Allow exact matches for rule names

Currently, when calling enable_rule, the provided rule name pattern is a
substring match, that is if the rules file has a rule "My fantastic
rule", and you call engine->enable_rule("fantastic", true), the rule
will be enabled.

This can cause problems if one rule name is a complete subset of another
rule name e.g. rules "My rule" and "My rule is great", and calling
engine->enable_rule("My rule", true).

To allow for this case, add an alternate method enable_rule_exact() in
both default ruleset and ruleset variants. In this case, the rule name
must be an exact match.

In the underlying ruleset code, add a "match_exact" option to
falco_ruleset::enable() that denotes whether the substring is an exact
or substring match.

This doesn't change the default behavior of falco in any way, as the
existing calls still use enable_rule().

Signed-off-by: Mark Stemm <mark.stemm@gmail.com>

userspace/engine/falco_engine.cpp

@@ -211,9 +211,10 @@ void falco_engine::load_rules_file(const string &rules_filename, bool verbose, b
 void falco_engine::enable_rule(const string &substring, bool enabled, const string &ruleset)
 {
 	uint16_t ruleset_id = find_ruleset_id(ruleset);
+	bool match_exact = false;
 
-	m_sinsp_rules->enable(substring, enabled, ruleset_id);
+	m_sinsp_rules->enable(substring, match_exact, enabled, ruleset_id);
-	m_k8s_audit_rules->enable(substring, enabled, ruleset_id);
+	m_k8s_audit_rules->enable(substring, match_exact, enabled, ruleset_id);
 }
 
 void falco_engine::enable_rule(const string &substring, bool enabled)
@@ -221,6 +222,20 @@ void falco_engine::enable_rule(const string &substring, bool enabled)
 	enable_rule(substring, enabled, m_default_ruleset);
 }
 
+void falco_engine::enable_rule_exact(const string &rule_name, bool enabled, const string &ruleset)
+{
+	uint16_t ruleset_id = find_ruleset_id(ruleset);
+	bool match_exact = true;
+
+	m_sinsp_rules->enable(rule_name, match_exact, enabled, ruleset_id);
+	m_k8s_audit_rules->enable(rule_name, match_exact, enabled, ruleset_id);
+}
+
+void falco_engine::enable_rule_exact(const string &rule_name, bool enabled)
+{
+	enable_rule_exact(rule_name, enabled, m_default_ruleset);
+}
+
 void falco_engine::enable_rule_by_tag(const set<string> &tags, bool enabled, const string &ruleset)
 {
 	uint16_t ruleset_id = find_ruleset_id(ruleset);

userspace/engine/falco_engine.h

@@ -85,6 +85,13 @@ public:
 	// Wrapper that assumes the default ruleset
 	void enable_rule(const std::string &substring, bool enabled);
 
+
+	// Like enable_rule, but the rule name must be an exact match.
+	void enable_rule_exact(const std::string &rule_name, bool enabled, const std::string &ruleset);
+
+	// Wrapper that assumes the default ruleset
+	void enable_rule_exact(const std::string &rule_name, bool enabled);
+
 	//
 	// Enable/Disable any rules with any of the provided tags (set, exact matches only)
 	//

userspace/engine/ruleset.cpp

@@ -201,7 +201,7 @@ void falco_ruleset::add(string &name,
 	}
 }
 
-void falco_ruleset::enable(const string &substring, bool enabled, uint16_t ruleset)
+void falco_ruleset::enable(const string &substring, bool match_exact, bool enabled, uint16_t ruleset)
 {
 	while(m_rulesets.size() < (size_t)ruleset + 1)
 	{
@@ -212,7 +212,17 @@ void falco_ruleset::enable(const string &substring, bool enabled, uint16_t rules
 	{
 		bool matches;
 
-		matches = (substring == "" || (val.first.find(substring) != string::npos));
+		if(match_exact)
+		{
+			size_t pos = val.first.find(substring);
+
+			matches = (substring == "" || (pos == 0 &&
+						       substring.size() == val.first.size()));
+		}
+		else
+		{
+			matches = (substring == "" || (val.first.find(substring) != string::npos));
+		}
 
 		if(matches)
 		{

userspace/engine/ruleset.h

@@ -45,8 +45,11 @@ public:
         // unnecessarily large vectors.
 
 	// Find those rules matching the provided substring and set
-	// their enabled status to enabled.
+	// their enabled status to enabled. If match_exact is true,
-	void enable(const std::string &substring, bool enabled, uint16_t ruleset = 0);
+	// substring must be an exact match for a given rule
+	// name. Otherwise, any rules having substring as a substring
+	// in the rule name are enabled/disabled.
+	void enable(const std::string &substring, bool match_exact, bool enabled, uint16_t ruleset = 0);
 
 	// Find those rules that have a tag in the set of tags and set
 	// their enabled status to enabled. Note that the enabled