IMDSv2 support

[condour]

Please ensure the following before submitting a PR:

• if suggesting code changes or improvements, open an issue first
• for all but trivial changes (e.g., typo fixes), add your name to DESCRIPTION
• for all but trivial changes (e.g., typo fixes), documentation your change in NEWS.md with a parenthetical reference to the issue number being addressed
• if changing documentation, edit files in /R not /man and run devtools::document() to update documentation
• add code or new test files to /tests for any new functionality or bug fix
• make sure R CMD check runs without error before submitting the PR

[laurenkahn]

Test 1: EC2 using IMDSv1, Sys.setenv(USE_IMDS_TOKEN="TRUE")
Expected result: Should be able to access S3.
Actual result: Success, able to access S3.

Test 2: EC2 using IMDSv1, Sys.setenv(USE_IMDS_TOKEN="FALSE") or not set at all.
Expected result: Should be able to access S3, as in the original code.
Actual result: Failure - see comment. Header cannot be NULL.

Test 3: EC2 using IMDSv2, Sys.setenv(USE_IMDS_TOKEN="TRUE")
Expected result: Should be able to access S3 (unlike before).
Actual result: Success, able to access S3.

Test 4: EC2 using IMDSv2, Sys.setenv(USE_IMDS_TOKEN="FALSE") or not set at all.
Expected result: Should not be able to access S3, as in the original code.
Actual result: Not able to access S3, but for wrong reason (header = NULL). Addressing test #2's failure will fix this.

[laurenkahn]

This fails if token = NULL. For example if I use an EC2 using IMDSv1, and I don't set USE_IMDS_TOKEN to TRUE, and I run aws.ec2metadata::metadata$iam_role_names() I get the following error:

Error in curl::handle_setheaders(handle, X-aws-ec2-metadata-token = token): All headers must be strings.

Using a blank string instead seems to work when a token isn't required (IMDSv1).

[condour]

I've added a check for is.null prior to setting the header. I'm unable to test at the moment, so I would appreciate if you can verify that it solves the issue. Thanks!

[laurenkahn]

This works! The tests described above all have the expected results now.

[condour]

Thanks! Now I guess we just need someone to merge?

[daltschu22]

Is there a reason this hasnt been merged?

[tyner]

Would be great to see it merged

[rokhmanov]

Please!

[jrandall]

@jon-mago would you be able to review and merge this, or would you be interested in considering new or additional maintainers for this repo (and possibly aws.signature as well)? If so, I might be interested. Though perhaps @condour or @laurenkahn can comment if they may be interested as well, since they have been the ones actively developing and reviewing the code in this PR.

[laurenkahn]

I hope we can get this merged as well! Sadly I don't have permissions to merge. I tried to reach out to Jonathan Stott (the current maintainer of the package) via email in March 2024 and the email bounced. I'm not sure how else to get in touch.