Resin 4 Security Tutorial
From Resin 4.0 Wiki
Basic Security and Resin's XmlAuthenticator
This tutorial covers the basics of JSP and Servlet security and the use of Resin's XmlAuthenticator.
Files in this example
File | Description |
---|---|
WEB-INF/web.xml |
The main JSP/Servlet configuration file |
index.jsp |
The home page for the website |
login.jsp |
The JSP page containing the login form |
logout.jsp |
A JSP page that causes a logout |
home.jsp |
The home page for authenticated users. |
professors/index.jsp |
The more specific home page for Professor's, available only to users in role 'professor' |
students/index.jsp |
The more specific home page for Student's, available to users in role 'student' or in role 'professor' |
staff/index.jsp |
The more specific home page for Staff, available to users in role 'staff' or in role 'professor' |
inc/buttonbar.jspf |
An include file to render a button bar |
inc/footer.jspf |
An include file to render a footer |
inc/nobrowsercache.jspf |
An include file to stop the browser from caching pages |
Specifying roles
Each user belongs to one or more roles. These roles are
similar to groups in Unix. The possible roles are specified
in web.xml
.
In this example, a user is either a professor, a student, or a staff. They can also optionally have an additional role of gryffindor, slytherin, hufflepuf, or ravenclaw, indicating which house they belong to (or none at all).
Specifying secure areas
You can limit areas of the website to users in a certain
role. You specify url patterns in web.xml
and the role
that is required. In JSP/Servlet terminology, this is called Declarative Security.
Declarative Security in web.xml
<web-app xmlns="http://caucho.com/ns/resin" xmlns:resin="urn:java:com.caucho.resin"> <resin:Allow url-pattern="/professors/*"> <resin:IfUserInRole role="professor"/> </resin:Allow> </web-app>
Making a login form
A login form can be used to retrieve the username and password from the user. The same form or a seperate form can be used when the login fails.
In this example the login form and the error form are in the
same JSP file. If the form is being redisplayed because of an
error thelogin_error
request parameter is set to '1'.
login-config: Getting Resin to use the login form
<web-app xmlns="http://caucho.com/ns/resin" xmlns:resin="urn:java:com.caucho.resin"> <resin:FormLogin> <login-page>/login.jsp</login-page> <error-page>/login.jsp?login_error=1</error-page> </resin:FormLogin> ... </web-app>
An example login form
<form action='j_security_check' method='POST'> <table> <tr><td>User:</td><td><input type='text' name='j_username'></td></tr> <tr><td>Password:</td><td><input type='password' name='j_password'></td></tr> <tr><td colspan='2'><input type=submit></td></tr> </table> <!-- - In case the user got here without a session, redirect - successful requests to the home page for authenticated - users. (This is a non-standard, but useful field.) --> <input type='hidden' name='j_uri' value='/home.jsp'/> </form>
Causing a login to occur
Resin will cause a login to occur when a url that points to a secure area is used. You do not make a url directly to the jsp page that contains the login form.
In this example, home.jsp
is in a secure area, so an
unauthenticated user trying to access it will first be
presented with the login form.
Accessing a jsp in a secure area causes the login to occur
<web-app xmlns="http://caucho.com/ns/resin" xmlns:resin="urn:java:com.caucho.resin"> <resin:Allow url-pattern="/home.jsp"> <!-- '*' for a <role-name> means "authenticated user with any role" The user must be logged in with some kind of role to access the home page. --> <resin:IfUserInRole role="*"/> </resin:Allow> </web-app>
Making a link to cause a login
<a href="<c:url value='/home.jsp'/>">login</a>
Determining if the user is authenticated
If the user has done a successfull login, we say that they
have been authenticated.
request.getUserPrincipal()
returns null
if the
user has not been authenticated.
In this example it is used to determine whether a 'login' or a 'logout' link should be presented.
Determining if the user is authenticated
<c:choose> <c:when test="${empty pageContext.request.userPrincipal}"> <a href="<c:url value='home.jsp'/>">login</a> </c:when> <c:otherwise> <a href="<c:url value='logout.jsp'/>">logout</a> </c:otherwise> </c:choose>
Getting the current username
Getting the current username
Welcome <c:out value="${pageContext.request.remoteUser}"/>.
Doing different things for different roles
You can also determine if a user is in a certain role in the
body of the page using request.isUserInRole("role")
.
In JSP/Servlet terminology, this is called
Programmatic Security.
In this example, the home.jsp
redirects the user to a
more specific home page if the user is a professor,
student, or staff.
Programmatic Security using Java code
<% /** redirect to a more specific homepage if one is available */ String home_url = null; if (request.isUserInRole("professor")) { home_url = "professors/"; } else if (request.isUserInRole("staff")) { home_url = "staff/"; } else if (request.isUserInRole("student")) { home_url = "students/"; } if (home_url != null) { home_url = response.encodeRedirectUrl(home_url); response.sendRedirect(home_url); return; // don't do any more of the page } %>
Stop the browser from caching pages
Pages with information that changes depending on whether or not there is a known user should not be cached by the browser.
In this example an include file inc/nobrowsercache.jspf
is used to send the HTTP headers that stop the browser from
caching the page. It is used for each page that shows the
button bar at the top, because the button bar changes
depending on whether or not the user is logged in.
Java code to stop the browser from caching the page
<%-- stop the browser from caching the page --%> <% response.setHeader("Cache-Control","no-cache,post-check=0,pre-check=0"); response.setHeader("Pragma","no-cache"); response.setHeader("Expires","Thu,01Dec199416:00:00GMT"); %>
Using inc/nobrowsercache.jsp
<%@ include file="/inc/nobrowsercache.jspf" %>
Causing a logout
A user can be logged out by invalidating the session. This causes all of the information stored in the session to be lost. It is especially important to make sure that the logout page is not cached by the browser.
Causing a logout with session.invalidate()
<%@ include file="/inc/nobrowsercache.jspf" %> <%-- invalidating the session causes a loss of all session information, including the identity of the user --%> <% session.invalidate(); %>
Using XmlAuthenticator
Resin provides an authenticator <a javadoc="com.caucho.http.security.XmlAuthenticator"/> which is useful for sites which have minimal security requirements. The developer places entries for users in the authenticator configuration, or in an xml file, or both.
The example below uses digest passwords. Digest passwords avoid the storage of passwords in cleartext, and are discussed under the security section of the Resin documentation.
Specifying the XmlAuthenticator as the authenticator to use
<web-app xmlns="http://caucho.com/ns/resin" resin:xmlns="urn:java:com.caucho.resin"> <!-- Resin-specific XmlAuthenticator configuration --> <resin:XmlAuthenticator> <!-- Optionally put user information here. --> <user>pince:Txpd1jQc/xwhISIqodEjfw==:staff,website</user> <user>filch:KmZIq2RKXAHV4BaoNHfupQ==:staff</user> <!-- You can also use an external file --> <path>WEB-INF/password.xml</path> </resin:XmlAuthenticator> </web-app>
An XML file with usernames, passwords, and roles
<!-- password.xml --> <authenticator> <!-- professors --> <user name='snape' password='I7HdZr7CTM6hZLlSd2o+CA==' roles='professor,slytherin'/> <user name='mcgonagall' password='4slsTREVeTo0sv5hGkZWag==' roles='professor,gryffindor'/> <!-- students --> <user name='harry' password='uTOZTGaB6pooMDvqvl2Lbg==' roles='student,gryffindor'/> <user name='dmalfoy' password='yI2uN1l97Rv5E6mdRnDFwQ==' roles='student,slytherin'/> <!-- alumni --> <user name='lmalfoy' password='sj/yhtU1h4LZPw7/Uy9IVA==' roles='alumni,gryffindor'/> </authenticator>
Documenting Roles
==
<web-app xmlns="http://caucho.com/ns/resin"> <security-role> <role-name>professor</role-name> </security-role> </web-app>