Bound preallocation by available input to prevent OOM (#119) - #266
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c-rack merged 1 commit intoAug 17, 2026
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A decoder preallocated a collection or buffer of the declared length before reading any data, so a small crafted message with a huge declared length -- e.g. an array header claiming 2^31-1 elements -- triggered an OutOfMemoryError. Cap preallocation at InputStream.available() so it can never exceed what the message can actually provide.
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Thanks @dngr2 ! |
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Fixes #119.
A crafted CBOR message can declare a huge array/map/string length, and the decoder preallocated a collection or buffer of that size before reading any data. So a 5-byte message like
9A 7F FF FF FF— an array claiming 2,147,483,647 elements — triggered anOutOfMemoryError.getPreallocationSizenow also caps the size atInputStream.available(), so preallocation can never exceed what the message can actually provide. Legitimate data is unaffected (the bytes are present, soavailable()≥ the length); a forged length allocates nothing and fails with the normal end-of-streamCborException. This applies by default, without needingsetMaxPreallocationSize.Updated the existing forged-length test (which previously expected the
OutOfMemoryError) and added array/map cases.