We run Jenkins in a proxy environment. Using the S3 plugin doesn't work from behind the proxy because these settings aren't propagated to the upload and the plugin times out trying to upload the artifacts.

A few interesting things:

• There seems to be 2 surfaces for proxy settings in the plugin: global settings (manage plugins -> advanced -> proxy settings) & the plugin specific settings in the 'Amazon S3 profiles' section of the system configuration. We've tried setting the proxy settings in both places, and neither option solves the issue.
• We are able to get it working fine outside of the proxy environment, however, it isn't possible for us to do this permanently.
• This pull request does fix the issue for us, however, it isn't a straightforward merge into master.

We might be able to work on this ourselves, please let us know if you are interested in a pull request.

Thanks!