Redmine

From your redacted URLs, it appears that you are accessing your Redmine via https while the generated content_url uses http. If that is actually the case, your Redmine may be configured incorrectly. If you are the admin, please check the settings in Administration -> Settings to be correct for the external URL.

As for actually downloading the attachment, you should use a GET request to the content_url using your usual API authentication mechanism.

Thanks, Holger Just for your prompt response.

As I'm new to Redmine, can you please help with how to correct it? Because I'm getting http in my content_url instead of https.

What do I need to do so that I can get content_url in the https form?

Thanks in advance.

Regards,
Parikshit

Well, it seems that your webserver does not properly inform your application server that the initial request was made over https. Thus, the application server (and thus Redmine) assumes that it was made over plain http. To fix this, you likely have to adapt your webserver config, depending on your exact setup.

Depending on your webserver, this usually requires setting an additoional request header before passing along the request to the application server. With Apache, this can look like this in your SSL virtual host:

RequestHeader set X-Forwarded-Proto "https" 

With nginx, this can look like this in your SSL server

proxy_set_header X-Forwarded-Proto https;

It depends on your specific setup where exactly you need to set these headers in your configuration.