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POjava will intermittently not resolve symlinks on Linux
 

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  1. POjava will intermittently not resolve symlinks on Linux
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    <p>I'm trying to resolve canonical paths for all the files in a folder tree, but for some reason it will not resolve them (and intermittently the JVM security code will resolve the symlink properly within the FilePermission and cause a security error).</p> <p>Env:</p> <pre><code>$ java -version java version "1.6.0_23" OpenJDK Runtime Environment (IcedTea6 1.11pre) (6b23~pre11-0ubuntu1.11.10.2) OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode) </code></pre> <p>A known symlink in the system is /usr/share/java/gnome-java-bridge.jar:</p> <pre><code>$ ls -l /usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar lrwxrwxrwx 1 root root 50 2012-02-24 13:39 /usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar -&gt; ../../../../../../share/java/gnome-java-bridge.jar </code></pre> <p>The following code should resolve this known symlink:</p> <pre><code>String symlinkedFilePath = "/usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar"; File symlinkedFile = new File(symlinkedFilePath); System.out.println(symlinkedFile.getAbsolutePath()); System.out.println(symlinkedFile.getCanonicalPath()); </code></pre> <p>but produces:</p> <pre><code>/usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar /usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar </code></pre> <p>A further test, using the following code, will sometimes return true for the permission check, but sometimes will return false:</p> <pre><code>String symlinkedFilePath = "/usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar"; File symlinkedFile = new File(symlinkedFilePath); FilePermission recursivePermission = new FilePermission( symlinkedFile.getParentFile().getParent() + "/-", "read"); FilePermission filePermission = new FilePermission( symlinkedFile.getAbsolutePath(), "read"); System.out.println(recursivePermission); System.out.println(filePermission); System.out.println( "Can read symlink: " + recursivePermission.implies(filePermission)); </code></pre> <p>The typical result is:</p> <pre><code>(java.io.FilePermission /usr/lib/jvm/java-6-openjdk/jre/lib/- read) (java.io.FilePermission /usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar read) Can read symlink: true </code></pre> <p>but when debugging, if I step through the creation of the FilePermission on the target file, internally the path is resolved to the symlink, and the output results in:</p> <pre><code>(java.io.FilePermission /usr/lib/jvm/java-6-openjdk/jre/lib/- read) (java.io.FilePermission /usr/lib/jvm/java-6-openjdk/jre/lib/ext/gnome-java-bridge.jar read) Can read symlink: false </code></pre> <p>The problem is that within the context of the app in which the permission checking actually takes place, the symlink is always resolved by the FilePermission object, but never by my own calls to file.getCanonicalPath() as demonstrated above.</p> <p>Does this make sense to anyone?</p>
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    1. COYou may wish to file a bug report; I cannot reproduce the initial `getCanonicalPath()` problem with either the openjdk or the sun jdk on my Ubuntu 11.04 system.
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    2. COsarnold, are you using the exact OpenJDK version? Wonder if perhaps it's an issue in the specific release. furthermore, I just discovered that I can get the canonical paths to resolve 100% of the time if I set either -Dsun.io.useCanonCaches=false or -Dsun.io.useCanonPrefixCache=false but that seems odd.
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    3. COI'm sorry I didn't think to include version numbers; `java -version` reports `OpenJDK Runtime Environment (IcedTea6 1.10.6) (6b22-1.10.6-0ubuntu1)` `OpenJDK 64-Bit Server VM (build 20.0-b11, mixed mode)`.
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