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",(0,r.jsx)(t.a,{href:"/world/reference/world-context#_msgsender",children:(0,r.jsx)(t.code,{children:"_msgSender()"})})," and ",(0,r.jsx)(t.a,{href:"/world/reference/world-context#_msgvalue",children:(0,r.jsx)(t.code,{children:"_msgValue()"})}),".\nThis means it can perform any action while pretending to be any user."]}),"\n"]}),"\n",(0,r.jsxs)(t.p,{children:["This violates the security principle of ",(0,r.jsx)(t.a,{href:"https://csrc.nist.gov/glossary/term/least_privilege",children:(0,r.jsx)(t.em,{children:"least privilege"})}),".\nIdeally, you should avoid running in the root namespace."]}),"\n",(0,r.jsx)(s.UW,{type:"error",emoji:"\uD83D\uDEAB",children:(0,r.jsxs)(t.p,{children:["If you ",(0,r.jsx)(t.em,{children:"have"})," to use a ",(0,r.jsx)(t.code,{children:"System"})," in the root namespace, avoid using\n",(0,r.jsx)(t.a,{href:"https://docs.soliditylang.org/en/v0.8.16/introduction-to-smart-contracts.html#delegatecall-callcode-and-libraries",children:(0,r.jsx)(t.code,{children:"delegatecall"})}),",\nexcept for libraries whose security you verified. Any contract you call with ",(0,r.jsx)(t.code,{children:"delegatecall"})," is going to inherit the\n",(0,r.jsx)(t.code,{children:"World"})," context, and have unlimited permissions on your application."]})}),"\n",(0,r.jsx)(t.h2,{id:"design-consideraions",children:"Design consideraions"}),"\n",(0,r.jsx)(t.h3,{id:"one-call-one-action",children:"One call, one action"}),"\n",(0,r.jsxs)(t.p,{children:["If you want a transaction to do multiple actions (for example: register, start a game, and then perform the first move in the game), you don't need a ",(0,r.jsx)(t.code,{children:"DoThis_DoThat_AndThen_DoTheOtherThing"})," function.\nJust use ",(0,r.jsx)(t.a,{href:"/world/batch-calls",children:"batch calls"}),", which preserve the message sender (in `_msgSender())."]}),"\n",(0,r.jsx)(t.h3,{id:"use-delegation-for-user-agents",children:"Use delegation for user agents"}),"\n",(0,r.jsxs)(t.p,{children:["If a ",(0,r.jsx)(t.code,{children:"System"})," is going to act on the users' behalf, it will need to call other ",(0,r.jsx)(t.code,{children:"System"}),"s, probably in other namespaces.\nThe way to do this is to request users to ",(0,r.jsx)(t.a,{href:"/world/account-delegation",children:"delegate their permissions"}),".\nThis is necessary because:"]}),"\n",(0,r.jsxs)(t.ul,{children:["\n",(0,r.jsxs)(t.li,{children:["If you call another ",(0,r.jsx)(t.code,{children:"System"})," through the ",(0,r.jsx)(t.code,{children:"World"}),", the message sender (",(0,r.jsx)(t.code,{children:"_msgSender()"}),") is the calling ",(0,r.jsx)(t.code,{children:"System"}),".\nThe called ",(0,r.jsx)(t.code,{children:"System"})," has no way of knowing if it can trust the caller ",(0,r.jsx)(t.code,{children:"System"})," to represent the wishes of the ultimate user.\nSee ",(0,r.jsx)(t.a,{href:"https://docs.soliditylang.org/en/v0.8.25/security-considerations.html#tx-origin",children:"the Solidity documentation"})," for an in-depth explanation."]}),"\n",(0,r.jsxs)(t.li,{children:["If you ",(0,r.jsx)(t.code,{children:"delegatecall"})," another ",(0,r.jsx)(t.code,{children:"System"})," directly you keep ",(0,r.jsx)(t.code,{children:"_msgSender()"}),"'s value, but the called ",(0,r.jsx)(t.code,{children:"System"})," is only allowed to perform actions allowed to the calling ",(0,r.jsx)(t.code,{children:"System"}),"."]}),"\n"]}),"\n",(0,r.jsx)(t.h3,{id:"dont-send-eth-with-your-calls",children:"Don't send ETH with your calls"}),"\n",(0,r.jsxs)(t.p,{children:["The way ",(0,r.jsx)(t.a,{href:"/world/balance",children:"ETH balances"})," work in MUD, ",(0,r.jsx)(t.em,{children:"all"})," ETH is stored in the ",(0,r.jsx)(t.code,{children:"World"})," contract and internally accounted as belonging to namespaces.\nIf your ",(0,r.jsx)(t.code,{children:"System"})," is in the root namespace it has access to this ETH, but if you transfer out except through ",(0,r.jsx)(t.a,{href:"https://github.com/latticexyz/mud/blob/main/packages/world/src/modules/init/implementations/BalanceTransferSystem.sol",children:(0,r.jsx)(t.code,{children:"BalanceTransferSystem"})}),", you need to update the accounting table.\nIf your ",(0,r.jsx)(t.code,{children:"System"})," is not in the root namespace it does not have direct access to the ETH anyway.\nYou ",(0,r.jsx)(t.em,{children:"have"})," to use ",(0,r.jsx)(t.code,{children:"BalanceTransferSystem"}),"."]}),"\n",(0,r.jsx)(t.h2,{id:"implementation-considerations",children:"Implementation considerations"}),"\n",(0,r.jsx)(t.h3,{id:"use-libraries-to-bypass-the-contract-size-limit",children:"Use libraries to bypass the contract size limit"}),"\n",(0,r.jsxs)(t.p,{children:["If you have a large ",(0,r.jsx)(t.code,{children:"System"})," and you come up against the ",(0,r.jsx)(t.a,{href:"https://ethereum.org/en/developers/docs/smart-contracts/#limitations",children:"contract size limit"}),", don't split it in two.\nInstead, use ",(0,r.jsx)(t.a,{href:"https://docs.soliditylang.org/en/latest/contracts.html#libraries",children:"public libraries"}),".\nLibraries are called using ",(0,r.jsx)(t.a,{href:"https://docs.soliditylang.org/en/latest/introduction-to-smart-contracts.html#delegatecall-and-libraries",children:(0,r.jsx)(t.code,{children:"delegatecall"})}),", so they have the same permissions as the calling contract.\nThis includes the ability to write to MUD tables when the calling ",(0,r.jsx)(t.code,{children:"System"})," is permitted to do so."]})]})}t.default=(0,a.j)(l)}},function(e){e.O(0,[3720,2888,179],function(){return e(e.s=86083)}),_N_E=e.O()}]);