2/me?oauth2_access_token='.

For me, there are two images under "pictureInfo" section, "croppedImage" and "masterImage". I have tried to replicate the problem you have mentioned and could not replicate this for sometime. At some point, I have received a different image URN for "masterImage". After a no. of tests I understood the 'masterImage' is updating once in every hour. With this I have further tried to understand the parameters in the image URN.

From these,

  • v=beta is clear. Earlier it was v=alpha for few.
  • e appears to be a timestamp which relates to some expiration.
  • t is changing when e changes.

Given this analysis if you are using 'masterImage' to trigger a DB call, you may put regex matching criteria to identify actual change in image.

PrabhakarP
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