Mitigate DoS vulnerability by limiting number of extracted arguments #2060
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victorhora
added
3.x
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Hi there. Anyone have an ETA on when this will be merged? Thank you :) |
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Closing this in favor of #2234. |
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A relatively small json payload (<1MB) can generate up to a hundred thousands keys and values, which can then take ages (>30 minutes) to process with OWASP's CRS 3 for example. The parser is not the issue, no particular rule is the issue, it's just the pure quantity of values.
Obviously, with the nginx connector, this completely locks the worker for the whole duration, so it is a DoS vulnerability.
This is the underlying issue behind #2019 and I guess, owasp-modsecurity/ModSecurity-nginx#89 too.
That's why I implemented a
SecArgumentsLimitvalue, disabled by default, allowing to set a limit to the number of extracted arguments. When the limit is reached, subsequent values are ignored. A limit of 1000 arguments should be enough for most applications, and reduces the maximum processing time to well under a second. Requests with more than 1000 arguments can be matched and rejected if wanted with a rule likeSecRule &ARGS "@gt 1000".In addition, I made the JSON processor cancel the parsing when the limit is reached.