curl: Fix use after free on a POST request - #2863
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Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
The string passed to libcurl is a copy made by `to_cstring`, it was unreachable from Nit and could be freed by the GC before libcurl reads it with `postfields`. Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
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When creating a POST request with the curl lib there was a potential use after free depending on when the GC triggered, causing issues in long running apps. We would allocate a C string and pass it to curl, losing a handle to it before triggering the
performwork. If the GC triggered between the two operations curl would read from freed memory.Let's use the curl service that takes ownership of a copy of this string. This is the foolproof solution but isn't ideal as the string content is usually copied twice, but the usual way around it (allocating the C string on the Nit side and releasing it later) would add boiler plate too all call sites.