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[heimdal.git] / doc / hx509.texi

\input texinfo @c -*- texinfo -*-
@c %**start of header
@c $Id$
@setfilename hx509.info
@settitle HX509
@iftex
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@set UPDATED $Date$
@set VERSION @value{PACKAGE_VERSION}
@set EDITION 1.0

@ifinfo
@dircategory Security
@direntry
* hx509: (hx509).               The X.509 distribution from KTH
@end direntry
@end ifinfo

@c title page
@titlepage
@title HX509
@subtitle X.509 distribution from KTH
@subtitle Edition @value{EDITION}, for version @value{VERSION}
@subtitle 2008
@author Love Hörnquist Åstrand
@author last updated @value{UPDATED}

@def@copynext{@vskip 20pt plus 1fil@penalty-1000}
@def@copyrightstart{}
@def@copyrightend{}
@page
@copyrightstart
Copyright (c) 1994-2008 Kungliga Tekniska Högskolan
(Royal Institute of Technology, Stockholm, Sweden).
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
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THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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@copynext

Copyright (c) 1988, 1990, 1993
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@copynext

Copyright 1992 Simmule Turner and Rich Salz.  All rights reserved.

This software is not subject to any license of the American Telephone
and Telegraph Company or of the Regents of the University of California.

Permission is granted to anyone to use this software for any purpose on
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to the following restrictions:

1. The authors are not responsible for the consequences of use of this
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   credits must appear in the documentation.

3. Altered versions must be plainly marked as such, and must not be
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4. This notice may not be removed or altered.

@copynext

IMath is Copyright 2002-2005 Michael J. Fromberger
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@copyrightend
@end titlepage

@macro manpage{man, section}
@cite{\man\(\section\)}
@end macro

@c Less filling! Tastes great!
@iftex
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@ifnottex
@node Top, Introduction, (dir), (dir)
@top Heimdal
@end ifnottex

This manual is last updated @value{UPDATED} for version
@value{VERSION} of hx509.

@menu
* Introduction::
* What is X.509 ?::
* Setting up a CA::
* CMS signing and encryption::
* Certificate matching::
* Software PKCS 11 module::

@detailmenu
 --- The Detailed Node Listing ---

Setting up a CA

@c * Issuing certificates::
* Creating a CA certificate::
* Issuing certificates::
* Issuing CRLs::
@c * Issuing a proxy certificate::
@c * Creating a user certificate::
@c * Validating a certificate::
@c * Validating a certificate path::
* Application requirements::

CMS signing and encryption

* CMS background::

Certificate matching

* Matching syntax::

Software PKCS 11 module

* How to use the PKCS11 module::

@end detailmenu
@end menu

@node Introduction, What is X.509 ?, Top, Top
@chapter Introduction

The goals of a PKI infrastructure (as defined in 
<a href="http://www.ietf.org/rfc/rfc3280.txt">RFC 3280</a>) is to meet 
@emph{the needs of deterministic, automated identification, authentication, access control, and authorization}.


The administrator should be aware of certain terminologies as explained by the aforementioned
RFC before attemping to put in place a PKI infrastructure. Briefly, these are: 

@itemize @bullet
@item CA
Certificate Authority
@item RA
Registration Authority, i.e., an optional system to which a CA delegates certain management functions.
@item CRL Issuer
An optional system to which a CA delegates the publication of certificate revocation lists.
@item Repository
A system or collection of distributed systems that stores certificates and CRLs 
and serves as a means of distributing these certificates and CRLs to end entities
@end itemize

hx509 (Heimdal x509 support) is a near complete X.509 stack that can
handle CMS messages (crypto system used in S/MIME and Kerberos PK-INIT)
and basic certificate processing tasks, path construction, path
validation, OCSP and CRL validation, PKCS10 message construction, CMS
Encrypted (shared secret encrypted), CMS SignedData (certificate
signed), and CMS EnvelopedData (certificate encrypted).

hx509 can use PKCS11 tokens, PKCS12 files, PEM files, and/or DER encoded
files.

@node What is X.509 ?, Setting up a CA, Introduction, Top
@chapter What is X.509, PKIX, PKCS7 and CMS ? 

X.509 was created by CCITT (later ITU) for the X.500 directory
service. Today, X.509 discussions and implementations commonly reference
the IETF's PKIX Certificate and CRL Profile of the X.509 v3 certificate
standard, as specified in RFC 3280.

ITU continues to develop the X.509 standard together with the IETF in a 
rather complicated dance.

X.509 is a public key based security system that has associated data
stored within a so called certificate. Initially, X.509 was a strict
hierarchical system with one root. However, ever evolving requiments and
technology advancements saw the inclusion of multiple policy roots,
bridges and mesh solutions.

x.509 can also be used as a peer to peer system, though often seen as a
common scenario.

@section Type of certificates

There are several flavors of certificate in X.509.

@itemize @bullet

@item Trust anchors

Trust anchors are strictly not certificates, but commonly stored in a
certificate format as they become easier to manage. Trust anchors are
the keys that an end entity would trust to validate other certificates.
This is done by building a path from the certificate you want to
validate to to any of the trust anchors you have.

@item End Entity (EE) certificates

End entity certificates are the most common types of certificates. End
entity certificates cannot issue (sign) certificate themselves and are generally
used to authenticate and authorize users and services.

@item Certification Authority (CA) certificates

Certificate authority certificates have the right to issue additional
certificates (be it sub-ordinate CA certificates to build an trust anchors
or end entity certificates). There is no limit to how many certificates a CA
may issue, but there might other restrictions, like the maximum path
depth.

@item Proxy certificates

Remember the statement "End Entity certificates cannot issue
certificates"?  Well that statement is not entirely true. There is an
extension called proxy certificates defined in RFC3820, that allows
certificates to be issued by end entity certificates. The service that
receives the proxy certificates must have explicitly turned on support
for proxy certificates, so their use is somewhat limited.

Proxy certificates can be limited by policies stored in the certificate to
what they can be used for. This allows users to delegate the proxy
certificate to services (by sending over the certificate and private
key) so the service can access services on behalf of the user.

One example of this would be a print service. The user wants to print a
large job in the middle of the night when the printer isn't used that
much, so the user creates a proxy certificate with the policy that it
can only be used to access files related to this print job, creates the
print job description and send both the description and proxy
certificate with key over to print service. Later at night when the
print service initializes (without any user intervention), access to the files 
for the print job is granted via the proxy certificate. As a result of (in-place) 
policy limitations, the certificate cannot be used for any other purposes.

@end itemize

@section Building a path

Before validating a certificate path (or chain), the path needs to be
constructed.  Given a certificate (EE, CA, Proxy, or any other type),
the path construction algorithm will try to find a path to one of the
trust anchors.

The process starts by looking at the issuing CA of the certificate, by
Name or Key Identifier, and tries to find that certificate while at the
same time evaluting any policies in-place.

@node Setting up a CA, Creating a CA certificate, What is X.509 ?, Top
@chapter Setting up a CA

Do not let information overload scare you off! If you are simply testing
or getting started with a PKI infrastructure, skip all this and go to
the next chapter (see: @pxref{Creating a CA certificate}).

Creating a CA certificate should be more the just creating a
certificate, CA's should define a policy. Again, if you are simply
testing a PKI, policies do not matter so much. However, when it comes to
trust in an organisation, it will probably matter more whom your users
and sysadmins will find it acceptable to trust.

At the same time, try to keep things simple, it's not very hard to run a
Certificate authority and the process to get new certificates should be simple.

You may find it helpful to answer the following policy questions for
your organization at a later stage:

@itemize @bullet
@item How do you trust your CA.
@item What is the CA responsibility.
@item Review of CA activity.
@item How much process should it be to issue certificate.
@item Who is allowed to issue certificates.
@item Who is allowed to requests certificates.
@item How to handle certificate revocation, issuing CRLs and maintain OCSP services.
@end itemize

@node Creating a CA certificate, Issuing certificates, Setting up a CA, Top
@section Creating a CA certificate

This section describes how to create a CA certificate and what to think
about.

@subsection Lifetime CA certificate

You probably want to create a CA certificate with a long lifetime, 10
years at the very minimum. This is because you don't want to push out the
certificate (as a trust anchor) to all you users again when the old
CA certificate expires. Although a trust anchor can't really expire, not all
software works in accordance with published standards.

Keep in mind the security requirements might be different 10-20 years
into the future. For example, SHA1 is going to be withdrawn in 2010, so
make sure you have enough buffering in your choice of digest/hash
algorithms, signature algorithms and key lengths.

@subsection Create a CA certificate

This command below can be used to generate a self-signed CA certificate.

@example
hxtool issue-certificate \
    --self-signed \
    --issue-ca \
    --generate-key=rsa \
    --subject="CN=CertificateAuthority,DC=test,DC=h5l,DC=se" \
    --lifetime=10years \
    --certificate="FILE:ca.pem"
@end example

@subsection Extending the lifetime of a CA certificate

You just realised that your CA certificate is going to expire soon and
that you need replace it with a new CA. The easiest way to do that
is to extend the lifetime of your existing CA certificate.

The example below will extend the CA certificate's lifetime by 10 years. 
You should compare this new certificate if it contains all the
special tweaks as the old certificate had.

@example
hxtool issue-certificate \
    --self-signed \
    --issue-ca \
    --lifetime="10years" \
    --template-certificate="FILE:ca.pem" \
    --template-fields="serialNumber,notBefore,subject,SPKI" \
    --ca-private-key=FILE:ca.pem \
    --certificate="FILE:new-ca.pem"
@end example

@subsection Subordinate CA

This example below creates a new subordinate certificate authority.

@example
hxtool issue-certificate \
    --ca-certificate=FILE:ca.pem \
    --issue-ca \
    --generate-key=rsa \
    --subject="CN=CertificateAuthority,DC=dev,DC=test,DC=h5l,DC=se" \
    --certificate="FILE:dev-ca.pem"
@end example


@node Issuing certificates, Issuing CRLs, Creating a CA certificate, Top
@section Issuing certificates

First you'll create a CA certificate, after that you have to deal with
your users and servers and issue certificates to them.

@c I think this section needs a bit of clarity. Can I add a separate
@c section which explains CSRs as well?


@itemize @bullet

@item Do all the work themself

Generate the key for the user. This has the problme that the the CA
knows the private key of the user. For a paranoid user this might leave
feeling of disconfort.

@item Have the user do part of the work

Receive PKCS10 certificate requests fromusers. PKCS10 is a request for a
certificate.  The user may specify what DN they want as well as provide
a certificate signing request (CSR).  To prove the user have the key,
the whole request is signed by the private key of the user.

@end itemize

@subsection Name space management

@c The explanation given below is slightly unclear. I will re-read the
@c RFC and document accordingly

What people might want to see.

Re-issue certificates just because people moved within the organization.

Expose privacy information.

Using Sub-component name (+ notation).

@subsection Certificate Revocation, CRL and OCSP

Certificates that a CA issues may need to be revoked at some stage. As
an example, an employee leaves the organization and does not bother
handing in his smart card (or even if the smart card is handed back --
the certificate on it must no longer be acceptable to services; the
employee has left).

You may also want to revoke a certificate for a service which is no
longer being offered on your network. Overlooking these scenarios can
lead to security holes which will quickly become a nightmare to deal
with.

There are two primary protocols for dealing with certificate
revokation. Namely:

@itemize @bullet
@item Certificate Revocation List (CRL)
@item Online Certificate Status Protocol (OCSP)
@end itemize

If however the certificate in qeustion has been destroyed, there is no
need to revoke the certificate because it can not be used by someone
else. This matter since for each certificate you add to CRL, the
download time and processing time for clients are longer.

CRLs and OCSP responders however greatly help manage compatible services
which may authenticate and authorize users (or services) on an on-going
basis. As an example, VPN connectivity established via certificates for
connecting clients would require your VPN software to make use of a CRL
or an OCSP service to ensure revoked certificates belonging to former
clients are not allowed access to (formerly subscribed) network
services.


@node Issuing CRLs, Application requirements, Issuing certificates, Top
@section Issuing CRLs

Create an empty CRL with no certificates revoked. Default expiration
value is one year from now.

@example
hxtool crl-sign \
        --crl-file=crl.der \
        --signer=FILE:ca.pem
@end example

Create a CRL with all certificates in the directory
@file{/path/to/revoked/dir} included in the CRL as revoked.  Also make
it expire one month from now.

@example
hxtool crl-sign \
        --crl-file=crl.der \
        --signer=FILE:ca.pem \
        --lifetime='1 month' \
        DIR:/path/to/revoked/dir
@end example

@node Application requirements, CMS signing and encryption, Issuing CRLs, Top
@section Application requirements

Application place different requirements on certificates. This section
tries to expand what they are and how to use hxtool to generate
certificates for those services.

@subsection HTTPS - server

@example
hxtool issue-certificate \
          --subject="CN=www.test.h5l.se,DC=test,DC=h5l,DC=se" \
          --type="https-server" \
          --hostname="www.test.h5l.se" \
          --hostname="www2.test.h5l.se" \
          ...
@end example

@subsection HTTPS - client

@example
hxtool issue-certificate \
          --subject="UID=testus,DC=test,DC=h5l,DC=se" \
          --type="https-client" \
          ...
@end example

@subsection S/MIME - email

There are two things that should be set in S/MIME certificates, one or
more email addresses and an extended eku usage (EKU), emailProtection.

The email address format used in S/MIME certificates is defined in
RFC2822, section 3.4.1 and it should be an ``addr-spec''.

There are two ways to specifify email address in certificates. The old
way is in the subject distinguished name, @emph{this should not be used}. The
new way is using a Subject Alternative Name (SAN).

Even though the email address is stored in certificates, they don't need
to be, email reader programs are required to accept certificates that
doesn't have either of the two methods of storing email in certificates
-- in which case, the email client will try to protect the user by
printing the name of the certificate instead.

S/MIME certificate can be used in another special way. They can be
issued with a NULL subject distinguished name plus the email in SAN,
this is a valid certificate. This is used when you wont want to share
more information then you need to.

hx509 issue-certificate supports adding the email SAN to certificate by
using the --email option, --email also gives an implicit emailProtection
eku. If you want to create an certificate without an email address, the
option --type=email will add the emailProtection EKU.

@example
hxtool issue-certificate \
          --subject="UID=testus-email,DC=test,DC=h5l,DC=se" \
          --type=email \
          --email="testus@@test.h5l.se" \
          ...
@end example

An example of an certificate without and subject distinguished name with
an email address in a SAN.

@example
hxtool issue-certificate \
          --subject="" \
          --type=email \
          --email="testus@@test.h5l.se" \
          ...
@end example

@subsection PK-INIT

A PK-INIT infrastructure allows users and services to pick up kerberos
credentials (tickets) based on their certificate. This, for example,
allows users to authenticate to their desktops using smartcards while
acquiring kerberos tickets in the process.

As an example, an office network which offers centrally controlled
desktop logins, mail, messaging (xmpp) and openafs would give users
single sign-on facilities via smartcard based logins.  Once the kerberos
ticket has been acquired, all kerberized services would immediately
become accessible based on deployed security policies.

Let's go over the process of initializing a demo PK-INIT framework:

@example
hxtool issue-certificate \
        --type="pkinit-kdc" \
        --pk-init-principal="krbtgt/TEST.H5L.SE@@TEST.H5L.SE" \
        --hostname=kerberos.test.h5l.se \
        --ca-certificate="FILE:ca.pem,ca.key" \
        --generate-key=rsa \
        --certificate="FILE:kdc.pem" \
        --subject="cn=kdc"
@end example

How to create a certificate for a user.

@example
hxtool issue-certificate \
        --type="pkinit-client" \
        --pk-init-principal="user@@TEST.H5L.SE" \
        --ca-certificate="FILE:ca.pem,ca.key" \
        --generate-key=rsa \
        --subject="cn=Test User" \
        --certificate="FILE:user.pem"
@end example

The --type field can be specified multiple times. The same certificate
can hence house extensions for both pkinit-client as well as S/MIME.

To use the PKCS11 module, please see the section:
@pxref{How to use the PKCS11 module}.

More about how to configure the KDC, see the documentation in the
Heimdal manual to set up the KDC.

@subsection XMPP/Jabber

The jabber server certificate should have a dNSname that is the same as
the user entered into the application, not the same as the host name of
the machine.

@example
hxtool issue-certificate \
          --subject="CN=xmpp1.test.h5l.se,DC=test,DC=h5l,DC=se" \
          --hostname="xmpp1.test.h5l.se" \
          --hostname="test.h5l.se" \
          ...
@end example

The certificate may also contain a jabber identifier (JID) that, if the
receiver allows it, authorises the server or client to use that JID.

When storing a JID inside the certificate, both for server and client,
it's stored inside a UTF8String within an otherName entity inside the
subjectAltName, using the OID id-on-xmppAddr (1.3.6.1.5.5.7.8.5).

To read more about the requirements, see RFC3920, Extensible Messaging
and Presence Protocol (XMPP): Core.

hxtool issue-certificate have support to add jid to the certificate
using the option @kbd{--jid}.

@example
hxtool issue-certificate \
          --subject="CN=Love,DC=test,DC=h5l,DC=se" \
          --jid="lha@@test.h5l.se" \
          ...
@end example


@node CMS signing and encryption, CMS background, Application requirements, Top
@chapter CMS signing and encryption

CMS is the Cryptographic Message System that among other, is used by
S/MIME (secure email) and Kerberos PK-INIT. It's an extended version of
the RSA, Inc standard PKCS7.

@node CMS background, Certificate matching, CMS signing and encryption, Top
@section CMS background


@node Certificate matching, Matching syntax, CMS background, Top
@chapter Certificate matching

To match certificates hx509 have a special query language to match
certifictes in queries and ACLs.

@node Matching syntax, Software PKCS 11 module, Certificate matching, Top
@section Matching syntax

This is the language definitions somewhat slopply descriped:

@example

expr = TRUE, 
     FALSE,
     ! expr,
     expr AND expr,
     expr OR expr,
     ( expr )
     compare

compare =
     word == word,
     word != word,
     word IN ( word [, word ...])
     word IN %@{variable.subvariable@}

word =
     STRING,
     %@{variable@}

@end example

@node Software PKCS 11 module, How to use the PKCS11 module, Matching syntax, Top
@chapter Software PKCS 11 module

PKCS11 is a standard created by RSA, Inc to support hardware and
software encryption modules. It can be used by smartcard to expose the
crypto primitives inside without exposing the crypto keys.

Hx509 includes a software implementation of PKCS11 that runs within the
memory space of the process and thus exposes the keys to the
application.

@node How to use the PKCS11 module, , Software PKCS 11 module, Top
@section How to use the PKCS11 module

@example
$ cat > ~/.soft-pkcs11.rc <<EOF
mycert  cert    User certificate        FILE:/Users/lha/Private/pkinit.pem
app-fatal       true
EOF
$ kinit -C PKCS11:/usr/heimdal/lib/hx509.so lha@@EXAMPLE.ORG
@end example


@c @shortcontents
@contents

@bye