Add C API to retrieve matched rules from a transaction

headers/modsecurity/transaction.h

@@ -35,6 +35,7 @@
 
 #include <stdlib.h>
 #include <stddef.h>
+#include <stdint.h>
 
 #ifndef __cplusplus
 typedef struct ModSecurity_t ModSecurity;
@@ -739,6 +740,13 @@ int msc_update_status_code(Transaction *transaction, int status);
 /** @ingroup ModSecurity_C_API */
 int msc_set_request_hostname(Transaction *transaction, const unsigned char *hostname);
 
+/** @ingroup ModSecurity_C_API */
+size_t msc_get_rules_messages_size(const Transaction *transaction);
+
+/** @ingroup ModSecurity_C_API */
+size_t msc_get_rules_messages_rule_ids(const Transaction *transaction,
+    int64_t *ids, size_t ids_len);
+
 #ifdef __cplusplus
 }
 }  // namespace modsecurity

src/transaction.cc

@@ -2325,5 +2325,60 @@
 }
 
 
+/**
+ * @name    msc_get_rules_messages_size
+ * @brief   Retrieve the number of RuleMessage records on a transaction.
+ *
+ * Returns the size of Transaction::m_rulesMessages: the number of
+ * RuleMessage records that were selected to be logged on the
+ * transaction. This is not necessarily the total number of rules that
+ * matched!
+ *
+ * @param transaction ModSecurity transaction.
+ *
+ * @returns The number of RuleMessage records on the transaction.
+ *
+ */
+extern "C" size_t msc_get_rules_messages_size(const Transaction *transaction) {
+    return transaction->m_rulesMessages.size();
+}
+
+
+/**
+ * @name    msc_get_rules_messages_rule_ids
+ * @brief   Copy the rule ids from Transaction::m_rulesMessages into a buffer.
+ *
+ * Copies the rule id of each RuleMessage into the caller-provided buffer.
+ * Only rule messages that were selected to be logged are included.
+ *
+ * The caller is expected to size the buffer using
+ * msc_get_rules_messages_size. If @p ids_len is smaller than the number
+ * of available records, only the first @p ids_len ids are written and
+ * the remaining records are skipped.
+ *
+ * @param transaction ModSecurity transaction.
+ * @param ids         Caller-provided buffer to receive the rule ids.
+ *                    May be NULL only if @p ids_len is 0.
+ * @param ids_len     Capacity of @p ids, in number of int64_t slots.
+ *
+ * @returns The number of rule ids written into @p ids.
+ *
+ */
+extern "C" size_t msc_get_rules_messages_rule_ids(const Transaction *transaction,
+    int64_t *ids, size_t ids_len) {
+    if (ids == nullptr || ids_len == 0) {
+        return 0;
+    }
+    size_t written = 0;
+    for (const auto &msg : transaction->m_rulesMessages) {
+        if (written >= ids_len) {
+            break;
+        }
+        ids[written++] = msg.m_rule.m_ruleId;
+    }
+    return written;
+}
+
+
 }  // namespace modsecurity