From 4570de440b7a0aaf74f2fd3adc1f2eac5252d332 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 | 92 ++++++++++++++++++++++++++++------------------- 1 file changed, 56 insertions(+), 36 deletions(-) diff --git a/plugins-root/check_dhcp.c b/plugins-root/check_dhcp.c index 2d22619b..9aeff2b0 100644 --- a/plugins-root/check_dhcp.c +++ b/plugins-root/check_dhcp.c @@ -156,6 +156,7 @@ typedef struct dhcp_offer_struct{ u_int32_t lease_time; /* lease time in seconds */ u_int32_t renewal_time; /* renewal time in seconds */ u_int32_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; @@ -199,6 +200,7 @@ typedef struct requested_server_struct{ #define ETHERNET_HARDWARE_ADDRESS_LENGTH 6 /* length of Ethernet hardware addresses */ u_int8_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]=""; @@ -900,6 +902,7 @@ 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){ @@ -945,7 +948,7 @@ 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; u_int32_t max_lease_time=0; @@ -976,16 +979,24 @@ int get_results(void){ if(temp_server->answered) printf(_(" (duplicate)")); printf(_("\n")); - } + } if(temp_server->answered == FALSE){ 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 == 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 */ else{ @@ -999,8 +1010,8 @@ int get_results(void){ /* see if we got the address we requested */ if(!memcmp(&requested_address,&temp_offer->offered_address,sizeof(requested_address))) received_requested_address=TRUE; - } - } + } + } result=STATE_OK; if(valid_responses==0) @@ -1012,6 +1023,9 @@ int get_results(void){ else if(request_specific_address==TRUE && received_requested_address==FALSE) result=STATE_WARNING; + if(exclusive && undesired_offer) + result=STATE_CRITICAL; + if(result==0) /* garrett honeycutt 2005 */ printf("OK: "); else if(result==1) @@ -1029,6 +1043,13 @@ 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); @@ -1071,16 +1092,16 @@ 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; @@ -1129,6 +1150,9 @@ int call_getopt(int argc, char **argv){ 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); @@ -1142,10 +1166,6 @@ int call_getopt(int argc, char **argv){ verbose=1; break; - case '?': /* help */ - usage5 (); - break; - default: break; } @@ -1357,7 +1377,7 @@ void print_help(void){ printf("%s\n", _("This plugin tests the availability of DHCP servers on a network.")); - printf ("\n\n"); + printf ("\n\n"); print_usage(); @@ -1367,19 +1387,21 @@ void print_help(void){ printf (UT_VERBOSE); printf (" %s\n", "-s, --serverip=IPADDRESS"); - printf (" %s\n", _("IP address of DHCP server that we must hear from")); - printf (" %s\n", "-r, --requestedip=IPADDRESS"); - printf (" %s\n", _("IP address that should be offered by at least one DHCP server")); - printf (" %s\n", "-t, --timeout=INTEGER"); - printf (" %s\n", _("Seconds to wait for DHCPOFFER before timeout occurs")); - printf (" %s\n", "-i, --interface=STRING"); - printf (" %s\n", _("Interface to to use for listening (i.e. eth0)")); - printf (" %s\n", "-m, --mac=STRING"); - 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 (UT_SUPPORT); + printf (" %s\n", _("IP address of DHCP server that we must hear from")); + printf (" %s\n", "-r, --requestedip=IPADDRESS"); + printf (" %s\n", _("IP address that should be offered by at least one DHCP server")); + printf (" %s\n", "-t, --timeout=INTEGER"); + printf (" %s\n", _("Seconds to wait for DHCPOFFER before timeout occurs")); + printf (" %s\n", "-i, --interface=STRING"); + printf (" %s\n", _("Interface to to use for listening (i.e. eth0)")); + printf (" %s\n", "-m, --mac=STRING"); + 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; } @@ -1387,12 +1409,10 @@ void print_help(void){ void print_usage(void){ - printf ("%s\n", _("Usage:")); - printf (" %s [-v] [-u] [-s serverip] [-r requestedip] [-t timeout]\n",progname); - printf (" [-i interface] [-m mac]\n"); + printf ("%s\n", _("Usage:")); + 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