1### NFC Replay Utility 2 3The NFC Replay tool allows a PN 532 module to reenact a NFC transaction from a 4snoop log. Currently, the tool is capable of replaying polling loop transactions 5and APDU exchanges. Once the transaction has been replayed, a test can 6optionally be generated based on the interaction between the module and 7emulator. 8 9The detailed design for this feature can be found at go/nfc-replay-utility-dd. 10 11### Using the tool 12 13#### Generating and replaying a test 14 151\. Obtain a snoop log from the device (see instructions below for how to do this). 16 172\. Connect the PN532 module via a serial port. 18 193\. To replay the transaction, substitute the name of the snoop file and the 20serial port that the PN 532 module is using. 21 22``` 23python3 nfcreplay.py -f $SNOOP_FILE -p $READER_PATH 24``` 25 26Alternatively, to replay a specific section of the snoop log, additional 27arguments should be added to denote the desired start and end time frame of the 28transaction. For instance: 29 30``` 31python3 nfcreplay.py -f $SNOOP_FILE -p $READER_PATH --start "2024-07-17 12:00:00" --end "2024-07-17 15:00:00" 32``` 33 34Information about the transaction will be printed out to console, including a 35list of all polling loop and APDU exchanges that took place. 36 375\. To generate and run a test from the snoop log, use the command: 38``` 39python3 nfcreplay.py -f $SNOOP_FILE -p $READER_PATH --generate_and_replay_test 40``` 41 42A Python file will be created, representing the test, along with a JSON file 43that contains all information pertaining to APDUs transacted. 44 45#### Using the Emulator App 46 47The generated test will always involve the installation of the emulator app 48(located at src/com/android/nfc/emulatorapp/) onto the emulator. The app handles 49APDU transactions in cases where the replayed transaction involves a third party 50app that the emulator does not access to. To guarantee that the emulator app is 51able to handle the transaction, all AIDs sent in the original transaction will 52be replaced with AIDs that the app is registered to handle (the specific values 53are located in @xml/aids). 54 55When the transaction is replayed, you should be able to see a list of APDU 56commands and responses received and sent by the Host APDU service displayed on 57the emulator app. 58 59To use the emulator app outside of a generated test, perform the following steps: 60 611\. To prepare a snoop log to be replayed with the app: 62 63``` 64python3 nfcreplay.py -f $SNOOP_FILE --parse_only 65``` 66 67The script will produce the name of the parsed log, which will be located within 68the folder emulatorapp/parsed_files. Save the name for Step 3. 69 702\. Build and install the emulator app. The following commands are specific to 71the Pixel 6 Pro (Raven). Non-Raven devices should substitute "raven" for the 72appropriate value. 73 74``` 75mma NfcEmulatorApduAppNonTest 76adb install -r -g ~/aosp-main-with-phones/out/target/product/raven/system/app/emulatorapp/NfcEmulatorApduAppNonTest.apk 77 78``` 79 803\. Start the activity. Make sure that $PARSED_SNOOP_FILE is the name of the 81file, rather than its path. It is assumed that this file is located within 82emulatorapp/parsed_files, where it was originally created. 83 84``` 85adb shell am start -n com.android.nfc.emulatorapp/.MainActivity --es "snoop_file" "$PARSED_SNOOP_FILE" 86``` 87 88When you are ready to start the transaction, press the "Start Host APDU Service" 89button. 90 914\. To replay the transaction with the PN532 module, follow the steps above to 92generate and replay a test case, though you should make sure to append the flag 93`--replay_with_app` to the end of each command. 94 95When the transaction is replayed, you should be able to see a list of APDU 96commands and responses received and sent by the Host APDU service displayed on 97the emulator app. Additionally, the replay script will output similar 98information. 99 100### Creating a Snoop Log 101 102To create a snoop log from your Android device, you should first go to Developer 103Options in Settings to make sure that "NFC NCI unfiltered log" is enabled. This 104will ensure that the data packets sent during NFC transactions are not truncated 105in the snoop log. 106 107After the NFC transaction is complete, enter the command `adb shell dumpsys 108nfc`. This will output the snoop log, which will begin with the line `--- 109BEGIN:NFCSNOOP_VS_LOG_SUMMARY` and end with the line `--- 110END:NFCSNOOP_VS_LOG_SUMMARY ---`. Copy the snoop log into a text file, and make 111sure to include both the start and end lines.