sylabs/singularity: Singularity 3.5.2 Release

Security Release

The 3.5.2 release of Singularity contains fixes for a security issue related to incorrect file permissions (CVE-2019-19724) on user configuration and cache directories.

In Singularity >=3.3.0 (on all OS/kernels) the $HOME/.singularity directory holding user configuration and caches is incorrectly created with 777 permissions. If the $HOME directory of a user has group/any x permission set, then a malicious user with login access to the host system may traverse into $HOME/.singularity and:

• Inject a remote.yaml configuration file that can direct interactions with Sylabs cloud services / Singularity Enterprise to a malicious server. This may result in the execution of malicious container images.

• Read the content of a user's cached containers, which may include sensitive private data.

In Singularity >=2.4.0 (on all OS/kernels) the $HOME/.singularity directory and any explicit SINGULARITY_CACHEDIR directory are created with 755, or umask dependent permissions. If a user's $HOME directory, or the directory containing an explicitly set SINGULARITY_CACHEDIR, have group/any x permission set, then a malicious user with login access to the host system may:

• Read the content of a user's cached containers, which may include sensitive private data.

Singularity 3.5.2 should be installed immediately, and all previous versions of Singularity should be removed.

Additionally, we recommend running chmod 700 against the .singularity directory within all user $HOME directories, especially if $HOME directories may have group/any x bits set on your system.

Mitigations / Notes

If no user $HOME directories have group/any x bits set, and SINGULARITY_CACHEDIR has never been set to a location open to shared access, the exploits listed above are not possible.

If Singularity is configured to only run containers signed with keys specified in an execution control list, and these keys are not compromised, arbitrary malicious containers cannot be run with a remote.yaml exploit.

Singularity 3.5.2 ensures 700 permissions are set on $HOME/.singularity when the singularity command is run by a user, and that 700 permissions are set for any existing or new explicit cache directory configured using the SINGULARITY_CACHEDIR environment variable.

This release makes additional permission changes to further harden plugin operations against weak directory permissions / sudo secure umask settings, that should not occur without explicit administrator action.

Singularity Desktop for Mac

Previous alpha and beta versions of Singularity Desktop for Mac are affected by this issue. A new beta release, beta-v0.2, is being prepared, and will be available shortly.

Patches against prior versions

In keeping with our commitment to the open source community to release security patches incorporated into Singularity PRO, Sylabs is also releasing patches that can be applied to the 3.1, 2.6, 2.5, and 2.4 series. Even though 3.5.2 technically deprecates all previous open-source versions of Singularity, interested parties can find the patches to fix this specific issue at the following links:

• 3.1: https://repo.sylabs.io/security/2019/CVE-2019-19724-31.diff
• 2.6 / 2.5 / 2.4: https://repo.sylabs.io/security/2019/CVE-2019-19724-2x.diff

Note - these prior versions of Singularity may be subject to additional security issues, addressed by further patches released previously. Please review the release history carefully before using a deprecated version of Singularity.

Release Notes Security related fix

• 700 permissions are enforced on $HOME/.singularity and SINGULARITY_CACHEDIR directories (CVE-2019-19724). Many thanks to Stuart Barkley for reporting this issue.

Bug Fixes

• Fixes an issue preventing use of .docker/config for docker registry authentication.
• Fixes the run-help command in the unprivileged workflow.
• Fixes a regression in the inspect command to support older image formats.
• Adds a workaround for an EL6 kernel bug regarding shared bind mounts.
• Fixes caching of http(s) sources with conflicting filenames.
• Fixes a fakeroot sandbox build error on certain filesystems, e.g. lustre, GPFS.
• Fixes a fakeroot build failure to a sandbox in $HOME.
• Fixes a fakeroot build failure from a bad def file section script location.
• Fixes container execution errors when CWD is a symlink.
• Provides a useful warning r.e. possible fakeroot build issues when seccomp support is not available.
• Fixes an issue where the --disable-cache option was not being honored.