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<section xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="pkcs11"><info><title>PKCS#11 (Cryptoki) support</title></info>
<para>
PKCS#11 (Public Key Cryptography Standard #11) defines a
platform-independent API for the control of hardware security
modules (HSMs) and other cryptographic support devices.
</para>
<para>
BIND 9 is known to work with three HSMs: The AEP Keyper, which has
been tested with Debian Linux, Solaris x86 and Windows Server 2003;
the Thales nShield, tested with Debian Linux; and the Sun SCA 6000
cryptographic acceleration board, tested with Solaris x86. In
addition, BIND can be used with all current versions of SoftHSM,
a software-based HSM simulator library produced by the OpenDNSSEC
project.
</para>
<para>
PKCS#11 makes use of a "provider library": a dynamically loadable
library which provides a low-level PKCS#11 interface to drive the HSM
hardware. The PKCS#11 provider library comes from the HSM vendor, and
it is specific to the HSM to be controlled.
</para>
<para>
There are two available mechanisms for PKCS#11 support in BIND 9:
OpenSSL-based PKCS#11 and native PKCS#11. When using the first
mechanism, BIND uses a modified version of OpenSSL, which loads
the provider library and operates the HSM indirectly; any
cryptographic operations not supported by the HSM can be carried
out by OpenSSL instead. The second mechanism enables BIND to bypass
OpenSSL completely; BIND loads the provider library itself, and uses
the PKCS#11 API to drive the HSM directly.
</para>
<section><info><title>Prerequisites</title></info>
<para>
See the documentation provided by your HSM vendor for
information about installing, initializing, testing and
troubleshooting the HSM.
</para>
</section>
<section><info><title>Native PKCS#11</title></info>
<para>
Native PKCS#11 mode will only work with an HSM capable of carrying
out <emphasis>every</emphasis> cryptographic operation BIND 9 may
need. The HSM's provider library must have a complete implementation
of the PKCS#11 API, so that all these functions are accessible. As of
this writing, only the Thales nShield HSM and SoftHSMv2 can be used
in this fashion. For other HSMs, including the AEP Keyper, Sun SCA
6000 and older versions of SoftHSM, use OpenSSL-based PKCS#11.
(Note: Eventually, when more HSMs become capable of supporting
native PKCS#11, it is expected that OpenSSL-based PKCS#11 will
be deprecated.)
</para>
<para>
To build BIND with native PKCS#11, configure as follows:
</para>
<screen>
$ <userinput>cd bind9</userinput>
$ <userinput>/configure --enable-native-pkcs11 \
--with-pkcs11=<replaceable>provider-library-path</replaceable></userinput>
</screen>
<para>
This will cause all BIND tools, including <command>named</command>
and the <command>dnssec-*</command> and <command>pkcs11-*</command>
tools, to use the PKCS#11 provider library specified in
<replaceable>provider-library-path</replaceable> for cryptography.
(The provider library path can be overridden using the
<option>-E</option> in <command>named</command> and the
<command>dnssec-*</command> tools, or the <option>-m</option> in
the <command>pkcs11-*</command> tools.)
</para>
<section><info><title>Building SoftHSMv2</title></info>
<para>
SoftHSMv2, the latest development version of SoftHSM, is available
from
<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://github.com/opendnssec/SoftHSMv2">
</link>.
It is a software library developed by the OpenDNSSEC project
</link>)
which provides a PKCS#11 interface to a virtual HSM, implemented in
the form of a SQLite3 database on the local filesystem. It provides
less security than a true HSM, but it allows you to experiment with
native PKCS#11 when an HSM is not available. SoftHSMv2 can be
configured to use either OpenSSL or the Botan library to perform
cryptographic functions, but when using it for native PKCS#11 in
BIND, OpenSSL is required.
</para>
<para>
By default, the SoftHSMv2 configuration file is
<replaceable>prefix</replaceable> is configured at compile time).
This location can be overridden by the SOFTHSM2_CONF environment
variable. The SoftHSMv2 cryptographic store must be installed and
initialized before using it with BIND.
</para>
<screen>
$ <userinput> cd SoftHSMv2 </userinput>
$ <userinput> configure --with-crypto-backend=openssl --prefix=/opt/pkcs11/usr --enable-gost </userinput>
$ <userinput> make </userinput>
$ <userinput> make install </userinput>
$ <userinput> /opt/pkcs11/usr/bin/softhsm-util --init-token 0 --slot 0 --label softhsmv2 </userinput>
</screen>
</section>
</section>
<section><info><title>OpenSSL-based PKCS#11</title></info>
<para>
OpenSSL-based PKCS#11 mode uses a modified version of the
OpenSSL library; stock OpenSSL does not fully support PKCS#11.
ISC provides a patch to OpenSSL to correct this. This patch is
based on work originally done by the OpenSolaris project; it has been
modified by ISC to provide new features such as PIN management and
key-by-reference.
</para>
<para>
There are two "flavors" of PKCS#11 support provided by
the patched OpenSSL, one of which must be chosen at
configuration time. The correct choice depends on the HSM
hardware:
</para>
<itemizedlist>
<listitem>
<para>
Use 'crypto-accelerator' with HSMs that have hardware
cryptographic acceleration features, such as the SCA 6000
board. This causes OpenSSL to run all supported
cryptographic operations in the HSM.
</para>
</listitem>
<listitem>
<para>
Use 'sign-only' with HSMs that are designed to
function primarily as secure key storage devices, but lack
hardware acceleration. These devices are highly secure, but
are not necessarily any faster at cryptography than the
system CPU — often, they are slower. It is therefore
most efficient to use them only for those cryptographic
functions that require access to the secured private key,
such as zone signing, and to use the system CPU for all
other computationally-intensive operations. The AEP Keyper
is an example of such a device.
</para>
</listitem>
</itemizedlist>
<para>
The modified OpenSSL code is included in the BIND 9 release,
in the form of a context diff against the latest versions of
OpenSSL. OpenSSL 0.9.8, 1.0.0, 1.0.1 and 1.0.2 are supported;
there are separate diffs for each version. In the examples to
follow, we use OpenSSL 0.9.8, but the same methods work with
OpenSSL 1.0.0 through 1.0.2.
</para>
<note><simpara>
The OpenSSL patches as of this writing (January 2016)
support versions 0.9.8zh, 1.0.0t, 1.0.1q and 1.0.2f.
ISC will provide updated patches as new versions of OpenSSL
are released. The version number in the following examples
is expected to change.
</simpara></note>
<para>
Before building BIND 9 with PKCS#11 support, it will be
necessary to build OpenSSL with the patch in place, and configure
it with the path to your HSM's PKCS#11 provider library.
</para>
<section><info><title>Patching OpenSSL</title></info>
<screen>
$ <userinput>wget <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="">http://www.openssl.org/source/openssl-0.9.8zc.tar.gz</link></userinput>
</screen>
<para>Extract the tarball:</para>
<screen>
</screen>
<para>Apply the patch from the BIND 9 release:</para>
<screen>
$ <userinput>patch -p1 -d openssl-0.9.8zc \
</screen>
<note><simpara>
The patch file may not be compatible with the
"patch" utility on all operating systems. You may need to
install GNU patch.
</simpara></note>
<para>
When building OpenSSL, place it in a non-standard
location so that it does not interfere with OpenSSL libraries
elsewhere on the system. In the following examples, we choose
when we configure BIND 9.
</para>
<para>
Later, when building BIND 9, the location of the custom-built
OpenSSL library will need to be specified via configure.
</para>
</section>
<section><info><title>Building OpenSSL for the AEP Keyper on Linux</title></info>
<!-- Example 1 -->
<para>
The AEP Keyper is a highly secure key storage device,
but does not provide hardware cryptographic acceleration. It
can carry out cryptographic operations, but it is probably
slower than your system's CPU. Therefore, we choose the
'sign-only' flavor when building OpenSSL.
</para>
<para>
The Keyper-specific PKCS#11 provider library is
delivered with the Keyper software. In this example, we place
</para>
<screen>
</screen>
<para>
The Keyper library requires threads, so we
must specify -pthread.
</para>
<screen>
$ <userinput>cd openssl-0.9.8zc</userinput>
$ <userinput>/Configure linux-x86_64 -pthread \
--pk11-flavor=sign-only \
</screen>
<para>
After configuring, run "<command>make</command>"
and "<command>make test</command>". If "<command>make
test</command>" fails with "pthread_atfork() not found", you forgot to
add the -pthread above.
</para>
</section>
<section><info><title>Building OpenSSL for the SCA 6000 on Solaris</title></info>
<!-- Example 2 -->
<para>
The SCA-6000 PKCS#11 provider is installed as a system
library, libpkcs11. It is a true crypto accelerator, up to 4
times faster than any CPU, so the flavor shall be
'crypto-accelerator'.
</para>
<para>
In this example, we are building on Solaris x86 on an
AMD64 system.
</para>
<screen>
$ <userinput>cd openssl-0.9.8zc</userinput>
$ <userinput>/Configure solaris64-x86_64-cc \
--pk11-flavor=crypto-accelerator \
</screen>
<para>
</para>
<para>
After configuring, run
<command>make</command> and
<command>make test</command>.
</para>
</section>
<section><info><title>Building OpenSSL for SoftHSM</title></info>
<!-- Example 3 -->
<para>
SoftHSM (version 1) is a software library developed by the
OpenDNSSEC project
</link>)
which provides a
PKCS#11 interface to a virtual HSM, implemented in the form of
a SQLite3 database on the local filesystem. SoftHSM uses
the Botan library to perform cryptographic functions. Though
less secure than a true HSM, it can allow you to experiment
with PKCS#11 when an HSM is not available.
</para>
<para>
The SoftHSM cryptographic store must be installed and
initialized before using it with OpenSSL, and the SOFTHSM_CONF
environment variable must always point to the SoftHSM configuration
file:
</para>
<screen>
$ <userinput> cd softhsm-1.3.7 </userinput>
$ <userinput> make </userinput>
$ <userinput> make install </userinput>
</screen>
<para>
SoftHSM can perform all cryptographic operations, but
since it only uses your system CPU, there is no advantage to using
it for anything but signing. Therefore, we choose the 'sign-only'
flavor when building OpenSSL.
</para>
<screen>
$ <userinput>cd openssl-0.9.8zc</userinput>
$ <userinput>/Configure linux-x86_64 -pthread \
--pk11-flavor=sign-only \
</screen>
<para>
After configuring, run "<command>make</command>"
and "<command>make test</command>".
</para>
</section>
<para>
Once you have built OpenSSL, run
that PKCS#11 support was compiled in correctly. The output
should be one of the following lines, depending on the flavor
selected:
</para>
<screen>
(pkcs11) PKCS #11 engine support (sign only)
</screen>
<para>Or:</para>
<screen>
(pkcs11) PKCS #11 engine support (crypto accelerator)
</screen>
<para>
Next, run
attempt to initialize the PKCS#11 engine. If it is able to
do so successfully, it will report
<quote><literal>[ available ]</literal></quote>.
</para>
<para>
If the output is correct, run
"<command>make install</command>" which will install the
</para>
<section><info><title>Configuring BIND 9 for Linux with the AEP Keyper</title></info>
<!-- Example 4 -->
<para>
To link with the PKCS#11 provider, threads must be
enabled in the BIND 9 build.
</para>
<screen>
$ <userinput>/configure --enable-threads \
</screen>
</section>
<section><info><title>Configuring BIND 9 for Solaris with the SCA 6000</title></info>
<!-- Example 5 -->
<para>
To link with the PKCS#11 provider, threads must be
enabled in the BIND 9 build.
</para>
<screen>
$ <userinput>/configure CC="cc -xarch=amd64" --enable-threads \
</screen>
<para>(For a 32-bit build, omit CC="cc -xarch=amd64".)</para>
<para>
If configure complains about OpenSSL not working, you
incorrectly specified the path to OpenSSL (it should be the
same as the --prefix argument to the OpenSSL
Configure).
</para>
</section>
<section><info><title>Configuring BIND 9 for SoftHSM</title></info>
<!-- Example 6 -->
<screen>
$ <userinput>/configure --enable-threads \
</screen>
</section>
<para>
After configuring, run
"<command>make</command>",
"<command>make test</command>" and
"<command>make install</command>".
</para>
<para>
(Note: If "make test" fails in the "pkcs11" system test, you may
have forgotten to set the SOFTHSM_CONF environment variable.)
</para>
</section>
<section><info><title>PKCS#11 Tools</title></info>
<para>
BIND 9 includes a minimal set of tools to operate the
HSM, including
<command>pkcs11-keygen</command> to generate a new key pair
within the HSM,
<command>pkcs11-list</command> to list objects currently
available,
<command>pkcs11-destroy</command> to remove objects, and
<command>pkcs11-tokens</command> to list available tokens.
</para>
<para>
9 is configured with the --with-pkcs11 option. (Note: If
--with-pkcs11 is set to "yes", rather than to the path of the
PKCS#11 provider, then the tools will be built but the
provider will be left undefined. Use the -m option or the
PKCS11_PROVIDER environment variable to specify the path to the
provider.)
</para>
</section>
<section><info><title>Using the HSM</title></info>
<para>
For OpenSSL-based PKCS#11, we must first set up the runtime
environment so the OpenSSL and PKCS#11 libraries can be loaded:
</para>
<screen>
</screen>
<para>
This causes <command>named</command> and other binaries to load
rather than from the default location. This step is not necessary
when using native PKCS#11.
</para>
<para>
Some HSMs require other environment variables to be set.
For example, when operating an AEP Keyper, it is necessary to
specify the location of the "machine" file, which stores
information about the Keyper for use by the provider
library. If the machine file is in
use:
</para>
<screen>
</screen>
<para>
Such environment variables must be set whenever running
any tool that uses the HSM, including
<command>pkcs11-keygen</command>,
<command>pkcs11-list</command>,
<command>pkcs11-destroy</command>,
<command>dnssec-keyfromlabel</command>,
<command>dnssec-signzone</command>,
<command>dnssec-keygen</command>, and
<command>named</command>.
</para>
<para>
We can now create and use keys in the HSM. In this case,
we will create a 2048 bit key and give it the label
"sample-ksk":
</para>
<screen>
$ <userinput>pkcs11-keygen -b 2048 -l sample-ksk</userinput>
</screen>
<para>To confirm that the key exists:</para>
<screen>
$ <userinput>pkcs11-list</userinput>
Enter PIN:
object[0]: handle 2147483658 class 3 label[8] 'sample-ksk' id[0]
object[1]: handle 2147483657 class 2 label[8] 'sample-ksk' id[0]
</screen>
<para>
Before using this key to sign a zone, we must create a
pair of BIND 9 key files. The "dnssec-keyfromlabel" utility
does this. In this case, we will be using the HSM key
"sample-ksk" as the key-signing key for "example.net":
</para>
<screen>
</screen>
<para>
The resulting K*.key and K*.private files can now be used
to sign the zone. Unlike normal K* files, which contain both
public and private key data, these files will contain only the
public key data, plus an identifier for the private key which
remains stored within the HSM. Signing with the private key takes
place inside the HSM.
</para>
<para>
If you wish to generate a second key in the HSM for use
as a zone-signing key, follow the same procedure above, using a
different keylabel, a smaller key size, and omitting "-f KSK"
from the dnssec-keyfromlabel arguments:
</para>
<para>
(Note: When using OpenSSL-based PKCS#11 the label is an arbitrary
string which identifies the key. With native PKCS#11, the label is
a PKCS#11 URI string which may include other details about the key
and the HSM, including its PIN. See
<xref linkend="man.dnssec-keyfromlabel"/> for details.)
</para>
<screen>
$ <userinput>pkcs11-keygen -b 1024 -l sample-zsk</userinput>
</screen>
<para>
Alternatively, you may prefer to generate a conventional
on-disk key, using dnssec-keygen:
</para>
<screen>
</screen>
<para>
This provides less security than an HSM key, but since
HSMs can be slow or cumbersome to use for security reasons, it
may be more efficient to reserve HSM keys for use in the less
frequent key-signing operation. The zone-signing key can be
rolled more frequently, if you wish, to compensate for a
reduction in key security. (Note: When using native PKCS#11,
there is no speed advantage to using on-disk keys, as cryptographic
operations will be done by the HSM regardless.)
</para>
<para>
Now you can sign the zone. (Note: If not using the -S
option to <command>dnssec-signzone</command>, it will be
necessary to add the contents of both <filename>K*.key</filename>
files to the zone master file before signing it.)
</para>
<screen>
Enter PIN:
Verifying the zone using the following algorithms:
NSEC3RSASHA1.
Zone signing complete:
Algorithm: NSEC3RSASHA1: ZSKs: 1, KSKs: 1 active, 0 revoked, 0 stand-by
</screen>
</section>
<section><info><title>Specifying the engine on the command line</title></info>
<para>
When using OpenSSL-based PKCS#11, the "engine" to be used by
OpenSSL can be specified in <command>named</command> and all of
the BIND <command>dnssec-*</command> tools by using the "-E
<engine>" command line option. If BIND 9 is built with
the --with-pkcs11 option, this option defaults to "pkcs11".
Specifying the engine will generally not be necessary unless
for some reason you wish to use a different OpenSSL
engine.
</para>
<para>
If you wish to disable use of the "pkcs11" engine —
for troubleshooting purposes, or because the HSM is unavailable
— set the engine to the empty string. For example:
</para>
<screen>
</screen>
<para>
This causes
<command>dnssec-signzone</command> to run as if it were compiled
without the --with-pkcs11 option.
</para>
<para>
When built with native PKCS#11 mode, the "engine" option has a
different meaning: it specifies the path to the PKCS#11 provider
library. This may be useful when testing a new provider library.
</para>
</section>
<section><info><title>Running named with automatic zone re-signing</title></info>
<para>
If you want <command>named</command> to dynamically re-sign zones
then <command>named</command> must have access to the HSM PIN. In OpenSSL-based PKCS#11,
this is accomplished by placing the PIN into the openssl.cnf file
(in the above examples,
</para>
<para>
The location of the openssl.cnf file can be overridden by
setting the OPENSSL_CONF environment variable before running
<command>named</command>.
</para>
<programlisting>
openssl_conf = openssl_def
[ openssl_def ]
engines = engine_section
[ engine_section ]
pkcs11 = pkcs11_section
[ pkcs11_section ]
PIN = <replaceable><PLACE PIN HERE></replaceable>
</programlisting>
<para>
This will also allow the dnssec-* tools to access the HSM
without PIN entry. (The pkcs11-* tools access the HSM directly,
not via OpenSSL, so a PIN will still be required to use
them.)
</para>
<para>
In native PKCS#11 mode, the PIN can be provided in a file specified
as an attribute of the key's label. For example, if a key had the label
then the PIN would be read from the file
</para>
<warning>
<para>
Placing the HSM's PIN in a text file in this manner may reduce the
security advantage of using an HSM. Be sure this is what you want to
do before configuring the system in this way.
</para>
</warning>
</section>
</section>