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  • 2017-01-18 -- Version gnupg-pkcs11-scd-0.7.4 available.

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gnupg-pkcs11-scd

 

NAME

gnupg-pkcs11-scd - GnuPG-compatible smart-card daemon with PKCS#11 support  

SYNOPSIS

gnupg-pkcs11-scd [--server] [--multi-server] [--daemon] [--verbose] [--quiet] [--sh] [--csh] [--options file ] [--no-detach] [--log-file file ] [--help]  

DESCRIPTION

gnupg-pkcs11-scd is a drop-in replacement for the smart-card daemon (scd) shipped with the next-generation GnuPG (gnupg-2). The daemon interfaces to smart-cards by using RSA Security Inc. PKCS#11 Cryptographic Token Interface (Cryptoki).

The interface with GnuPG is restricted to feching existing keys from the card. Neither new key generation nor key transfer is possible through this interface. Instead, when the smart-card is asked to generate a key in a particular slot, the existing public key in that slot is returned. This facilitates the transfer of keys on the smart-card to usage as a subkey on an existing GnuPG master key. See the GNUPG INTEGRATION section for example usage.

The following options are available:

--server
Run in server mode (foreground). If not redirected, input and output are over stdin/stdout.
--multi-server
Run in multi-server mode (foreground). In addition to communicating over stdin/stdout, the server also opens an additional listening UNIX socket.
--daemon
Detach and run in background.
--verbose
Be verbose while running.
--quiet
Be as quiet as possible.
--sh
Output sh-style environment variable definition.
--csh
Output csh-style environment variable definition.
--options file
Read options from file Some of the configuration options can only be set in the configuration file (see the Sx CONFIGURATION section).
--no-detach
Do not detach from console (useful for debugging purposes).
--log-file file
Output log to file
--help
Print help information.

When the daemon receives any of the SIGHUP, SIGTERM and SIGINT signals, it cleans up and exits.

gnupg-pkcs11-scd works only with already personalized cards and supports (for the time being) only RSA keypairs. The following constraints must be satisfied:

  1. For each private key object, a certificate object must exist on the card. The existence of the corresponding public key object is not important (since the certificate includes public key).
  2. The certificate and the corresponding private key must have identical CKA_ID attribute.

The PKCS#11 implementation is not obliged to enforce any of the above rules. However, practice has shown that popular PKCS#11 implementations found "in the wild" seem to respect them.  

NOTES

Unlike gpg-agent, gnupg-pkcs11-scd supports more than one token available at the same time. In order to make gpg-agent happy, gnupg-pkcs11-scd always returns the same card serial number to gpg-agent. When unavailable token is requested, gnupg-pkcs11-scd will use NEEDPIN callback in order to ask for the requested token. When and if gpg-agent will support more than one serial number or NEEDTOKEN callback, this behavior will be modified.  

ENVIRONMENT

HOME
Used to locate the home directory.
GNUPGHOME
Used instead of ~/.gnupg
USERPROFILE
Used only on Win32 to locate the home directory.

Additionally, the \\Software\\GNU\\GnuPG\\HomeDir registry key is used on Win32 to locate the default GNUPGHOME.  

FILES

Files affecting the operation of gnupg-pkcs11-scd

~/.gnupg/gnupg-pkcs11-scd.conf
gnupg-pkcs11-scd uses this as a default configuration file.
/etc/gnupg-pkcs11-scd.conf
gnupg-pkcs11-scd uses this as a default system wide configuration file.
~/.gnupg/gpg-agent.conf
Default configuration file for gpg-agent.

 

CONFIGURATION

To tell gpg-agent to use another smart-card daemon, the following needs to be put in ~/.gnupg/gpg-agent.conf
scdaemon-program /usr/bin/gnupg-pkcs11-scd
pinentry-program /usr/bin/pinentry-qt

The first line is mandatory in order to use gnupg-pkcs11-scd With the second line you can set your preferred pinentry program (it has to be one compatible with GnuPG). Of course, you need to adjust the paths according to your system setup.

An example ~/.gnupg/gnupg-pkcs11-scd.conf file (lines beginning with # are comments):

# Log file.
#log-file log1

# Default is not verbose.
#verbose

# Default is no debugging.
#debug-all

# Pin cache period in seconds; default is infinite.
#pin-cache 20

# Comma-separated list of available provider names. Then set
# attributes for each provider using the provider-[name]-attribute
# syntax.
providers p1

# Provider attributes (see below for detailed description)
provider-p1-library /usr/lib/pkcs11/p1.so
#provider-p1-allow-protected-auth
#provider-p1-cert-private
#provider-p1-private-mask 0

#emulate-openpgpg
#openpgp-sign 5C661B8C07CFD957F7D98D5B9A0F31D236BFAC2A
#openpgp-encr D2DC0BD1EDD185969748B6025B452816F97CBA57
#openpgp-auth A7B8C1A3A8F71FCEC018886F8767927B9C8D871F

The following attributes can be set for each provider:

library
Full path to the PKCS#11 shared library (= provider).
allow-protected-auth
Allow protected authentication for provider. This needs to be supported by the provider and you should have appropriate reader hardware.
cert-private
Authentication is required before certificates can be accessed. Most configurations store certificates as public, so there is no need to use this option.
private-mask
Private key mask mode. Use this only when you have problem using private key operations. The value is hex encoded mask number.

0
Determine automatically.
1
Force sign.
2
Force sign with recovery.
4
Force decrypt.
8
Force decrypt with unwrap.

emulate-openpgp
Emulate OpenPGP card. Unfortunately, gnupg cannot handle the OpenPGP card with certificates. So you need to turn this on in order to learn card keys.

In OpenPGP card emulation we cannot guess which key should match a type, so you have to specify the SHA1 of the key explicitly.

In order to determine which key is which, use the following command:

gpg-agent --server gpg-connect-agent
Enter "SCD LEARN" and look for "KEY-FRIEDNLY" responses, the first field is the hash, the second is the subject name.

You still have to store a certificate (may be self-signed) that corresponds to the keypair.

openpgp-sign
Hex string (Upper letter, no space) SHA1 of signing public key.
openpgp-encr
Hex string (Upper letter, no space) SHA1 of encryption public key.
openpgp-auth
Hex string (Upper letter, no space) SHA1 of authentication public key.

 

GNUPG INTEGRATION

Typical steps to set up a card for gpgsm usage:

  1. Import the CA certificate of your issuer:
    gpgsm --import < ca-certificate
    You should also manually import all self-signed certificates.
  2. Instruct GnuPG to discover all useful certificates on the card:
    gpgsm --learn-card

Signing, verification, etc. work as usual with gpgsm.

Typical steps to set up a card for gpg usage:

  1. Aquire key ids:
    gpg-agent --server gpg-connect-agent
    Enter "SCD LEARN" and look for "KEY-FRIEDNLY" responses, the first field is the hash, the second is the subject name.
  2. Configure gnupg-pkcs11-scd for opengpg emulation, specify the public key hashes to be used for signature, encryption and authentication.
  3. Instruct GnuPG to discover all useful information of card:
    gpg --card-status
    You should see valid card status.
  4. Now, you should virtual generate keys, the keys are not actually generated, but returned to gpg to be registered.
    gpg --card-edit
    admin
    generate (DO NOT BACKUP KEYS)
  5. Alternatively, you can add the existing keys as subkeys on an existing GPG master key:
    gpg --edit-key MASTER_KEY_ID
    addcardkey
  6. Disable the opengpg emulation, if your card requires it to work with GPG.

Now you can use the same card with your gpg and gpgsm keys. We don't know if this is a bug or feature in gnupg, but we glad that it works.

Signing, verification, etc. work as usual with gpg.  

SECURITY CONSIDERATIONS

All communication between components is currently unprotected and in plain text (that's how the Assuan protocol operates). It is trivial to trace (using e.g. the strace(1) program) individual components (e.g. pinentry) and steal sensitive data (such as the smart-card PIN) or even change it (e.g. the hash to be signed).

When using the software in production scenario, be sure to turn off debugging/verbose options in configuration of all components. Otherwise, some sensitive data might be displayed on the screen (most notably, the PIN).  

SEE ALSO

strace(1) truss(1) gnupg(7)
"GnuPG Home Page" http://www.gnupg.org
"gnupg-pkcs11 Home Page" http://gnupg-pkcs11.sourceforge.net
 

AUTHORS AND COPYRIGHT

Copyright (c) 2006-2007 Zeljko Vrba <zvrba@globalnet.hr>

Copyright (c) 2006-2011 Alon Bar-Lev <alon.barlev@gmail.com>

All rights reserved.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


 

Index

NAME
SYNOPSIS
DESCRIPTION
NOTES
ENVIRONMENT
FILES
CONFIGURATION
GNUPG INTEGRATION
SECURITY CONSIDERATIONS
SEE ALSO
AUTHORS AND COPYRIGHT

This document was created by man2html, using the manual pages.
Time: 20:25:39 GMT, January 18, 2017

gnupg-pkcs11