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Adding warning to pin to digest #2311

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Oct 5, 2022
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Adding warning to pin to digest #2311

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4 changes: 4 additions & 0 deletions cmd/cosign/cli/sign/sign.go
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,10 @@ func SignCmd(ro *options.RootOptions, ko options.KeyOpts, regOpts options.Regist
return fmt.Errorf("unable to resolve attachment %s for image %s", attachment, inputImg)
}

if _, ok := ref.(name.Tag); ok {
fmt.Println("Warning: Tag used in reference to identify the image. Consider supplying the digest for immutability.")
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I know it's annoying, but I'm going to bikeshed the message a little bit. Appreciate your patience 🙂

Can you revise the message to something like:

WARNING: Image reference %s uses a tag, not a digest, to identify the image to sign.

This can lead you to sign a different image than the intended one. Please use a digest (example.com/ubuntu@sha256:abcdef...) rather than tag (example.com/ubuntu:latest) for the input to cosign. The ability to refer to images by tag will be removed in a future release.

%s: inputImg

Feel free to make modifications, but I want to hit the following points:

  1. "Warning" should be "WARNING" for consistency with other messages in the codebase.
  2. Gives motivation.
  3. Tells you how to fix the issue with examples.
  4. Mentions that digest references will be required in the future.

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If we print the warning after we resolve the digest, the error message can give you exactly the command to run instead, without needing a placeholder digest.

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If we print the warning after we resolve the digest, the error message can give you exactly the command to run instead, without needing a placeholder digest.

I was thinking this... but by telling the user the digest they should plan to use... doesn't that hold them susceptible for the very problem that the warning tries to avoid? Instead the warning should say "make sure you figure out what the digest of the image is, but we are not the ones to tell you now, just know for next time". Maybe I have other thought it @imjasonh

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+1 to @ChaosInTheCRD here.

BTW I'm following up in #2313 so we can have discussion there.

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Can we use fmt.Fprintln(os.Stderr, "...") instead? We like to reserve STDOUT for the output of the command.

}

if digest, ok := ref.(name.Digest); ok && !recursive {
se, err := ociremote.SignedEntity(ref, opts...)
if err != nil {
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