Morpheus: Automated Safety Verification of Data-dependent Parser Combinator Programs

TL;DR

Morpheus is a novel framework that enables automated safety verification of complex, data-dependent parser combinator programs by providing abstractions and a rich specification language, making verification more tractable.

Contribution

It introduces Morpheus, a parser combinator framework with abstractions for effects and safety specifications, improving automated verification of data-dependent parsers.

Findings

Successfully verified complex parsing applications

Handled non-trivial data-dependent relations

Enhanced verification tractability

Abstract

Parser combinators are a well-known mechanism used for the compositional construction of parsers, and have shown to be particularly useful in writing parsers for rich grammars with data-dependencies and global state. Verifying applications written using them, however, has proven to be challenging in large part because of the inherently effectful nature of the parsers being composed and the difficulty in reasoning about the arbitrarily rich data-dependent semantic actions that can be associated with parsing actions. In this paper, we address these challenges by defining a parser combinator framework called Morpheus equipped with abstractions for defining composable effects tailored for parsing and semantic actions and a rich specification language used to define safety properties over the constituent parsers comprising a program. Even though its abstractions yield many of the same expressivity benefits as other parser combinator systems, Morpheus is carefully engineered to yield a substantially more tractable automated verification pathway. We demonstrate its utility in verifying a number of realistic, challenging parsing applications, including several cases that involve non-trivial data-dependent relations.