Unsupported checksum algorithm: md5

[TheUltimateAbsol]

Describe the bug

It appears that, with the new checksum algorithms that have been introduced to the S3 APIs (SHA512, MD5, XXHASH64, XXHASH3, XXHASH128), the cli binary does not correctly identify MD5. Doing a call with a parameter like --checksum-algorithm MD5 will result in the error: Unsupported checksum algorithm: md5

Theoretically this should be true for any s3 call with the checksum parameter.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

AWS CLI creates proper checksum header for appropriate actions and posts correctly. Does not refuse md5 checksum requests.

Current Behavior

Unsupported checksum algorithm: md5

Reproduction Steps

aws s3api put-bucket-policy --bucket --policy --checksum-algorithm MD5

Possible Solution

Is this on the roadmap but not implemented yet? It's currently live in the docs: https://docs.aws.amazon.com/cli/latest/reference/s3api/put-bucket-policy.html

Additional Information/Context

No response

CLI version used

2.34.45

Environment details (OS name and version, etc.)

Ubuntu 22.04

[shreyaskommuri]

Hi, I ran into this same issue and have a fix ready in PR #10304.

Root cause — two gaps:

1. awscli/customizations/s3/subcommands.py — MD5 was missing from the --checksum-algorithm choices list, so the CLI was rejecting it client-side before the request was ever made.
2. botocore/httpchecksum.py — no Md5Checksum implementation existed in _CHECKSUM_CLS, so even if the CLI accepted the value, the checksum couldn't be computed at the request layer.

Fix: The aws-cli PR adds MD5 to the accepted choices. The companion botocore change adds a Md5Checksum class (backed by hashlib.md5) and registers it in _CHECKSUM_CLS. Both changes include unit tests.

Written, reviewed, and tested by shreyaskommuri. AI used for context and guidance.

[SamRemis]

Hi @shreyaskommuri and @TheUltimateAbsol ,

Thank you for raising the issue. I've closed the PR opened by @shreyaskommuri for the reasons I've mentioned in my comment on the PR.

The docs that were linked by @TheUltimateAbsol are incorrect for the put-bucket-policy command as of today. The documentation is defined upstream by the S3 team, so we will raise this to them for correction.

If you're able to share your use cases for wanting to use MD5 instead of one of our preferred algorithms, we would be happy to raise that to the S3 team as well. Any updates to support MD5 for more APIs or for auto-calculation would likely come from the S3 team and be supported across all SDKs, not just the AWS CLI.

[shreyaskommuri]

Thanks for the thorough explanation, @SamRemis — that makes sense. The incorrect docs were the main driver of confusion here, glad that's being flagged to the S3 team. No specific use case to add on our end; we were just investigating what appeared to be a missing feature.

[RyanFitzSimmonsAK]

Ticket # for internal use : P433644211