Fix stack overflow when parsing deeply nested configs #6325
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Parsing a configuration file as a JSON document which contains deeply nested elements can lead to a stack overflow when using the recursive parser of RapidJSON. Since the configuration isn't changed or parsed frequently, use the slower iterative parser instead. Copying the configuration JSON document that contains deeply nested elements, using the CopyFrom API, can lead to a stack overflow, due to the recursive nature of the RapidJSON GenericValue construction. Detect the depth/nesting level of a config document and limit it to 32 levels. Using an iterative parser, while it avoids stack overflows, can cause memory exhaustion if the config size is too big. Limit the maximum config size, stripped from its comments, to 1MiB. Addresses https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20779
theopolis
approved these changes
Mar 27, 2020
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Parsing a configuration file as a JSON document
which contains deeply nested elements can lead to a stack overflow
when using the recursive parser of RapidJSON.
Since the configuration isn't changed or parsed frequently,
use the slower iterative parser instead.
Copying the configuration JSON document
that contains deeply nested elements, using the CopyFrom API,
can lead to a stack overflow, due to the recursive nature
of the RapidJSON GenericValue construction.
Detect the depth/nesting level of a config document
and limit it to 32 levels.
Using an iterative parser, while it avoids stack overflows,
can cause memory exhaustion if the config size is too big.
Limit the maximum config size, stripped from its comments, to 1MiB.
Addresses https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20779