Does Java do anything to prevent files from changing out from under it?

[Xueming Shen]

Pete Soper wrote:
> Peter B. Kessler wrote:
>> Does the Java platform do anything to prevent files from changing
>> out from under it?  E.g., once one has opened a jar file for class
>> loading, could a malicious (or oblivious) user write to the jar
>> file and disturb the VM?  Or is that all relegated to "the operating
>> system", file system permissions, etc.?
>>
>>             ... peter
> No, yes, and yes for Sun Java SE on Solaris, Linux, and Windows. But 
> somebody can just dd /dev/zero over the top of a raw disk device too 
> if they "just have the permissions."
>
> Deletion of a file is prevented by another process having it open on 
> Windows, but that doesn't keep it from being overwritten and for 
> rt.jar the program will explode when it tries to load the next class 
> (depending on where the damage is).
>
> -Pete
>
If someone has the permission to touch your rt.jar and/or the access to 
the rest of the filesystem, your app,
the jvm and the system are no longer secured anyway.