diff options
Diffstat (limited to 'services/net/java/android/net/dhcp/DhcpPacket.java')
| -rw-r--r-- | services/net/java/android/net/dhcp/DhcpPacket.java | 97 |
1 files changed, 67 insertions, 30 deletions
diff --git a/services/net/java/android/net/dhcp/DhcpPacket.java b/services/net/java/android/net/dhcp/DhcpPacket.java index cbf8fc2..8927bfa 100644 --- a/services/net/java/android/net/dhcp/DhcpPacket.java +++ b/services/net/java/android/net/dhcp/DhcpPacket.java @@ -114,6 +114,11 @@ abstract class DhcpPacket { protected static final int MAX_LENGTH = 1500; /** + * The magic cookie that identifies this as a DHCP packet instead of BOOTP. + */ + private static final int DHCP_MAGIC_COOKIE = 0x63825363; + + /** * DHCP Optional Type: DHCP Subnet Mask */ protected static final byte DHCP_SUBNET_MASK = 1; @@ -123,7 +128,7 @@ abstract class DhcpPacket { * DHCP Optional Type: DHCP Router */ protected static final byte DHCP_ROUTER = 3; - protected Inet4Address mGateway; + protected List <Inet4Address> mGateways; /** * DHCP Optional Type: DHCP DNS Server @@ -403,7 +408,7 @@ abstract class DhcpPacket { (HWADDR_LEN - mClientMac.length) // pad addr to 16 bytes + 64 // empty server host name (64 bytes) + 128); // empty boot file name (128 bytes) - buf.putInt(0x63825363); // magic number + buf.putInt(DHCP_MAGIC_COOKIE); // magic number finishPacket(buf); // round up to an even number of octets @@ -668,6 +673,20 @@ abstract class DhcpPacket { return new String(bytes, 0, length, StandardCharsets.US_ASCII); } + private static boolean isPacketToOrFromClient(short udpSrcPort, short udpDstPort) { + return (udpSrcPort == DHCP_CLIENT) || (udpDstPort == DHCP_CLIENT); + } + + private static boolean isPacketServerToServer(short udpSrcPort, short udpDstPort) { + return (udpSrcPort == DHCP_SERVER) && (udpDstPort == DHCP_SERVER); + } + + public static class ParseException extends Exception { + public ParseException(String msg, Object... args) { + super(String.format(msg, args)); + } + } + /** * Creates a concrete DhcpPacket from the supplied ByteBuffer. The * buffer may have an L2 encapsulation (which is the full EthernetII @@ -677,7 +696,7 @@ abstract class DhcpPacket { * A subset of the optional parameters are parsed and are stored * in object fields. */ - public static DhcpPacket decodeFullPacket(ByteBuffer packet, int pktType) + public static DhcpPacket decodeFullPacket(ByteBuffer packet, int pktType) throws ParseException { // bootp parameters int transactionId; @@ -687,8 +706,8 @@ abstract class DhcpPacket { Inet4Address nextIp; Inet4Address relayIp; byte[] clientMac; - List<Inet4Address> dnsServers = new ArrayList<Inet4Address>(); - Inet4Address gateway = null; // aka router + List<Inet4Address> dnsServers = new ArrayList<>(); + List<Inet4Address> gateways = new ArrayList<>(); // aka router Inet4Address serverIdentifier = null; Inet4Address netMask = null; String message = null; @@ -720,7 +739,8 @@ abstract class DhcpPacket { // check to see if we need to parse L2, IP, and UDP encaps if (pktType == ENCAP_L2) { if (packet.remaining() < MIN_PACKET_LENGTH_L2) { - return null; + throw new ParseException("L2 packet too short, %d < %d", + packet.remaining(), MIN_PACKET_LENGTH_L2); } byte[] l2dst = new byte[6]; @@ -732,18 +752,20 @@ abstract class DhcpPacket { short l2type = packet.getShort(); if (l2type != OsConstants.ETH_P_IP) - return null; + throw new ParseException("Unexpected L2 type 0x%04x, expected 0x%04x", + l2type, OsConstants.ETH_P_IP); } if (pktType <= ENCAP_L3) { if (packet.remaining() < MIN_PACKET_LENGTH_L3) { - return null; + throw new ParseException("L3 packet too short, %d < %d", + packet.remaining(), MIN_PACKET_LENGTH_L3); } byte ipTypeAndLength = packet.get(); int ipVersion = (ipTypeAndLength & 0xf0) >> 4; if (ipVersion != 4) { - return null; + throw new ParseException("Invalid IP version %d", ipVersion); } // System.out.println("ipType is " + ipType); @@ -759,8 +781,9 @@ abstract class DhcpPacket { ipSrc = readIpAddress(packet); ipDst = readIpAddress(packet); - if (ipProto != IP_TYPE_UDP) // UDP - return null; + if (ipProto != IP_TYPE_UDP) { + throw new ParseException("Protocol not UDP: %d", ipProto); + } // Skip options. This cannot cause us to read beyond the end of the buffer because the // IPv4 header cannot be more than (0x0f * 4) = 60 bytes long, and that is less than @@ -776,13 +799,19 @@ abstract class DhcpPacket { short udpLen = packet.getShort(); short udpChkSum = packet.getShort(); - if ((udpSrcPort != DHCP_SERVER) && (udpSrcPort != DHCP_CLIENT)) + // Only accept packets to or from the well-known client port (expressly permitting + // packets from ports other than the well-known server port; http://b/24687559), and + // server-to-server packets, e.g. for relays. + if (!isPacketToOrFromClient(udpSrcPort, udpDstPort) && + !isPacketServerToServer(udpSrcPort, udpDstPort)) { return null; + } } // We need to check the length even for ENCAP_L3 because the IPv4 header is variable-length. if (pktType > ENCAP_BOOTP || packet.remaining() < MIN_PACKET_LENGTH_BOOTP) { - return null; + throw new ParseException("Invalid type or BOOTP packet too short, %d < %d", + packet.remaining(), MIN_PACKET_LENGTH_BOOTP); } byte type = packet.get(); @@ -805,7 +834,7 @@ abstract class DhcpPacket { packet.get(ipv4addr); relayIp = (Inet4Address) Inet4Address.getByAddress(ipv4addr); } catch (UnknownHostException ex) { - return null; + throw new ParseException("Invalid IPv4 address: %s", Arrays.toString(ipv4addr)); } // Some DHCP servers have been known to announce invalid client hardware address values such @@ -828,8 +857,10 @@ abstract class DhcpPacket { int dhcpMagicCookie = packet.getInt(); - if (dhcpMagicCookie != 0x63825363) - return null; + if (dhcpMagicCookie != DHCP_MAGIC_COOKIE) { + throw new ParseException("Bad magic cookie 0x%08x, should be 0x%08x", dhcpMagicCookie, + DHCP_MAGIC_COOKIE); + } // parse options boolean notFinishedOptions = true; @@ -852,8 +883,9 @@ abstract class DhcpPacket { expectedLen = 4; break; case DHCP_ROUTER: - gateway = readIpAddress(packet); - expectedLen = 4; + for (expectedLen = 0; expectedLen < optionLen; expectedLen += 4) { + gateways.add(readIpAddress(packet)); + } break; case DHCP_DNS_SERVER: for (expectedLen = 0; expectedLen < optionLen; expectedLen += 4) { @@ -937,18 +969,20 @@ abstract class DhcpPacket { } if (expectedLen != optionLen) { - return null; + throw new ParseException("Invalid length %d for option %d, expected %d", + optionLen, optionType, expectedLen); } } } catch (BufferUnderflowException e) { - return null; + throw new ParseException("BufferUnderflowException"); } } DhcpPacket newPacket; switch(dhcpType) { - case -1: return null; + case (byte) 0xFF: + throw new ParseException("No DHCP message type option"); case DHCP_MESSAGE_TYPE_DISCOVER: newPacket = new DhcpDiscoverPacket( transactionId, secs, clientMac, broadcast); @@ -981,14 +1015,13 @@ abstract class DhcpPacket { clientMac); break; default: - System.out.println("Unimplemented type: " + dhcpType); - return null; + throw new ParseException("Unimplemented DHCP type %d", dhcpType); } newPacket.mBroadcastAddress = bcAddr; newPacket.mDnsServers = dnsServers; newPacket.mDomainName = domainName; - newPacket.mGateway = gateway; + newPacket.mGateways = gateways; newPacket.mHostName = hostName; newPacket.mLeaseTime = leaseTime; newPacket.mMessage = message; @@ -1009,7 +1042,7 @@ abstract class DhcpPacket { * Parse a packet from an array of bytes, stopping at the given length. */ public static DhcpPacket decodeFullPacket(byte[] packet, int length, int pktType) - { + throws ParseException { ByteBuffer buffer = ByteBuffer.wrap(packet, 0, length).order(ByteOrder.BIG_ENDIAN); return decodeFullPacket(buffer, pktType); } @@ -1044,7 +1077,11 @@ abstract class DhcpPacket { } catch (IllegalArgumentException e) { return null; } - results.gateway = mGateway; + + if (mGateways.size() > 0) { + results.gateway = mGateways.get(0); + } + results.dnsServers.addAll(mDnsServers); results.domains = mDomainName; results.serverAddress = mServerIdentifier; @@ -1086,11 +1123,11 @@ abstract class DhcpPacket { public static ByteBuffer buildOfferPacket(int encap, int transactionId, boolean broadcast, Inet4Address serverIpAddr, Inet4Address clientIpAddr, byte[] mac, Integer timeout, Inet4Address netMask, Inet4Address bcAddr, - Inet4Address gateway, List<Inet4Address> dnsServers, + List<Inet4Address> gateways, List<Inet4Address> dnsServers, Inet4Address dhcpServerIdentifier, String domainName) { DhcpPacket pkt = new DhcpOfferPacket( transactionId, (short) 0, broadcast, serverIpAddr, INADDR_ANY, clientIpAddr, mac); - pkt.mGateway = gateway; + pkt.mGateways = gateways; pkt.mDnsServers = dnsServers; pkt.mLeaseTime = timeout; pkt.mDomainName = domainName; @@ -1106,11 +1143,11 @@ abstract class DhcpPacket { public static ByteBuffer buildAckPacket(int encap, int transactionId, boolean broadcast, Inet4Address serverIpAddr, Inet4Address clientIpAddr, byte[] mac, Integer timeout, Inet4Address netMask, Inet4Address bcAddr, - Inet4Address gateway, List<Inet4Address> dnsServers, + List<Inet4Address> gateways, List<Inet4Address> dnsServers, Inet4Address dhcpServerIdentifier, String domainName) { DhcpPacket pkt = new DhcpAckPacket( transactionId, (short) 0, broadcast, serverIpAddr, INADDR_ANY, clientIpAddr, mac); - pkt.mGateway = gateway; + pkt.mGateways = gateways; pkt.mDnsServers = dnsServers; pkt.mLeaseTime = timeout; pkt.mDomainName = domainName; |