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<!-- $Id$ -->
<sect1 id="pkcs11">
<title>PKCS #11 (Cryptoki) support</title>
<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 two HSMs: The Sun SCA 6000
cryptographic acceleration board, tested under Solaris x86, and
the AEP Keyper network-attached key storage device, tested with
Debian Linux, Solaris x86 and Windows Server 2003.</para>
<sect2>
<title>Prerequisites</title>
<para>See the HSM vendor documentation for information about
installing, initializing, testing and troubleshooting the
HSM.</para>
<para>BIND 9 uses OpenSSL for cryptography, but stock OpenSSL
does not yet fully support PKCS #11. However, a PKCS #11 engine
for OpenSSL is available from the OpenSolaris project. It has
been modified by ISC to work with with BIND 9, and to provide
new features such as PIN management and key by
reference.</para>
<para>The patched OpenSSL depends on a "PKCS #11 provider".
This is a shared library object, providing a low-level PKCS #11
interface to the HSM hardware. It is dynamically loaded by
OpenSSL at runtime. The PKCS #11 provider comes from the HSM
vendor, and and is specific to the HSM to be controlled.</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 verions of
OpenSSL. OpenSSL 0.9.8 and 1.0.0 are both 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.
</para>
<note>
The latest OpenSSL versions at the time of the BIND release
are 0.9.8s and 1.0.0f.
ISC will provide an updated patch as new versions of OpenSSL
are released. The version number in the following examples
is expected to change.</note>
<para>
Before building BIND 9 with PKCS #11 support, it will be
necessary to build OpenSSL with this patch in place and inform
it of the path to the HSM-specific PKCS #11 provider
library.</para>
<para>Obtain OpenSSL 0.9.8s:</para>
<screen>
$ <userinput>wget <ulink>http://www.openssl.org/source/openssl-0.9.8s.tar.gz</ulink></userinput>
</screen>
<para>Extract the tarball:</para>
<screen>
$ <userinput>tar zxf openssl-0.9.8s.tar.gz</userinput>
</screen>
<para>Apply the patch from the BIND 9 release:</para>
<screen>
$ <userinput>patch -p1 -d openssl-0.9.8s \
< bind9/bin/pkcs11/openssl-0.9.8s-patch</userinput>
</screen>
<note>(Note that the patch file may not be compatible with the
"patch" utility on all operating systems. You may need to
install GNU patch.)</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
to install into "/opt/pkcs11/usr". We will use this location
when we configure BIND 9.</para>
<sect3>
<!-- Example 1 -->
<title>Building OpenSSL for the AEP Keyper on Linux</title>
<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
it /opt/pkcs11/usr/lib:</para>
<screen>
$ <userinput>cp pkcs11.GCC4.0.2.so.4.05 /opt/pkcs11/usr/lib/libpkcs11.so</userinput>
</screen>
<para>This library is only available for Linux as a 32-bit
binary. If we are compiling on a 64-bit Linux system, it is
necessary to force a 32-bit build, by specifying -m32 in the
build options.</para>
<para>Finally, the Keyper library requires threads, so we
must specify -pthread.</para>
<screen>
$ <userinput>cd openssl-0.9.8s</userinput>
$ <userinput>./Configure linux-generic32 -m32 -pthread \
--pk11-libname=/opt/pkcs11/usr/lib/libpkcs11.so \
--pk11-flavor=sign-only \
--prefix=/opt/pkcs11/usr</userinput>
</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>
</sect3>
<sect3>
<!-- Example 2 -->
<title>Building OpenSSL for the SCA 6000 on Solaris</title>
<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-0.9.8s</userinput>
$ <userinput>./Configure solaris64-x86_64-cc \
--pk11-libname=/usr/lib/64/libpkcs11.so \
--pk11-flavor=crypto-accelerator \
--prefix=/opt/pkcs11/usr</userinput>
</screen>
<para>(For a 32-bit build, use "solaris-x86-cc" and
/usr/lib/libpkcs11.so.)</para>
<para>After configuring, run
<command>make</command> and
<command>make test</command>.</para>
</sect3>
<sect3>
<!-- Example 3 -->
<title>Building OpenSSL for SoftHSM</title>
<para>SoftHSM is a software library provided by the OpenDNSSEC
project (http://www.opendnssec.org) which provides a PKCS#11
interface to a virtual HSM, implemented in the form of encrypted
data on the local filesystem. It uses the Botan library for
encryption and SQLite3 for data storage. Though less secure
than a true HSM, it can provide more secure key storage than
traditional key files, and 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-1.3.0 </userinput>
$ <userinput> configure --prefix=/opt/pkcs11/usr </userinput>
$ <userinput> make </userinput>
$ <userinput> make install </userinput>
$ <userinput> export SOFTHSM_CONF=/opt/pkcs11/softhsm.conf </userinput>
$ <userinput> echo "0:/opt/pkcs11/softhsm.db" > $SOFTHSM_CONF </userinput>
$ <userinput> /opt/pkcs11/usr/bin/softhsm --init-token 0 --slot 0 --label softhsm </userinput>
</screen>
<para>SoftHSM can perform all cryptographic operations, but
since it only uses your system CPU, there is no need to use it
for anything but signing. Therefore, we choose the 'sign-only'
flavor when building OpenSSL.</para>
<screen>
$ <userinput>cd openssl-0.9.8s</userinput>
$ <userinput>./Configure linux-x86_64 -pthread \
--pk11-libname=/opt/pkcs11/usr/lib/libpkcs11.so \
--pk11-flavor=sign-only \
--prefix=/opt/pkcs11/usr</userinput>
</screen>
<para>After configuring, run "<command>make</command>"
and "<command>make test</command>".</para>
</sect3>
<para>Once you have built OpenSSL, run
"<command>apps/openssl engine pkcs11</command>" to confirm
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
"<command>apps/openssl engine pkcs11 -t</command>". This will
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
modified OpenSSL suite to
<filename>/opt/pkcs11/usr</filename>.</para>
</sect2>
<sect2>
<title>Building BIND 9 with PKCS#11</title>
<para>When building BIND 9, the location of the custom-built
OpenSSL library must be specified via configure.</para>
<sect3>
<!-- Example 4 -->
<title>Configuring BIND 9 for Linux with the AEP Keyper</title>
<para>To link with the PKCS #11 provider, threads must be
enabled in the BIND 9 build.</para>
<para>The PKCS #11 library for the AEP Keyper is currently
only available as a 32-bit binary. If we are building on a
64-bit host, we must force a 32-bit build by adding "-m32" to
the CC options on the "configure" command line.</para>
<screen>
$ <userinput>cd ../bind9</userinput>
$ <userinput>./configure CC="gcc -m32" --enable-threads \
--with-openssl=/opt/pkcs11/usr \
--with-pkcs11=/opt/pkcs11/usr/lib/libpkcs11.so</userinput>
</screen>
</sect3>
<sect3>
<!-- Example 5 -->
<title>Configuring BIND 9 for Solaris with the SCA 6000</title>
<para>To link with the PKCS #11 provider, threads must be
enabled in the BIND 9 build.</para>
<screen>
$ <userinput>cd ../bind9</userinput>
$ <userinput>./configure CC="cc -xarch=amd64" --enable-threads \
--with-openssl=/opt/pkcs11/usr \
--with-pkcs11=/usr/lib/64/libpkcs11.so</userinput>
</screen>
<para>(For a 32-bit build, omit CC="cc -xarch=amd64".)</para>
<para>If configure complains about OpenSSL not working, you
may have a 32/64-bit architecture mismatch. Or, you may have
incorrectly specified the path to OpenSSL (it should be the
same as the --prefix argument to the OpenSSL
Configure).</para>
</sect3>
<sect3>
<!-- Example 6 -->
<title>Configuring BIND 9 for SoftHSM</title>
<screen>
$ <userinput>cd ../bind9</userinput>
$ <userinput>./configure --enable-threads \
--with-openssl=/opt/pkcs11/usr \
--with-pkcs11=/opt/pkcs11/usr/lib/libpkcs11.so</userinput>
</screen>
</sect3>
<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>
</sect2>
<sect2>
<title>PKCS #11 Tools</title>
<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, and
<command>pkcs11-destroy</command> to remove objects.</para>
<para>In UNIX/Linux builds, these tools are built only if BIND
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>
</sect2>
<sect2>
<title>Using the HSM</title>
<para>First, we must set up the runtime environment so the
OpenSSL and PKCS #11 libraries can be loaded:</para>
<screen>
$ <userinput>export LD_LIBRARY_PATH=/opt/pkcs11/usr/lib:${LD_LIBRARY_PATH}</userinput>
</screen>
<para>When operating an AEP Keyper, it is also necessary to
specify the location of the "machine" file, which stores
information about the Keyper for use by PKCS #11 provider
library. If the machine file is in
<filename>/opt/Keyper/PKCS11Provider/machine</filename>,
use:</para>
<screen>
$ <userinput>export KEYPER_LIBRARY_PATH=/opt/Keyper/PKCS11Provider</userinput>
</screen>
<!-- TODO: why not defined at compile time? -->
<para>These 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>(which will use the HSM for
random number generation), 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>
$ <userinput>dnssec-keyfromlabel -l sample-ksk -f KSK example.net</userinput>
</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. The HSM handles signing with the
private key.</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>
<screen>
$ <userinput>pkcs11-keygen -b 1024 -l sample-zsk</userinput>
$ <userinput>dnssec-keyfromlabel -l sample-zsk example.net</userinput>
</screen>
<para>Alternatively, you may prefer to generate a conventional
on-disk key, using dnssec-keygen:</para>
<screen>
$ <userinput>dnssec-keygen example.net</userinput>
</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.</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>
$ <userinput>dnssec-signzone -S example.net</userinput>
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
example.net.signed
</screen>
</sect2>
<sect2>
<title>Specifying the engine on the command line</title>
<para>The OpenSSL engine 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>
$ <userinput>dnssec-signzone -E '' -S example.net</userinput>
</screen>
<para>This causes
<command>dnssec-signzone</command> to run as if it were compiled
without the --with-pkcs11 option.</para>
</sect2>
<sect2>
<title>Running named with automatic zone re-signing</title>
<para>If you want
<command>named</command> to dynamically re-sign zones using HSM
keys, and/or to to sign new records inserted via nsupdate, then
named must have access to the HSM PIN. This can be accomplished
by placing the PIN into the openssl.cnf file (in the above
examples,
<filename>/opt/pkcs11/usr/ssl/openssl.cnf</filename>).</para>
<para>The location of the openssl.cnf file can be overridden by
setting the OPENSSL_CONF environment variable before running
named.</para>
<para>Sample openssl.cnf:</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>
<!--
If the PIN is not known, I believe the first time named needs the
PIN to open a key, it'll ask you to type in the PIN, which will be
a problem because it probably won't be running on a terminal
-->
<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
OpenSSL in this way.</para>
</warning>
</sect2>
<!-- TODO: what is alternative then for named dynamic re-signing? -->
<!-- TODO: what happens if PIN is not known? named will log about it? -->
</sect1>