diff options
author | Yawning Angel <yawning@schwanenlied.me> | 2014-05-12 04:51:06 +0000 |
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committer | Yawning Angel <yawning@schwanenlied.me> | 2014-05-12 04:51:06 +0000 |
commit | 9712aec73b2b483a4426ca670ee208b44ad1bc25 (patch) | |
tree | 9f46805aa32166d627e8038ddfd308b2f078bf99 /packet.go | |
parent | 8a1f58cd5a1e2345b7321259c074c044a0ecbefd (diff) |
Preliminary support padding, log on panic.
This adds preliminary support for data padding by adding another layer
of encapsulation inside each AEAD frame containing a type and length.
For now, data is still sent unpadded, but the infrastructure for
supporting it is mostly there.
Additionally, use log.Panic[f]() instead of panic through out the code
so that some panics are logged.
Diffstat (limited to 'packet.go')
-rw-r--r-- | packet.go | 111 |
1 files changed, 111 insertions, 0 deletions
diff --git a/packet.go b/packet.go new file mode 100644 index 0000000..7a6b3fb --- /dev/null +++ b/packet.go @@ -0,0 +1,111 @@ +/* + * Copyright (c) 2014, Yawning Angel <yawning at torproject dot org> + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * * Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +package obfs4 + +import ( + "encoding/binary" + "fmt" + "log" + + "github.com/yawning/obfs4/framing" +) + +const ( + packetOverhead = 2 + 1 + maxPacketPayloadLength = framing.MaximumFramePayloadLength - packetOverhead + maxPacketPaddingLength = maxPacketPayloadLength +) + +const ( + packetTypePayload = iota + packetTypePrngSeed +) + +// InvalidPacketLengthError is the error returned when decodePacket detects a +// invalid packet length/ +type InvalidPacketLengthError int + +func (e InvalidPacketLengthError) Error() string { + return fmt.Sprintf("packet: Invalid packet length: %d", int(e)) +} + +// InvalidPacketLengthError is the error returned when decodePacket rejects the +// payload length. +type InvalidPayloadLengthError int + +func (e InvalidPayloadLengthError) Error() string { + return fmt.Sprintf("packet: Invalid payload length: %d", int(e)) +} + +var zeroPadBytes [maxPacketPaddingLength]byte + +func makePacket(pkt []byte, pktType uint8, data []byte, padLen uint16) int { + pktLen := packetOverhead + len(data) + int(padLen) + + if len(data)+int(padLen) > maxPacketPayloadLength { + log.Panicf("BUG: makePacket() len(data) + padLen > maxPacketPayloadLength: %d + %d > %d", + len(data), padLen, maxPacketPayloadLength) + } + + // Packets are: + // uint8_t type packetTypePayload (0x00) + // uint16_t length Length of the payload (Big Endian). + // uint8_t[] payload Data payload. + // uint8_t[] padding Padding. + + pkt[0] = pktType + binary.BigEndian.PutUint16(pkt[1:], uint16(len(data))) + copy(pkt[3:], data[:]) + copy(pkt[3+len(data):], zeroPadBytes[:padLen]) + + return pktLen +} + +func (c *Obfs4Conn) decodePacket(pkt []byte) error { + if len(pkt) < packetOverhead { + return InvalidPacketLengthError(len(pkt)) + } + + pktType := pkt[0] + payloadLen := binary.BigEndian.Uint16(pkt[1:]) + if int(payloadLen) > len(pkt)-packetOverhead { + return InvalidPayloadLengthError(int(payloadLen)) + } + + payload := pkt[3 : 3+payloadLen] + switch pktType { + case packetTypePayload: + // packetTypePayload + c.receiveDecodedBuffer.Write(payload) + default: + // Ignore unrecognised packet types. + log.Printf("[INFO] - Ignoring packet type: %d", pktType) + } + + return nil +} |