Purity checker does not filter STATICCALL opcode

[paulhauner]

As defined in EIP214, the STATICCALL opcode allows a contract to read the mutable state of another contract.

The purity checker does not blacklist this opcode. I think it should.

EDIT: STATICCALL should not be blacklisted - instead filtered so that it may only be used upon pre-approved addresses.

[ChihChengLiang]

Looks like this can be better handled by adding STATICCALL in the banned opcode lists in #169 .

[paulhauner]

Actually I was wrong when I said "blacklist". It actually needs to be treated like other CALL codes and filtered so it can only be directed at pre-approved contracts. Will update title.

[paulhauner]

Here's a thought... blacklist CALL and permit only STATICCALL? Probably unnecessary.

EDIT: I retract this statement. I don't see a good reason to blacklist CALL.

[ChihChengLiang]

looks like it's handled here https://github.com/ethereum/casper/pull/169/files#diff-33d26a5c0d90fb3b88e7aed738a11fc5R71

Where

CALL = 0xf1
CALLCODE = 0xf2
DELEGATECALL = 0xf4
STATICCALL = 0xfa

[paulhauner]

Where exactly? I don't see 0xfa in the is_some_call() code.

[ChihChengLiang]

ah sorry, I mean 0xfa are treated differently from other CALLs. Is that what you want?

[paulhauner]

Oh, sorry I think I misunderstood!

Yes, I think STATICCALL should be added to that code you linked. ☺️