RFR: 8280409: JarFile::verifiableEntry can fail with NPE accessing ze.getName() [v2]

[Sean Mullan]

On Thu, 10 Feb 2022 20:35:19 GMT, Sean Mullan <mullan at openjdk.org> wrote:

>> So a bit more on this.  If the ZipEntry passed to `ZipFile::getInputStream` does not represent an entry within the current Zip/Jar,  `ZipFile::getInputStream` will return a null for the InputStream:
>> 
>> 
>>     @Test
>>     public static void ZipFileZipEntryNullGetInputStreamTest() throws Exception {
>>         try (ZipFile zf = new ZipFile(VALID_ENTRY_NAME_JAR.toFile())) {
>>             var ze = new ZipEntry("org/gotham/Batcave.class");
>>             var is = zf.getInputStream(ze);
>>             // As the ZipEntry cannot be found, the returned InpuStream is null
>>             assertNull(is);
>>         }
>>     }
>> 
>> 
>>   JarFile::getInputStream will also return null when the jar is not signed or we are not verifying the jar:
>> 
>> 
>>  @Test
>>     public static void JarFileZipEntryNullGetInputStreamTest() throws Exception {
>>         try (JarFile jf = new JarFile(VALID_ENTRY_NAME_JAR.toFile())) {
>>             var ze = new ZipEntry("org/gotham/Batcave.class");
>>             var is = jf.getInputStream(ze);
>>             // As the ZipEntry cannot be found, the returned InpuStream is null
>>             assertNull(is);
>>         }
>> 
>>         try (JarFile jf = new JarFile(SIGNED_INVALID_ENTRY_NAME_JAR.toFile(), false)) {
>>             var ze = new ZipEntry("org/gotham/Batcave.class");
>>             var is = jf.getInputStream(ze);
>>             // As the ZipEntry cannot be found, the returned InpuStream is null
>>             assertNull(is);
>>         }
>>     }
>> 
>> 
>> 
>> This behavior dates back to at least JDK 1.3
>> 
>> So I think we should return null  instead of throwing an Exception when the resulting ZipEntry is null that is returned from the call to`JarFile::getJarEntry` (which calls `ZipFile::getEntry`) for consistency with ZipFile and when the Jar is not signed or not verified.
>> 
>> I also noticed that `ZipFile::getInputStream` and `JarFile::getInputStream` do not mention that a null will be returned if the specified ZipEntry is not found within the Jar/Zip.  I guess I could open a CSR as part of this fix to clarify this 20+ year behavior.
>
> Agree on returning null to maintain current behavior. I would also lean towards amending the specification to specify what has been long-standing behavior.

If we had to do it over again, I do think throwing IAE is more appropriate because this case would probably be due to a bug in the application code. Now code has to defensively check for a null return value. I don't know, maybe we don't want to modify the specification at this point and leave this as undefined behavior.

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

PR: https://git.openjdk.java.net/jdk/pull/7348