Eric Wild e03530f89a GP: LOAD/STORE DATA chunk size from SCP overhead ...

SCP.overhead was so far set at construction time (SCP02: 8, SCP03:
s_mode), so the C-MAC length only.
Unfortunately sec lvl >= 3 pads the data field to the cipher block size
before encryption, so the real worst-case overhead is larger,
scc.max_cmd_len (255 - overhead) was too big, and ADF_SD.load()
used a hardcoded chunk_len=240.

Real world issue with a 286 byte CAP + SCP02 + sec lvl 3:
- 240-byte LOAD block is padded to 248,
- encrypted
- gets 8 byte C-MAC appended
-> Lc = 256
That dies with a weird "ValueError: bytes must be in range(0, 256)".
The only "fix" for that was to downgrade the seclevel.

STORE DATA has the same overflow with large max_cmd_len
(247 + padding + MAC = 256 as well).

Therefore the overhead must be properly calculated from the sec level.

While at it adjust the error in case I missed something to get a more
useful ValueError.

Change-Id: Ic208f3959a38896f64fb6ccefb24cc360a3ac3a2

2026-09-07 19:51:23 +02:00

..

__init__.py

GP: LOAD/STORE DATA chunk size from SCP overhead

2026-09-07 19:51:23 +02:00

http.py

Use osmocom.construct.{Bytes,GreedyBytes} for hexstring input support

2025-04-28 09:32:52 +02:00

install_param.py

global_platform: refactor gen_install_parameters()

2026-03-25 18:05:30 +00:00

scp.py

GP: LOAD/STORE DATA chunk size from SCP overhead

2026-09-07 19:51:23 +02:00

uicc.py

comment in uicc.py on Security Domain Keys: add SCP81

2026-04-25 05:15:14 +07:00