2 files changed, 285 insertions, 4 deletions

diff --git a/plugins/check_dig.c b/plugins/check_dig.c
index c27e5f13..2db0f66b 100644
--- a/plugins/check_dig.c
+++ b/plugins/check_dig.c
@@ -3,7 +3,7 @@
  * Monitoring check_dig plugin
  *
  * License: GPL
- * Copyright (c) 2002-2024 Monitoring Plugins Development Team
+ * Copyright (c) 2002-2025 Monitoring Plugins Development Team
  *
  * Description:
  *
@@ -33,9 +33,10 @@
  *  because on some architectures those strings are in non-writable memory */
 
 const char *progname = "check_dig";
-const char *copyright = "2002-2024";
+const char *copyright = "2002-2025";
 const char *email = "devel@monitoring-plugins.org";
 
+#include <ctype.h>
 #include "common.h"
 #include "netutils.h"
 #include "utils.h"
@@ -56,6 +57,16 @@ void print_usage(void);
 
 static int verbose = 0;
 
+/* helpers for flag parsing */
+typedef struct {
+        char **items;
+        size_t count;
+} flag_list;
+static flag_list parse_flags_line(const char *line);
+static flag_list split_csv_trim(const char *csv);
+static bool flag_list_contains(const flag_list *list, const char *needle);
+static void free_flag_list(flag_list *list);
+
 int main(int argc, char **argv) {
         setlocale(LC_ALL, "");
         bindtextdomain(PACKAGE, LOCALEDIR);
@@ -101,13 +112,35 @@ int main(int argc, char **argv) {
         output chld_out;
         output chld_err;
         char *msg = NULL;
+        flag_list dig_flags = {.items = NULL, .count = 0};
         mp_state_enum result = STATE_UNKNOWN;
+
         /* run the command */
         if (np_runcmd(command_line, &chld_out, &chld_err, 0) != 0) {
                 result = STATE_WARNING;
                 msg = (char *)_("dig returned an error status");
         }
 
+        /* extract ';; flags: ...' from stdout (first occurrence) */
+        for (size_t i = 0; i < chld_out.lines; i++) {
+                if (strstr(chld_out.line[i], "flags:")) {
+                        if (verbose) {
+                                printf("Raw flags line: %s\n", chld_out.line[i]);
+                        }
+
+                        dig_flags = parse_flags_line(chld_out.line[i]);
+
+                        if (verbose && dig_flags.count > 0) {
+                                printf(_("Parsed flags:"));
+                                for (size_t k = 0; k < dig_flags.count; k++) {
+                                        printf(" %s", dig_flags.items[k]);
+                                }
+                                printf("\n");
+                        }
+                        break;
+                }
+        }
+
         for (size_t i = 0; i < chld_out.lines; i++) {
                 /* the server is responding, we just got the host name... */
                 if (strstr(chld_out.line[i], ";; ANSWER SECTION:")) {
@@ -174,6 +207,57 @@ int main(int argc, char **argv) {
                 result = STATE_WARNING;
         }
 
+        /* Optional: evaluate dig flags only if -E/-X were provided */
+        if ((config.require_flags && *config.require_flags) ||
+                (config.forbid_flags && *config.forbid_flags)) {
+
+                if (dig_flags.count > 0) {
+
+                        if (config.require_flags && *config.require_flags) {
+                                flag_list req = split_csv_trim(config.require_flags);
+
+                                for (size_t r = 0; r < req.count; r++) {
+                                        if (!flag_list_contains(&dig_flags, req.items[r])) {
+                                                result = STATE_CRITICAL;
+                                                if (!msg) {
+                                                        xasprintf(&msg, _("Missing required DNS flag: %s"), req.items[r]);
+                                                } else {
+                                                        char *newmsg = NULL;
+                                                        xasprintf(&newmsg, _("%s; missing required DNS flag: %s"), msg,
+                                                                          req.items[r]);
+                                                        msg = newmsg;
+                                                }
+                                        }
+                                }
+
+                                free_flag_list(&req);
+                        }
+
+                        if (config.forbid_flags && *config.forbid_flags) {
+                                flag_list bad = split_csv_trim(config.forbid_flags);
+
+                                for (size_t r = 0; r < bad.count; r++) {
+                                        if (flag_list_contains(&dig_flags, bad.items[r])) {
+                                                result = STATE_CRITICAL;
+                                                if (!msg) {
+                                                        xasprintf(&msg, _("Forbidden DNS flag present: %s"), bad.items[r]);
+                                                } else {
+                                                        char *newmsg = NULL;
+                                                        xasprintf(&newmsg, _("%s; forbidden DNS flag present: %s"), msg,
+                                                                          bad.items[r]);
+                                                        msg = newmsg;
+                                                }
+                                        }
+                                }
+
+                                free_flag_list(&bad);
+                        }
+                }
+        }
+
+        /* cleanup flags buffer */
+        free_flag_list(&dig_flags);
+
         printf("DNS %s - %.3f seconds response time (%s)|%s\n", state_text(result), elapsed_time,
                    msg ? msg : _("Probably a non-existent host/domain"),
                    fperfdata("time", elapsed_time, "s", (config.warning_interval > UNDEFINED),
@@ -190,6 +274,8 @@ check_dig_config_wrapper process_arguments(int argc, char **argv) {
                                                                            {"critical", required_argument, 0, 'c'},
                                                                            {"timeout", required_argument, 0, 't'},
                                                                            {"dig-arguments", required_argument, 0, 'A'},
+                                                                           {"require-flags", required_argument, 0, 'E'},
+                                                                           {"forbid-flags", required_argument, 0, 'X'},
                                                                            {"verbose", no_argument, 0, 'v'},
                                                                            {"version", no_argument, 0, 'V'},
                                                                            {"help", no_argument, 0, 'h'},
@@ -212,7 +298,8 @@ check_dig_config_wrapper process_arguments(int argc, char **argv) {
 
         int option = 0;
         while (true) {
-                int option_index = getopt_long(argc, argv, "hVvt:l:H:w:c:T:p:a:A:46", longopts, &option);
+                int option_index =
+                        getopt_long(argc, argv, "hVvt:l:H:w:c:T:p:a:A:E:X:46", longopts, &option);
 
                 if (option_index == -1 || option_index == EOF) {
                         break;
@@ -263,6 +350,12 @@ check_dig_config_wrapper process_arguments(int argc, char **argv) {
                 case 'A': /* dig arguments */
                         result.config.dig_args = strdup(optarg);
                         break;
+                case 'E': /* require flags */
+                        result.config.require_flags = strdup(optarg);
+                        break;
+                case 'X': /* forbid flags */
+                        result.config.forbid_flags = strdup(optarg);
+                        break;
                 case 'v': /* verbose */
                         verbose++;
                         break;
@@ -343,6 +436,10 @@ void print_help(void) {
         printf("    %s\n", _("was in -l"));
         printf(" %s\n", "-A, --dig-arguments=STRING");
         printf("    %s\n", _("Pass STRING as argument(s) to dig"));
+        printf(" %s\n", "-E, --require-flags=LIST");
+        printf("    %s\n", _("Comma-separated dig flags that must be present (e.g. 'aa,qr')"));
+        printf(" %s\n", "-X, --forbid-flags=LIST");
+        printf("    %s\n", _("Comma-separated dig flags that must NOT be present"));
         printf(UT_WARN_CRIT);
         printf(UT_CONN_TIMEOUT, DEFAULT_SOCKET_TIMEOUT);
         printf(UT_VERBOSE);
@@ -359,5 +456,185 @@ void print_usage(void) {
         printf("%s\n", _("Usage:"));
         printf("%s -l <query_address> [-H <host>] [-p <server port>]\n", progname);
         printf(" [-T <query type>] [-w <warning interval>] [-c <critical interval>]\n");
-        printf(" [-t <timeout>] [-a <expected answer address>] [-v]\n");
+        printf(" [-t <timeout>] [-a <expected answer address>] [-E <flags>] [-X <flags>] [-v]\n");
+}
+
+/* helpers */
+
+/**
+ * parse_flags_line - Parse a dig output line and extract DNS header flags.
+ *
+ * Input:
+ *   line - NUL terminated dig output line, e.g. ";; flags: qr rd ra; ..."
+ *
+ * Returns:
+ *   flag_list where:
+ *     - items: array of NUL terminated flag strings (heap allocated)
+ *     - count: number of entries in items
+ *   On parse failure or if no flags were found, count is 0 and items is NULL.
+ */
+static flag_list parse_flags_line(const char *line) {
+        flag_list result = {.items = NULL, .count = 0};
+
+        if (!line) {
+                return result;
+        }
+
+        /* Locate start of DNS header flags in dig output */
+        const char *p = strstr(line, "flags:");
+        if (!p) {
+                return result;
+        }
+        p += 6; /* skip literal "flags:" */
+
+        /* Skip whitespace after "flags:" */
+        while (*p && isspace((unsigned char)*p)) {
+                p++;
+        }
+
+        /* Flags are terminated by the next semicolon e.g. "qr rd ra;" */
+        const char *q = strchr(p, ';');
+        if (!q) {
+                return result;
+        }
+
+        /* Extract substring containing the flag block */
+        size_t len = (size_t)(q - p);
+        if (len == 0) {
+                return result;
+        }
+
+        char *buf = (char *)malloc(len + 1);
+        if (!buf) {
+                return result;
+        }
+        memcpy(buf, p, len);
+        buf[len] = '\0';
+
+        /* Tokenize flags separated by whitespace */
+        char **arr = NULL;
+        size_t cnt = 0;
+        char *saveptr = NULL;
+        char *tok = strtok_r(buf, " \t", &saveptr);
+
+        while (tok) {
+                /* Expand array for the next flag token */
+                char **tmp = (char **)realloc(arr, (cnt + 1) * sizeof(char *));
+                if (!tmp) {
+                        /* On allocation failure keep what we have and return it */
+                        break;
+                }
+                arr = tmp;
+                arr[cnt++] = strdup(tok);
+                tok = strtok_r(NULL, " \t", &saveptr);
+        }
+
+        free(buf);
+
+        result.items = arr;
+        result.count = cnt;
+        return result;
+}
+
+/**
+ * split_csv_trim - Split a comma separated string into trimmed tokens.
+ *
+ * Input:
+ *   csv - NUL terminated string, e.g. "aa, qr , rd"
+ *
+ * Returns:
+ *   flag_list where:
+ *     - items: array of NUL terminated tokens (heap allocated, whitespace trimmed)
+ *     - count: number of tokens
+ *   On empty input, count is 0 and items is NULL
+ */
+static flag_list split_csv_trim(const char *csv) {
+        flag_list result = {.items = NULL, .count = 0};
+
+        if (!csv || !*csv) {
+                return result;
+        }
+
+        char *tmp = strdup(csv);
+        if (!tmp) {
+                return result;
+        }
+
+        char *s = tmp;
+        char *token = NULL;
+
+        /* Split CSV by commas, trimming whitespace on each token */
+        while ((token = strsep(&s, ",")) != NULL) {
+                /* trim leading whitespace */
+                while (*token && isspace((unsigned char)*token)) {
+                        token++;
+                }
+
+                /* trim trailing whitespace */
+                char *end = token + strlen(token);
+                while (end > token && isspace((unsigned char)end[-1])) {
+                        *--end = '\0';
+                }
+
+                if (*token) {
+                        /* Expand the items array and append the token */
+                        char **arr = (char **)realloc(result.items, (result.count + 1) * sizeof(char *));
+                        if (!arr) {
+                                /* Allocation failed, stop and return what we have */
+                                break;
+                        }
+                        result.items = arr;
+                        result.items[result.count++] = strdup(token);
+                }
+        }
+
+        free(tmp);
+        return result;
+}
+
+/**
+ * flag_list_contains - Case-insensitive membership test in a flag_list.
+ *
+ * Input:
+ *   list   - pointer to a flag_list
+ *   needle - NUL terminated string to search for
+ *
+ * Returns:
+ *   true  if needle is contained in list (strcasecmp)
+ *   false otherwise
+ */
+static bool flag_list_contains(const flag_list *list, const char *needle) {
+        if (!list || !needle || !*needle) {
+                return false;
+        }
+
+        for (size_t i = 0; i < list->count; i++) {
+                if (strcasecmp(list->items[i], needle) == 0) {
+                        return true;
+                }
+        }
+        return false;
+}
+
+/**
+ * free_flag_list - Release all heap allocations held by a flag_list.
+ *
+ * Input:
+ *   list - pointer to a flag_list whose items were allocated by
+ *          parse_flags_line() or split_csv_trim().
+ *
+ * After this call list->items is NULL and list->count is 0.
+ */
+static void free_flag_list(flag_list *list) {
+        if (!list || !list->items) {
+                return;
+        }
+
+        for (size_t i = 0; i < list->count; i++) {
+                free(list->items[i]);
+        }
+        free(list->items);
+
+        list->items = NULL;
+        list->count = 0;
 }
diff --git a/plugins/check_dig.d/config.h b/plugins/check_dig.d/config.h
index a570b633..392848e5 100644
--- a/plugins/check_dig.d/config.h
+++ b/plugins/check_dig.d/config.h
@@ -19,6 +19,8 @@ typedef struct {
 
         double warning_interval;
         double critical_interval;
+        char *require_flags;
+        char *forbid_flags;
 } check_dig_config;
 
 check_dig_config check_dig_config_init() {
@@ -34,6 +36,8 @@ check_dig_config check_dig_config_init() {
 
                 .warning_interval = UNDEFINED,
                 .critical_interval = UNDEFINED,
+                .require_flags = NULL,
+                .forbid_flags = NULL,
 
         };
         return tmp;