New opcode: STATICCALL #214

chriseth · 2017-02-13T13:52:30Z

To increase smart contract security, this proposal adds a new opcode that can be used to call another contract (or itself) while disallowing any modifications to the state during the call (and its subcalls, if present).

Replaces #116

Arachnid · 2017-02-13T15:26:05Z

It's worth considering if state-changing operations should actually throw, or just be reverted after the call returns; the latter would permit calling operations that would normally create side-effects in a side-effect free fashion.

Also, if REVERT is implemented, is STATIC_CALL necessary? You could create an equivalent effect by calling yourself, then calling the target contract, and REVERTing afterwards.

axic · 2017-02-13T16:27:21Z

It's worth considering if state-changing operations should actually throw

If they do throw, a VM implementation may choose to be optimised in the STATIC_CALL case as it would not need to keep changes even temporarily. Additionally compilers may not need to verify upfront that state changing operations are used, because that is enforced by the VM.

That would leave the non-throwing STATIC_CALL to be implemented via a mechanism as you've explained.

pirapira · 2017-02-14T11:25:49Z

EIPS/static_call.md

+
+Opcode: `0xfa`.
+
+`STATIC_CALL` functions equivalently to a `CALL`, except it takes 6 arguments not including value, and calls the child with a `STATIC` flag on. Any calls, static or otherwise, made by an execution instance with a `STATIC` flag on will also have a `STATIC` flag on. Any attempts to make state-changing operations inside an execution instance with a `STATIC` flag on will instead throw an exception. These operations include nonzero-value calls, creates, `LOG` calls, `SSTORE`, `SSTOREBYTES` and `SUICIDE`.


Is SSTOREBYTES an instruction?

This was taken from vitalik's draft that assumed another EIP which introduced SSTOREBYTES.

pirapira · 2017-02-14T11:29:16Z

EIPS/static_call.md

+
+## Rationale
+
+This allows contracts to make calls that are clearly non-state-changing, reassuring developers and reviewers that re-entrancy bugs or other problems cannot possibly arise from that particular call; it is a pure function that returns an output and does nothing else. This may also make purely functional HLLs easier to implement.


I guess HLL stands for "Haskell-like languages", but maybe not.

My guess is that it stands for just "high level language".

pirapira · 2017-02-17T15:43:48Z

EIPS/static_call.md

+
+Opcode: `0xfa`.
+
+`STATIC_CALL` functions equivalently to a `CALL`, except it takes 6 arguments not including value, and calls the child with a `STATIC` flag on. Any calls, static or otherwise, made by an execution instance with a `STATIC` flag on will also have a `STATIC` flag on. Any attempts to make state-changing operations inside an execution instance with a `STATIC` flag on will instead throw an exception. These operations include nonzero-value calls, creates, `LOG` calls, `SSTORE`, `SSTOREBYTES` and `SUICIDE`.


So far we haven't separated words in the mnemonics: CALLCODE and DELEGATECALL. Maybe STATICCALL is more consistent.

pirapira · 2017-02-20T09:41:26Z

I filed an yellow paper PR about this ethereum/yellowpaper#237

chriseth · 2017-02-24T11:07:32Z

Changed the name to STATICCALL, but note that the name is not a consensus-relevant issue ;-)

debris · 2017-03-10T12:01:01Z

From: https://github.com/ethcore/parity/pull/4851#pullrequestreview-26245124

Also one thing bothers me:
I think currently STATICCALL will kill empty accounts when it touches them - that is arguably a state alteration. Since we don't allow empty accounts to be created any more it shouldn't cause a problem if there are not empty accounts already existing on chain, but nevertheless I think we should either avoid killing empty accounts in such case or clarify that in the specification.

What should happen in such case?

axic · 2017-03-17T14:55:56Z

Also, if REVERT is implemented, is STATIC_CALL necessary?

Implemented it in Solidity here: https://gist.github.com/axic/fc61daf7775c56da02d21368865a9416

Without language support it is quite expensive as the calldata has to be copied. With language support there are at least two ways:

always include the signature of staticWrapInternal when building the calldata
use the same signature as the recipient if available

cdetrio · 2017-03-17T15:43:37Z

See also EIP 140: REVERT instruction.

pirapira · 2017-03-23T12:03:24Z

@debris my Yellow Paper PR would also kill dead accounts that are touched during a STATICCALL ethereum/yellowpaper#270

debris · 2017-03-23T15:31:13Z

great, thanks for clarification! 😄

Arachnid · 2017-04-14T11:55:12Z

Please renumber as eip-214 and we will merge this as a draft.

axic · 2017-04-23T17:01:26Z

EIPS/static_call.md

+
+
+## Motivation
+


Shouldn't this be filled with something?

ethereum/EIPs#214

pirapira · 2017-11-20T11:35:15Z

EIPS/eip-214.md

+
+## Motivation
+
+Currently, there is no restriction about what a called contract can do, as long as the computation can be performed with the amount of gas provided. This poses certain difficulties about smart contract engineers: After a regular call, unless you know the called contract, you cannot make any assumptions about the state of the contracts. Furthermore, because you cannot know the order of transactions before they are confirmed by miners, not even an outside observer can be sure about that in all cases.


Maybe ; after instead of : After.

pirapira · 2017-11-20T11:36:12Z

EIPS/eip-214.md

+
+Currently, there is no restriction about what a called contract can do, as long as the computation can be performed with the amount of gas provided. This poses certain difficulties about smart contract engineers: After a regular call, unless you know the called contract, you cannot make any assumptions about the state of the contracts. Furthermore, because you cannot know the order of transactions before they are confirmed by miners, not even an outside observer can be sure about that in all cases.
+
+This EIP adds a way to call other contracts and restrict what they can do in the simplest way. It can be safely assumed that the state of all contracts is the same before and after a static call.


Perhaps all accounts instead of all contracts.

pirapira · 2017-11-20T11:41:07Z

EIPS/eip-214.md

+    Author: Vitalik Buterin <[email protected]>, Christian Reitwiessner <[email protected]>;
+    Type: Standard Track
+    Category: Core
+    Status: Draft


Now the status should be Accepted.

pirapira · 2017-11-20T11:44:37Z

@axic Requires and Replaces fields are optional. eip-X.md says so.

pirapira

The copyrights need to be abandoned as in other EIPs.

pirapira · 2017-12-01T11:55:30Z

@chriseth do you mind if I add

Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).

?

lithp · 2018-12-04T01:53:49Z

EIPS/eip-214.md

+
+`STATICCALL` functions equivalently to a `CALL`, except it takes only 6 arguments (the "value" argument is not included and taken to be zero), and calls the child with the `STATIC` flag set to `true` for the execution of the child. Once this call returns, the flag is reset to its value before the call.
+
+Any attempts to make state-changing operations inside an execution instance with `STATIC` set to `true` will instead throw an exception. These operations include `CREATE`, `CREATE2`, `LOG0`, `LOG1`, `LOG2`, `LOG3`, `LOG4`, `SSTORE`, and `SELFDESTRUCT`. They also include `CALL` with a non-zero value. As an exception, `CALLCODE` is not considered state-changing, even with a non-zero value.


Why does the exception for CALLCODE exist?

Add STATIC_CALL opcode.

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chriseth mentioned this pull request Feb 13, 2017

New opcode: STATIC_CALL #116

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Byzantium changes ethereum/yellowpaper#229

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Updated preamble.

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chriseth changed the title ~~New opcode: STATIC_CALL~~ New opcode: STATICCALL Feb 24, 2017

Rename static_call to staticcall.

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EIP214: STATICCALL instruction ethereum/aleth#3616

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Byzantium release openethereum/parity-ethereum#4833

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All Core Devs Meeting 12 Agenda ethereum/pm#7

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REVERT instruction #206

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Metropolis: static call ethereum/yellowpaper#270

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EIP-116 (214), #4833 openethereum/parity-ethereum#4851

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EIPS/static_call.md Outdated

## Motivation

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Shouldn't this be filled with something?

axic mentioned this pull request Aug 25, 2017

Proposal for read only calls #697

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Add STATICCALL opcode

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ethereum/EIPs#214

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Add STATICCALL opcode

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Move static_call.md to eip-214.md

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Enforce the EVM_STATIC modifier in state changing operations ewasm/hera#73

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New opcode: STATICCALL #214

New opcode: STATICCALL #214

chriseth commented Feb 13, 2017

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lithp Dec 4, 2018


		Opcode: `0xfa`.

		`STATIC_CALL` functions equivalently to a `CALL`, except it takes 6 arguments not including value, and calls the child with a `STATIC` flag on. Any calls, static or otherwise, made by an execution instance with a `STATIC` flag on will also have a `STATIC` flag on. Any attempts to make state-changing operations inside an execution instance with a `STATIC` flag on will instead throw an exception. These operations include nonzero-value calls, creates, `LOG` calls, `SSTORE`, `SSTOREBYTES` and `SUICIDE`.


		## Rationale

		This allows contracts to make calls that are clearly non-state-changing, reassuring developers and reviewers that re-entrancy bugs or other problems cannot possibly arise from that particular call; it is a pure function that returns an output and does nothing else. This may also make purely functional HLLs easier to implement.


		## Motivation

		Currently, there is no restriction about what a called contract can do, as long as the computation can be performed with the amount of gas provided. This poses certain difficulties about smart contract engineers: After a regular call, unless you know the called contract, you cannot make any assumptions about the state of the contracts. Furthermore, because you cannot know the order of transactions before they are confirmed by miners, not even an outside observer can be sure about that in all cases.


		Currently, there is no restriction about what a called contract can do, as long as the computation can be performed with the amount of gas provided. This poses certain difficulties about smart contract engineers: After a regular call, unless you know the called contract, you cannot make any assumptions about the state of the contracts. Furthermore, because you cannot know the order of transactions before they are confirmed by miners, not even an outside observer can be sure about that in all cases.

		This EIP adds a way to call other contracts and restrict what they can do in the simplest way. It can be safely assumed that the state of all contracts is the same before and after a static call.


		`STATICCALL` functions equivalently to a `CALL`, except it takes only 6 arguments (the "value" argument is not included and taken to be zero), and calls the child with the `STATIC` flag set to `true` for the execution of the child. Once this call returns, the flag is reset to its value before the call.

		Any attempts to make state-changing operations inside an execution instance with `STATIC` set to `true` will instead throw an exception. These operations include `CREATE`, `CREATE2`, `LOG0`, `LOG1`, `LOG2`, `LOG3`, `LOG4`, `SSTORE`, and `SELFDESTRUCT`. They also include `CALL` with a non-zero value. As an exception, `CALLCODE` is not considered state-changing, even with a non-zero value.

New opcode: STATICCALL #214

New opcode: STATICCALL #214

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