Bound Slice and array length in idl codecs - #1624
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Description
The IDL codecs build every vec and bytes field as encodings.NewSlice(codec, builder.Int(4)). The upstream slice decoder reads that 4-byte count and passes it straight to reflect.MakeSlice, checking only that it is non-negative — so it allocates for the declared count before discovering the data isn't there. A few bytes of untrusted input allocate 2 GB for vec, up to 64 GB for vec.
Adds commoncodec.NewBoundedSlice, which wraps the length-prefix codec so a count whose implied footprint exceeds the 10 MiB Solana account limit is rejected while decoding the prefix, before MakeSlice runs. The bound uses the larger of the element's on-wire and in-memory size — a nested vec is 4 bytes on the wire but a 24-byte slice header in memory.
Wire format is unchanged and asserted byte-identical against the unbounded codec. The cap equals the whole account limit, so legitimate data — which must be smaller than its containing account or log — is never rejected.
Requires Dependencies
Resolves Dependencies