From 53bc99da8861ca5309c0fd128a059872d26c6f09 Mon Sep 17 00:00:00 2001
From: Thomas Stromberg <t+github@chainguard.dev>
Date: Fri, 13 Jan 2023 11:38:19 -0500
Subject: [PATCH] new detector: unexpected xattr calls

---
 .../unexpected-xattr-calls-macos.sql          | 59 +++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 detection/execution/unexpected-xattr-calls-macos.sql

diff --git a/detection/execution/unexpected-xattr-calls-macos.sql b/detection/execution/unexpected-xattr-calls-macos.sql
new file mode 100644
index 0000000..6bc2b2c
--- /dev/null
+++ b/detection/execution/unexpected-xattr-calls-macos.sql
@@ -0,0 +1,59 @@
+-- Detect unusual calls to xattr, used to remove filesystem attributes
+--
+-- false positives:
+--   * none observed, but they are expected
+--
+-- interval: 300
+-- platform: darwin
+-- tags: process events
+SELECT pe.path AS path,
+  REGEX_MATCH (pe.path, '.*/(.*)', 1) AS name,
+  TRIM(pe.cmdline) AS cmd,
+  pe.pid AS pid,
+  pe.euid AS euid,
+  pe.parent AS parent_pid,
+  TRIM(IIF(pp.cmdline != NULL, pp.cmdline, ppe.cmdline)) AS parent_cmd,
+  TRIM(IIF(pp.path != NULL, pp.path, ppe.path)) AS parent_path,
+  REGEX_MATCH (
+    IIF(pp.path != NULL, pp.path, ppe.path),
+    '.*/(.*)',
+    1
+  ) AS parent_name,
+  TRIM(IIF(pp.path != NULL, hash.sha256, ehash.sha256)) AS parent_hash,
+  TRIM(IIF(gp.cmdline != NULL, gp.cmdline, gpe.cmdline)) AS gparent_cmd,
+  TRIM(IIF(gp.path != NULL, gp.path, gpe.path)) AS gparent_path,
+  REGEX_MATCH (
+    IIF(gp.path != NULL, gp.path, gpe.path),
+    '.*/(.*)',
+    1
+  ) AS gparent_name,
+  IIF(pp.parent != NULL, pp.parent, ppe.parent) AS gparent_pid,
+  IIF(
+    signature.identifier != NULL,
+    signature.identifier,
+    esignature.identifier
+  ) AS parent_identifier,
+  IIF(
+    signature.authority != NULL,
+    signature.authority,
+    esignature.authority
+  ) AS parent_authority
+FROM process_events pe
+  LEFT JOIN processes p ON pe.pid = p.pid
+  LEFT JOIN processes pp ON pe.parent = pp.pid
+  LEFT JOIN process_events ppe ON pe.parent = ppe.pid
+  LEFT JOIN processes gp ON gp.pid = pp.parent
+  LEFT JOIN process_events gpe ON ppe.parent = gpe.pid
+  LEFT JOIN hash ON pp.path = hash.path
+  LEFT JOIN hash ehash ON ppe.path = ehash.path
+  LEFT JOIN signature ON pp.path = signature.path
+  LEFT JOIN signature esignature ON ppe.path = esignature.path
+WHERE pe.path = '/usr/bin/xattr'
+  AND pe.time > (strftime('%s', 'now') -300)
+  AND NOT (
+    pe.euid > 500 AND
+    cmd LIKE '%xattr -l %'
+  )
+GROUP BY pe.pid
+
+