Merge pull request #1038 from eve-mem/linux_check_afinfo_member_checks

Linux: add member presence checks to linux.checks_afinfo

volatility3/framework/plugins/linux/check_afinfo.py

@@ -51,10 +51,22 @@ def _check_members(self, var_ops, var_name, members):
                 yield check, addr
 
     def _check_afinfo(self, var_name, var, op_members, seq_members):
-        for hooked_member, hook_address in self._check_members(
-            var.seq_fops, var_name, op_members
-        ):
-            yield var_name, hooked_member, hook_address
+        # check if object has a least one of the members used for analysis by this function
+        required_members = ["seq_fops", "seq_ops", "seq_show"]
+        has_required_member = any(
+            [var.has_member(member) for member in required_members]
+        )
+        if not has_required_member:
+            vollog.debug(
+                f"{var_name} object at {hex(var.vol.offset)} had none of the required members: {', '.join([member for member in required_members])}"
+            )
+            raise exceptions.PluginRequirementException
+
+        if var.has_member("seq_fops"):
+            for hooked_member, hook_address in self._check_members(
+                var.seq_fops, var_name, op_members
+            ):
+                yield var_name, hooked_member, hook_address
 
         # newer kernels
         if var.has_member("seq_ops"):
@@ -64,8 +76,10 @@ def _check_afinfo(self, var_name, var, op_members, seq_members):
                 yield var_name, hooked_member, hook_address
 
         # this is the most commonly hooked member by rootkits, so a force a check on it
-        elif not self._is_known_address(var.seq_show):
-            yield var_name, "show", var.seq_show
+        else:
+            if var.has_member("seq_show"):
+                if not self._is_known_address(var.seq_show):
+                    yield var_name, "show", var.seq_show
 
     def _generator(self):
         vmlinux = self.context.modules[self.config["kernel"]]
@@ -85,6 +99,12 @@ def _generator(self):
         )
         protocols = [tcp, udp]
 
+        # used to track the calls to _check_afinfo and the
+        # number of errors produced due to missing members
+        symbols_checked = set()
+        symbols_with_errors = set()
+
+        # loop through all symbols
         for struct_type, global_vars in protocols:
             for global_var_name in global_vars:
                 # this will lookup fail for the IPv6 protocols on kernels without IPv6 support
@@ -97,10 +117,20 @@ def _generator(self):
                     object_type=struct_type, offset=global_var.address
                 )
 
-                for name, member, address in self._check_afinfo(
-                    global_var_name, global_var, op_members, seq_members
-                ):
-                    yield 0, (name, member, format_hints.Hex(address))
+                symbols_checked.add(global_var_name)
+                try:
+                    for name, member, address in self._check_afinfo(
+                        global_var_name, global_var, op_members, seq_members
+                    ):
+                        yield 0, (name, member, format_hints.Hex(address))
+                except exceptions.PluginRequirementException:
+                    symbols_with_errors.add(global_var_name)
+
+        # if every call to _check_afinfo failed show a warning
+        if symbols_checked == symbols_with_errors:
+            vollog.warning(
+                "This plugin was not able to check for hooks. This means you are either analyzing an unsupported kernel version or that your symbol table is corrupt."
+            )
 
     def run(self):
         return renderers.TreeGrid(