RFR: 8306461: ObjectInputStream::readObject() should handle negative array sizes without throwing NegativeArraySizeExceptions

[Roger Riggs]

On Thu, 20 Apr 2023 10:57:07 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This issue was reported by: Yakov Shafranovich ([yakovsh at amazon.com](mailto:yakovsh at amazon.com))
>> 
>> Currently, `ObjectInputStream::readObject()` doesn't explicitly checks for a negative array length in the deserialization stream. Instead it calls `j.l.r.Array::newInstance(..)` with the negative length which results in a `NegativeArraySizeException`. NegativeArraySizeException is an unchecked exception which is neither declared in the signature of `ObjectInputStream::readObject()` nor mentioned in its API specification. It is therefore not obvious for users of `ObjectInputStream::readObject()` that they may have to handle `NegativeArraySizeException`s. It would therefor be better if a negative array length in the deserialization stream would be automatically wrapped in an `InvalidClassException` which is a checked exception (derived from `IOException` via `ObjectStreamException`) and declared in the signature of `ObjectInputStream::readObject()`.
>> 
>> If we do the negative array length check in `ObjectInputStream::readObject()` before filtering, this will then also fix `ObjectInputFilter.FilterInfo::arrayLength()` which is defined as:
>> 
>> Returns:
>> the non-negative number of array elements when deserializing an array of the class, otherwise -1
>> 
>> but currently returns a negative value if the array length is negative.
>
> src/java.base/share/classes/java/io/ObjectInputStream.java line 2142:
> 
>> 2140:         int len = bin.readInt();
>> 2141:         if (len < 0) {
>> 2142:             throw new InvalidClassException(desc.getName(), "Array length < 0 (" + len + ")");
> 
> Suggestion:
> 
>             throw new InvalidClassException(desc.getName(), "Array length (" + len + ") is negative");

I'd keep the exception logic simple/minimal.  Especially since this is a manual and exceptional case that is not the result of any input provided through an API.

throw new InvalidClassException(desc.getName(), "Array length is negative");

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PR Review Comment: https://git.openjdk.org/jdk/pull/13540#discussion_r1172965774