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safer code: check for request id in response

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This commit is contained in:
Anton Keks 2014-08-31 19:53:17 +03:00
parent 483b8f519a
commit 0beb26136e
2 changed files with 16 additions and 14 deletions
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28
src/net/azib/ipscan/util/MDNSResolver.java
View File

@ -39,32 +39,34 @@ public class MDNSResolver {
return s.toString();
}
public byte[] dnsRequest(String name) throws IOException {
byte[] dnsRequest(int id, String name) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream out = new DataOutputStream(baos);
out.write(new byte[] {0x17, 0x57, 1, 0x20, 0, 1, 0, 0, 0, 0, 0, 1});
out.writeShort(id);
out.write(new byte[] { 1, 0x20, 0, 1, 0, 0, 0, 0, 0, 1});
writeName(out, name);
out.write(new byte[] {0, 0xc, 0, 1});
out.write(new byte[]{0, 0, 0x29, 0x10, 0, 0, 0, 0, 0, 0, 0});
return baos.toByteArray();
}
String reverseName(InetAddress ip) {
byte[] addr = ip.getAddress(); // note: only IPv4 is supported here
String reverseName(byte[] addr) {
// note: only IPv4 is supported here
return (addr[3]&0xFF) + "." + (addr[2]&0xFF) + "." + (addr[1]&0xFF) + "." + (addr[0]&0xFF) + ".in-addr.arpa";
}
public String resolve(InetAddress ip) throws IOException {
byte[] data = dnsRequest(reverseName(ip));
byte[] addr = ip.getAddress();
int requestId = addr[2]*0xFF + addr[3];
byte[] request = dnsRequest(requestId, reverseName(addr));
mdns.send(new DatagramPacket(request, request.length, mdnsIP, mdnsPort));
DatagramPacket query = new DatagramPacket(data, data.length, mdnsIP, mdnsPort);
mdns.send(query);
DatagramPacket resp = new DatagramPacket(new byte[512], 512);
mdns.receive(resp);
data = resp.getData();
int offset = query.getLength() - 11 + 12;
return decodeName(data, offset, resp.getLength() - offset);
DatagramPacket respPacket = new DatagramPacket(new byte[512], 512);
mdns.receive(respPacket);
byte[] response = respPacket.getData();
if (response[0] != request[0] && response[1] != request[1]) return null;
int offset = request.length + 1;
return decodeName(response, offset, respPacket.getLength() - offset);
}
public static void main(String[] args) throws IOException {

2
test/net/azib/ipscan/util/MDNSResolverTest.java
View File

@ -33,6 +33,6 @@ public class MDNSResolverTest {
@Test
public void reverseLookupName() throws Exception {
assertEquals("2.0.168.192.in-addr.arpa", resolver.reverseName(InetAddress.getByName("192.168.0.2")));
assertEquals("2.0.168.192.in-addr.arpa", resolver.reverseName(InetAddress.getByName("192.168.0.2").getAddress()));
}
}