Security Architecture of the Java Platform (BG OUG, Plovdiv, 13.06.2015)

Java Security Architecture
Demystified
Martin Toshev,
BGOUG, 13.06.2015

Who am I
Software engineer @ EPAM Bulgaria
BG JUG governance board member (http://jug.bg)
OpenJDK contributor

Agenda
• Evolution of the Java security model
• Outside the sandbox - APIs for secure coding
• Designing and coding with security in mind

Evolution of the Java security
model

Evolution of the
Java security model
• Traditionally - companies protect they assets
using strict physical and network access policies
• Tools such as anti-virus software, firewalls,
IPS/IDS systems facilitate this approach

Evolution of the
Java security model
• With the introduction of various technologies for
loading and executing code on the client machine
from the browser (such as Applets) - a new range
of concerns emerge related to client security –
this is when the Java security sandbox starts to
evolve …

Evolution of the
Java security model
• The goal of the Java security sandbox is to allow
untrusted code from applets to be executed in a
trusted environment such as the user's browser

Evolution of the
Java security model
• JDK 1.0 (when it all started …) – the original
sandbox model was introduced
Applet
(untrusted)
System code
(trusted)
JVM
Browser
http://javaday.bg/demoapplet

Evolution of the
Java security model
• Code executed by the JVM is divided in two
domains – trusted and untrusted
• Strict restriction are applied by default on the
security model of applets such as denial to
read/write data from disk, connect to the
network and so on

Evolution of the
Java security model
• JDK 1.1 (gaining trust …) – applet signing
introduced
Applet
(untrusted)
System code
(trusted)
JVM
Browser
Signed Applet
(trusted)
http://javaday.bg/trustedapplet

Evolution of the
Java security model
• Trusted local code and untrusted remote code
from applets restricted to a predefined set of
operations OR signed applet code that is trusted

Evolution of the
Java security model
• Steps needed to sign and run an applet:
– Compile the applet
– Create a JAR file for the applet
– Generate a pair of public/private keys
– Sign the applet JAR with the private key
– Export a certificate for the public key
– Import the Certificate as a Trusted Certificate
– Create the policy file
– Load and run the applet

Evolution of the
Java security model
• JDK 1.2 (gaining more trust …) – fine-grained
access control
Applet
System code
JVM
Browser
grant codeBase http://javaday.bg/demoapplet {
permission java.io.FilePermissions “C:Windows” “delete”
}
security.policy
SecurityManager.checkPermission(…)
AccessController.checkPermission(…)

Evolution of the
Java security model
• Since the security model is code-centric -
additional access control decisions are specified
in a security policy
• No more notion of trusted and untrusted code

Evolution of the
Java security model
• The notion of protection domain introduced –
determined by the security policy
• Two types of protection domains – system and
application

Evolution of the
Java security model
• The protection domain is set during classloading
and contains the code source and the list of
permissions for the class
applet.getClass().getProtectionDomain();

Evolution of the
Java security model
• One permission can imply another permission
java.io.FilePermissions “C:Windows” “delete”
implies
java.io.FilePermissions “C:Windowssystem32” “delete”

Evolution of the
Java security model
• One code source can imply another code source
codeBase http://javaday.bg/
implies
codeBase http://javaday.bg/demoapplet

Evolution of the
Java security model
• Since an execution thread may pass through
classes loaded by different classloaders (and
hence – have different protection domains) the
following rule of thumb applies:
The permission set of an execution thread is considered
to be the intersection of the permissions of all protection
domains traversed by the execution thread

Evolution of the
Java security model
• JDK 1.3, 1,4 (what about entities running the
code … ?) – JAAS
Applet
System code
JVM
Browser
grant principal javax.security.auth.x500.X500Principal "cn=Tom"
{ permission java.io.FilePermissions “C:Windows” “delete” }
security.policy

Evolution of the
Java security model
• JAAS (Java Authentication and Authorization
Service) extends the security model with role-
based permissions
• The protection domain of a class now may
contain not only the code source and the
permissions but a list of principals

Evolution of the
Java security model
• The authentication component of JAAS is
independent of the security sandbox in Java and
hence is typically used in more wider context
(such as j2ee app servers)
• The authorization component is the one that
extends the Java security policy

Evolution of the
Java security model
• Core classes of JAAS:
– javax.security.auth.Subject - an authenticated subject
– java.security.Principal - identifying characteristic of a subject
– javax.security.auth.spi.LoginModule - interface for
implementors of login (PAM) modules
– javax.security.auth.login.LoginContext - creates objects used
for authentication

Evolution of the
Java security model
• Up to JDK 1.4 the following is a typical flow for
permission checking:
1) upon system startup a security policy is set and a
security manager is installed
Policy.setPolicy(…)
System.setSecurityManager(…)

Evolution of the
Java security model
2) during classloading (e.g. of a remote applet) bytecode
verification is done and the protection domain is set
for the current classloader (along with the code
source, the set of permissions and the set of JAAS
principals)

Evolution of the
Java security model
3) when system code is invoked from the remote code
the SecurityManager is used to check against the
intersection of protection domains based on the chain
of threads and their call stacks

Evolution of the
Java security model
SocketPermission permission = new
SocketPermission("javaday.bg:8000-
9000","connect,accept");
SecurityManager sm = System.getSecurityManager();
if (sm != null) sm.checkPermission(permission);

Evolution of the
Java security model
4) application code can also do permission checking
against remote code using a SecurityManager or an
AccessController

Evolution of the
Java security model
SocketPermission permission = new
SocketPermission("javaday.bg:8000-9000",
"connect,accept");
AccessController.checkPermission(permission)

Evolution of the
Java security model
5) application code can also do permission checking with
all permissions of the calling domain or a particular
JAAS subject
AccessController.doPrivileged(…)
Subject.doAs(…)
Subject.doAsPrivileged(…)

Evolution of the
Java security model
• The security model defined by
java.lang.SecurityManager is customizable
• For example: Oracle JVM uses a custom
SecurityManager with additional permission
classes where the code source is a database
schema (containing e.g. Java stored procedures)

Evolution of the
Java security model
• JDK 1.5, 1.6 (enhancing the model …) – new
additions to the sandbox model (e.g. LDAP
support for JAAS)

Evolution of the
Java security model
• JDK 1.7, 1.8 (further enhancing the model …) –
enhancements to the sandbox model (e.g.
AccessController.doPrivileged() for checking
against a subset of permissions)

Evolution of the
Java security model
• JDK 1.9 and beyond … (applying the model to
modules …)
application module
system
module 1
JVM
Browser
http://javaday.bg/appmodule
security.policy
system
module 2

Evolution of the
Java security model
• By modules we understand modules in JDK as
defined by project Jigsaw
• Modules must conform to the same security
model as applets – moreover each module is
loaded by a different classloader – hence classes
in different modules must have different
protection domains

Evolution of the
Java security model
• Modularization of the JDK system classes
allows further to define fine-grained access
control permissions for classes in the system
domain
• This is not currently allowed due to the
monolithic nature of the JDK

Outside the sandbox - APIs for
secure coding

Outside the sandbox - APIs for secure
coding
• The security sandbox defines a strict model for
execution of remote code in the JVM
• The other side of the coin are the security APIs
that provide utilities for implementing the
different aspects of application security …

coding
• The additional set of APIs includes:
– JCA (Java Cryptography Architecture)
– PKI (Public Key Infrastructure) utilities
– JSSE (Java Secure Socket Extension)
– Java GSS API (Java Generic Security Services)
– Java SASL API (Java Simple Authentication and Security
Layer)

coding
• JCA provides utilities for:
– creating digital signatures
– creating message digests
– using cryptographic ciphers (symetric/asymetric,
block/stream)
– using different other types of cryptographic services and
algorithms

coding
• JCA has a pluggable architecture
• JCA is independent from particular cryptographic
algorithms
• JCA continues to evolve (especially by providing
stronger cryptographic algorithms)

coding
• PKI utilities provide means for working with:
– certificates
– certificate revocation lists (CRL)
– OCSP (Online Certificate Status Protocol)
– key stores and trust stores (also based on the PKCS -
public-key cryptography standards)

coding
• PKI certificate revocation check (revision):
• PKI utilities continue to evolve (especially in
providing more support for managing certificates
and keys)
certificate
authorityrevocation
checking
OCSP
CRL
certificate
certificate

coding
• JSSE provides an implementation of the TSL/SSL
sockets for working with remote communication
• JSSE continues to evolve (especially in the
support for additional features such as Server
Name Identication)

coding
• Java GSS API provides an alternative of JSSE
for secure communication
• Java GSS API is a framework for providing
token-based security services that is
independent of the underlying protocols

coding
• Java GSS API can be used along with JAAS for
authentication purposes
• Java GSS API continues to evolve (especially in
the support for Kerberos authentication)

coding
• Java SASL defines a protocol for exchange of
authentication data
• Java SASL is a framework where external
providers give concrete semantics to the
authentication data being exchanged

coding
• Java SASL continues to evolve (especially with
support for additional and enhanced
properties for exchanging authentication data)

Designing and coding with
security in mind

Designing and coding
with security in mind
• First of all - follow programing guidelines and
best practices - most are not bound to the Java
programming language (input validation, error
handling, type safety, access modifiers, resource
cleanup, prepared SQL queries and whatever you
can think of …)

• Respect the SecurityManager - design libraries so
that they work in environments with installed
SecurityManager
• Example: GSON library does not respect the
SecurityManager and cannot be used without additional
reflective permissions in some scenarios

• Grant minimal permissions to code that requires
them - the principle of "least privilege"
• Copy-pasting, of course, increases the risk of
security flows (if the copied code is flawed)

• Sanitize exception messages from sensitive
information - often this results in an unintended
exposal of exploitable information
• Let alone exception stacktraces … in many cases
they convey a wealth of information about the
system

References
• Java Security Overview (white paper)
http://www.oracle.com/technetwork/java/js-white-paper-
149932.pdf
• Java SE Platform Security Architecture Spec
http://docs.oracle.com/javase/7/docs/technotes/guides/sec
urity/spec/security-spec.doc.html
• Inside Java 2 Platform Security, 2nd edition
http://www.amazon.com/Inside-Java%C2%BF-Platform-
Security-Implementation/dp/0201787911

References
• Java Security, 2nd edition, Scott Oaks
http://shop.oreilly.com/product/9780596001575.do
• Securing Java, Gary McGraw, Ed Felden
http://www.securingjava.com
• Secure Coding Guidelines for Java SE
http://www.oracle.com/technetwork/java/seccodeguide
-139067.html#0

References
• Java 2 Network Security
http://www.amazon.com/JAVA-Network-Security-2nd-
Edition/dp/0130155926
• Java Security Documentation
http://docs.oracle.com/javase/8/docs/technotes/guides/
security/index.html

References
• Core Java Security: Class Loaders, Security
Managers and Encryption
http://www.informit.com/articles/article.aspx?p=118796
7
• Overview of Java Security Models
http://docs.oracle.com/cd/E12839_01/core.1111/e1004
3/introjps.htm#CHDCEJGH

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