From 65237fd7a5e70b05ba39f26141d8fc8aa1fc99dc Mon Sep 17 00:00:00 2001 From: Patrick Cervicek Date: Fri, 9 Oct 2015 11:46:51 +0200 Subject: check_dhcp.c merged patch from #752 - added dhcp rogue detection contributed by Patrick Cervicek (patrick AT cervicek.de) - closes #752 --- plugins-root/check_dhcp.c | 44 ++++++++++++++++++++++++++++++++++---------- 1 file changed, 34 insertions(+), 10 deletions(-) diff --git a/plugins-root/check_dhcp.c b/plugins-root/check_dhcp.c index 0ddace5b..8b8bb985 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 */ + u_int8_t desired; /* is this offer desired (necessary in exclusive mode) */ struct dhcp_offer_struct *next; }dhcp_offer; @@ -193,6 +194,7 @@ typedef struct requested_server_struct{ #define ETHERNET_HARDWARE_ADDRESS_LENGTH 6 /* length of Ethernet hardware addresses */ uint8_t unicast = 0; /* unicast mode: mimic a DHCP relay */ +u_int8_t exclusive = 0; /* 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; @@ -979,6 +982,13 @@ int get_results(void){ } } + /* exclusive mode: check for undesired offers */ + for(temp_offer=dhcp_offer_list;temp_offer!=NULL;temp_offer=temp_offer->next) { + if (temp_offer->desired == FALSE) { + 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 +1016,9 @@ 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 +1036,13 @@ 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_responses0)?"only ":"",requested_responses,requested_servers); @@ -1065,16 +1085,16 @@ 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} }; + int c=0; while(1){ - int c=0; - - c=getopt_long(argc,argv,"+hVvt:s:r:t:i:m:u",long_options,&option_index); + c=getopt_long(argc,argv,"+hVvxt:s:r:t:i:m:u",long_options,&option_index); if(c==-1||c==EOF||c==1) break; @@ -1120,9 +1140,12 @@ int call_getopt(int argc, char **argv){ break; - case 'u': /* unicast testing */ - unicast=1; - break; + case 'u': /* unicast testing */ + unicast=1; + break; + case 'x': /* exclusive testing aka "rogue DHCP server detection" */ + exclusive=1; + break; case 'V': /* version */ print_revision(progname, NP_VERSION); @@ -1135,7 +1158,6 @@ int call_getopt(int argc, char **argv){ case 'v': /* verbose */ verbose=1; break; - case '?': /* help */ usage5 (); break; @@ -1372,6 +1394,8 @@ 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; @@ -1382,8 +1406,8 @@ 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; -} + } -- cgit v1.2.3-74-g34f1