JavaMail security permissions best practices
In many of its activities, the JavaMail API needs to access certain configuration files. The JavaMail and JavaBeans Activation Framework binary packages themselves already contain the necessary configuration files. However, JavaMail allows the user to define user-specific and installation-specific configuration files to meet special requirements.
The two locations where such configuration files can exist are <user.home>and <java.home>/lib. For example, if the JavaMail API needs to access a file named mailcap when sending a message, it first tries to access <user.home>/.mailcap. If that attempt fails, either due to lack of security permission or a nonexistent file, the API continues to try<java.home> /lib/mailcap. If that attempts also fails, it will continue and try META-INF/mailcap in the classpath, which actually leads to the configuration files contained in the mail.jar and activation.jar files. WebSphere Application Server uses the general-purpose JavaMail configuration files contained in the mail.jar and activation.jar files and does not put any mail configuration files in <user.home>and <java.home>/lib. File read permission for both the mail.jar and activation.jar files is granted to all applications to ensure proper functioning of the JavaMail API, as shown in the following segment of the app.policy file:
grant codeBase "file:${application}" { // The following are required by Java mail permission java.io.FilePermission "${was.install.root}${/}java${/}jre${/}lib${/}ext${/}mail.jar", "read"; permission java.io.FilePermission "${was.install.root}${/}java${/}jre${/}lib${/}ext${/}activation.jar", "read"; };
JavaMail code attempts to access configuration files at <user.home>and <java.home>/lib causing AccessControlExceptions to be thrown, since there is no file read permission granted for those two locations by default. This activity does not affect the proper functioning of the JavaMail API, but you might see a large amount of JavaMail-related security exceptions reported in the system log, which might swamp harmful errors that you are looking for. If this situation is a problem, consider adding two more permission lines to the permission block above. This should eliminate most, if not all, JavaMail-related harmless security exceptions from the log file. The application permission block in the app.policy file now looks like:
grant codeBase "file:${application}" { // The following are required by Java mail permission java.io.FilePermission "${was.install.root}${/}java${/}jre${/}lib${/}ext${/}mail.jar", "read"; permission java.io.FilePermission "${was.install.root}${/}java${/}jre${/}lib${/}ext${/}activation.jar", "read"; permission java.io.FilePermission "${user.home}${/}.mailcap", "read"; permission java.io.FilePermission "${java.home}${/}lib${/}mailcap", "read"; };