1 files changed, 34 insertions, 9 deletions

diff --git a/plugins-root/check_dhcp.c b/plugins-root/check_dhcp.c
index 0ddace5..5ba9372 100644
--- a/plugins-root/check_dhcp.c
+++ b/plugins-root/check_dhcp.c
@@ -150,6 +150,7 @@ typedef struct dhcp_offer_struct{
         uint32_t lease_time;            /* lease time in seconds */
         uint32_t renewal_time;          /* renewal time in seconds */
         uint32_t rebinding_time;        /* rebinding time in seconds */
+        bool desired;                 /* is this offer desired (necessary in exclusive mode) */
         struct dhcp_offer_struct *next;
 }dhcp_offer;
 
@@ -192,7 +193,8 @@ typedef struct requested_server_struct{
 #define ETHERNET_HARDWARE_ADDRESS            1     /* used in htype field of dhcp packet */
 #define ETHERNET_HARDWARE_ADDRESS_LENGTH     6     /* length of Ethernet hardware addresses */
 
-uint8_t unicast = 0;        /* unicast mode: mimic a DHCP relay */
+bool unicast = false;        /* unicast mode: mimic a DHCP relay */
+bool exclusive = false;      /* exclusive mode aka "rogue DHCP server detection" */
 struct in_addr my_ip;        /* our address (required for relay) */
 struct in_addr dhcp_ip;      /* server to query (if in unicast mode) */
 unsigned char client_hardware_address[MAX_DHCP_CHADDR_LENGTH]="";
@@ -894,6 +896,7 @@ int add_dhcp_offer(struct in_addr source,dhcp_packet *offer_packet){
         new_offer->lease_time=dhcp_lease_time;
         new_offer->renewal_time=dhcp_renewal_time;
         new_offer->rebinding_time=dhcp_rebinding_time;
+        new_offer->desired=false; /* exclusive mode: we'll check that in get_results */
 
 
         if(verbose){
@@ -939,7 +942,7 @@ int free_requested_server_list(void){
 
 /* gets state and plugin output to return */
 int get_results(void){
-        dhcp_offer *temp_offer;
+        dhcp_offer *temp_offer, *undesired_offer=NULL;
         requested_server *temp_server;
         int result;
         uint32_t max_lease_time=0;
@@ -974,11 +977,19 @@ int get_results(void){
                                         if(!temp_server->answered){
                                                 requested_responses++;
                                                 temp_server->answered=true;
+                                                temp_offer->desired=true;
                                         }
                                 }
                         }
                 }
 
+                /* exclusive mode: check for undesired offers */
+                for(temp_offer=dhcp_offer_list;temp_offer!=NULL;temp_offer=temp_offer->next) {
+                        if (!temp_offer->desired) {
+                                undesired_offer=temp_offer; /* Checks only for the first undesired offer */
+                                break; /* no further checks needed */
+                        }
+                }
         }
 
         /* else check and see if we got our requested address from any server */
@@ -1006,6 +1017,9 @@ int get_results(void){
         else if(request_specific_address && !received_requested_address)
                 result=STATE_WARNING;
 
+        if(exclusive && undesired_offer)
+                result=STATE_CRITICAL;
+
         if(result==0)               /* garrett honeycutt 2005 */
                 printf("OK: ");
         else if(result==1)
@@ -1023,6 +1037,13 @@ int get_results(void){
 
         printf(_("Received %d DHCPOFFER(s)"),valid_responses);
 
+
+        if(exclusive && undesired_offer){
+                printf(_(", Rogue DHCP Server detected! Server %s"),inet_ntoa(undesired_offer->server_address));
+                printf(_(" offered %s \n"),inet_ntoa(undesired_offer->offered_address));
+                return result;
+        }
+
         if(requested_servers>0)
                 printf(_(", %s%d of %d requested servers responded"),((requested_responses<requested_servers) && requested_responses>0)?"only ":"",requested_responses,requested_servers);
 
@@ -1065,16 +1086,16 @@ int call_getopt(int argc, char **argv){
                 {"interface",      required_argument,0,'i'},
                 {"mac",            required_argument,0,'m'},
                 {"unicast",        no_argument,      0,'u'},
+                {"exclusive",      no_argument,      0,'x'},
                 {"verbose",        no_argument,      0,'v'},
                 {"version",        no_argument,      0,'V'},
                 {"help",           no_argument,      0,'h'},
                 {0,0,0,0}
         };
 
-        while(1){
-                int c=0;
-
-                c=getopt_long(argc,argv,"+hVvt:s:r:t:i:m:u",long_options,&option_index);
+        int c=0;
+        while(true){
+                c=getopt_long(argc,argv,"+hVvxt:s:r:t:i:m:u",long_options,&option_index);
 
                 if(c==-1||c==EOF||c==1)
                         break;
@@ -1121,7 +1142,10 @@ int call_getopt(int argc, char **argv){
                                 break;
 
                         case 'u': /* unicast testing */
-                                unicast=1;
+                                unicast=true;
+                                break;
+                        case 'x': /* exclusive testing aka "rogue DHCP server detection" */
+                                exclusive=true;
                                 break;
 
                         case 'V': /* version */
@@ -1135,7 +1159,6 @@ int call_getopt(int argc, char **argv){
                         case 'v': /* verbose */
                                 verbose=1;
                                 break;
-
                         case '?': /* help */
                                 usage5 ();
                                 break;
@@ -1372,6 +1395,8 @@ void print_help(void){
         printf ("    %s\n", _("MAC address to use in the DHCP request"));
         printf (" %s\n", "-u, --unicast");
         printf ("    %s\n", _("Unicast testing: mimic a DHCP relay, requires -s"));
+        printf (" %s\n", "-x, --exclusive");
+        printf ("    %s\n", _("Only requested DHCP server may response (rogue DHCP server detection), requires -s"));
 
         printf (UT_SUPPORT);
         return;
@@ -1382,7 +1407,7 @@ void
 print_usage(void){
 
         printf ("%s\n", _("Usage:"));
-        printf (" %s [-v] [-u] [-s serverip] [-r requestedip] [-t timeout]\n",progname);
+        printf (" %s [-v] [-u] [-x] [-s serverip] [-r requestedip] [-t timeout]\n",progname);
         printf ("                  [-i interface] [-m mac]\n");
 
         return;