This actually breaks the docker-commons plugin: when it tries to 'materialize' the credentials, it relies on a chmod() call to create a folder (seems this is the behavior of native API), which now leads to an exception:

15:38:55 java.nio.file.NoSuchFileException: /var/lib/jenkins/.docker/7d36d1a6-4917-4dc8-97b6-2babbb2ae3d7
15:38:55 at sun.nio.fs.UnixException.translateToIOException(UnixException.java:86)
15:38:55 at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102)
15:38:55 at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107)
15:38:55 at sun.nio.fs.UnixFileAttributeViews$Posix.setMode(UnixFileAttributeViews.java:238)
15:38:55 at sun.nio.fs.UnixFileAttributeViews$Posix.setPermissions(UnixFileAttributeViews.java:260) 15:38:55 at java.nio.file.Files.setPosixFilePermissions(Files.java:2045)
15:38:55 at hudson.FilePath._chmod(FilePath.java:1618) 15:38:55 at hudson.FilePath.access$1500(FilePath.java:197)
15:38:55 at hudson.FilePath$29.invoke(FilePath.java:1600)
15:38:55 at hudson.FilePath$29.invoke(FilePath.java:1597)
15:38:55 at hudson.FilePath.act(FilePath.java:998)
15:38:55 at hudson.FilePath.act(FilePath.java:976)
15:38:55 at hudson.FilePath.chmod(FilePath.java:1597)
15:38:55 at org.jenkinsci.plugins.docker.commons.impl.ServerKeyMaterialFactory.materialize(ServerKeyMaterialFactory.java:86)
15:38:55 at org.jenkinsci.plugins.docker.commons.impl.CompositeKeyMaterialFactory.materialize(CompositeKeyMaterialFactory.java:69)
15:38:55 at org.jenkinsci.plugins.docker.commons.impl.CompositeKeyMaterialFactory.materialize(CompositeKeyMaterialFactory.java:69)
15:38:55 at com.cloudbees.dockerpublish.DockerBuilder$Perform.executeCmd(DockerBuilder.java:459)
15:38:55 at com.cloudbees.dockerpublish.DockerBuilder$Perform.executeCmd(DockerBuilder.java:431)
15:38:55 at com.cloudbees.dockerpublish.DockerBuilder$Perform.buildAndTag(DockerBuilder.java:373)
15:38:55 at com.cloudbees.dockerpublish.DockerBuilder$Perform.exec(DockerBuilder.java:311)
15:38:55 at com.cloudbees.dockerpublish.DockerBuilder$Perform.access$100(DockerBuilder.java:291)
15:38:55 at com.cloudbees.dockerpublish.DockerBuilder.perform(DockerBuilder.java:262)
15:38:55 at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
15:38:55 at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:744)
15:38:55 at hudson.model.Build$BuildExecution.build(Build.java:206)
15:38:55 at hudson.model.Build$BuildExecution.doRun(Build.java:163)
15:38:55 at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:504)
15:38:55 at hudson.model.Run.execute(Run.java:1727)
15:38:55 at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
15:38:55 at hudson.model.ResourceController.execute(ResourceController.java:97)
15:38:55 at hudson.model.Executor.run(Executor.java:429)
15:38:55 Build step 'Docker Build and Publish' marked build as failure

typz Thanks for reporting the bug. My guess is that previously the call to `FilePath#chmod` failed, but the return value was not checked and so no exception was thrown, and it went unnoticed because ServerKeyMaterialFactory#copyInto calls FilePath#write which created parent directories if they don't already exist.

I will test to see what happens when the native chmod is used on a non-existent file or directory. If it fails silently before this change, I will file a PR against docker-commons to create the file before changing permissions. If it succeeds, I will change the new code to create the file or directory first if necessary.

The following test passes against master, which implies that before PR #3135, FilePath#chmod on a non-existent file or directory would fail silently:

    @Test
    public void chmodFileDoesNotExist() throws Exception {
        assumeFalse(Functions.isWindows());
        Util.NATIVE_CHMOD_MODE = true; // Use native chmod
        File f = File.createTempFile("chmod-test", ".tmp");
        f.delete();
        FilePath fp = new FilePath(f);
        fp.chmod(0666);
        assertFalse(f.exists());
    }

Changing Util.NATIVE_CHMOD_MODE to false (to use NIO) causes the test to throw NoSuchFileException as noted by typz. The native implementation of IOUtils#mode threw an exception if the file did not exist, so it seems only the behavior of FilePath#chmod has changed.

I searched through the jenkinsci org for chmod to see if any other uses were likely to break after this change.
Almost all uses call one of mkdirs, touch, exists, write, or createTempFile/Dir immediately before chmod which should prevent them from seeing a NoSuchFileException.There are a few uses such as android-emulator-plugin and copy-data-to-workspace-plugin that could hit new exceptions if files are deleted while the directories are being traversed.

I think there is value in throwing NoSuchFileException to catch legitimate bugs as in docker-commons, and it doesn't appear that there will be widespread issues with the exception being thrown in plugins where it wouldn't have been before, so I will file a PR against docker-commons to create the directory before calling chmod. If anyone feels strongly that that we should preserve the old behavior I am also happy to catch NoSuchFileException in FilePath#chmod.

Code changed in jenkins
User: Jesse Glick
Path:
src/main/java/org/jenkinsci/plugins/docker/commons/impl/ServerKeyMaterialFactory.java
src/test/java/org/jenkinsci/plugins/docker/commons/credentials/DockerServerEndpointTest.java
http://jenkins-ci.org/commit/docker-commons-plugin/c871b5e85fc96df8f70ef65aa96d2d73edf16615
Log:
Merge pull request #62 from dwnusbaum/JENKINS-36088-exposed-bug

Create directory before calling chmod

Compare: https://github.com/jenkinsci/docker-commons-plugin/compare/c0d9723d787a...c871b5e85fc9

dnusbaum I linked the PR with this JIRA number in title in the Core, and assigned it to you to clarify.

Please update/clarify if you shouldn't be the assignee. Thanks!