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Use GetAdaptersAddresses, not Registry, for DNS servers

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In addition to being simpler, this approach allows us to limit to
adapters that are up and configured. Fixes #3114
This commit is contained in:
dmiller
2025-05-23 17:13:06 +00:00
parent a55708ba5e
commit d72beec963
1 changed files with 68 additions and 100 deletions
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168
nmap_dns.cc
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@@ -119,8 +119,8 @@
#ifdef WIN32
#include "nmap_winconfig.h"
/* Need DnetName2PcapName */
#include "libnetutil/netutil.h"
#include <winsock2.h>
#include <iphlpapi.h>
#endif
#include "nmap.h"
@@ -932,11 +932,30 @@ static void connect_evt_handler(nsock_pool nsp, nsock_event evt, void *srv_v) {
srv->status = dns_server::status_t::CONNECTED;
}
static void add_dns_server(const struct sockaddr_storage *addr, size_t addr_len, const char *hostname) {
std::list<dns_server>::iterator servI;
for(servI = servs.begin(); servI != servs.end(); servI++) {
// Already added!
if (memcmp(addr, &servI->addr, addr_len) == 0) break;
}
// If it hasn't already been added, add it!
if (servI == servs.end()) {
dns_server tpserv;
tpserv.hostname = hostname;
memcpy(&tpserv.addr, addr, addr_len);
tpserv.addr_len = addr_len;
servs.push_front(tpserv);
if (o.debugging) log_write(LOG_STDOUT, "mass_dns: Using DNS server %s\n", hostname);
}
}
// Adds DNS servers to the dns_server list. They can be separated by
// commas or spaces - NOTE this doesn't actually do any connecting!
static void add_dns_server(char *ipaddrs) {
std::list<dns_server>::iterator servI;
const char *hostname;
struct sockaddr_storage addr;
size_t addr_len = sizeof(addr);
@@ -947,24 +966,7 @@ static void add_dns_server(char *ipaddrs) {
o.spoofsource ? o.af() : PF_UNSPEC) != 0)
continue;
for(servI = servs.begin(); servI != servs.end(); servI++) {
// Already added!
if (memcmp(&addr, &servI->addr, sizeof(addr)) == 0) break;
}
// If it hasn't already been added, add it!
if (servI == servs.end()) {
dns_server tpserv;
tpserv.hostname = hostname;
memcpy(&tpserv.addr, &addr, sizeof(addr));
tpserv.addr_len = addr_len;
servs.push_front(tpserv);
if (o.debugging) log_write(LOG_STDOUT, "mass_dns: Using DNS server %s\n", hostname);
}
add_dns_server(&addr, addr_len, hostname);
}
}
@@ -991,90 +993,56 @@ static void connect_dns_servers() {
#ifdef WIN32
static bool interface_is_known_by_guid(const char *guid) {
const struct interface_info *iflist;
int i, n;
iflist = getinterfaces(&n, NULL, 0);
if (iflist == NULL)
return false;
for (i = 0; i < n; i++) {
char pcap_name[1024];
const char *pcap_guid;
if (!DnetName2PcapName(iflist[i].devname, pcap_name, sizeof(pcap_name)))
continue;
pcap_guid = strchr(pcap_name, '{');
if (pcap_guid == NULL)
continue;
if (strcasecmp(guid, pcap_guid) == 0)
return true;
void win32_get_servers() {
ULONG ret = ERROR_SUCCESS;
std::vector<IP_ADAPTER_ADDRESSES> advec;
ULONG len = 0;
for (int i=0; i < 3; i++) {
if (len == 0) {
advec.resize(8);
}
else {
size_t count = len / sizeof(IP_ADAPTER_ADDRESSES);
advec.resize(count);
}
len = advec.size() * sizeof(IP_ADAPTER_ADDRESSES);
ret = GetAdaptersAddresses(AF_UNSPEC, (
GAA_FLAG_SKIP_UNICAST |
GAA_FLAG_SKIP_ANYCAST |
GAA_FLAG_SKIP_MULTICAST |
GAA_FLAG_SKIP_FRIENDLY_NAME),
NULL, &advec[0], &len);
if (ret != ERROR_BUFFER_OVERFLOW) {
break;
}
}
return false;
}
// Reads the Windows registry and adds all the nameservers found via the
// add_dns_server() function.
void win32_read_registry() {
HKEY hKey;
HKEY hKey2;
char keybasebuf[2048];
char buf[2048], keyname[2048], *p;
DWORD sz, i;
Snprintf(keybasebuf, sizeof(keybasebuf), "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters");
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keybasebuf,
0, KEY_READ, &hKey) != ERROR_SUCCESS) {
if (firstrun) error("mass_dns: warning: Error opening registry to read DNS servers. Try using --system-dns or specify valid servers with --dns-servers");
if (ret != ERROR_SUCCESS) {
error("Unable to get DNS servers: %08x", ret);
return;
}
sz = sizeof(buf);
if (RegQueryValueEx(hKey, "NameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
sz = sizeof(buf);
if (RegQueryValueEx(hKey, "DhcpNameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
RegCloseKey(hKey);
Snprintf(keybasebuf, sizeof(keybasebuf), "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces");
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keybasebuf,
0, KEY_ENUMERATE_SUB_KEYS, &hKey) == ERROR_SUCCESS) {
for (i=0; sz = sizeof(buf), RegEnumKeyEx(hKey, i, buf, &sz, NULL, NULL, NULL, NULL) != ERROR_NO_MORE_ITEMS; i++) {
// If we don't have pcap, interface_is_known_by_guid will crash. Just use any servers we can find.
if (o.have_pcap && !interface_is_known_by_guid(buf)) {
if (o.debugging > 1)
log_write(LOG_PLAIN, "Interface %s is not known; ignoring its nameservers.\n", buf);
continue;
}
Snprintf(keyname, sizeof(keyname), "SYSTEM\\CurrentControlSet\\Services\\Tcpip\\Parameters\\Interfaces\\%s", buf);
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keyname,
0, KEY_READ, &hKey2) == ERROR_SUCCESS) {
sz = sizeof(buf);
if (RegQueryValueEx(hKey2, "DhcpNameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
sz = sizeof(buf);
if (RegQueryValueEx(hKey2, "NameServer", NULL, NULL, (LPBYTE) buf, (LPDWORD) &sz) == ERROR_SUCCESS)
add_dns_server(buf);
RegCloseKey(hKey2);
}
for (IP_ADAPTER_ADDRESSES *a = &advec[0]; a != NULL; a = a->Next) {
if (a->OperStatus != IfOperStatusUp)
continue;
for (IP_ADAPTER_DNS_SERVER_ADDRESS_XP *d = a->FirstDnsServerAddress;
d != NULL; d = d->Next) {
const sockaddr_storage* ss = (sockaddr_storage*)d->Address.lpSockaddr;
size_t sslen = d->Address.iSockaddrLength;
if (ss->ss_family == AF_INET) {
if (!a->Ipv4Enabled) continue;
}
else if (ss->ss_family == AF_INET6) {
if (!a->Ipv6Enabled) continue;
/* Windows default site-local IPv6 DNS servers */
if (0 == memcmp(&((sockaddr_in6*)ss)->sin6_addr,
"\xfe\xc0\x00\x00\x00\x00\xff\xff", 8))
continue;
}
else {
continue;
}
add_dns_server(ss, sslen, inet_ntop_ez(ss, sslen));
}
RegCloseKey(hKey);
}
}
#endif // WIN32