A significant logical vulnerability in the _decodeReceiptUndelegateDone function is the absence of a check to ensure that the parsing of the CBOR data structure in the result byte array completes properly by processing all bytes in the array. This oversight can allow improperly formatted CBOR data that includes extraneous bytes after a legitimate amount value to be processed without error. Essentially, if the result is padded with additional, unrelated data beyond what is expected, the function will not validate whether it has parsed the entire array, as long as it found an amount key.
Attack Scenario\
Crafting Malicious Input:
An attacker can exploit this vulnerability by crafting a result byte array that includes a correct CBOR-encoded map with an amount key, followed by extraneous bytes that are irrelevant but won't trigger an error. Particularly:
Start with a valid CBOR-encoded map that has the amount key (0xA1) encoding the valid uint128 scalar value.
Append additional bytes that are non-conforming with the expected format but don't disrupt reading the initial amount. This could include random bytes or additional CBOR items that are deliberately misleading or malformed.
Executing with Crafted Input:
When the function _decodeReceiptUndelegateDone is called with this maliciously crafted input, it would successfully decode the amount from the initial part of the data. Given it does not verify that all data in the array was consumed, processing would stop right after reading the amount, disregarding the trailing bytes.
Impact:
The function completes without any errors since it successfully detects and decodes the amount key.
The trailing bytes can be manipulated to perform operations that might remain unnoticed since they aren't validated against any structure or expected format.
Implementation of the Check:
To prevent such exploitation, _decodeReceiptUndelegateDone should incorporate an additional check at the end of the function execution to confirm that offset matches result.length:
By adding this check, the function ensures that it has processed exactly all the bytes provided in the input array, thus validating the integrity and format of the CBOR data structure entirely and avoiding exploitation, where extraneous data might be overlooked. This not only ensures stricter adherence to expected input formats but also significantly improves the contract's robustness against malformed or malicious data inputs.
0xRizwan
commented
2 months ago
Github username: -- Twitter username: -- Submission hash (on-chain): 0xe192f9ab7971ade759bd5402f34a8c444b1416c9b8c59e147213af92ef5943aa Severity: low
Description: Description\
A significant logical vulnerability in the
_decodeReceiptUndelegateDonefunction is the absence of a check to ensure that the parsing of the CBOR data structure in theresultbyte array completes properly by processing all bytes in the array. This oversight can allow improperly formatted CBOR data that includes extraneous bytes after a legitimateamountvalue to be processed without error. Essentially, if the result is padded with additional, unrelated data beyond what is expected, the function will not validate whether it has parsed the entire array, as long as it found anamountkey.Attack Scenario\
Crafting Malicious Input: An attacker can exploit this vulnerability by crafting a
resultbyte array that includes a correct CBOR-encoded map with anamountkey, followed by extraneous bytes that are irrelevant but won't trigger an error. Particularly:amountkey (0xA1) encoding the validuint128scalar value.amount. This could include random bytes or additional CBOR items that are deliberately misleading or malformed.Executing with Crafted Input: When the function
_decodeReceiptUndelegateDoneis called with this maliciously crafted input, it would successfully decode theamountfrom the initial part of the data. Given it does not verify that all data in the array was consumed, processing would stop right after reading theamount, disregarding the trailing bytes.Impact:
amountkey.Implementation of the Check:
To prevent such exploitation,
_decodeReceiptUndelegateDoneshould incorporate an additional check at the end of the function execution to confirm thatoffsetmatchesresult.length:By adding this check, the function ensures that it has processed exactly all the bytes provided in the input array, thus validating the integrity and format of the CBOR data structure entirely and avoiding exploitation, where extraneous data might be overlooked. This not only ensures stricter adherence to expected input formats but also significantly improves the contract's robustness against malformed or malicious data inputs.
Attachments
Proof of Concept (PoC) File
Revised Code File (Optional)