[JENKINS-75370] Deprecate hudson.util.Scrambler

[daniel-beck]

See JENKINS-75370.

Scrambler does not really have a good reason to exist: To encode/decode Base64, use java.util.Base64 directly. To protect secrets, use Secret.

Removal of backward compatibility can easily be removed from this PR if a more focused PR is desired, as it's just Base64 decode. I just thought it was time and used the opportunity: 2011 and 2009 have been a while ago.

Testing done

None so far, waiting for autotests.

Proposed changelog entries

• Remove support for loading user data from before Jenkins 1.283.
• Remove support for loading proxy configuration from before Jenkins 1.415.
• Developer: Deprecate hudson.util.Scrambler. Use java.util.Base64 instead.

Proposed changelog category

/label developer removed rfe

Proposed upgrade guidelines

N/A

Submitter checklist

• The Jira issue, if it exists, is well-described.
• The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
• There is automated testing or an explanation as to why this change has no tests.
• New public classes, fields, and methods are annotated with @Restricted or have @since TODO Javadocs, as appropriate.
• New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO"), if applicable.
• New or substantially changed JavaScript is not defined inline and does not call eval to ease future introduction of Content Security Policy (CSP) directives (see documentation).
• For dependency updates, there are links to external changelogs and, if possible, full differentials.
• For new APIs and extension points, there is a link to at least one consumer.

Desired reviewers

@mention

Before the changes are marked as ready-for-merge:

Maintainer checklist

• There are at least two (2) approvals for the pull request and no outstanding requests for change.
• Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
• Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
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[MarkEWaite]

Includes a question about a change of behavior when the authorization header contains invalid base64 data

[MarkEWaite]

This seems like it will change behavior in the case where the authorization.substring(6) is not a valid base64 encoded string. The previous Scrambler.descramble() call returns an empty string while the Base64.getDecoder() throws an illegal argument exception.

I experimented with this from the Jenkins script console with the following working code:

import java.util.Base64;
import hudson.util.Scrambler;
import java.nio.charset.StandardCharsets;

def password = 'Not a very good password';
def authorization = 'Basic:' + Scrambler.scramble(password);
println(authorization.substring(6));
println('Scrambled decodes to "' + Scrambler.descramble(authorization.substring(6)) + '"');
println('Base64 decodes to "' + new String(Base64.getDecoder().decode(authorization.substring(6).getBytes(StandardCharsets.UTF_8)), StandardCharsets.UTF_8) + '"');

That reports output:

Tm90IGEgdmVyeSBnb29kIHBhc3N3b3Jk
Scrambled decodes to "Not a very good password"
Base64 decodes to "Not a very good password"

The Jenkins script console with the following intentionally broken code shows the behavioral difference:

import java.util.Base64;
import hudson.util.Scrambler;
import java.nio.charset.StandardCharsets;

def password = 'Not a very good password';
def authorization = 'Basic:X' + Scrambler.scramble(password);
println(authorization.substring(6));
println('Scrambled decodes to "' + Scrambler.descramble(authorization.substring(6)) + '"');
println('Base64 decodes to "' + new String(Base64.getDecoder().decode(authorization.substring(6).getBytes(StandardCharsets.UTF_8)), StandardCharsets.UTF_8) + '"');

That results in the following output:

XTm90IGEgdmVyeSBnb29kIHBhc3N3b3Jk
Scrambled decodes to ""
java.lang.IllegalArgumentException: Last unit does not have enough valid bits
	at java.base/java.util.Base64$Decoder.decode0(Unknown Source)
	at java.base/java.util.Base64$Decoder.decode(Unknown Source)

Is that change of behavior OK?