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287 lines
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287 lines
11 KiB
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Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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This Source Code Form is subject to the terms of the Mozilla Public
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License, v. 2.0. If a copy of the MPL was not distributed with this
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file, you can obtain one at https://mozilla.org/MPL/2.0/.
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See the COPYRIGHT file distributed with this work for additional
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information regarding copyright ownership.
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.. _pkcs11:
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PKCS#11 (Cryptoki) Support
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--------------------------
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Public Key Cryptography Standard #11 (PKCS#11) defines a
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platform-independent API for the control of hardware security modules
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(HSMs) and other cryptographic support devices.
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BIND 9 is known to work with three HSMs: the AEP Keyper, which has been
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tested with Debian Linux, Solaris x86, and Windows Server 2003; the
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Thales nShield, tested with Debian Linux; and the Sun SCA 6000
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cryptographic acceleration board, tested with Solaris x86. In addition,
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BIND can be used with all current versions of SoftHSM, a software-based
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HSM simulator library produced by the OpenDNSSEC project.
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PKCS#11 uses a "provider library": a dynamically loadable
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library which provides a low-level PKCS#11 interface to drive the HSM
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hardware. The PKCS#11 provider library comes from the HSM vendor, and it
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is specific to the HSM to be controlled.
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There are two available mechanisms for PKCS#11 support in BIND 9:
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OpenSSL-based PKCS#11 and native PKCS#11. With OpenSSL-based PKCS#11,
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BIND uses a modified version of OpenSSL, which loads the
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provider library and operates the HSM indirectly; any cryptographic
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operations not supported by the HSM can be carried out by OpenSSL
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instead. Native PKCS#11 enables BIND to bypass OpenSSL completely;
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BIND loads the provider library itself, and uses the PKCS#11 API to
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drive the HSM directly.
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Prerequisites
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~~~~~~~~~~~~~
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See the documentation provided by the HSM vendor for information about
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installing, initializing, testing, and troubleshooting the HSM.
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Native PKCS#11
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~~~~~~~~~~~~~~
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Native PKCS#11 mode only works with an HSM capable of carrying out
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*every* cryptographic operation BIND 9 may need. The HSM's provider
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library must have a complete implementation of the PKCS#11 API, so that
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all these functions are accessible. As of this writing, only the Thales
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nShield HSM and SoftHSMv2 can be used in this fashion. For other HSMs,
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including the AEP Keyper, Sun SCA 6000, and older versions of SoftHSM,
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use OpenSSL-based PKCS#11. (Note: Eventually, when more HSMs become
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capable of supporting native PKCS#11, it is expected that OpenSSL-based
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PKCS#11 will be deprecated.)
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To build BIND with native PKCS#11, configure it as follows:
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::
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$ cd bind9
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$ ./configure --enable-native-pkcs11 \
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--with-pkcs11=provider-library-path
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This causes all BIND tools, including ``named`` and the ``dnssec-*``
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and ``pkcs11-*`` tools, to use the PKCS#11 provider library specified in
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provider-library-path for cryptography. (The provider library path can
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be overridden using the ``-E`` argument in ``named`` and the ``dnssec-*`` tools,
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or the ``-m`` argument in the ``pkcs11-*`` tools.)
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Building SoftHSMv2
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^^^^^^^^^^^^^^^^^^
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SoftHSMv2, the latest development version of SoftHSM, is available from
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https://github.com/opendnssec/SoftHSMv2. It is a software library
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developed by the OpenDNSSEC project (https://www.opendnssec.org) which
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provides a PKCS#11 interface to a virtual HSM, implemented in the form
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of a SQLite3 database on the local filesystem. It provides less security
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than a true HSM, but it allows users to experiment with native PKCS#11
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when an HSM is not available. SoftHSMv2 can be configured to use either
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OpenSSL or the Botan library to perform cryptographic functions, but
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when using it for native PKCS#11 in BIND, OpenSSL is required.
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By default, the SoftHSMv2 configuration file is ``prefix/etc/softhsm2.conf``
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(where ``prefix`` is configured at compile time). This location can be
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overridden by the SOFTHSM2_CONF environment variable. The SoftHSMv2
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cryptographic store must be installed and initialized before using it
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with BIND.
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::
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$ cd SoftHSMv2
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$ configure --with-crypto-backend=openssl --prefix=/opt/pkcs11/usr
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$ make
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$ make install
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$ /opt/pkcs11/usr/bin/softhsm-util --init-token 0 --slot 0 --label softhsmv2
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OpenSSL-based PKCS#11
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~~~~~~~~~~~~~~~~~~~~~
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OpenSSL-based PKCS#11 uses engine_pkcs11 OpenSSL engine from libp11 project.
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For more information, see https://gitlab.isc.org/isc-projects/bind9/-/wikis/BIND-9-PKCS11
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PKCS#11 Tools
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~~~~~~~~~~~~~
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BIND 9 includes a minimal set of tools to operate the HSM, including
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``pkcs11-keygen`` to generate a new key pair within the HSM,
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``pkcs11-list`` to list objects currently available, ``pkcs11-destroy``
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to remove objects, and ``pkcs11-tokens`` to list available tokens.
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In UNIX/Linux builds, these tools are built only if BIND 9 is configured
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with the ``--with-pkcs11`` option. (Note: If ``--with-pkcs11`` is set to ``yes``,
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rather than to the path of the PKCS#11 provider, the tools are
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built but the provider is left undefined. Use the ``-m`` option or the
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``PKCS11_PROVIDER`` environment variable to specify the path to the
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provider.)
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Using the HSM
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~~~~~~~~~~~~~
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For OpenSSL-based PKCS#11, the runtime environment must first be set up
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so the OpenSSL and PKCS#11 libraries can be loaded:
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::
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$ export LD_LIBRARY_PATH=/opt/pkcs11/usr/lib:${LD_LIBRARY_PATH}
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This causes ``named`` and other binaries to load the OpenSSL library
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from ``/opt/pkcs11/usr/lib``, rather than from the default location. This
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step is not necessary when using native PKCS#11.
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Some HSMs require other environment variables to be set. For example,
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when operating an AEP Keyper, the location of
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the "machine" file, which stores information about the Keyper for use by
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the provider library, must be specified. If the machine file is in
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``/opt/Keyper/PKCS11Provider/machine``, use:
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::
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$ export KEYPER_LIBRARY_PATH=/opt/Keyper/PKCS11Provider
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Such environment variables must be set when running any tool that
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uses the HSM, including ``pkcs11-keygen``, ``pkcs11-list``,
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``pkcs11-destroy``, ``dnssec-keyfromlabel``, ``dnssec-signzone``,
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``dnssec-keygen``, and ``named``.
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HSM keys can now be created and used. In this case, we will create
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a 2048-bit key and give it the label "sample-ksk":
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::
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$ pkcs11-keygen -b 2048 -l sample-ksk
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To confirm that the key exists:
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::
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$ pkcs11-list
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Enter PIN:
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object[0]: handle 2147483658 class 3 label[8] 'sample-ksk' id[0]
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object[1]: handle 2147483657 class 2 label[8] 'sample-ksk' id[0]
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Before using this key to sign a zone, we must create a pair of BIND 9
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key files. The ``dnssec-keyfromlabel`` utility does this. In this case, we
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are using the HSM key "sample-ksk" as the key-signing key for
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"example.net":
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::
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$ dnssec-keyfromlabel -l sample-ksk -f KSK example.net
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The resulting K*.key and K*.private files can now be used to sign the
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zone. Unlike normal K\* files, which contain both public and private key
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data, these files contain only the public key data, plus an
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identifier for the private key which remains stored within the HSM.
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Signing with the private key takes place inside the HSM.
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To generate a second key in the HSM for use as a
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zone-signing key, follow the same procedure above, using a different
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keylabel, a smaller key size, and omitting ``-f KSK`` from the
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``dnssec-keyfromlabel`` arguments:
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::
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$ pkcs11-keygen -b 1024 -l sample-zsk
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$ dnssec-keyfromlabel -l sample-zsk example.net
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Alternatively, a conventional on-disk key can be generated
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using ``dnssec-keygen``:
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::
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$ dnssec-keygen example.net
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This provides less security than an HSM key, but since HSMs can be slow
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or cumbersome to use for security reasons, it may be more efficient to
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reserve HSM keys for use in the less frequent key-signing operation. The
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zone-signing key can be rolled more frequently, if desired, to
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compensate for a reduction in key security. (Note: When using native
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PKCS#11, there is no speed advantage to using on-disk keys, as
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cryptographic operations are done by the HSM.)
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Now the zone can be signed. Please note that, if the -S option is not used for
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``dnssec-signzone``, the contents of both
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``K*.key`` files must be added to the zone master file before signing it.
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::
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$ dnssec-signzone -S example.net
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Enter PIN:
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Verifying the zone using the following algorithms:
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NSEC3RSASHA1.
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Zone signing complete:
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Algorithm: NSEC3RSASHA1: ZSKs: 1, KSKs: 1 active, 0 revoked, 0 stand-by
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example.net.signed
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Specifying the Engine on the Command Line
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When using OpenSSL-based PKCS#11, the "engine" to be used by OpenSSL can
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be specified in ``named`` and all of the BIND ``dnssec-*`` tools by
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using the ``-E <engine>`` command line option. If BIND 9 is built with the
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``--with-pkcs11`` option, this option defaults to "pkcs11". Specifying the
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engine is generally not necessary unless
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a different OpenSSL engine is used.
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To disable use of the "pkcs11" engine - for
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troubleshooting purposes, or because the HSM is unavailable - set
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the engine to the empty string. For example:
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::
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$ dnssec-signzone -E '' -S example.net
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This causes ``dnssec-signzone`` to run as if it were compiled without
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the ``--with-pkcs11`` option.
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When built with native PKCS#11 mode, the "engine" option has a different
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meaning: it specifies the path to the PKCS#11 provider library. This may
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be useful when testing a new provider library.
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Running ``named`` With Automatic Zone Re-signing
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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For ``named`` to dynamically re-sign zones using HSM keys,
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and/or to sign new records inserted via nsupdate, ``named`` must
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have access to the HSM PIN. In OpenSSL-based PKCS#11, this is
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accomplished by placing the PIN into the ``openssl.cnf`` file (in the above
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examples, ``/opt/pkcs11/usr/ssl/openssl.cnf``).
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The location of the openssl.cnf file can be overridden by setting the
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``OPENSSL_CONF`` environment variable before running ``named``.
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Here is a sample ``openssl.cnf``:
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::
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openssl_conf = openssl_def
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[ openssl_def ]
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engines = engine_section
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[ engine_section ]
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pkcs11 = pkcs11_section
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[ pkcs11_section ]
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PIN = <PLACE PIN HERE>
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This also allows the ``dnssec-\*`` tools to access the HSM without PIN
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entry. (The ``pkcs11-\*`` tools access the HSM directly, not via OpenSSL, so
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a PIN is still required to use them.)
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In native PKCS#11 mode, the PIN can be provided in a file specified as
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an attribute of the key's label. For example, if a key had the label
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``pkcs11:object=local-zsk;pin-source=/etc/hsmpin``, then the PIN would
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be read from the file ``/etc/hsmpin``.
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.. warning::
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Placing the HSM's PIN in a text file in this manner may reduce the
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security advantage of using an HSM. Use caution
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when configuring the system in this way.
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