ROX-33034: Track xattr changes

fact-ebpf/src/bpf/events.h

@@ -37,7 +37,11 @@ __always_inline static void __submit_event(struct submit_event_args_t* args,
   event->monitored = args->monitored;
   inode_copy(&event->inode, &args->inode);
   inode_copy(&event->parent_inode, &args->parent_inode);
-  bpf_probe_read_str(event->filename, PATH_MAX, args->filename);
+  if (args->filename != NULL) {
+    bpf_probe_read_str(event->filename, PATH_MAX, args->filename);
+  } else {
+    event->filename[0] = '\0';
+  }
 
   struct helper_t* helper = get_helper();
   if (helper == NULL) {
@@ -144,3 +148,15 @@ __always_inline static void submit_rmdir_event(struct submit_event_args_t* args)
 
   __submit_event(args, path_hooks_support_bpf_d_path);
 }
+
+__always_inline static void submit_xattr_event(struct submit_event_args_t* args,
+                                               file_activity_type_t event_type,
+                                               const char* xattr_name) {
+  if (!reserve_event(args)) {
+    return;
+  }
+  args->event->type = event_type;
+  bpf_probe_read_str(args->event->xattr.name, XATTR_NAME_MAX_LEN, xattr_name);
+
+  __submit_event(args, false);
+}

fact-ebpf/src/bpf/main.c

@@ -389,6 +389,48 @@ int BPF_PROG(trace_d_instantiate, struct dentry* dentry, struct inode* inode) {
   return 0;
 }
 
+__always_inline static int handle_xattr(struct metrics_by_hook_t* hook_metrics,
+                                        struct dentry* dentry,
+                                        const char* xattr_name,
+                                        file_activity_type_t event_type) {
+  struct submit_event_args_t args = {.metrics = hook_metrics};
+
+  args.metrics->total++;
+
+  args.inode = inode_to_key(dentry->d_inode);
+  args.parent_inode = inode_to_key(BPF_CORE_READ(dentry, d_parent, d_inode));
+
+  args.monitored = inode_is_monitored(inode_get(&args.inode), inode_get(&args.parent_inode));
+
+  if (args.monitored == NOT_MONITORED) {
+    args.metrics->ignored++;
+    return 0;
+  }
+
+  submit_xattr_event(&args, event_type, xattr_name);
+  return 0;
+}
+
+SEC("lsm/inode_setxattr")
+int BPF_PROG(trace_inode_setxattr, struct mnt_idmap* idmap, struct dentry* dentry,
+             const char* name, const void* value, size_t size, int flags) {
+  struct metrics_t* m = get_metrics();
+  if (m == NULL) {
+    return 0;
+  }
+  return handle_xattr(&m->inode_setxattr, dentry, name, FILE_ACTIVITY_SETXATTR);
+}
+
+SEC("lsm/inode_removexattr")
+int BPF_PROG(trace_inode_removexattr, struct mnt_idmap* idmap, struct dentry* dentry,
+             const char* name) {
+  struct metrics_t* m = get_metrics();
+  if (m == NULL) {
+    return 0;
+  }
+  return handle_xattr(&m->inode_removexattr, dentry, name, FILE_ACTIVITY_REMOVEXATTR);
+}
+
 SEC("lsm/path_rmdir")
 int BPF_PROG(trace_path_rmdir, struct path* dir, struct dentry* dentry) {
   struct metrics_t* m = get_metrics();

fact-ebpf/src/bpf/types.h

@@ -15,6 +15,10 @@
 
 #define LINEAGE_MAX 2
 
+// Matches Linux kernel XATTR_NAME_MAX (255) + null terminator.
+// https://github.com/torvalds/linux/blob/66affa37cfac0aec061cc4bcf4a065b0c52f7e19/include/uapi/linux/limits.h#L15
+#define XATTR_NAME_MAX_LEN 256
+
 #define LPM_SIZE_MAX 256
 
 typedef struct lineage_t {
@@ -64,6 +68,8 @@ typedef enum file_activity_type_t {
   FILE_ACTIVITY_RENAME,
   DIR_ACTIVITY_CREATION,
   DIR_ACTIVITY_UNLINK,
+  FILE_ACTIVITY_SETXATTR,
+  FILE_ACTIVITY_REMOVEXATTR,
 } file_activity_type_t;
 
 struct event_t {
@@ -90,6 +96,9 @@ struct event_t {
       inode_key_t inode;
       monitored_t monitored;
     } rename;
+    struct {
+      char name[XATTR_NAME_MAX_LEN];
+    } xattr;
   };
 };
 
@@ -132,4 +141,6 @@ struct metrics_t {
   struct metrics_by_hook_t path_mkdir;
   struct metrics_by_hook_t d_instantiate;
   struct metrics_by_hook_t path_rmdir;
+  struct metrics_by_hook_t inode_setxattr;
+  struct metrics_by_hook_t inode_removexattr;
 };

fact-ebpf/src/lib.rs

@@ -145,6 +145,8 @@ impl metrics_t {
         self.path_mkdir = self.path_mkdir.accumulate(&other.path_mkdir);
         self.path_rmdir = self.path_rmdir.accumulate(&other.path_rmdir);
         self.d_instantiate = self.d_instantiate.accumulate(&other.d_instantiate);
+        self.inode_setxattr = self.inode_setxattr.accumulate(&other.inode_setxattr);
+        self.inode_removexattr = self.inode_removexattr.accumulate(&other.inode_removexattr);
         self
     }
 }

fact/src/event/mod.rs

@@ -9,7 +9,9 @@ use std::{
 use globset::GlobSet;
 use serde::Serialize;
 
-use fact_ebpf::{PATH_MAX, event_t, file_activity_type_t, inode_key_t, monitored_t};
+use fact_ebpf::{
+    PATH_MAX, XATTR_NAME_MAX_LEN, event_t, file_activity_type_t, inode_key_t, monitored_t,
+};
 
 use crate::host_info;
 use process::Process;
@@ -131,6 +133,10 @@ impl Event {
         matches!(self.file, FileData::Creation(_) | FileData::MkDir(_))
     }
 
+    pub fn is_xattr(&self) -> bool {
+        matches!(self.file, FileData::SetXattr(_) | FileData::RemoveXattr(_))
+    }
+
     pub fn is_mkdir(&self) -> bool {
         matches!(self.file, FileData::MkDir(_))
     }
@@ -162,6 +168,8 @@ impl Event {
             FileData::Chmod(data) => &data.inner.inode,
             FileData::Chown(data) => &data.inner.inode,
             FileData::Rename(data) => &data.new.inode,
+            FileData::SetXattr(data) => &data.inner.inode,
+            FileData::RemoveXattr(data) => &data.inner.inode,
         }
     }
 
@@ -176,6 +184,8 @@ impl Event {
             FileData::Chmod(data) => &data.inner.parent_inode,
             FileData::Chown(data) => &data.inner.parent_inode,
             FileData::Rename(data) => &data.new.parent_inode,
+            FileData::SetXattr(data) => &data.inner.parent_inode,
+            FileData::RemoveXattr(data) => &data.inner.parent_inode,
         }
     }
 
@@ -199,6 +209,8 @@ impl Event {
             FileData::Chmod(data) => &data.inner.filename,
             FileData::Chown(data) => &data.inner.filename,
             FileData::Rename(data) => &data.new.filename,
+            FileData::SetXattr(data) => &data.inner.filename,
+            FileData::RemoveXattr(data) => &data.inner.filename,
         }
     }
 
@@ -219,6 +231,8 @@ impl Event {
             FileData::Chmod(data) => &data.inner.host_file,
             FileData::Chown(data) => &data.inner.host_file,
             FileData::Rename(data) => &data.new.host_file,
+            FileData::SetXattr(data) => &data.inner.host_file,
+            FileData::RemoveXattr(data) => &data.inner.host_file,
         }
     }
 
@@ -243,6 +257,8 @@ impl Event {
             FileData::Chmod(data) => data.inner.host_file = host_path,
             FileData::Chown(data) => data.inner.host_file = host_path,
             FileData::Rename(data) => data.new.host_file = host_path,
+            FileData::SetXattr(data) => data.inner.host_file = host_path,
+            FileData::RemoveXattr(data) => data.inner.host_file = host_path,
         }
     }
 
@@ -264,6 +280,8 @@ impl Event {
             FileData::Chmod(data) => data.inner.monitored,
             FileData::Chown(data) => data.inner.monitored,
             FileData::Rename(data) => data.new.monitored,
+            FileData::SetXattr(data) => data.inner.monitored,
+            FileData::RemoveXattr(data) => data.inner.monitored,
         }
     }
 
@@ -356,6 +374,8 @@ pub enum FileData {
     Chmod(ChmodFileData),
     Chown(ChownFileData),
     Rename(RenameFileData),
+    SetXattr(XattrFileData),
+    RemoveXattr(XattrFileData),
 }
 
 impl FileData {
@@ -407,6 +427,18 @@ impl FileData {
                 };
                 FileData::Rename(data)
             }
+            file_activity_type_t::FILE_ACTIVITY_SETXATTR => {
+                let xattr_name = slice_to_string(
+                    &unsafe { extra_data.xattr }.name[..XATTR_NAME_MAX_LEN as usize],
+                )?;
+                FileData::SetXattr(XattrFileData { inner, xattr_name })
+            }
+            file_activity_type_t::FILE_ACTIVITY_REMOVEXATTR => {
+                let xattr_name = slice_to_string(
+                    &unsafe { extra_data.xattr }.name[..XATTR_NAME_MAX_LEN as usize],
+                )?;
+                FileData::RemoveXattr(XattrFileData { inner, xattr_name })
+            }
             invalid => unreachable!("Invalid event type: {invalid:?}"),
         };
 
@@ -433,6 +465,14 @@ impl From<FileData> for fact_api::file_activity::File {
             FileData::RmDir(_) => {
                 unreachable!("RmDir event reached protobuf conversion");
             }
+            FileData::SetXattr(event) => {
+                let f_act = fact_api::FileXattrChange::from(event);
+                fact_api::file_activity::File::XattrSet(f_act)
+            }
+            FileData::RemoveXattr(event) => {
+                let f_act = fact_api::FileXattrChange::from(event);
+                fact_api::file_activity::File::XattrRemove(f_act)
+            }
             FileData::Unlink(event) => {
                 let activity = Some(fact_api::FileActivityBase::from(event));
                 let f_act = fact_api::FileUnlink { activity };
@@ -465,6 +505,8 @@ impl PartialEq for FileData {
             (FileData::Unlink(this), FileData::Unlink(other)) => this == other,
             (FileData::Chmod(this), FileData::Chmod(other)) => this == other,
             (FileData::Rename(this), FileData::Rename(other)) => this == other,
+            (FileData::SetXattr(this), FileData::SetXattr(other)) => this == other,
+            (FileData::RemoveXattr(this), FileData::RemoveXattr(other)) => this == other,
             _ => false,
         }
     }
@@ -595,6 +637,29 @@ impl PartialEq for RenameFileData {
     }
 }
 
+#[derive(Debug, Clone, Serialize)]
+pub struct XattrFileData {
+    inner: BaseFileData,
+    xattr_name: String,
+}
+
+impl From<XattrFileData> for fact_api::FileXattrChange {
+    fn from(value: XattrFileData) -> Self {
+        let activity = fact_api::FileActivityBase::from(value.inner);
+        fact_api::FileXattrChange {
+            activity: Some(activity),
+            xattr_name: value.xattr_name,
+        }
+    }
+}
+
+#[cfg(test)]
+impl PartialEq for XattrFileData {
+    fn eq(&self, other: &Self) -> bool {
+        self.xattr_name == other.xattr_name && self.inner == other.inner
+    }
+}
+
 #[cfg(test)]
 mod test_utils {
     use std::os::raw::c_char;

fact/src/metrics/kernel_metrics.rs

@@ -16,6 +16,8 @@ pub struct KernelMetrics {
     path_mkdir: EventCounter,
     path_rmdir: EventCounter,
     d_instantiate: EventCounter,
+    inode_setxattr: EventCounter,
+    inode_removexattr: EventCounter,
     map: PerCpuArray<MapData, metrics_t>,
 }
 
@@ -61,6 +63,16 @@ impl KernelMetrics {
             "Events processed by the d_instantiate LSM hook",
             &[], // Labels are not needed since `collect` will add them all
         );
+        let inode_setxattr = EventCounter::new(
+            "kernel_inode_setxattr_events",
+            "Events processed by the inode_setxattr LSM hook",
+            &[], // Labels are not needed since `collect` will add them all
+        );
+        let inode_removexattr = EventCounter::new(
+            "kernel_inode_removexattr_events",
+            "Events processed by the inode_removexattr LSM hook",
+            &[], // Labels are not needed since `collect` will add them all
+        );
 
         file_open.register(reg);
         path_unlink.register(reg);
@@ -70,6 +82,8 @@ impl KernelMetrics {
         path_mkdir.register(reg);
         path_rmdir.register(reg);
         d_instantiate.register(reg);
+        inode_setxattr.register(reg);
+        inode_removexattr.register(reg);
 
         KernelMetrics {
             file_open,
@@ -80,6 +94,8 @@ impl KernelMetrics {
             path_mkdir,
             path_rmdir,
             d_instantiate,
+            inode_setxattr,
+            inode_removexattr,
             map: kernel_metrics,
         }
     }
@@ -132,6 +148,8 @@ impl KernelMetrics {
         KernelMetrics::refresh_labels(&self.path_mkdir, &metrics.path_mkdir);
         KernelMetrics::refresh_labels(&self.path_rmdir, &metrics.path_rmdir);
         KernelMetrics::refresh_labels(&self.d_instantiate, &metrics.d_instantiate);
+        KernelMetrics::refresh_labels(&self.inode_setxattr, &metrics.inode_setxattr);
+        KernelMetrics::refresh_labels(&self.inode_removexattr, &metrics.inode_removexattr);
 
         Ok(())
     }