RFR: 8321396: Retire test/jdk/java/util/zip/NoExtensionSignature.java

[Eirik Bjorsnos]

On Tue, 5 Dec 2023 15:58:14 GMT, Eirik Bjorsnos <duke at openjdk.org> wrote:

> Please review this PR which suggests we retire the ZIP test `NoExtensionSignature` along with its `test.jar` test vector. 
> 
> The concern of a missing data descriptor signature is covered by the recently updated  `DataDescriptorSignatureMissing` test. That test is more complete, includes more documentation and uses a programmatically generated test vector.
> 
> One might argue that 'more tests are always better', but in this case I think the 21 year old `NoExtensionSignature` test with its binary test vector is nebulous and requires extensive analysis to understand, more so to update. I think it does not carry its weight and should be retired.
> 
> Careful analysis of the deleted `test.jar` test vector revealed that it contains a local header with non-zero `compressed size` and `uncompressed size` fields for a streaming-mode entry. `APPNOTE.TXT` mandates that when bit 3 of the general purpose bit flag is set, then these fields and the `crc` field should all be set to zero. 
> 
> By injecting assertions into `ZipInputStream.readLOC` I was able to determine that `NoExtensionSignature` is the only test currently parsing a ZIP file with such non-zero fields in streaming mode. 
> 
> Because of this, and out of caution, this PR introduces a new test `DataDescriptorIgnoreCrcAndSizeFields` which  explicitly verifies that `ZipInputStream` does not read any non-zero `crc`, `compressed size` and `uncompressed size` field values from a local header when in streaming mode. `ZipInputStream` should ignore these values and it would be good to have a test which asserts that this invariant holds even when the fields are non-zero.

For completeness, here is a trace of the deleted `test.zip`:


------  Local File Header  ------
000000  signature          0x04034b50     
000004  version            20             
000006  flags              0x0008         
000008  method             8              Deflated
000010  time               0x9a45         19:18:10
000012  date               0x2c47         2002-02-07
000014  crc                0x00000000     
000018  csize              2              
000022  size               2              
000026  nlen               8              
000028  elen               0              
000030  name               8 bytes        'test.txt'

------  File Data  ------
000038  data               4 bytes        

------  Data Descriptor  ------
000042  crc                0xd8932aac     
000046  csize              4              
000050  size               2              

------  Central Directory File Header  ------
000054  signature          0x02014b50     
000058  made by version    788            
000060  extract version    20             
000062  flags              0x0008         
000064  method             8              Deflated
000066  time               0x9a45         19:18:10
000068  date               0x2c47         2002-02-07
000070  crc                0xd8932aac     
000074  csize              4              
000078  size               2              
000082  diskstart          0              
000084  nlen               8              
000086  elen               0              
000088  clen               0              
000090  iattr              0x00           
000092  eattr              0x81b60000     
000096  loc offset         0              
000100  name               8 bytes        'test.txt'

------  End of Central Directory  ------
000108  signature          0x06054b50     
000112  this disk          0              
000114  cen disk           0              
000116  entries disk       1              
000118  entries total      1              
000120  cen size           54             
000124  cen offset         54             
000128  clen               0

-------------

PR Comment: https://git.openjdk.org/jdk/pull/16975#issuecomment-1845780545