[Pkg-privacy-commits] [obfs4proxy] 21/151: First pass at cleaning up the read code.

[Ximin Luo]

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infinity0 pushed a commit to branch master
in repository obfs4proxy.

commit 582aa3a366cb06bf793440f62fcf3d54b85d8270
Author: Yawning Angel <yawning at schwanenlied.me>
Date:   Wed May 14 05:48:43 2014 +0000

    First pass at cleaning up the read code.
---
 obfs4.go  | 39 +++++-------------------------------
 packet.go | 68 ++++++++++++++++++++++++++++++++++++++++++++++-----------------
 2 files changed, 55 insertions(+), 52 deletions(-)

diff --git a/obfs4.go b/obfs4.go
index 3cb464e..f2a0139 100644
--- a/obfs4.go
+++ b/obfs4.go
@@ -252,49 +252,20 @@ func (c *Obfs4Conn) ServerHandshake() error {
 	return err
 }
 
-func (c *Obfs4Conn) Read(b []byte) (int, error) {
+func (c *Obfs4Conn) Read(b []byte) (n int, err error) {
 	if !c.isOk {
 		return 0, syscall.EINVAL
 	}
 
-	if c.receiveDecodedBuffer.Len() > 0 {
-		n, err := c.receiveDecodedBuffer.Read(b)
-		return n, err
-	}
-
-	// Consume and decode frames off the network.
-	buf := make([]byte, defaultReadSize)
 	for c.receiveDecodedBuffer.Len() == 0 {
-		n, err := c.conn.Read(buf)
+		err = c.consumeFramedPackets()
 		if err != nil {
-			return 0, err
-		}
-		c.receiveBuffer.Write(buf[:n])
-
-		// Decode the data just read.
-		for c.receiveBuffer.Len() > 0 {
-			_, frame, err := c.decoder.Decode(&c.receiveBuffer)
-			if err == framing.ErrAgain {
-				break
-			} else if err != nil {
-				// Any other frame decoder errors are fatal.
-				c.isOk = false
-				return 0, err
-			}
-
-			// Decode the packet, if there is payload, it will be placed in
-			// receiveDecodedBuffer automatically.
-			err = c.decodePacket(frame)
-			if err != nil {
-				// All packet decoder errors are fatal.
-				c.isOk = false
-				return 0, err
-			}
+			return
 		}
 	}
 
-	n, err := c.receiveDecodedBuffer.Read(b)
-	return n, err
+	n, err = c.receiveDecodedBuffer.Read(b)
+	return
 }
 
 func (c *Obfs4Conn) Write(b []byte) (int, error) {
diff --git a/packet.go b/packet.go
index 756ee7a..6726ed4 100644
--- a/packet.go
+++ b/packet.go
@@ -30,6 +30,7 @@ package obfs4
 import (
 	"encoding/binary"
 	"fmt"
+	"syscall"
 
 	"github.com/yawning/obfs4/framing"
 )
@@ -38,6 +39,8 @@ const (
 	packetOverhead         = 2 + 1
 	maxPacketPayloadLength = framing.MaximumFramePayloadLength - packetOverhead
 	maxPacketPaddingLength = maxPacketPayloadLength
+
+	consumeReadSize = framing.MaximumSegmentLength * 16
 )
 
 const (
@@ -98,32 +101,61 @@ func (c *Obfs4Conn) makeAndEncryptPacket(pktType uint8, data []byte, padLen uint
 	return n, frame, err
 }
 
-func (c *Obfs4Conn) decodePacket(pkt []byte) error {
-	if len(pkt) < packetOverhead {
-		return InvalidPacketLengthError(len(pkt))
+func (c *Obfs4Conn) consumeFramedPackets() (err error) {
+	if !c.isOk {
+		return syscall.EINVAL
 	}
 
-	pktType := pkt[0]
-	payloadLen := binary.BigEndian.Uint16(pkt[1:])
-	if int(payloadLen) > len(pkt)-packetOverhead {
-		return InvalidPayloadLengthError(int(payloadLen))
+	var buf [consumeReadSize]byte
+	n, err := c.conn.Read(buf[:])
+	if err != nil {
+		return
 	}
+	c.receiveBuffer.Write(buf[:n])
+
+	for c.receiveBuffer.Len() > 0 {
+		// Decrypt an AEAD frame.
+		_, pkt, err := c.decoder.Decode(&c.receiveBuffer)
+		if err == framing.ErrAgain {
+			// The accumulated payload does not make up a full frame.
+			return nil
+		} else if err != nil {
+			break
+		} else if len(pkt) < packetOverhead {
+			err = InvalidPacketLengthError(len(pkt))
+			break
+		}
 
-	payload := pkt[3 : 3+payloadLen]
-	switch pktType {
-	case packetTypePayload:
-		if len(payload) > 0 {
-			c.receiveDecodedBuffer.Write(payload)
+		// Decode the packet.
+		pktType := pkt[0]
+		payloadLen := binary.BigEndian.Uint16(pkt[1:])
+		if int(payloadLen) > len(pkt)-packetOverhead {
+			err = InvalidPayloadLengthError(int(payloadLen))
+			break
 		}
-	case packetTypePrngSeed:
-		if len(payload) == distSeedLength {
-			c.probDist.reset(payload)
+		payload := pkt[3 : 3+payloadLen]
+
+		switch pktType {
+		case packetTypePayload:
+			if payloadLen > 0 {
+				c.receiveDecodedBuffer.Write(payload)
+			}
+		case packetTypePrngSeed:
+			// Only regenerate the distribution if we are the client.
+			if len(payload) >= distSeedLength && !c.isServer {
+				c.probDist.reset(payload[:distSeedLength])
+			}
+		default:
+			// Ignore unrecognised packet types.
 		}
-	default:
-		// Ignore unrecognised packet types.
 	}
 
-	return nil
+	// All errors that reach this point are fatal.
+	if err != nil {
+		c.isOk = false
+	}
+
+	return
 }
 
 /* vim :set ts=4 sw=4 sts=4 noet : */

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