thodg/libgit2/tests/resources

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  • Hash : b7dcea04
    Author : Patrick Steinhardt
    Date : 2019-09-26T15:06:12

    config_entries: micro-optimize storage of multivars Multivars are configuration entries that have many values for the same name; we can thus micro-optimize this case by just retaining the name of the first configuration entry and freeing all the others, letting them point to the string of the first entry. The attached test case is an extreme example that demonstrates this. It contains a section name that is approximately 500kB in size with 20.000 entries "a=b". Without the optimization, this would require at least 20000*500kB bytes, which is around 10GB. With this patch, it only requires 500kB+20000*1B=20500kB. The obvious culprit here is the section header, which we repeatedly include in each of the configuration entry's names. This makes it very easier for an adversary to provide a small configuration file that disproportionally blows up in memory during processing and is thus a feasible way for a denial-of-service attack. Unfortunately, we cannot fix the root cause by e.g. having a separate "section" field that may easily be deduplicated due to the `git_config_entry` structure being part of our public API. So this micro-optimization is the best we can do for now.

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