fix(protocol): cap decompressed payload size to prevent gzip bombs (#942) - #943
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Message.Decode decompressed gzip/snappy payloads with io.ReadAll and no output cap, before service lookup or auth. MaxMessageLength only bounds the compressed wire length, so a small frame could expand to gigabytes and OOM the server pre-authentication (issue #942). - util: add UnzipLimited using io.LimitReader to bound output; Unzip honors package-level MaxDecompressedSize (default 0 = unlimited). - protocol: add optional LimitedUnzipper interface, implement on Gzip and Snappy compressors; Decode caps output via MaxDecompressedLength. - server: add WithMaxDecompressedLength / WithMaxMessageLength options. Defaults stay unlimited for backward compatibility. Fixes #942
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Summary
Fixes #942 โ an unauthenticated gzip decompression bomb in the rpcx wire protocol.
Message.Decodedecompressed gzip (and snappy) payloads withio.ReadAlland no cap on output size, before service lookup or auth.MaxMessageLengthonly bounds the compressed wire length, so a small frame (<2MB) could expand to gigabytes and OOM the server fully pre-authentication.Changes
UnzipLimited(data, maxSize)usingio.LimitReader(gr, maxSize+1)to detect overflow without allocating the oversized payload; returns newErrDecompressedSizeTooLarge.Unzipnow honors package-levelMaxDecompressedSize.LimitedUnzipperinterface, implemented onGzipCompressorandSnappyCompressor(snappy had the same unboundedio.ReadAll).MaxDecompressedLength;Decodecaps decompression viaLimitedUnzipperwhen set โ bounded before service lookup and auth.WithMaxDecompressedLength(int64)andWithMaxMessageLength(int)options.Backward compatibility
Caps default to
0(unlimited), so behavior is unchanged unless configured. Servers accepting untrusted traffic should set one, e.g.:Tests
util.TestUnzipLimitedโ payload over/at/under the cap.protocol.TestDecodeDecompressBombโ a small compressed frame expanding to 1 MiB is rejected when the cap is set, decodes fine when unlimited.All of
./util,./protocol,./serverbuild, vet, and test green.