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Permissions whitelist with address-level granularity

Manages an Access Control List which maps source and destination addresses to function signatures. Intended to be used as an authority for ds-auth where it acts as a lookup table for the canCall function to provide boolean answers as to whether a particular address is authorized to call agiven function at another address.

The acl is a mapping of [src][dst][sig] => boolean where an address src can be either permitted or forbidden access to a function sig at address dst according to the boolean value. When used as an authority by DSAuth the src is considered to be the msg.sender, the dst is the including contract and sig is the function which invoked the auth modifier.

// Permit a specific address to call a specific function on a specific contract
src = '0011111111111111111111111111111111111111'
dst = '0022222222222222222222222222222222222222'
guard.permit(src, dst, bytes4(sha3('mint(address,uint256)')));

The ANY constant can be stored in place of src, dst or sig where it will act as a wildcard and be considered to match any item in that position.

// Permit ANY address to call a specific function on a specific contract
guard.permit(ANY, dst, bytes4(sha3('mint(address,uint256)')));

// Permit ANY address to call a ANY function on a specific contract
guard.permit(ANY, dst, ANY);

Warning: Statements in the access control list are evaluated with the OR operator, meaning that the most open permission will take precedence. If all of the the above 3 examples were in place for example, it is the last that would take precedence, regardless of the more restrictive permissions defined prior. Developers are encouraged to think carefully before using ANY.

permit an address to call a function at a contract (requires auth)

forbid an address from calling a function at a contract (requires auth)