[ruby-core:117449] [Ruby master Bug#20412] UTF-8 String encoding behavior differs between 3.2, 3.3 and master

["bannable (Joe Truba) via ruby-core" <ruby-core@ml.ruby-lang.org>]

Issue #20412 has been reported by bannable (Joe Truba).

----------------------------------------
Bug #20412: UTF-8 String encoding behavior differs between 3.2, 3.3 and master
https://bugs.ruby-lang.org/issues/20412

* Author: bannable (Joe Truba)
* Status: Open
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
When a String that contains only a `\0` byte is mutated by an extension to an invalid UTF-8 sequence, calling `.encode('UTF-8')` does not consistently raise `UndefinedConversionError` across ruby versions. When the string is longer than 1 byte, all versions I've tested correctly raise `UndefinedConversionError`.

For Ruby 3.2, `UndefinedConversionError` being raised appears to depend on where the string was originally allocated.

For Ruby 3.3, `UndefinedConversionError` is never raised.

For master ad90fdd24c, `UndefinedConversionError` is always correctly raised.

I haven't been able to find a bug for this, but it seems like there is a fix in master that should be backported to at least 3.2 and 3.3.

I have not tested 3.1.

The attached reproducer depends on `rbnacl` because it is minimized from a cryptographic project, and I wasn't able to 

## Expected Output

For all versions:
```
$ ruby repro.rb 1
"RUBY: [version]"
"OK: ciphertext_rbnacl is not valid UTF-8"
"OK: ciphertext_local is not valid UTF-8"
"OK: plaintext_rbnacl is not valid UTF-8"
"OK: plaintext_local is not valid UTF-8"

$ ruby repro.rb 2
"RUBY: [version]"
"OK: ciphertext_rbnacl is not valid UTF-8"
"OK: ciphertext_local is not valid UTF-8"
"OK: plaintext_rbnacl is not valid UTF-8"
"OK: plaintext_local is not valid UTF-8"
```

## Actual Output

### Ruby 3.2
```
$ ASDF_RUBY_VERSION=3.2.3 ruby -v; ASDF_RUBY_VERSION=3.2.3 ruby repro.rb 1
ruby 3.2.3 (2024-01-18 revision 52bb2ac0a6) [x86_64-linux]
"RUBY: 3.2.3"
"OK: ciphertext_rbnacl is not valid UTF-8"
"FAIL: ciphertext_local is not valid UTF-8 and did not error during encoding to UTF-8"
"OK: plaintext_rbnacl is not valid UTF-8"
"FAIL: plaintext_local is not valid UTF-8 and did not error during encoding to UTF-8"

$ ASDF_RUBY_VERSION=3.2.3 ruby -v; ASDF_RUBY_VERSION=3.2.3 ruby repro.rb 2
ruby 3.2.3 (2024-01-18 revision 52bb2ac0a6) [x86_64-linux]
"RUBY: 3.2.3"
"OK: ciphertext_rbnacl is not valid UTF-8"
"OK: ciphertext_local is not valid UTF-8"
"OK: plaintext_rbnacl is not valid UTF-8"
"OK: plaintext_local is not valid UTF-8"
```

### Ruby 3.3
```
$ ASDF_RUBY_VERSION=3.3.0 ruby -v; ASDF_RUBY_VERSION=3.3.0 ruby repro.rb 1
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-linux]
"RUBY: 3.3.0"
"FAIL: ciphertext_rbnacl is not valid UTF-8 and did not error during encoding to UTF-8"
"FAIL: ciphertext_local is not valid UTF-8 and did not error during encoding to UTF-8"
"FAIL: plaintext_rbnacl is not valid UTF-8 and did not error during encoding to UTF-8"
"FAIL: plaintext_local is not valid UTF-8 and did not error during encoding to UTF-8"

$ ASDF_RUBY_VERSION=3.3.0 ruby -v; ASDF_RUBY_VERSION=3.3.0 ruby repro.rb 2
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-linux]
"RUBY: 3.3.0"
"OK: ciphertext_rbnacl is not valid UTF-8"
"OK: ciphertext_local is not valid UTF-8"
"OK: plaintext_rbnacl is not valid UTF-8"
"OK: plaintext_local is not valid UTF-8"
```

### Ruby Master
```
$ ASDF_RUBY_VERSION=ruby-dev ruby -v; ASDF_RUBY_VERSION=ruby-dev ruby repro.rb 1
ruby 3.4.0dev (2024-04-06T17:33:16Z master ad90fdd24c) [x86_64-linux]
"RUBY: 3.4.0"
"OK: ciphertext_rbnacl is not valid UTF-8"
"OK: ciphertext_local is not valid UTF-8"
"OK: plaintext_rbnacl is not valid UTF-8"
"OK: plaintext_local is not valid UTF-8"

$ ASDF_RUBY_VERSION=ruby-dev ruby -v; ASDF_RUBY_VERSION=ruby-dev ruby repro.rb 2
ruby 3.4.0dev (2024-04-06T17:33:16Z master ad90fdd24c) [x86_64-linux]
"RUBY: 3.4.0"
"OK: ciphertext_rbnacl is not valid UTF-8"
"OK: ciphertext_local is not valid UTF-8"
"OK: plaintext_rbnacl is not valid UTF-8"
"OK: plaintext_local is not valid UTF-8"
```

---Files--------------------------------
repro.rb (2.31 KB)


-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
 ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/