Segault while checking pkcs11 card signature

[Olivier Martin]

Here are some traces:

```
P:1449015; T:0x140679159284416 13:52:27.127 [opensc-pkcs11] sec.c:59:sc_compute_signature: called
P:1449015; T:0x140679159284416 13:52:27.127 [opensc-pkcs11] card-piv.c:2409:piv_compute_signature: called
P:1449015; T:0x140679159284416 13:52:27.128 [opensc-pkcs11] card-piv.c:2322:piv_validate_general_authentication: called
P:1449015; T:0x140679159284416 13:52:27.128 [opensc-pkcs11] card-piv.c:502:piv_general_io: called
P:1449015; T:0x140679159284416 13:52:27.128 [opensc-pkcs11] card.c:473:sc_lock: called
P:1449015; T:0x140679159284416 13:52:27.128 [opensc-pkcs11] card.c:513:sc_lock: returning with: 0 (Success)
P:1449015; T:0x140679159284416 13:52:27.128 [opensc-pkcs11] apdu.c:548:sc_transmit_apdu: called
P:1449015; T:0x140679159284416 13:52:27.128 [opensc-pkcs11] card.c:473:sc_lock: called
P:1449015; T:0x140679159284416 13:52:27.128 [opensc-pkcs11] card.c:513:sc_lock: returning with: 0 (Success)
P:1449015; T:0x140679159284416 13:52:27.129 [opensc-pkcs11] apdu.c:515:sc_transmit: called
P:1449015; T:0x140679159284416 13:52:27.129 [opensc-pkcs11] apdu.c:363:sc_single_transmit: called
P:1449015; T:0x140679159284416 13:52:27.129 [opensc-pkcs11] apdu.c:367:sc_single_transmit: CLA:0, INS:87, P1:11, P2:9A, data(38) 0x7ffcc4478280
P:1449015; T:0x140679159284416 13:52:27.129 [opensc-pkcs11] reader-pcsc.c:323:pcsc_transmit: reader 'MyReader 00 00'
P:1449015; T:0x140679159284416 13:52:27.129 [opensc-pkcs11] reader-pcsc.c:324:pcsc_transmit:
Outgoing APDU (44 bytes):
00 87 11 9A 26 7C 24 82 00 81 20 40 DD 29 19 4B ....&|$... @.).K
DE D5 92 6D ED 8B AC EA EC 76 79 7C 30 4F 74 2E ...m.....vy|0Ot.
AE 0A 95 38 D2 7F 90 95 77 1F BF 00 ...8....w...

P:1449015; T:0x140679159284416 13:52:27.129 [opensc-pkcs11] reader-pcsc.c:242:pcsc_internal_transmit: called
P:1449015; T:0x140679159284416 13:52:27.220 [opensc-pkcs11] reader-pcsc.c:333:pcsc_transmit:
Incoming APDU (77 bytes):
7C 49 82 47 30 45 02 20 16 31 BE 5A B7 0C 50 4D |I.G0E. .1.Z..PM
96 FD 21 01 C2 13 6B B9 12 91 D3 9E EA 2D B9 4D ..!...k......-.M
63 2D 38 1E 7A 8D A9 60 02 21 00 F8 D2 7E BF 9D c-8.z..`.!...~..
9D B5 1A D6 46 3C 51 00 BF 12 C2 3E 0D C1 4E 54 ....F<Q....>..NT
63 AD 41 5D 06 95 02 F2 59 6E EB 90 00 c.A]....Yn...

P:1449015; T:0x140679159284416 13:52:27.221 [opensc-pkcs11] apdu.c:382:sc_single_transmit: returning with: 0 (Success)
P:1449015; T:0x140679159284416 13:52:27.221 [opensc-pkcs11] apdu.c:537:sc_transmit: returning with: 0 (Success)
P:1449015; T:0x140679159284416 13:52:27.221 [opensc-pkcs11] card.c:523:sc_unlock: called
P:1449015; T:0x140679159284416 13:52:27.221 [opensc-pkcs11] card.c:523:sc_unlock: called
P:1449015; T:0x140679159284416 13:52:27.221 [opensc-pkcs11] card-piv.c:544:piv_general_io: returning with: 75
P:1449015; T:0x140679159284416 13:52:27.222 [opensc-pkcs11] card-piv.c:2390:piv_validate_general_authentication: returning with: 71
P:1449015; T:0x140679159284416 13:52:27.222 [opensc-pkcs11] card-piv.c:2466:piv_compute_signature: returning with: 64
P:1449015; T:0x140679159284416 13:52:27.222 [opensc-pkcs11] sec.c:63:sc_compute_signature: returning with: 64
P:1449015; T:0x140679159284416 13:52:27.222 [opensc-pkcs11] card.c:523:sc_unlock: called
P:1449015; T:0x140679159284416 13:52:27.222 [opensc-pkcs11] pkcs15-sec.c:169:use_key: returning with: 64
P:1449015; T:0x140679159284416 13:52:27.223 [opensc-pkcs11] pkcs15-sec.c:759:sc_pkcs15_compute_signature: returning with: 64
P:1449015; T:0x140679159284416 13:52:27.223 [opensc-pkcs11] card.c:523:sc_unlock: called
P:1449015; T:0x140679159284416 13:52:27.223 [opensc-pkcs11] reader-pcsc.c:737:pcsc_unlock: called
P:1449015; T:0x140679159284416 13:52:27.224 [opensc-pkcs11] framework-pkcs15.c:4255:pkcs15_prkey_sign: Sign complete. Result 64.
P:1449015; T:0x140679159284416 13:52:27.224 [opensc-pkcs11] mechanism.c:478:sc_pkcs11_signature_final: returning with: 0 (Success)
P:1449015; T:0x140679159284416 13:52:27.224 [opensc-pkcs11] mechanism.c:336:sc_pkcs11_sign_final: returning with: 0 (Success)
P:1449015; T:0x140679159284416 13:52:27.224 [opensc-pkcs11] pkcs11-object.c:731:C_Sign: C_Sign() = CKR_OK
DEBUG:pkcs11_lib.c:1834: signature[64] = [16:31:be:...:eb]
DEBUG:pam_pkcs11.c:727: verifying signature...
DEBUG:cert_vfy.c:518: public key type: 0x00000198
DEBUG:cert_vfy.c:519: public key bits: 0x00000100
Segmentation fault (core dumped)
```

To duplicate this issue:

```
$ cat /etc/pam.d/pkcs11
auth sufficient pam_pkcs11.so
```

and I used `pamtester`: `OPENSC_DEBUG=9 pamtester pkcs11 olivier authenticate`

After investigated this issue into the code, I actually found the issue and have a fix for it: https://salsa.debian.org/debian/pam-pkcs11/-/merge_requests/3

My commit is sufficient to fix the issue.

[Olivier Martin (olivier-martin)]

I have just created a merge-request for Ubuntu package: https://code.launchpad.net/~olivier-martin/ubuntu/+source/pam-pkcs11/+git/pam-pkcs11/+merge/436857