martinpaljak
commented
3 years ago Things to consider:
- metadata from the card is often incorrect (or some vendor-specific NDA document tells the actual implementation is limited compared to the spec); the best to do is to use it as a hint to provide better defaults, but in a failsafe way.
- explicit user input should be respected over implicit assumptions: if giving input of 400 bytes, length should be encoded as necessary (in 2.3 style) and command sent no matter what (because previous point). But a helpful warning might be relevant. In GPTool, not in the library part.
So encoding all lengths "properly" as default is OK. Just need to check the specs if there are fancy corner cases, because GPC 2.2.1 11.1.5 tells:
All length fields of GlobalPlatform messages and data objects defined in this specification, except for Lc and Le, are coded as defined for ASN.1 BER-TLV (see ISO 8825-1): 1 byte for a length up to 127, 2 bytes for a length up to 255, and 3 bytes for a length up to 65535, except where otherwise stated.
and there were corner cases for one byte encoding with keys at least.
xavo95
Fix #241