Fix: Remove incorrect casts #720
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This patch removes a narrowing static cast from `bsl::string::size_type` to `int` which could cause an invalid configuration of sufficient length to print an arbitrarily long error message. When an invalid configuration is detected in the current behavior, we statically cast its length from `bsl::string::size_type` (a.k.a. `bsl::size_t`) to `int`. If the JSON configuration is too large, the results of this are implementation defined; on many common implementations, though, this may result in a negative `int`, depending on the exact length of the configuration. We then use `bsl::min` to limit it to a maximum of 1024, with the type of the integral literal `1024` deduced to `int`. If the casted `int` is negative, it is propagated through. Finally, we pass the resulting `int` to a function that expects a `bsl::string::size_type` again, causing another implementation-defined conversion. Here again, if the `int` is negative, we may get a very large value. The combination of a narrowing cast and the conversions between `unsigned` and `signed` integers cause this pernitious behavior. Instead of a cast and extra type conversions, this patch makes the integral literal have the type `bsl::string::size_type`. The value 1024 is representable with this type, so this is safe. As a result, there are no casts or other conversions, and the entire operation is done in the input and result type `bsl::string::size_type`, avoiding this bug. Signed-off-by: Patrick M. Niedzielski <[email protected]>
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Previous PRs have added casts to silence warnings, but these warnings were in many cases real bugs. This PR will remove several casts that have the potential to introduce incorrect and exploitable behavior. Analyses of each are given in the commit messages in this PR.