\input texinfo @c -*- Texinfo -*- @setfilename scute.info @settitle The Scute Manual @dircategory GNU Utilities @direntry * Scute: (scute). PKCS #11 module for the OpenPGP Card @end direntry @include version.texi @c Unify some of the indices. @syncodeindex tp fn @syncodeindex pg fn @ifinfo This file documents the Scute module. This is Edition @value{EDITION}, last updated @value{UPDATED}, of @cite{The Scute Manual}, for Version @value{VERSION}. @c NOTE: Don't forget to update the year for the TeX version, too. Copyright @copyright{} 2002, 2003, 2004, 2005, 2006, 2007 g10 Code GmbH. The Scute Manual is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The Scute Manual is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA @end ifinfo @iftex @shorttitlepage The Scute Manual @end iftex @titlepage @center @titlefont{The Scute Manual} @sp 6 @center Edition @value{EDITION} @sp 1 @center last updated @value{UPDATED} @sp 1 @center for version @value{VERSION} @page @vskip 0pt plus 1filll Copyright @copyright{} 2002, 2003, 2004, 2005, 2006, 2007 g10 Code GmbH. The Scute Manual is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The Scute Manual is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA @end titlepage @page @ifnottex @node Top @top Main Menu This is Edition @value{EDITION}, last updated @value{UPDATED}, of @cite{The Scute Manual}, for Version @value{VERSION} of the Scute module. @end ifnottex @menu * Introduction:: How to use this manual. * Preparation:: What you should do before using Scute. * Client Authentication:: How to use Scute for client authentication. * Troubleshooting:: What to do when things go wrong. * Internals:: Technical details about Scute. Appendices * Copying:: The GNU General Public License says how you can copy and share Scute. Indices * Concept Index:: Index of concepts and programs. @detailmenu --- The Detailed Node Listing --- Introduction * Getting Started:: Purpose of the manual, and how to use it. * Features:: Reasons to install and use Scute. * Overview:: Basic architecture of the Scute module. Preparation * Prerequisites:: Dependencies of Scute. * Building the Source:: How to build Scute. * Certificate Preparation:: Preparing certificates for use with Scute. Client Authentication * Application Configuration:: Preparing the application for use with Scute. * Authentication With Service:: Using Scute for client authentication. Troubleshooting Internals * Features and Limitations:: Details about the interfaces implemented. * Developing Scute:: How to understand or improve Scute. * Mozilla Compatibility:: Interoperability notes for Mozilla NSS. @end detailmenu @end menu @node Introduction @chapter Introduction This is a PKCS #11 implementation for the GnuPG Agent using the GnuPG Smart Card Daemon. Currently, only the OpenPGP card is supported. Scute enables use of the OpenPGP smart card in applications supporting PKCS #11 compliant security tokens. The main application at this time is client authentication in Mozilla-based web browsers. In the future, other applications will be supported. @menu * Getting Started:: Purpose of the manual, and how to use it. * Features:: Reasons to install and use Scute. * Overview:: Basic architecture of the Scute module. @end menu @node Getting Started @section Getting Started This manual documents the Scute module, how it can be used for common applications supported by it, and how it can be extended and improved by programmers. It is thus a user manual as well as a developer manual. The reader is assumed to possess basic knowledge about cryptography in general, and public key cryptography in particular. The underlying cryptographic engines that are used by the library are not explained, but where necessary, special features or requirements are provided. This manual can be used in several ways. If read from the beginning to the end, it gives a good introduction into the module and how it can be used in an application. Forward references are included where necessary. Later on, the manual can be used as a reference manual to get just the information needed about any particular application of the module. @node Features @section Features Scute is currently the only implementation of PKCS #11 for the OpenPGP smart card. Apart from that, it offers a couple of other benefits: @table @asis @item it's free software Anybody can use, modify, and redistribute it under the terms of the GNU General Public License (@pxref{Copying}). @item it's built to grow Although Scute currently only provides a single function, client authentication using OpenPGP smart cards in Mozilla-based web browsers, it was built with the intention of supporting other applications as well in the future. @item it's easy Building and installing Scute is easy, and preparing smart cards for use with Scute is a snatch using the GnuPG 2.0 framework. The integration of Scute into the application is seamless. @end table @node Overview @section Overview Scute is a security device that implements the PKCS #11 interface for security tokens. Applications which know how to use the PKCS #11 interface to access security tokens for crytpographic operations can use Scute to access the OpenPGP smart card. An important example of such an application is the Firefox web browser by the Mozilla project, which uses the Mozilla Network Security Services library (NSS). Scute itself does not include a driver for the smart card itself. Instead, it uses the GnuPG 2.0 framework to access the smart cards and associated data like certificates. Scute acts as the glue between the application and GnuPG 2.0. Currently, only client authentication over HTTPS with Firefox using the OpenPGP card is supported. In this configuration, Scute allows users to authenticate themselves to a remote web service without entering their log-in information. @node Preparation @chapter Preparation To use Scute, you first have to install the software. You also have to prepare each card you want to use with Scute before it can be used. Furthermore, you need to configure the application to make use of Scute for cryptographic operations. This chapter explains each of these steps in detail. @menu * Prerequisites:: Dependencies of Scute. * Building the Source:: How to build Scute. * Certificate Preparation:: Preparing certificates for use with Scute. @end menu @node Prerequisites @section Prerequisites There are two types of dependencies for Scute: compile-time dependencies and run-time dependencies. The compile-time dependencies only need to be fulfilled when Scute is compiled and installed. The run-time dependencies need to be fulfilled when Scute is used in an application. Scute depends, in addition to the essential build utilities, on the following packages at build time: @table @code @item libgpg-error Scute uses the GnuPG 2.0 framework for error handling, so it depends on the GPG error library. The minimum version required is 0.7. @item libassuan Scute uses the GnuPG 2.0 framework for communication with the GPG Agent, so it depends on the Assuan library. The minimum version required is 0.6.10. @end table At run-time, in addition to the run-time versions of the above libraries, you also need the following packages installed and configured: @table @asis @item GnuPG Scute uses the GnuPG 2.0 framework to access the OpenPGP card and for certificate management. The minimum version required is 2.0.0. @strong{Caution:} A functional installation of GnuPG 2.0 requires a running GPG Agent process, which must be advertised to the applications via the @code{GPG_AGENT_INFO} environment variable. Please make sure that you fulfill this requirement before using Scute in an application, running the Scute test suite, or preparing certificates as described in @ref{Certificate Preparation}. @xref{Invoking GPG-AGENT, , , gnupg, Using the GNU Privacy Guard}, for details on how to run the GPG Agent. @item Pinentry Pinentry is a dependency of GnuPG 2.0, so it also needs to be installed with it. @item Firefox et al. Firefox is the first application supported by Scute. In the future, other applications may be supported. The applications are not dependencies of Scute, but Scute can not be used stand-alone, so you can not experience it without an application. @end table @node Building the Source @section Building the Source Scute does comply to the GNU coding standards and thus can be compiled and installed according to the generic installation instructions found in the source package in the file @code{INSTALL}. There are no Scute specific options to the configure script. After installation, the @code{libscute.so} module file can be found in the library directory of the installation path. @node Certificate Preparation @section Certificate Preparation To use an OpenPGP card with Scute, it first has to be initialized by generating or loading a key on the card, see @uref{http://www.gnupg.org/(en)/howtos/card-howto/en/smartcard-howto.html, the OpenPGP Card How-To}. Then a certificate has to be created and imported into GPGSM. This task involves three steps: First, a certificate signing request (@acronym{CSR}) has to be created that matches the key on the card. This certificate signing request then has to be submitted to a certificate authority (@acronym{CA}), which will create the certificate and send it back to you. At last, the certificate has to be imported into GPGSM. This section will explain all of these steps in detail. Before you start, make sure that the GPG Agent is running, see @ref{Prerequisites}. There is no need to configure GPGSM, so you can create a CSR with the command: @example $ gpgsm-gencert.sh > floppy-head.p10 Key type [1] RSA [2] Existing key [3] Direct from card Your selection: 3 You selected: Direct from card @end example As we create a certificate for the OpenPGP Card, the option ``@code{[3] Direct from card}'' should be selected. @example Card with S/N D27600012401010100010000051B0000 found gpg-agent uses OPENPGP.3 as ssh key Select key [1] OPENPGP.1 [2] OPENPGP.2 [3] OPENPGP.3 [4] back Your selection: 3 You selected: OPENPGP.3 Key usage [1] sign, encrypt [2] sign [3] encrypt Your selection: 2 You selected: sign @end example The only operation currently supported is client authentication. For this, the authentication key has to be selected. This is the third key on the card, so the options ``@code{[3] OPENPGP.3}'' and ``@code{[2] sign}'' should be chosen. Note that the key usage is only advisory, and the CA may assign different capabilities. @example Name (DN) > CN=Floppy Head,OU="Webserver Team",O="Snake Oil, Ltd",L="Snake Town",ST="Snake Desert",C=XY E-Mail addresses (end with an empty line) > floppy.head@@example.com E-Mail addresses (end with an empty line) > DNS Names (optional; end with an empty line) > URIs (optional; end with an empty line) > @end example As a last step, the common name and e-mail address of the key owner need to be specified by you. The above are only an example for a fictious person working at a fictious company. DNS names are only meaningful for server certificates and thus should be left empty. We have now entered all required information and gpgsm will display what it has gathered and ask whether to create the certificate request: @example Parameters for certificate request to create: 1 Key-Type: card:OPENPGP.3 2 Key-Length: 3 Key-Usage: sign 4 Name-DN: CN=Floppy Head,OU="Webserver Team",O="Snake Oil, Ltd",L="Snake Town",ST="Snake Desert",C=XY 5 Name-Email: floppy.head@@example.com Really create such a CSR? [1] yes [2] no Your selection: 1 You selected: yes @end example GPGSM will now start working on creating the request. During this time you will be asked once for a passphrase to unprotect the authentication key on the card. A pop up window will appear to ask for it. When it is ready, you should see the final notice: @example gpgsm: certificate request created @end example Now, you may look at the created request: @example $ cat floppy-head.p10 -----BEGIN CERTIFICATE REQUEST----- MIICCDCCAXECAQAwgYExCzAJBgNVBAYTAlhZMRUwEwYDVQQIEwxTbmFrZSBEZXNl cnQxEzARBgNVBAcTClNuYWtlIFRvd24xFzAVBgNVBAoTDlNuYWtlIE9pbCwgTHRk MRcwFQYDVQQLEw5XZWJzZXJ2ZXIgVGVhbTEUMBIGA1UEAxMLRmxvcHB5IEhlYWQw gaAwDQYJKoZIhvcNAQEBBQADgY4AMIGKAoGBANWaM9YS89AOx3GX1Rua+4DUHwbL wt0rBYdBddlabMMteVjUcOOhbFMirLpLAi1S8fUXNiy84ysOmFStmvSIXDsAgXq5 1ESOU4SNg2zEkPDF1WYJ5BFIXdYq9i2k5W7+ctV8PkKv3e5IeYXTa5qppIPD31de gM8Qj7tK0hL/eNCfAgQAAQABoEUwQwYJKoZIhvcNAQkOMTYwNDAiBgNVHREEGzAZ gRdmbG9wcHkuaGVhZEBleGFtcGxlLmNvbTAOBgNVHQ8BAf8EBAMCBsAwDQYJKoZI hvcNAQEFBQADgYEAFC9q6+ib9YGCLB/2AlZR+/dvb+pEeXR1EbpV/dw/gjP1yPY6 29n8ZIDLUvQvNCtfCcXFxFimVSSB/KmFXXsJbM+NXQyT6Ocn34iHmkf9IVRMWQWg ZBYfQVeXAd7XlxI6d1wXDLwD/26lTU/rH2JU6H1+zSfZxqwVC4Iu+kiN4Y8= -----END CERTIFICATE REQUEST----- $ @end example The next step is to submit this certificate request to the CA, which can then create a certificate and send it back to you. If, for example, you use the CA @uref{http://www.cacert.org, CAcert}, then you can log into your account at the CAcert website, choose ``FIXME'', check ``FIXME'', paste the above request block into the text field and click on ``Submit''. If everything works correctly, a certificate will be shown, which you can cut and paste into a new file @file{floppy-head.crt}. Alternatively if, for example, you set up your own CA with OpenSSL, then you can create your own certificate by issueing a command similar @code{openssl ca -in floppy-head.p10 -cert snakeoil-ca-rsa.crt -keyfile snakeoil-ca-rsa.key -out floppy-head.crt}. Please see the OpenSSL documentation for more details on how to set up and administrate a certificate authority infrastructure. In any way you should end up with a certificate file @file{floppy-head.crt}, which you then have to import into GPGSM. It is also recommended that you import the root certificate of the CA first in the same fashion. @example $ gpgsm --import floppy-head.crt gpgsm: certificate imported gpgsm: total number processed: 1 gpgsm: imported: 1 @end example gpgsm tells you that it has imported the certificate. It is now associated with the key you used when creating the request. To see the content of your certificate, you may now enter: @example $ gpgsm -K Floppy /home/foo/.gnupg/pubring.kbx --------------------------- Serial number: 10 Issuer: /CN=Snake Oil CA/OU=Certificate Authority/O=Snake Oil, Ltd/L=Snake Town/ST=Snake Desert/C=XY/EMail=ca@@snakeoil.dom Subject: /CN=Floppy Head/OU=Webserver Team/O=Snake Oil, Ltd/ST=Snake Desert/C=XY validity: 2006-11-11 14:09:12 through 2007-11-11 14:09:12 key type: 1024 bit RSA fingerprint: EC:93:A2:55:C6:58:7F:C9:9E:96:DB:12:6E:64:99:54:BB:E1:94:68 @end example The option ``@code{-K}'' is used above because this will only list certificates for which a private key is available. To see more details, you may use ``@code{--dump-secret-keys}'' instead of ``@code{-K}''. @node Client Authentication @chapter Client Authentication @menu * Application Configuration:: Preparing the application for use with Scute. * Authentication With Service:: Using Scute for client authentication. @end menu Scute allows you to authenticate yourself to a website securely without entering a username or password by simply using your OpenPGP card. Currently, only Mozilla-based browsers like Firefox are supported, although other applications using Mozilla NSS or supporting PKCS #11 modules may work. @node Application Configuration @section Application Configuration To prepare your application for use with Scute, you have to load the Scute module as a PKCS #11 module into the application. With Firefox, this can be done by choosing @code{Edit->Preferences} in the menu. In the preferences configuration dialog, you should select the @code{Advanced} configuration section, then the @code{Security} tab, and then select @code{Security Devices} in the category @code{Certificates}. @image{firefox-pref} In the devices manager dialog, you can select @code{Load} to load a new PKCS #11 device. @image{firefox-dm-load-before} In the pop-up dialog that follows, you can give a module name (e.g. ``@code{Scute}'') and a module filename. The latter should correspond to the full file name of the installed Scute module file @file{libscute.so}. The default installation path is @file{/usr/local/lib}, which would mean that you have to provide the file name @file{/usr/local/lib/libscute.so}. If you or your system administrator installed Scute in a different location, you have to adjust the file name correspondingly. @image{firefox-dm-load} After confirming installation of the security device, a pop-up window should confirm that the module was successfully loaded, and an entry for the security device should appear in the device manager list of @code{Security Modules and Devices}. @image{firefox-dm-load-after} When you insert the OpenPGP card for which you generated and imported a certificate earlier (see @ref{Certificate Preparation}), the device manager should detect this security token and display some information about it in the @code{Details} list when you select it from the module list. @image{firefox-dm-token-present} FIXME: Add some documentation and screenshots for the certificate manager. @node Authentication With Service @section Authentication With Service Before you access a web service which requires client authentication, for instance a fictious web service @ifnottex @indicateurl{https://example.com}, @end ifnottex @iftex @code{https://example.com}, @end iftex the OpenPGP card should be present. In this case, a pop-up window will appear that requests you to enter the PIN number protecting the authentication key on the OpenPGP card. After entering the PIN number, your browser will be authenticated to the server. If the server accepts your request and certificate, this is all which is required. You should leave the card in the reader as long as the connection persists. Depending on how aggressively GPG Agent caches your PIN number, you may have to enter the PIN number again later to keep up the connection to the server. If the card is not present, or you enter the wrong PIN, or the server does not admit your certificate, you will get an error message. This error message is generated by the application and Scute can not influence it. Unfortunately, in Firefox 1, this error message is not very user friendly: ``@code{example.com has received an incorrect or unexpected message. Error code: -12227}''. FIXME: Screenshot. FIXME: Document possible error codes. @node Troubleshooting @chapter Troubleshooting @strong{Symptom:} Loading the Scute security device in the security device manager of Firefox fails with "Unable to load module". @strong{Solution:} Make sure that Scute is correctly installed, and that all libraries and executables are available. Make sure that the GPG Agent is running and can be found via the environment variable @code{GPG_AGENT_INFO}. @xref{Invoking GPG-AGENT, , , gnupg, Using the GNU Privacy Guard}, for details on how to run the GPG Agent. @strong{Symptom:} Client authentication fails with " has received an incorrect or unexpected message. Error code: -12227". @strong{Solution:} Make sure that the correct OpenPGP card is inserted and the certificate available in GPGSM. Check that the OpenPGP card is detected correctly in the security device manager and the corresponding certificate is displayed in the certificate manager of Firefox. @xref{Authentication With Service}. @strong{Symptom:} The OpenPGP card is detected and displayed in the security device manager in Firefox, but no corresponding certificate is displayed in the certificate manager of Firefox. @strong{Solution:} Make sure that the corresponding certificate is imported in GPGSM. FIXME: Can this really happen??? @node Internals @chapter Internals The following notes are intended for people interested in more technical details about Scute and its implementation. They give an overview about its scope and potential compatibility issues with applications. @menu * Features and Limitations:: Details about the interfaces implemented. * Developing Scute:: How to understand or improve Scute. * Mozilla Compatibility:: Interoperability notes for Mozilla NSS. @end menu @node Features and Limitations @section Features and Limitations Scute implements version 2.20 of the @uref{http://www.rsasecurity.com/rsalabs/node.asp?id=2133, PKCS #11} specification. The @uref{http://www.g10code.com/p-card.html,OpenPGP smart card} application is supported in read-only mode. The following functions are not supported: @table @code @item C_Initialize No support for native thread package. Locking callbacks must be provided if multi-threaded operation is desired. @item C_WaitForSlotEvent Not implemented. The interface as specified by PKCS #11 is broken anyway, as the function can not safely be canceled. Thus, we require polling. @item C_GetOperationState @itemx C_SetOperationState Not supported. @item C_InitToken @itemx C_InitPIN @itemx C_SetPIN Not supported. No write operations are allowed. To configure the token, please use the tools accompanying the GnuPG software suite. @item C_Login @itemx C_Logout Not supported. No login into the token by the software is required. Passphrase queries are implemented by the use of GPG Agent and Pinentry. @item C_EncryptInit @itemx C_Encrypt @itemx C_EncryptUpdate @itemx C_EncryptFinal @itemx C_DigestInit @itemx C_Digest @itemx C_DigestUpdate @itemx C_DigestKey @itemx C_DigestFinal @itemx C_VerifyInit @itemx C_Verify @itemx C_VerifyUpdate @itemx C_VerifyFinal @itemx C_VerifyRecoverInit @itemx C_VerifyRec Not supported. Only secret key operations are supported. @item C_SignInit @itemx C_Sign Currently, only signing 36 bytes (MD5+SHA1) hashes is supported (used for client authentication). @item C_DecryptInit @itemx C_Decrypt Not yet supported, but will be in the future. @item C_SignUpdate @itemx C_SignFinal @itemx C_DecryptUpdate @itemx C_DecryptFinal No progressive crypto-operations are supported. @item C_SignRecoverInit @itemx C_SignRecover Not supported. @item C_DigestEncryptUpdate @itemx C_DecryptDigestUpdate @itemx C_SignEncryptUpdate @itemx C_DecryptVerifyUpdate Dual-purpose cryptographic functions are not supported. @item C_GenerateKey @itemx C_GenerateKeyPair @itemx C_WrapKey @itemx C_UnwrapKey @itemx C_DeriveKey Key management functions are not supported. Please use the tools accompanying the GnuPG software suite to generate and import keys for use with the token. @item C_SeedRandom @itemx C_GenerateRandom Not supported at this point. @code{C_GenerateRandom} may be supported in the future, though. @item C_CreateObject @itemx C_CopyObject @itemx C_DestroyObject @itemx C_SetAttributeValue: Only read-only operations are supported on objects. @item C_GetObjectSize Not supported. @item CKO_CERTIFICATE The label specifies the key on the card used (e.g. @code{OPENPGP.3}). The ID is the fingerprint. @item CKO_PRIVATE_KEY: The @code{CKA_LOCAL} attribute can not be supported by the OpenPGP card. It is always set to false (as the key on the card may be copied to the card from an external source). @end table @node Developing Scute @section Developing Scute Scute is single-threaded. There is a global lock that is taken in all entry points of Scute, except for @code{C_Initialize}, @code{C_Finalize}, @code{C_GetFunctionList}, and stubs. Here are a couple of hints on how to develop PKCS #11 modules for Mozilla: @code{libopensc2} ships with a @code{pkcs11-spy} library that can be loaded as a wrapper around the PKCS #11 library you want to use to log all functions invoked by Mozilla. Here is how to use it: Set the @code{PKCS11SPY_OUTPUT} environment variable to a filename. @code{pkcs11-spy} appends its log messages at the end of this file. Set the @code{PKCS11SPY} environment variable to the filename of the PKCS #11 module you actually want to use. Start Mozilla within this environment. There is a different, probably more powerful way to debug Mozilla PKCS #11 libraries. However, to be able to use it, you need to configure and compile the Mozilla NSS sources with @code{--enable-debug}. Instructions can be found at: @uref{http://www.mozilla.org/projects/security/pki/nss/tech-notes/tn2.html} Here are a couple of links to more information about implementing a PKCS #11 module for Mozilla: @table @uref @item http://docs.sun.com/source/816-6150-10/index.htm @itemx http://docs.sun.com/source/816-6150-10/pkcs.htm Implementing PKCS #11 for the Netscape Security Library (Caution: The content may be out of date) @item http://www.mozilla.org/projects/security/pki/pkcs11/netscape/problems.html Common PKCS #11 Implementation Problems @item http://www.mozilla.org/projects/security/pki/pkcs11/ PKCS #11 Conformance Testing @item http://www.mozilla.org/projects/security/pki/nss/ The Mozilla NSS web page @end table @node Mozilla Compatibility @section Mozilla Compatibility Mozilla has a bug that causes the wrong security device to be unloaded when unloading a security device. Also, the displayed list becomes corrupt. When closing and reopening the security device manager, the list displayed is correct, but in anyway the wrong security module is unloaded. @include gpl.texi @node Concept Index @unnumbered Concept Index @printindex cp @summarycontents @contents @bye