Handle get_challenge corner cases

[Jakuje]

Problem Description

The get_challenge() function in coolkey applet is broken. Before 410cdf0 the function was returning some garbage from the heap:

[jjelen@t470s OpenSC (master)]$ pkcs11-tool --generate-random 8 | hexdump -C
Using slot 0 with a present token (0x0)
00000000  00 00 00 00 00 00 00 00                           |........|
00000008
[jjelen@t470s OpenSC (master)]$ pkcs11-tool --generate-random 32 | hexdump -C
Using slot 0 with a present token (0x0)
00000000  d0 1c f3 96 82 55 00 00  41 47 20 43 61 72 64 4d  |.....U..AG CardM|
00000010  61 6e 20 33 31 32 31 20  30 30 20 30 30 00 00 00  |an 3121 00 00...|
00000020
[jjelen@t470s OpenSC (master)]$ pkcs11-tool --generate-random 64 | hexdump -C
Using slot 0 with a present token (0x0)
00000000  00 90 5c 32 a6 55 00 00  03 0c 0b 4a 61 6b 75 62  |..\2.U.....Jakub|
00000010  20 4a 65 6c 65 6e 31 17  30 15 06 03 55 04 0a 0c  | Jelen1.0...U...|
00000020  0e 54 6f 6b 65 6e 20 4b  65 79 20 55 73 65 72 31  |.Token Key User1|
00000030  16 30 14 06 0a 09 92 26  89 93 f2 2c 64 01 01 0c  |.0.....&...,d...|
00000040

After the refactoring (410cdf0), the card is cycling in the following code:

0x7f643fc17880 16:30:28.816 [opensc-pkcs11] card-coolkey.c:1613:coolkey_get_challenge: called
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] card-coolkey.c:935:coolkey_apdu_io: called
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] card-coolkey.c:940:coolkey_apdu_io: 73 00 00 0 : 255 256
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] card-coolkey.c:1004:coolkey_apdu_io: calling sc_transmit_apdu flags=0 le=8, resplen=8, resp=0x147cc70
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] apdu.c:554:sc_transmit_apdu: called
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] card.c:415:sc_lock: called
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] card.c:455:sc_lock: returning with: 0 (Success)
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] apdu.c:521:sc_transmit: called
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] apdu.c:371:sc_single_transmit: called
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] apdu.c:378:sc_single_transmit: CLA:B0, INS:73, P1:0, P2:0, data(0) (nil)
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] reader-pcsc.c:284:pcsc_transmit: reader 'OMNIKEY AG CardMan 3121 00 00'
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] reader-pcsc.c:285:pcsc_transmit: 
Outgoing APDU (5 bytes):
B0 73 00 00 08 .s...
0x7f643fc17880 16:30:28.816 [opensc-pkcs11] reader-pcsc.c:213:pcsc_internal_transmit: called
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] reader-pcsc.c:294:pcsc_transmit: 
Incoming APDU (2 bytes):
90 00 ..
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] apdu.c:390:sc_single_transmit: returning with: 0 (Success)
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] apdu.c:543:sc_transmit: returning with: 0 (Success)
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] card.c:465:sc_unlock: called
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] card-coolkey.c:1011:coolkey_apdu_io: result r=0 apdu.resplen=0 sw1=90 sw2=00
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] card-coolkey.c:891:coolkey_check_sw: sw1 = 0x90, sw2 = 0x00
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] card-coolkey.c:1037:coolkey_apdu_io: returning with: 0 (Success)
0x7f643fc17880 16:30:28.821 [opensc-pkcs11] card-coolkey.c:1623:coolkey_get_challenge: returning with: 0 (Success)

There are two issues: First of all, coolkey get_random APDU does not work at all. I will need to figure out what is the problem here. Second issue is the handling of the get_random by the OpenSC, which is assuming that if user requested N bytes of random data, the driver will be able to return it.

Proposed Resolution

• (1) There should be some showstopper, when the card fails to provide requested amount of data (returning length of zero), rather than optimistically cycling forever.
• (2) The coolkey get_challenge needs to be fixed to work (or return some error if the random is not supported?)
• (3) The p11tests should be extended with this test to avoid issues later.

Steps to reproduce

Try to generate random data with coolkey card with master (will cycle forever):

# ./src/tools/pkcs11-tool --login --pin redhat --module ./src/pkcs11/.libs/pkcs11-spy.so --generate-random 8

[Jakuje]

The (2) is fixed by #1441. The other issues still apply. I will change the title to reflect this.