How to test/demonstrate Helloworld with gp

[wpd]

The HelloWorld sample application in the Java Card appears to be a simple "ping" test, which is great. I have successfully compiled and loaded it onto a Smart Card. But now I am wondering how/if I can use gp to test it.

Can I send arbitrary APDU packets to my application?

I tried:

$ gp -d --applet A00000006203010C01 --apdu 12345678
SCardConnect("SCM Microsystems Inc. SCR 3310 [CCID Interface] (53312118210918) 00 00", T=*) -> T=1, 3BFA180000910131FE454A33523138302D323535F5
# GlobalPlatformPro 325fe84
# Running on Linux 5.4.0-153-generic amd64, Java 17.0.7 by Private Build
A>> T=1 (4+0009) 00A40400 09 A00000006203010C01
A<< (0000+2) (16ms) 9000
Error: Channel not open: 2
SCardDisconnect("SCM Microsystems Inc. SCR 3310 [CCID Interface] (53312118210918) 00 00", true) tx:14/rx:2

and, as you can see, it returns an Error: Channel not open: 2.

I was able to test this with gpshell with a script that looked something like:

mode_211
enable_trace
establish_context

card_connect -readerNumber 1

select -AID a00000006203010c01
send_apdu -APDU 12345678
card_disconnect
release_context

It seems like there must be a very simple option to gp that would do the same thing... but I just can't figure out what it is.

So now I'm asking :-)

--wpd

[wpd]

Perhaps I'm supposed to know what I'm doing if I want to use the --apdu option and I should probably construct a valid APDU with something like this (which appears to have worked):

$ gp -d -v --applet A00000006203010C01 --apdu 000000000412345678
# 
# gp -d -v --applet A00000006203010C01 --apdu 000000000412345678
SCardConnect("SCM Microsystems Inc. SCR 3310 [CCID Interface] (53312118210918) 00 00", T=*) -> T=1, 3BFA180000910131FE454A33523138302D323535F5
# GlobalPlatformPro 325fe84
# Running on Linux 5.4.0-153-generic amd64, Java 17.0.7 by Private Build
# Selecting A00000006203010C01
A>> T=1 (4+0009) 00A40400 09 A00000006203010C01
A<< (0000+2) (17ms) 9000
A>> T=1 (4+0004) 00000000 04 12345678
A<< (0009+2) (11ms) 000000000412345678 9000
A>> T=1 (4+0000) 00A40400 00 
A<< (0018+2) (11ms) 6F108408A000000151000000A5049F6501FF 9000
[DEBUG] GPSession - Auto-detected ISD: A000000151000000
Warning: no keys given, defaulting to 404142434445464748494A4B4C4D4E4F
SCardDisconnect("SCM Microsystems Inc. SCR 3310 [CCID Interface] (53312118210918) 00 00", true) tx:28/rx:33

Sorry for the spam.

--wpd

[martinpaljak]

That helps indeed! CLA byte has special semantics in the underlying structure..