NFC: Emulating a UID of a previously saved ISO-14443A-4 does not work because SAK tells there should be an ATS

[doegox]

Describe the bug.

Flipper allows to emulate the UID of cards it can't fully emulate, such as a MIFARE DESFire. But it emulates the recorded SAK as well. The SAK of an ISO-14443-4 has bit6=1 (e.g. SAK=20), contrarily to ISO-14443-3 cards such as MIFARE Classic, NTAG, Ultralight, with a SAK with bit6=0. The problem is that when emulating a UID, the Flipper emulates an ISO-14443-3 without an ATS, but the reader seeing a SAK=20 is waiting for the ATS that never comes.

Reproduction

Steps:

• read an ISO-14443A-4, for example a MIFARE DESFire.
• emulate the UID of the saved card A reader will fail detecting the emulated card.

Target

Tested on today Release and Development firmwares

Logs

No response

Anything else?

Two possible solutions:

1. record and save the ATS in ISO-14443A-4 dumps, then when "emulating UID", replay the ATS in the anticollision.
2. clear bit6 of SAK when "emulating UID"

To make it robust, they can be combined:

• record and save the ATS in ISO-14443A-4 dumps
• "emulating UID" : check that if bit6 of SAK=1. If yes, then check if ATS is available in the saved file. If not, clear SAK bit6 during the emulation

[gornekich]

Hello! Thanks for bug report and solution. Now I will add quick fix to clear 6 bit in SAK in UID emulation. Then we will save ATS and follow your suggestions

[skotopes]

Please check latest release and reopen if issue persist