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updates to faq and codebase article

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10
docs/articles/src/docbook/codebase-structure.xml
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@ -9,7 +9,7 @@
<personname>Luke Taylor</personname>
<affiliation><orgname>SpringSource</orgname></affiliation></author>
<abstract>
<para>An quick introduction to the code modules and package structure of the Spring
<para>A quick introduction to the code modules and package structure of the Spring
Security 3.0 codebase.</para>
</abstract>
</info>
@ -18,7 +18,7 @@
<para>In versions prior to 3.0, most of Spring Security's code was contained in the
<filename>spring-security-core</filename> jar<footnote>
<para>There was also an additional <filename>spring-security-core-tiger</filename>
jar which contained the Java 5 specific code. In Spring Security 3.0 Java 5 is
jar which contained the Java 5 specific code. In Spring Security 3.0, Java 5 is
the minimum supported platform, so this code is now part of the core.</para>
</footnote>. Over the years, as more features have been added, it has become more
difficult to track the dependencies both within the codebase itself and also on third
@ -79,8 +79,8 @@
table.<table xml:id="jar-files-3.0">
<title>Spring Security Jars</title>
<tgroup cols="3" align="left">
<colspec colnum="1" colname="c1" colwidth="0.6*"/>
<colspec colnum="2" colname="c2" colwidth="0.9*"/>
<colspec colnum="1" colname="c1" colwidth="0.59*"/>
<colspec colnum="2" colname="c2" colwidth="0.92*"/>
<colspec colnum="3" colname="c3" colwidth="0.88*"/>
<colspec colnum="4" colname="c4" colwidth="1.61*"/>
<thead>
@ -183,7 +183,7 @@
<interfacename>AuthenticationManager</interfacename> and related classes (such
as authentication exception classes), the simple DAO-based authentication provider
and password-encoders. <figure xml:id="structure-3.0">
<title>Spring Security 2.0.4 Package Structure</title>
<title>Spring Security 3.0.0.M1 Package Structure</title>
<mediaobject>
<imageobject>
<imagedata fileref="images/spring-security-3.0.0.M1.png" align="center"

350
docs/faq/src/docbook/faq.xml
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@ -23,79 +23,80 @@
</question>
<answer>
<para>Let's assume you're developing an enterprise application based on Spring. There are four security concerns you typically need to address: authentication, web request security, service layer security (i.e. your methods that implement business logic), and domain object instance security (i.e. different domain objects have different permissions). With these typical requirements in mind: <orderedlist>
<listitem>
<para><emphasis>Authentication</emphasis>: The servlet specification provides an approach to authentication. However, you will need to configure the container to perform authentication which typically requires editing of container-specific "realm" settings. This makes a non-portable configuration, and if you need to write an actual Java class to implement the container's authentication interface, it becomes even more non-portable. With Spring Security you achieve complete portability - right down to the WAR level. Also, Spring Security offers a choice of production-proven authentication providers and mechanisms, meaning you can switch your authentication approaches at deployment time. This is particularly valuable for software vendors writing products that need to work in an unknown target environment.</para>
</listitem>
<listitem>
<para><emphasis>Web request security:</emphasis> The servlet specification provides an approach to secure your request URIs. However, these URIs can only be expressed in the servlet specification's own limited URI path format. Spring Security provides a far more comprehensive approach. For instance, you
can use Ant paths or regular expressions, you can consider parts
of the URI other than simply the requested page (eg you can
consider HTTP GET parameters), and you can implement your own
runtime source of configuration data. This means your web
request security can be dynamically changed during the actual
execution of your webapp.</para>
</listitem>
<listitem>
<para><emphasis>Service layer and domain object security:</emphasis>
The absence of support in the servlet specification for services
layer security or domain object instance security represent
serious limitations for multi-tiered applications. Typically
developers either ignore these requirements, or implement
security logic within their MVC controller code (or even worse,
inside the views). There are serious disadvantages with this
approach: <orderedlist>
<listitem>
<para><emphasis>Separation of concerns:</emphasis>
Authorization is a crosscutting concern and should
be implemented as such. MVC controllers or views
implementing authorization code makes it more
difficult to test both the controller and
authorization logic, more difficult to debug, and
will often lead to code duplication.</para>
</listitem>
<listitem>
<para><emphasis>Support for rich clients and web
services:</emphasis> If an additional client type
must ultimately be supported, any authorization code
embedded within the web layer is non-reusable. It
should be considered that Spring remoting exporters
only export service layer beans (not MVC
controllers). As such authorization logic needs to
be located in the services layer to support a
multitude of client types.</para>
</listitem>
<listitem>
<para><emphasis>Layering issues:</emphasis> An MVC
controller or view is simply the incorrect
architectural layer to implement authorization
decisions concerning services layer methods or
domain object instances. Whilst the Principal may be
passed to the services layer to enable it to make
the authorization decision, doing so would introduce
an additional argument on every services layer
method. A more elegant approach is to use a
ThreadLocal to hold the Principal, although this
would likely increase development time to a point
where it would become more economical (on a
cost-benefit basis) to simply use a dedicated
security framework.</para>
</listitem>
<listitem>
<para><emphasis>Authorisation code quality:</emphasis>
It is often said of web frameworks that they "make
it easier to do the right things, and harder to do
the wrong things". Security frameworks are the same,
because they are designed in an abstract manner for
a wide range of purposes. Writing your own
authorization code from scratch does not provide the
"design check" a framework would offer, and in-house
authorization code will typically lack the
improvements that emerge from widespread deployment,
peer review and new versions. </para>
</listitem>
</orderedlist></para>
</listitem>
</orderedlist></para>
<listitem>
<para><emphasis>Authentication</emphasis>: The servlet specification provides an approach to authentication. However, you will need to configure the container to perform authentication which typically requires editing of container-specific "realm" settings. This makes a non-portable configuration, and if you need to write an actual Java class to implement the container's authentication interface, it becomes even more non-portable. With Spring Security you achieve complete portability - right down to the WAR level. Also, Spring Security offers a choice of production-proven authentication providers and mechanisms, meaning you can switch your authentication approaches at deployment time. This is particularly valuable for software vendors writing products that need to work in an unknown target environment.</para>
</listitem>
<listitem>
<para><emphasis>Web request security:</emphasis> The servlet specification provides an approach to secure your request URIs. However, these URIs can only be expressed in the servlet specification's own limited URI path format. Spring Security provides a far more comprehensive approach. For instance, you
can use Ant paths or regular expressions, you can consider parts
of the URI other than simply the requested page (e.g. you can
consider HTTP GET parameters) and you can implement your own
runtime source of configuration data. This means your web
request security can be dynamically changed during the actual
execution of your webapp.</para>
</listitem>
<listitem>
<para><emphasis>Service layer and domain object security:</emphasis>
The absence of support in the servlet specification for services
layer security or domain object instance security represent
serious limitations for multi-tiered applications. Typically
developers either ignore these requirements, or implement
security logic within their MVC controller code (or even worse,
inside the views). There are serious disadvantages with this
approach:
<orderedlist>
<listitem>
<para><emphasis>Separation of concerns:</emphasis>
Authorization is a crosscutting concern and should
be implemented as such. MVC controllers or views
implementing authorization code makes it more
difficult to test both the controller and
authorization logic, more difficult to debug, and
will often lead to code duplication.</para>
</listitem>
<listitem>
<para><emphasis>Support for rich clients and web
services:</emphasis> If an additional client type
must ultimately be supported, any authorization code
embedded within the web layer is non-reusable. It
should be considered that Spring remoting exporters
only export service layer beans (not MVC
controllers). As such authorization logic needs to
be located in the services layer to support a
multitude of client types.</para>
</listitem>
<listitem>
<para><emphasis>Layering issues:</emphasis> An MVC
controller or view is simply the incorrect
architectural layer to implement authorization
decisions concerning services layer methods or
domain object instances. Whilst the Principal may be
passed to the services layer to enable it to make
the authorization decision, doing so would introduce
an additional argument on every services layer
method. A more elegant approach is to use a
ThreadLocal to hold the Principal, although this
would likely increase development time to a point
where it would become more economical (on a
cost-benefit basis) to simply use a dedicated
security framework.</para>
</listitem>
<listitem>
<para><emphasis>Authorisation code quality:</emphasis>
It is often said of web frameworks that they "make
it easier to do the right things, and harder to do
the wrong things". Security frameworks are the same,
because they are designed in an abstract manner for
a wide range of purposes. Writing your own
authorization code from scratch does not provide the
"design check" a framework would offer, and in-house
authorization code will typically lack the
improvements that emerge from widespread deployment,
peer review and new versions. </para>
</listitem>
</orderedlist></para>
</listitem>
</orderedlist></para>
<para> For simple applications, servlet specification security may just be
enough. Although when considered within the context of web container
portability, configuration requirements, limited web request security
@ -112,10 +113,39 @@
<para> Spring Security 2.0.x requires a minimum JDK version of 1.4 and is built
against Spring 2.0.x. It should also be compatible with applications using
Spring 2.5.x. </para>
<para> Spring Security 3.0 will require JDK 1.5 as a minimum and will also
<para> Spring Security 3.0 requires JDK 1.5 as a minimum and will also
require Spring 3.0. </para>
</answer>
</qandaentry></qandadiv>
</qandaentry>
<qandaentry>
<question>
<para>
I'm new to Spring Security and I need to build an application that supports CAS single sign-on over HTTPS,
while allowing Basic authentication locally for certain URLs, authenticating against multiple back end user information sources
(LDAP and JDBC). I've copied some configuration files I found but it doesn't work. What could be wrong?
</para>
<para>Or subsititute an alternative complex scenario...</para>
</question>
<answer>
<para>
Realistically, you need an understanding of the technolgies you are intending to use before you can successfully
build applications with them. Security is complicated. Setting up a simple configuration using a login
form and some hard-coded users using Spring Security's namespace is reasonably straightforward. Moving to using a
backed JDBC database is also easy enough. But if you try and jump
straight to a complicated deployment scenario like this you will almost certainly be frustrated.
There is a big jump in the learning curve required to set up systems like CAS, configure LDAP servers and install SSL
certificates properly. So you need to take things one step at a time.
</para>
<para>
From a Spring Security perspective, the first thing you should do is follow the <quote>Getting Started</quote>
guide on the web site. This will take you through a series of steps to get up and running and get some idea of
how the framework operates. If you are using other technologies which you aren't familiar with then you should
do some research and try to make sure you can use them in isolation before combining them in a complex system.
</para>
</answer>
</qandaentry>
</qandadiv>
<qandadiv>
<title>Common Problems</title>
<qandaentry xml:id="faq-login-loop">
@ -181,7 +211,8 @@
<answer>
<para> This happens because Tomcat sessions created under HTTPS cannot
subsequently be used under HTTP and any session state is lost (including the
security context information). Starting in HTTP first should work. </para>
security context information). Starting a session in HTTP first should work as the
session cookie won't be marked as secure. </para>
</answer>
</qandaentry>
<qandaentry xml:id="faq-no-security-on-forward">
@ -208,17 +239,40 @@
essential to make sure that the Spring Security session registry is notified
when a session is destroyed. Without it, the session information will not be
removed from the registry.</para>
<programlisting>
&lt;listener&gt;
&lt;listener-classorg.springframework.security.ui.session.HttpSessionEventPublisher&lt;/listener-class&gt;
&lt;/listener&gt;
<programlisting><![CDATA[
<listener>
<listener-class>org.springframework.security.ui.session.HttpSessionEventPublisher</listener-class>
</listener> ]]>
</programlisting>
</answer>
</qandaentry>
</qandadiv>
<qandadiv>
<title>Spring Security Architecture Questions</title>
<qandaentry xml:id="faq-where-is-class-x">
<question><para>How do I know which package class X is in?</para></question>
<answer><para>The best way of locating classes is by installing the Spring Security source in your IDE.
The distribution includes source jars for each of the modules the project is divided up into.
Add these to your project source path and you can navigate directly to Spring Security classes
(<command>Ctrl-Shift-T</command> in Eclipse). This also makes debugging easer and allows you to troubleshoot
exceptions by looking directly at the code where they occur to see what's going on there.
</para></answer>
</qandaentry>
<qandaentry xml:id="faq-namespace-to-bean-mapping">
<question><para>How do the namespace elements map to conventional bean configurations?</para></question>
<answer>
<para>There is a general overview of what beans are created by the namespace in the namespace
appendix of the reference guide. If want to know the full details then the code
is in the <filename>spring-security-config</filename> module within the Spring Security 3.0
distribution. You should probably read the chapters on namespace parsing in the
standard Spring Framework reference documentation first.
</para>
</answer>
</qandaentry>
</qandadiv>
<qandadiv>
<title>Common <quote>Howto</quote> Requests</title>
<qandaentry xml:id="extra-login-fields">
<qandaentry xml:id="faq-extra-login-fields">
<question>
<para>I need to login in with more information than just the username. How do I
add support for extra login fields (e.g. a company name)?</para>
@ -244,25 +298,149 @@
and loads the appropriate user data for authentication. </para>
</answer>
</qandaentry>
<qandaentry xml:id="what-dependencies">
<qandaentry>
<question xml:id="faq-dynamic-url-metadata">
<para>How do I define the secured URLs withing an application dynamically?</para>
</question>
<answer>
<para>People often ask about how to store the mapping between secured URLs and
security metadata attributes in a database, rather than in the application
context.
</para>
<para>
The first thing you should ask yourself is if you really need to do this. If an
application requires securing, then it also requires that the security be tested
thoroughly based on a defined policy. It may require auditing and acceptance
testing before being rolled out into a production environment. A security-conscious
organization should be aware that the benefits of their diligent testing process could
be wiped out instantly by allowing the security settings to be modified at runtime
by changing a row or two in a configuration database.
If you have taken this into account (perhaps using multiple layers of security within your
application) then Spring Security allows you to fully customize the source of security metadata.
You can make it fully dynamic if you choose.
</para>
<para>
Both method and web security are protected by subclasses of
<classname>AbstractSecurityInterceptor</classname> which is configured with a
<interfacename>SecurityMetadataSource</interfacename> from which it obtains
the metadata for a particular method or filter invocation <footnote><para>This
class previouly went by the rather obscure name of <classname>ObjectDefinitionSource</classname>,
but has been renamed in Spring Security 3.0</para></footnote>. For web security, the
interceptor class is <classname>FilterSecurityInterceptor</classname> and it uses
the marker interface <interfacename>FilterInvocationSecurityMetadataSource</interfacename>.
The <quote>secured object</quote> type it operates on is a <classname>FilterInvocation</classname>.
The default implementation which is used (both in the namespace <literal>&lt;http&gt;</literal>
and when configuring the interceptor explicitly, stores the list of URL patterns and their
corresponding list of <quote>configuration attributes</quote> (instances of <interfacename>ConfigAttribute</interfacename>)
in an in-memory map.
</para>
<para>
To load the data from an alternative source, you must be using an explicitly declared security filter
chain (typically Spring Security's <classname>FilterChainProxy</classname>) in order to customize the
<classname>FilterSecurityInterceptor</classname> bean. You can't use the namespace. You would then implement
<interfacename>FilterInvocationSecurityMetadataSource</interfacename> to load the data as you please for
a particular <classname>FilterInvocation</classname><footnote><para>The <classname>FilterInvocation</classname>
object contains the <classname>HttpServletRequest</classname>, so you can obtain the URL or any other
relevant information on which to base your decision on what the list of returned attributes will contain.</para></footnote>.
A very basic outline would look something like this:
<programlisting language="java"><![CDATA[
public class MyFilterSecurityMetadataSource implements FilterInvocationSecurityMetadataSource {
public List<ConfigAttribute> getAttributes(Object object) {
FilterInvocation fi = (FilterInvocation) object;
String url = fi.getRequestUrl();
String httpMethod = fi.getRequest().getMethod();
List<ConfigAttribute> attributes = new ArrayList<ConfigAttribute>();
// Lookup your database (or other source) using this information and populate the
// list of attributes
return attributes;
}
public Collection<ConfigAttribute> getAllConfigAttributes() {
return null;
}
public boolean supports(Class<?> clazz) {
return FilterInvocation.class.isAssignableFrom(clazz);
}
}
]]></programlisting>
For more information, look at the code for <classname>DefaultFilterInvocationSecurityMetadataSource</classname>.
</para>
</answer>
</qandaentry>
<qandaentry xml:id="faq-what-dependencies">
<question>
<para>How do I know what dependencies to add to my application to work with
<para>How do I know which dependencies to add to my application to work with
Spring Security?</para>
</question>
<answer>
<para> There is no definite answer here, (it will depend on what features you
are using), but a good starting point is to copy those from one of the
<para>It will depend on what features you
are using and what type of application you are developing. With Spring Security 3.0,
the project jars are divided into clearly distinct areas of functionality, so it is
straightforward to work out which Spring Security jars you need from your application requirements.
All applications will need the <filename>spring-security-core</filename> jar.
If you're developing a web application,
you need the <filename>spring-security-web</filename> jar. If you're using security namespace
configuration you need the <filename>spring-security-config</filename> jar, for LDAP support you need the
<filename>spring-security-ldap</filename> jar and so on.
</para>
<para>
For third-party jars the situation isn't always quite so obvious.
A good starting point is to copy those from one of the
pre-built sample applications WEB-INF/lib directories. For a basic
application, you can start with the tutorial sample. If you want to use
LDAP, with an embedded test server, then use the LDAP sample as a starting
point. </para>
<para> If you are building your project with maven, then adding the appropriate
Spring Security modules to your pom.xml will automatically pull in the core
Spring Security modules as dependencies to your pom.xml will automatically pull in the core
jars that the framework requires. Any which are marked as "optional" in the
Spring Security POM files will have to be added to your own pom.xml file if
you need them. </para>
</answer>
</qandaentry>
<qandaentry xml:id="faq-ldap-authorities">
<question><para>How do I authenticate against LDAP but load user roles from a database?</para></question>
<answer>
<para>
The <code>LdapAuthenticationProvider</code> bean (which handles normal LDAP authentication in Spring
Security) is configured with two separate strategy interfaces, one
which performs the authenticatation and one which loads the user authorities, called
<interfacename>LdapAuthenticator</interfacename> and <interfacename>LdapAuthoritiesPopulator</interfacename>
respectively. The <classname>DefaultLdapAuthoitiesPopulator</classname> loads the user authorities
from the LDAP directory and has various configuration parameters to allow you to
specify how these should be retrieved.
</para>
<para>
To use JDBC instead, you can implement the interface yourself, using whatever SQL is appropriate for your schema:
<programlisting language="java"><![CDATA[
public class MyAuthoritiesPopulator implements LdapAuthoritiesPopulator {
@Autowired
JdbcTemplate template;
List<GrantedAuthority> getGrantedAuthorities(DirContextOperations userData, String username) {
List<GrantedAuthority> = template.query("select role from roles where username = ?", new String[] {username}, new RowMapper<GrantedAuthority>() {
/**
* We're assuming here that you're using the standard convention of using the role
* prefix "ROLE_" to mark attributes which are supported by Spring Security's RoleVoter.
*/
public GrantedAuthority mapRow(ResultSet rs, int rowNum) throws SQLException {
return new GrantedAuthorityImpl("ROLE_" + rs.getString(1);
}
}
}
}
]]></programlisting>
You would then add a bean of this type to your application context and inject it into the <code>LdapAuthenticationProvider</code>.
This is covered in the section on configuring LDAP using explicit Spring beans in the LDAP chapter of the reference manual.
Note that you can't use the namespace for configuration in this case.
You should also consult the Javadoc for the relevant classes and interfaces.
</para>
</answer>
</qandaentry>
</qandadiv>
</qandaset>
</article>

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padding-left: 7px;
padding-right: 7px;
}
.question {
font-weight: bold;
}