Patch

salt/base/harden/copy-fail.sls

@@ -0,0 +1,38 @@
+# Mitigation for CVE-2026-31431 ("Copy Fail")
+#
+# Blocks the algif_aead kernel module — the user-space front door used by
+# Copy Fail's container-escape primitive — by writing a modprobe.d "install"
+# rule and unloading the module if it is currently in memory.
+#
+# Safe across the full PSF fleet (Ubuntu 12.04 .. 24.04). On kernels that
+# never had the buggy algif_aead optimization (pre-2017), the file is inert.
+# On kernels where it matters, it removes the attack surface until the host
+# is upgraded to a patched kernel containing mainline a664bf3d603d.
+#
+# Disabling algif_aead does NOT affect dm-crypt/LUKS, kTLS, IPsec/XFRM,
+# OpenSSL/GnuTLS/NSS, SSH, or kernel keyring crypto — those use the in-kernel
+# crypto API directly and do not traverse AF_ALG.
+#
+# Refs:
+#   https://copy.fail/
+#   https://github.com/theori-io/copy-fail-CVE-2026-31431
+
+/etc/modprobe.d/disable-algif.conf:
+  file.managed:
+    - contents: |
+        # Managed by Salt: salt/base/harden/copy-fail.sls
+        # Mitigation for CVE-2026-31431 (Copy Fail).
+        # Remove this file once the host is on a kernel containing a664bf3d603d.
+        install algif_aead /bin/false
+    - user: root
+    - group: root
+    - mode: "0644"
+
+# Unload the module if it is currently loaded. Idempotent: the `unless` check
+# makes this a no-op when algif_aead is not in /proc/modules.
+copy-fail-unload-algif-aead:
+  cmd.run:
+    - name: rmmod algif_aead
+    - unless: '! grep -q "^algif_aead " /proc/modules'
+    - require:
+      - file: /etc/modprobe.d/disable-algif.conf

salt/base/harden/init.sls

@@ -4,3 +4,4 @@ include:
   - .minimize_access
   - .pam
   - .profile
+  - .copy-fail