Hydra is the two-layer scalability solution for Cardano. Prior to version 0.13.0, it is possible for a malicious head initializer to extract one or more PTs for the head they are initializing due to incorrect data validation logic in the head token minting policy which then results in an flawed check for burning the head ST in the initial validator. This is possible because it is not checked in HeadTokens.hs that the datums of the outputs at the initial validator are equal to the real head ID, and it is also not checked in the off-chain code.
During the Initial state of the protocol, if the malicious initializer removes a PT from the Hydra scripts it becomes impossible for any other participant to reclaim any funds they have attempted to commit into the head, as to do so the Abort transaction must burn all the PTs for the head, but they cannot burn the PT which the attacker controls and so cannot satisfy this requirement. That means the initializer can lock the other participants committed funds forever or until they choose to return the PT (ransom).
The malicious initializer can also use the PT to spoof that they have committed a particular TxO when progressing the head into the Open state. For example, they could say they committed a TxO residing at their address containing 100 ADA, but in fact this 100 ADA was not moved into the head, and thus in order for an other participant to perform the fanout they will be forced to pay the attacker the 100 ADA out of their own funds, as the fanout transaction must pay all the committed TxOs (even though the attacker did not really commit that TxO). They can do this by placing the PT in a UTxO with a well-formed Commit datum with whatever contents they like, then use this UTxO in the collectCom transaction. There may be other possible ways to abuse having control of a PT.
Version 0.13.0 fixes this issue.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Hydra | Iohk | * | 0.13.0 (excluding) |
Input validation is a frequently-used technique for checking potentially dangerous inputs in order to ensure that the inputs are safe for processing within the code, or when communicating with other components. When software does not validate input properly, an attacker is able to craft the input in a form that is not expected by the rest of the application. This will lead to parts of the system receiving unintended input, which may result in altered control flow, arbitrary control of a resource, or arbitrary code execution. Input validation is not the only technique for processing input, however. Other techniques attempt to transform potentially-dangerous input into something safe, such as filtering (CWE-790) - which attempts to remove dangerous inputs - or encoding/escaping (CWE-116), which attempts to ensure that the input is not misinterpreted when it is included in output to another component. Other techniques exist as well (see CWE-138 for more examples.) Input validation can be applied to:
Data can be simple or structured. Structured data can be composed of many nested layers, composed of combinations of metadata and raw data, with other simple or structured data. Many properties of raw data or metadata may need to be validated upon entry into the code, such as:
Implied or derived properties of data must often be calculated or inferred by the code itself. Errors in deriving properties may be considered a contributing factor to improper input validation.
Note that “input validation” has very different meanings to different people, or within different classification schemes. Caution must be used when referencing this CWE entry or mapping to it. For example, some weaknesses might involve inadvertently giving control to an attacker over an input when they should not be able to provide an input at all, but sometimes this is referred to as input validation. Finally, it is important to emphasize that the distinctions between input validation and output escaping are often blurred, and developers must be careful to understand the difference, including how input validation is not always sufficient to prevent vulnerabilities, especially when less stringent data types must be supported, such as free-form text. Consider a SQL injection scenario in which a person’s last name is inserted into a query. The name “O’Reilly” would likely pass the validation step since it is a common last name in the English language. However, this valid name cannot be directly inserted into the database because it contains the “’” apostrophe character, which would need to be escaped or otherwise transformed. In this case, removing the apostrophe might reduce the risk of SQL injection, but it would produce incorrect behavior because the wrong name would be recorded.