contracts: fix CBOR unsigned int decoding in Subcall.sol

[CedarMist]

fixes #323

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[CedarMist]

Ok, minor last thing.

I need to make the subcall stuff not error out if it encounters and unknown key.

[matevz]

FYI this section https://www.rfc-editor.org/rfc/rfc8949.html#name-tag-validity mentions that the 128- and 256-bit integers are encoded as 0x40 (byte arrays).

[matevz]

FYI this section https://www.rfc-editor.org/rfc/rfc8949.html#name-tag-validity mentions that the 128- and 256-bit integers are encoded as 0x40 (byte arrays).

Having the _cborParseUInt() split into 64-bit and smaller uints and 128-bit and greater uints codepaths opens potential gas attacks? Should we use gas padding to mitigate this?

[CedarMist]

FYI this section https://www.rfc-editor.org/rfc/rfc8949.html#name-tag-validity mentions that the 128- and 256-bit integers are encoded as 0x40 (byte arrays).

Having the _cborParseUInt() split into 64-bit and smaller uints and 128-bit and greater uints codepaths opens potential gas attacks? Should we use gas padding to mitigate this?

I'd prefer if the caller of the receipt parser does the gas padding if it's deemed necessary rather than building it into the parser itself. But yes, I'll add a note in the code about it.

[lubej]

Also returns null(0xf6) in case epoch is not reached yet.