This adds artifact inspection after download to detect any issues
with the content fetched. Currently this means checking for any
symlinks within the artifact that resolve outside the task or
allocation directories. On platforms where lockdown is available
(some Linux) this inspection is not performed.
The inspection can be disabled with the DisableArtifactInspection
option. A dedicated option for disabling this behavior allows
the DisableFilesystemIsolation option to be enabled but still
have artifacts inspected after download.
When attempting to clone a git repository within a sandbox that is
configured with landlock, the clone will fail with error messages
related to inability to get random bytes for a temporary file.
Including a read rule for `/dev/urandom` resolves the error
and the git clone works as expected.
This PR fixes a bug where nodes configured with populated
/etc/ssh/ssh_known_hosts files would be unable to read them during
artifact downloading.
Fixes#17086
* landlock: git needs more files for private repositories
This PR fixes artifact downloading so that git may work when cloning from
private repositories. It needs
- file read on /etc/passwd
- dir read on /root/.ssh
- file write on /root/.ssh/known_hosts
Add these rules to the landlock rules for the artifact sandbox.
* cr: use nonexistent instead of devnull
Co-authored-by: Michael Schurter <mschurter@hashicorp.com>
* cr: use go-homdir for looking up home directory
* pr: pull go-homedir into explicit require
* cr: fixup homedir tests in homeless root cases
* cl: fix root test for real
---------
Co-authored-by: Michael Schurter <mschurter@hashicorp.com>
* client: disable running artifact downloader as nobody
This PR reverts a change from Nomad 1.5 where artifact downloads were
executed as the nobody user on Linux systems. This was done as an attempt
to improve the security model of artifact downloading where third party
tools such as git or mercurial would be run as the root user with all
the security implications thereof.
However, doing so conflicts with Nomad's own advice for securing the
Client data directory - which when setup with the recommended directory
permissions structure prevents artifact downloads from working as intended.
Artifact downloads are at least still now executed as a child process of
the Nomad agent, and on modern Linux systems make use of the kernel Landlock
feature for limiting filesystem access of the child process.
* docs: update upgrade guide for 1.5.1 sandboxing
* docs: add cl
* docs: add title to upgrade guide fix
This PR adjusts the artifact sandbox on Linux to enable reading from known
system-wide git or mercurial configuration, if they exist.
Folks doing something odd like specifying custom paths for global config will
need to use the standard locations, or disable artifact filesystem isolation.
This PR fixes the artifact sandbox (new in Nomad 1.5) to allow downloading
artifacts into the shared 'alloc' directory made available to each task in
a common allocation. Previously we assumed the 'alloc' dir would be mounted
under the 'task' dir, but this is only the case in fs isolation: chroot; in
other modes the alloc dir is elsewhere.
* artifact: enable inheriting environment variables from client
This PR adds client configuration for specifying environment variables that
should be inherited by the artifact sandbox process from the Nomad Client agent.
Most users should not need to set these values but the configuration is provided
to ensure backwards compatability. Configuration of go-getter should ideally be
done through the artifact block in a jobspec task.
e.g.
```hcl
client {
artifact {
set_environment_variables = "TMPDIR,GIT_SSH_OPTS"
}
}
```
Closes#15498
* website: update set_environment_variables text to mention PATH
* client: sandbox go-getter subprocess with landlock
This PR re-implements the getter package for artifact downloads as a subprocess.
Key changes include
On all platforms, run getter as a child process of the Nomad agent.
On Linux platforms running as root, run the child process as the nobody user.
On supporting Linux kernels, uses landlock for filesystem isolation (via go-landlock).
On all platforms, restrict environment variables of the child process to a static set.
notably TMP/TEMP now points within the allocation's task directory
kernel.landlock attribute is fingerprinted (version number or unavailable)
These changes make Nomad client more resilient against a faulty go-getter implementation that may panic, and more secure against bad actors attempting to use artifact downloads as a privilege escalation vector.
Adds new e2e/artifact suite for ensuring artifact downloading works.
TODO: Windows git test (need to modify the image, etc... followup PR)
* landlock: fixup items from cr
* cr: fixup tests and go.mod file
