32 lines
1.8 KiB
Markdown
32 lines
1.8 KiB
Markdown
Safety and Protection Against DoS Attacks
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{{#include links.md}}
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For scripting systems open to untrusted user-land scripts, it is always best to limit the amount of
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resources used by a script so that it does not consume more resources that it is allowed to.
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The most important resources to watch out for are:
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* **Memory**: A malicous script may continuously grow a [string], an [array] or [object map] until all memory is consumed.
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It may also create a large [array] or [object map] literal that exhausts all memory during parsing.
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* **CPU**: A malicous script may run an infinite tight loop that consumes all CPU cycles.
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* **Time**: A malicous script may run indefinitely, thereby blocking the calling system which is waiting for a result.
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* **Stack**: A malicous script may attempt an infinite recursive call that exhausts the call stack.
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Alternatively, it may create a degenerated deep expression with so many levels that the parser exhausts the call stack
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when parsing the expression; or even deeply-nested statement blocks, if nested deep enough.
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* **Overflows**: A malicous script may deliberately cause numeric over-flows and/or under-flows, divide by zero, and/or
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create bad floating-point representations, in order to crash the system.
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* **Files**: A malicous script may continuously [`import`] an external module within an infinite loop,
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thereby putting heavy load on the file-system (or even the network if the file is not local).
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Furthermore, the module script may simply [`import`] itself in an infinite recursion.
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Even when modules are not created from files, they still typically consume a lot of resources to load.
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* **Data**: A malicous script may attempt to read from and/or write to data that it does not own. If this happens,
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it is a severe security breach and may put the entire system at risk.
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