Test bad password about rncryptor

I've been doing some testing, and sometimes, when I decrypt with a bad password, this line in performOperation of RNCryptor will throw an exception:
*aFooter = [readBuffer subdataWithRange:NSMakeRange([readBuffer length] - aFooterSize, aFooterSize)];

The exception is: 'NSRangeException', reason: '*** -[NSConcreteMutableData subdataWithRange:]: range {4294967294, 32} causes integer overflow'

The value of [readBuffer length] is 30, and when aFooterSize, which is 32 is subtracted from it, it wraps to the number 4294967294.

BTW, thanks for all your hard work on this library, it is very useful to me.

[rnapier]

Thanks for testing. I'm really glad to have someone trying this out before I announce it to the world.

I've now built a test case that demonstrates this problem. It's not actually related to bad passwords. It's a function of the file size relative to the block size (you get the same crash for a good password as a bad password when the file size is 993 bytes for instance).

You can follow Issue #19 to track when I fix this.