Certain combinations of permissions can produce significant capability increases and should not be granted. Other permissions should be granted only to special code.
java.security.AllPermission grants all possible permissions to code. This facility was included to reduce the burden of managing a multitude of permissions during routine testing as well as when a body of code is completely trusted. Code is typically granted
AllPermission via the security policy file; it is also possible to programmatically associate
AllPermission with a
ProtectionDomain. This permission is dangerous in production environments. Never grant
AllPermission to untrusted code.
ReflectPermission on the target
suppressAccessChecks suppresses all standard Java language access checks when the permitted class attempts to operate on package-private, protected, or private members of another class. Consequently, the permitted class can obtain permissions to examine any field or invoke any method belonging to an arbitrary class [Reflect 2006]. As a result,
ReflectPermission must never be granted with target
Warning: Extreme caution should be taken before granting this permission to code, for it provides the ability to access fields and invoke methods in a class. This includes not only public, but protected and private fields and methods as well.
java.lang.RuntimePermission applied to target
createClassLoader grants code the permission to create a
ClassLoader object. This permission is extremely dangerous because malicious code can create its own custom class loader and load classes by assigning them arbitrary permissions. A custom class loader can define a class (or
ProtectionDomain) with permissions that override any restrictions specified in the systemwide security policy file.
Permissions in the Java SE 6 Development Kit [Permissions 2008] states:
This is an extremely dangerous permission to grant. Malicious applications that can instantiate their own class loaders could then load their own rogue classes into the system. These newly loaded classes could be placed into any protection domain by the class loader, thereby automatically granting the classes the permissions for that domain.
Noncompliant Code Example (Security Policy File)
This noncompliant example grants
AllPermission to the
The permission itself is specified in the security policy file used by the security manager. Program code can obtain a permission object by subclassing the
java.security.Permission class or any of its subclasses (
BasicPermission, for example). The code can use the resulting object to grant
AllPermission to a
This compliant solution shows a policy file that can be used to enforce fine-grained permissions:
To check whether the caller has the requisite permissions, standard Java APIs use code such as the following:
Always assign appropriate permissions to code. Define custom permissions when the granularity of the standard permissions is insufficient.
Noncompliant Code Example (
This noncompliant code example shows an overridden
getPermissions() method, defined in a custom class loader. It grants
java.lang.ReflectPermission with target
suppressAccessChecks to any class that it loads.
This compliant solution does not grant
java.lang.ReflectPermission with target
suppressAccessChecks to any class that it loads:
ENV03-J-EX0: It may be necessary to grant
AllPermission to trusted library code so that callbacks work as expected. For example, it is common practice, and acceptable, to grant
AllPermission to the optional Java packages (extension libraries):
AllPermission to untrusted code allows it to perform privileged operations.
Static detection of potential uses of dangerous permissions is a trivial search. Automated determination of the correctness of such uses is not feasible.
CVE-2007-5342 describes a vulnerability in Apache Tomcat 5.5.9 through 5.5.25 and 6.0.0 through 6.0.15. The security policy used in the JULI logging component failed to restrict certain permissions for web applications. An attacker could modify the log level, directory, or prefix attributes in the
org.apache.juli.FileHandler handler, permitting them to modify logging configuration options and overwrite arbitrary files.
Android Implementation Details
java.security package exists on Android for compatibility purposes only, and it should not be used. Android uses another permission mechanism for security purposes.
Section 2.5, "Reflection"