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https://issues.apache.org/jira/browse/KAFKA-8013?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16779973#comment-16779973
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ASF GitHub Bot commented on KAFKA-8013:
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kkonstantine commented on pull request #6340: KAFKA-8013: Avoid underflow when
reading a Struct from a partially correct buffer
URL: https://github.com/apache/kafka/pull/6340
Protocol compatibility can be facilitated if a Struct, that has been defined
as an extension of a previous Struct by adding fields at the end of the older
version, can read a message of an older version by ignoring the absence of the
missing new fields. Reading the missing fields should be allowed by the
definition of these fields (they have to be nullable).
* Tested by adding unit tests around Schema.read in both directions
### Committer Checklist (excluded from commit message)
- [ ] Verify design and implementation
- [ ] Verify test coverage and CI build status
- [ ] Verify documentation (including upgrade notes)
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> Avoid buffer underflow when reading a Struct from a partially correct buffer
> ----------------------------------------------------------------------------
>
> Key: KAFKA-8013
> URL: https://issues.apache.org/jira/browse/KAFKA-8013
> Project: Kafka
> Issue Type: Bug
> Reporter: Konstantine Karantasis
> Assignee: Konstantine Karantasis
> Priority: Major
> Fix For: 2.3.0
>
>
> Protocol compatibility can be facilitated if a {{Struct}}, that has been
> defined as an extension of a previous {{Struct}} by adding fields at the end
> of the older version, can read an older version by ignoring the absence of
> the missing new fields. Of course this has to be allowed by the definition of
> these fields (they have to be {{nullable}}).
> For example, this should work:
> {code:java}
> Schema oldSchema = new Schema(new Field("field1", Type.NULLABLE_STRING));
> Schema newSchema = new Schema(new Field("field1", Type.NULLABLE_STRING), new
> Field("field2" , Type.NULLABLE_STRING));
> String value = "foo bar baz";
> Struct oldFormat = new Struct(oldSchema).set("field1", value);
> ByteBuffer buffer = ByteBuffer.allocate(oldSchema.sizeOf(oldFormat));
> oldFormat.writeTo(buffer);
> buffer.flip();
> Struct newFormat = newSchema.read(buffer);
> assertEquals(value, newFormat.get("field1"));
> assertEquals(null, newFormat.get("field2"));
> {code}
> Currently it does not.
> A fix to the above is considered safe, because depending on buffer underflow
> to detect missing data at the end of a {{Struct}} is not an appropriate
> check.
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