Add input length cap and parenthesis depth limit to expression parser#13
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Add input length cap and parenthesis depth limit to expression parser#13
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parseAtom recurses into parseExpression on each open parenthesis with no
depth bound, so a long run of '(' overflows the goroutine stack and
fatally crashes the process. Adds a depth counter on the parser struct
checked on each open paren, and a 1 MiB input length cap at the top of
Parse and ParseStrict. Both return ErrExpressionTooLarge.
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`parseAtom` recurses into `parseExpression` on every `(` with no depth bound, so a sufficiently long run of open parentheses overflows the goroutine stack and fatally crashes the process rather than returning an error. `Valid()` does not protect against this either since it just calls `Parse`.
Adds a `depth` counter to the parser struct, incremented and checked against `maxParseDepth` (256) in the `tokenOpenParen` branch of `parseAtom`. Also adds a 1 MiB input length cap at the top of `Parse` and `ParseStrict`. Both limits return `ErrExpressionTooLarge`.