Add ability to append to rules/macros

Add the ability to append to rules/macros, like we already do with
lists. For rules/macros, if the object has an append: true key, the
condition value is appended to the condition of an existing rule/macro
with the same name.

Like lists, it's an error to specify append: true without there being an
existing rule/macro.

Also add tests that test the same kind of things we did for lists:
 - That append: true really does append
 - That append: false overwrites the rule/macro
 - That it's an error to append with a prior rule/macro existing.

test/falco_tests.yaml

@@ -599,3 +599,44 @@ trace_files: !mux
     rules_file:
       - rules/list_append_false.yaml
     trace_file: trace_files/cat_write.scap
+
+  macro_append_failure:
+    exit_status: 1
+    stderr_contains: "Macro my_macro has 'append' key but no macro by that name already exists. Exiting"
+    rules_file:
+      - rules/macro_append_failure.yaml
+    trace_file: trace_files/cat_write.scap
+
+  macro_append:
+    detect: True
+    detect_level: WARNING
+    rules_file:
+      - rules/macro_append.yaml
+    trace_file: trace_files/cat_write.scap
+
+  macro_append_false:
+    detect: False
+    rules_file:
+      - rules/macro_append_false.yaml
+    trace_file: trace_files/cat_write.scap
+
+  rule_append_failure:
+    exit_status: 1
+    stderr_contains: "Rule my_rule has 'append' key but no rule by that name already exists. Exiting"
+    rules_file:
+      - rules/rule_append_failure.yaml
+    trace_file: trace_files/cat_write.scap
+
+  rule_append:
+    detect: True
+    detect_level: WARNING
+    rules_file:
+      - rules/rule_append.yaml
+    trace_file: trace_files/cat_write.scap
+
+  rule_append_false:
+    detect: False
+    rules_file:
+      - rules/rule_append_false.yaml
+    trace_file: trace_files/cat_write.scap
+

test/rules/macro_append.yaml

@@ -0,0 +1,12 @@
+- macro: my_macro
+  condition: proc.name=not-cat
+
+- macro: my_macro
+  append: true
+  condition: or proc.name=cat
+
+- rule: Open From Cat
+  desc: A process named cat does an open
+  condition: evt.type=open and my_macro
+  output: "An open was seen (command=%proc.cmdline)"
+  priority: WARNING

test/rules/macro_append_failure.yaml

@@ -0,0 +1,3 @@
+- macro: my_macro
+  condition: proc.name=not-cat
+  append: true

test/rules/macro_append_false.yaml

@@ -0,0 +1,12 @@
+- macro: my_macro
+  condition: proc.name=cat
+
+- macro: my_macro
+  append: false
+  condition: proc.name=not-cat
+
+- rule: Open From Cat
+  desc: A process named cat does an open
+  condition: evt.type=open and my_macro
+  output: "An open was seen (command=%proc.cmdline)"
+  priority: WARNING

test/rules/rule_append.yaml

@@ -0,0 +1,9 @@
+- rule: my_rule
+  desc: A process named cat does an open
+  condition: evt.type=open and fd.name=not-a-real-file
+  output: "An open of /dev/null was seen (command=%proc.cmdline)"
+  priority: WARNING
+
+- rule: my_rule
+  append: true
+  condition: or fd.name=/dev/null

test/rules/rule_append_failure.yaml

@@ -0,0 +1,3 @@
+- rule: my_rule
+  condition: evt.type=open
+  append: true

test/rules/rule_append_false.yaml

@@ -0,0 +1,9 @@
+- rule: my_rule
+  desc: A process named cat does an open
+  condition: evt.type=open and fd.name=/dev/null
+  output: "An open of /dev/null was seen (command=%proc.cmdline)"
+  priority: WARNING
+
+- rule: my_rule
+  append: true
+  condition: and fd.name=not-a-real-file

userspace/engine/lua/rule_loader.lua

@@ -208,7 +208,23 @@ function load_rules(rules_content, rules_mgr, verbose, all_events, extra, replac
 	    end
 	 end
 
-	 state.macros_by_name[v['macro']] = v
+	 -- Possibly append to the condition field of an existing macro
+	 append = false
+
+	 if v['append'] then
+	    append = v['append']
+	 end
+
+	 if append then
+	    if state.macros_by_name[v['macro']] == nil then
+	       error ("Macro " ..v['macro'].. " has 'append' key but no macro by that name already exists")
+	    end
+
+	    state.macros_by_name[v['macro']]['condition'] = state.macros_by_name[v['macro']]['condition'] .. " " .. v['condition']
+
+	 else
+	    state.macros_by_name[v['macro']] = v
+	 end
 
       elseif (v['list']) then
 
@@ -247,25 +263,49 @@ function load_rules(rules_content, rules_mgr, verbose, all_events, extra, replac
 	    error ("Missing name in rule")
 	 end
 
-	 for i, field in ipairs({'condition', 'output', 'desc', 'priority'}) do
+	 -- Possibly append to the condition field of an existing rule
-	    if (v[field] == nil) then
+	 append = false
-	       error ("Missing "..field.." in rule with name "..v['rule'])
+
+	 if v['append'] then
+	    append = v['append']
+	 end
+
+	 if append then
+
+	    -- For append rules, all you need is the condition
+	    for i, field in ipairs({'condition'}) do
+	       if (v[field] == nil) then
+		  error ("Missing "..field.." in rule with name "..v['rule'])
+	       end
 	    end
+
+	    if state.rules_by_name[v['rule']] == nil then
+	       error ("Rule " ..v['rule'].. " has 'append' key but no rule by that name already exists")
+	    end
+
+	    state.rules_by_name[v['rule']]['condition'] = state.rules_by_name[v['rule']]['condition'] .. " " .. v['condition']
+
+	 else
+
+	    for i, field in ipairs({'condition', 'output', 'desc', 'priority'}) do
+	       if (v[field] == nil) then
+		  error ("Missing "..field.." in rule with name "..v['rule'])
+	       end
+	    end
+
+	    -- Note that we can overwrite rules, but the rules are still
+	    -- loaded in the order in which they first appeared,
+	    -- potentially across multiple files.
+	    if state.rules_by_name[v['rule']] == nil then
+	       state.ordered_rule_names[#state.ordered_rule_names+1] = v['rule']
+	    end
+
+	    -- The output field might be a folded-style, which adds a
+	    -- newline to the end. Remove any trailing newlines.
+	    v['output'] = compiler.trim(v['output'])
+
+	    state.rules_by_name[v['rule']] = v
 	 end
-
-	 -- Note that we can overwrite rules, but the rules are still
-	 -- loaded in the order in which they first appeared,
-	 -- potentially across multiple files.
-	 if state.rules_by_name[v['rule']] == nil then
-	    state.ordered_rule_names[#state.ordered_rule_names+1] = v['rule']
-	 end
-
-	 -- The output field might be a folded-style, which adds a
-	 -- newline to the end. Remove any trailing newlines.
-	 v['output'] = compiler.trim(v['output'])
-
-	 state.rules_by_name[v['rule']] = v
-
       else
 	 error ("Unknown rule object: "..table.tostring(v))
       end