NXP HSE PKCS#11 Module

1. Prerequisites

The current implementation has been tested with the following:

• libp11 0.4.11 (2020-Oct-11)
• OpenSSL 1.1.1 (2018-Sep-11)

The HSE PKCS11 module is compiled for aarch64, and depends on both libp11 and OpenSSL. As such, libp11 and OpenSSL need to be cross-compiled for aarch64, as well.

Take note that the paths provided in the following sections are provided simply as examples, and can be changed to fit your build environment.

Before you begin cross-compiling, make sure you have a cross-compiler installed, which fits your desired target system's architecture. Furthermore, you should export a CROSS_COMPILE environment variable, which will be auto-detected by the makefiles of the projects. Your CROSS_COMPILE env var should resemble the following:

export CROSS_COMPILE=<path/to/cross/compiler>/aarch64-linux-gnu-

Going forth, it will be assumed you have set your CROSS_COMPILE env var.

1.1. Cross-compiling libp11 0.4.11 for aarch64

First, you will need the source code, which you can download from the project's GitHub page:

https://github.com/OpenSC/libp11/releases

Next, you'll need to configure the build system for aarch64 cross-compilation:

./configure --host=aarch64-linux-gnu --prefix=$HOME/libp11-aarch64

--host will (confusingly) specify the target architecture, while --prefix will indicate a directory separate from your host's file system in which to place the cross-compiled files. The path provided for --prefix is an example.

You can now build libp11:

make
sudo make install

You can find the compiled files under $HOME/libp11-aarch64.

1.2. Cross-compiling OpenSSL 1.1.1 for aarch64

First, you will need the source code, which can be download from the project's website:

https://www.openssl.org/source/old/1.1.1/

Next, you'll need to configure the build system for aarch64 cross-compilation:

./Configure linux-aarch64 --prefix=$HOME/openssl-aarch64

As before, --prefix will indicate a directory separate from your host's file system in which to place the cross-compiled files. The path provided is an example.

You can now build OpenSSL:

make
sudo make install

You can find the compiled files under $HOME/openssl-aarch64.

2. Building the HSE PKCS11 module

Assuming you have set your CROSS_COMPILE env var, compilation is straight-forward. From the pkcs11-hse repo, run:

make

and the pkcs11-hse.so file will be compiled. This is the module that is the middle man in communication between OpenSSL/libp11 and HSE.

2.1. Building the HSE PKCS11 modules example

A usage example is provided in the repo under examples/. The sample application will link against OpenSSL (libcrypto) and libp11 (libp11) to use functions provided by both. In short, what the application does is:

1. initialize libp11 with the pkcs11-hse.so module
2. find the slot and token corresponding to HSE
3. use openssl to generate an RSA key pair
4. store the key pair in HSE
5. enumerate the stored keys
6. remove the key pair from HSE

Since the application must be linked against both libcrypto and libp11, the directories in which the cross-compiled OpenSSL and libp11 are stored must be specified:

make OPENSSL_DIR=$HOME/openssl-aarch64 LIBP11_DIR=$HOME/libp11-aarch64

Moreover, since the application is dynamically linked, both libcrypto and libp11 must be present in the target's file system, (usually) under /usr/lib/. In this case, you can use the files under openssl-aarch64/lib/ and libp11-aarch64/lib/, and copy the libp11.so.* and libcrypto.so.* files to the target's /usr/lib/ directory.

Afterwards, you can run the example on the target system:

./pkcs-keyop <path>/pkcs11-hse.so

The application will output a message for each step described previously.

2.2. Building the OpenSC pkcs11-tool

First, you will need the source code, which can be download from the project's GitHub page:

https://github.com/OpenSC/OpenSC/releases

This release has been tested with OpenSC-0.21.0. Make sure to install the pre-requisites beforehand:

sudo apt-get install pcscd libccid libpcsclite-dev libssl-dev libreadline-dev autoconf automake build-essential docbook-xsl xsltproc libtool pkg-config

Next, you'll need to configure the build system for aarch64 cross-compilation. You'll also need to have cross-compiled OpenSSL beforehand, since OpenSC needs to link against it:

./bootstrap
./configure --host=aarch64-linux --prefix=$HOME/opensc-aarch64-test --enable-openssl \
	CC= <path>/<to>/<cross>/<compiler>/aarch64-linux-gnu-gcc \
	LDFLAGS=-g -Wl,-rpath,$HOME/openssl-aarch64/lib \
	OPENSSL_LIBS=-lcrypto -L$HOME/openssl-aarch64/lib \
	OPENSSL_CFLAGS=-I$HOME/openssl-aarch64/include

As before, --prefix will indicate a directory separate from your host's file system in which to place the cross-compiled files. The path provided is an example.

You can now build OpenSC:

make
sudo make install

You can find the compiled files under $HOME/opensc-aarch64. You'll need to place opensc-aarch64/lib/libopensc.so.7.0.0 in the target's lib directory (e.g. in /usr/lib); opensc-aarch64/bin/pkcs11-tool can be placed anywhere on the target (e.g. /home/<user>).

You can use pkcs11-tool to load RSA keys (public/pair), EC keys (public) and AES keys. Some examples:

./pkcs11-tool --module /<path>/libpkcs-hse.so --write-object /<path>/rsa_keypair.der --type privkey --label "HSE-RSAPRIV-KEY" --usage-decrypt --usage-sign
./pkcs11-tool --module /<path>/libpkcs-hse.so --write-object /<path>/rsa_keypub.der --type pubkey --label "HSE-RSAPUB-KEY" --usage-decrypt --usage-sign
./pkcs11-tool --module /<path>/libpkcs-hse.so --write-object /<path>/ec_keypub.der --type pubkey --label "HSE-ECPUB-prime256v1-KEY" --usage-sign
./pkcs11-tool --module /<path>/libpkcs-hse.so --write-object /<path>/aes.key --type secrkey --key-type AES:256 --label "HSE-AES-256-KEY" --usage-decrypt

The tool will display a message if the key import operation is successful.