PivApplet

Table of Contents

• About
• Current status
• Installing
• Default admin key & PINs
• ECDSA hash-on-card extension
• Building the project
• Simulation

About

This is an attempt at making a PIV (NIST SP 800-73-4) compatible JavaCard applet. Current target is JavaCard 2.2.2, with 2-3k of transient memory.

Current status

What works:

• OpenSC, MacOS (piv.tokend for login), Windows PIV

• RSA-1024 and -2048 key generation on card, signing

• EC P-256 key generation (but no ECDSA)

• EC Diffie-Hellman on P-256

• PINs and change of PIN, PUK reset

• Most YubiKeyPIV-compatible extensions are implemented and working:

  • PIN policy

  • Version indicator (we pretend to be a YK5)

  • Fetch serial number (randomly generated)

  • Set management key

  • Import asymmetric key

  • Reset after PIN+PUK blocked

  • Change PIN/PUK retry limits

  • Attestation using slot F9

What doesn’t work:

• PIV-compatible ECDSA (probably not fixable without JavaCard 3.0.5 or proprietary APIs)

  • There is support for it in the code, but it will not work without a client that is specifically aware of the double-hashing issue (uses a proprietary algorithm ID).

• YubicoPIV touch policy

  • No standard JavaCard APIs for accessing GPIO or sensors so this is probably not happening.

Installing

The pre-built .cap files for each release can be found on the project release page.

You can use the Global Platform command-line tool (gp) to upload the applet to your JavaCard:

$ gp -install PivApplet.cap
CAP loaded

Now you have a PIV card ready to initialise. It’s easiest to do the initialisation with the yubico-piv-tool:

$ yubico-piv-tool -r '' -a list-readers
Alcor Micro AU9560 00 00
Yubico Yubikey 4 OTP+U2F+CCID 01 00

$ yubico-piv-tool -r Alcor -a generate -s 9e > pubkey-9e.pem
Successfully generated a new private key.

$ yubico-piv-tool -r Alcor -a selfsign-certificate -s 9e \
    -S '/CN=test' < pubkey-9e.pem > cert-9e.pem
Successfully generated a new self signed certificate.

$ yubico-piv-tool -r Alcor -a import-certificate -s 9e < cert-9e.pem
Successfully imported a new certificate.

Now your PIV token is set up with a self-signed Card Authentication (9e) key. You can generate keys and certificates in the other slots in a similar fashion (remember that most other slots default to requiring a PIN entry, which you have to do with -a verify-pin -a selfsign-certificate …​ when using yubico-piv-tool).

Sample output of yubico-piv-tool -a status:

CHUID:	301900000000000000000000000000000000000000000000000000341047132924dfd1f7581290d383781dc81a350832303530303130313e00fe00
CCC:	f015a000000116ff02b8907468b1e6d143231c5c7c452df10121f20121f300f400f50110f600f700fa00fb00fc00fd00fe00
Slot 9e:
	Algorithm:	RSA2048
	Subject DN:	CN=test
	Issuer DN:	CN=test
	Fingerprint:	acbc68b8ec8a25432a296801e4deb375a14b4d78f35016f8729a7c481040eb9a
	Not Before:	Jun 19 05:33:06 2017 GMT
	Not After:	Jun 19 05:33:06 2018 GMT
PIN tries left:	5

Default admin key & PINs

Default PIN

123456

Default PUK

12345678

Default card administration (9B) key

01 02 03 04 05 06 07 08 01 02 03 04 05 06 07 08 …​

(This is the default used by Yubikeys, so that the yubico-piv-tool will work with PivApplet.)

ECDSA hash-on-card extension

The applet supports an extension for doing ECDSA with hash-on-card, which client software will have to specifically add support for if it wants to use ECDSA signing with this applet. As of writing, the only PIV client with support for this extension known to the authors is piv-agent.

Unfortunately, regular PIV ECDSA signing is not possible with the JavaCard standard crypto functions, which only support a single operation that combines hashing and signing. The current PIV standard demands that the data to be signed is hashed by the host, and then the hash is sent to the card.

In addition to the algorithm ID 0x11 for ECCP256, we introduce two new IDs, ECCP256-SHA1 (0xF0) and ECCP256-SHA256 (0xF1). For key generation the client should continue to use ECCP256 (as well as for ECDH), but for signing one of the two new algorithm IDs must be used (ECCP256 will be rejected).

These two new algorithms are "hash-on-card" algorithms, where the "challenge" tag sent by the host to the card should include the full data to be signed without any hashing applied. The card will hash the data and return the signature in the same was as a normal EC signature.

For example, to sign the payload "foo\n" with the Card Authentication (9e) key, with SHA-256, the host could send the following APDU:

00 87 F1 9E 0A 7C 08 82 00 81 04 66 6F 6F 0A

This extension, naturally, will not work with existing PIV host software that is not aware of it. It is supported as a workaround for users who are ok with customising their host software who really want to use ECDSA.

Support for these new algorithms is advertised in the 0xAC (supported algorithms) tag in the response to INS_SELECT. Client software may detect it there to decide whether to attempt use hash-on-card or not.

Building the project

We use ant-javacard for builds.

$ git clone https://github.com/arekinath/PivApplet
...

$ cd PivApplet
$ git submodule init && git submodule update
...

$ export JC_HOME=/path/to/jckit-2.2.2
$ ant

The capfile will be output in the ./bin directory, along with the .class files (which can be used with jCardSim).

Simulation

Simulator testing for this project has so far been done on Linux, using jCardSim (both with and without a Virtual Smartcard Reader).

The easiest way to do it on Linux is with a virtual reader:

1. Install vsmartcard (see here, but it might also be in your distro’s package manager). Once it’s installed (and PCSCd restarted) your list of smartcard readers on the system (try opensc-tool -l or yubico-piv-tool -a list-readers) should include a bunch of Virtual PCD entries.

2. Clone my fork of jCardSim (https://github.com/arekinath/jcardsim) and build it (using mvn initialize && mvn clean install)

3. From the pivapplet directory (after running ant to build), run: java -noverify -cp bin/:../jcardsim/target/jcardsim-3.0.5-SNAPSHOT.jar com.licel.jcardsim.remote.VSmartCard test/jcardsim.cfg

Now you should see a card appear in the first of the Virtual PCD readers. To start the PivApplet up, send it a command like this:

$ opensc-tool -r 'Virtual PCD 00 00' -s '80 b8 00 00 12 0b a0 00 00 03 08 00 00 10 00 01 00 05 00 00 02 0F 0F 7f'

Then you should see the simulated PivApplet come to life! The forked jCardSim currently spits out debug output on the console including full APDUs sent and received, and stack traces of exceptions (very useful!).

You can also use the simulator with jdb, the Java debugger:

$ jdb -noverify -classpath bin/:../jcardsim/target/jcardsim-3.0.5-SNAPSHOT.jar com.licel.jcardsim.remote.VSmartCard test/jcardsim.cfg
Initializing jdb ...
> stop at net.cooperi.pivapplet.PivApplet:1769
Deferring breakpoint net.cooperi.pivapplet.PivApplet:1769.
It will be set after the class is loaded.
> run
run com.licel.jcardsim.remote.VSmartCard test/jcardsim.cfg
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started:

== APDU
0000:  00 A4 04 00  09 A0 00 00
0008:  03 08 00 00  10 00 00
javacard.framework.ISOException
  at javacard.framework.ISOException.throwIt(Unknown Source)
  at net.cooperi.pivapplet.PivApplet.sendOutgoing(PivApplet.java:470)
  at net.cooperi.pivapplet.PivApplet.sendSelectResponse(PivApplet.java:435)
  at net.cooperi.pivapplet.PivApplet.process(PivApplet.java:284)
  at com.licel.jcardsim.base.SimulatorRuntime.transmitCommand(SimulatorRuntime.java:303)
  at com.licel.jcardsim.base.Simulator.transmitCommand(Simulator.java:263)
  at com.licel.jcardsim.base.CardManager.dispatchApduImpl(CardManager.java:66)
  at com.licel.jcardsim.base.CardManager.dispatchApdu(CardManager.java:36)
  at com.licel.jcardsim.remote.VSmartCard$IOThread.run(VSmartCard.java:151)
== Reply APDU
0000:  61 3D 4F 0B  A0 00 00 03
0008:  08 00 00 10  00 01 00 79
0010:  0D 4F 0B A0  00 00 03 08
0018:  00 00 10 00  01 00 50 09
0020:  50 69 76 41  70 70 6C 65
0028:  74 AC 14 80  01 03 80 01
0030:  06 80 01 07  80 01 11 80
0038:  01 F0 80 01  F1 06 00 90
0040:  00
== APDU
0000:  00 CB 3F FF  03 5C 01 7E
0008:  08

Breakpoint hit: "thread=Thread-0", net.cooperi.pivapplet.PivApplet.processGetData(), line=1,769 bci=70

Thread-0[1] wherei
  [1] net.cooperi.pivapplet.PivApplet.processGetData (PivApplet.java:1,769), pc = 70
  [2] net.cooperi.pivapplet.PivApplet.process (PivApplet.java:290), pc = 146
  [3] com.licel.jcardsim.base.SimulatorRuntime.transmitCommand (SimulatorRuntime.java:303), pc = 223
  [4] com.licel.jcardsim.base.Simulator.transmitCommand (Simulator.java:263), pc = 12
  [5] com.licel.jcardsim.base.CardManager.dispatchApduImpl (CardManager.java:66), pc = 102
  [6] com.licel.jcardsim.base.CardManager.dispatchApdu (CardManager.java:36), pc = 5
  [7] com.licel.jcardsim.remote.VSmartCard$IOThread.run (VSmartCard.java:151), pc = 109
Thread-0[1] dump buffer
 buffer = {
0, -53, 63, -1, 3, 92, 1, 126, 8
}
Thread-0[1] dump tlv.s
 tlv.s = {
0, 0, 3, 3
}
Thread-0[1] dump incoming.state
 incoming.state = {
0, 63, 63, 0, 63, 63, 0, 0
}
Thread-0[1] ...