addes first simple satp packets

1 files changed, 146 insertions, 0 deletions

diff --git a/satp/packet.go b/satp/packet.go
new file mode 100644
index 0000000..a24b69a
--- /dev/null
+++ b/satp/packet.go
@@ -0,0 +1,146 @@
+//
+// Copyright (c) 2017 anygone contributors (see AUTHORS file)
+// 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.
+//
+// * Neither the name of anygone nor the names of its
+//   contributors may be used to endorse or promote products derived from
+//   this software without specific prior written permission.
+//
+// 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 satp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+)
+
+//      0                   1                   2                   3
+//      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+//     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//     |                         sequence number                       | |
+//     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+//     |           sender ID           |              MUX              | |
+//   +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+ |
+//   | |         payload type          |                               | |
+//   | +-------------------------------+                               | |
+//   | |              ....        payload        ...                   | |
+//   | |                               +-------------------------------+ |
+//   | |                               | padding (OPT) | pad count(OPT)| |
+//   +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+-+
+//   | :                 authentication tag (RECOMMENDED)              : |
+//   | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+//   |                                                                   |
+//   +- Encrypted Portion                       Authenticated Portion ---+
+
+type PlainPacket struct {
+	Type    uint16
+	Payload []byte
+}
+
+func NewPlainPacket(PayloadType uint16) (pp *PlainPacket) {
+	pp = &PlainPacket{}
+	pp.Type = PayloadType
+	return
+}
+
+func (pp *PlainPacket) MarshalBinary() (data []byte, err error) {
+	buf := &bytes.Buffer{}
+	if err = binary.Write(buf, binary.BigEndian, pp.Type); err != nil {
+		return
+	}
+	buf.Write(pp.Payload) // returned error is always nil
+	return buf.Bytes(), nil
+}
+
+func (pp *PlainPacket) UnmarshalBinary(data []byte) (err error) {
+	buf := bytes.NewReader(data)
+	if err = binary.Read(buf, binary.BigEndian, &(pp.Type)); err != nil {
+		return
+	}
+	if buf.Len() > 0 {
+		pp.Payload = make([]byte, buf.Len())
+		buf.Read(pp.Payload)
+	}
+	return
+}
+
+type EncryptedPacket struct {
+	SequenceNumber uint32
+	SenderID       uint16
+	Mux            uint16
+	Payload        []byte
+	AuthTag        []byte
+}
+
+func NewEncryptedPacket(AuthTagLength uint) (ep *EncryptedPacket) {
+	ep = &EncryptedPacket{}
+	ep.AuthTag = make([]byte, AuthTagLength)
+	return
+}
+
+func (ep *EncryptedPacket) MarshalBinary() (data []byte, err error) {
+	buf := &bytes.Buffer{}
+	if err = binary.Write(buf, binary.BigEndian, ep.SequenceNumber); err != nil {
+		return
+	}
+	if err = binary.Write(buf, binary.BigEndian, ep.SenderID); err != nil {
+		return
+	}
+	if err = binary.Write(buf, binary.BigEndian, ep.Mux); err != nil {
+		return
+	}
+	if len(ep.Payload) >= 2 { // Payload must at least have a payload type which is a uint16 -> 2 bytes
+		buf.Write(ep.Payload) // returned error is always nil
+	} else {
+		return nil, errors.New("Unable to marshal packet: payload is empty/too short")
+	}
+
+	if len(ep.AuthTag) > 0 {
+		buf.Write(ep.AuthTag) // returned error is always nil
+	}
+	return buf.Bytes(), nil
+}
+
+func (ep *EncryptedPacket) UnmarshalBinary(data []byte) (err error) {
+	buf := bytes.NewReader(data)
+	if err = binary.Read(buf, binary.BigEndian, &(ep.SequenceNumber)); err != nil {
+		return
+	}
+	if err = binary.Read(buf, binary.BigEndian, &(ep.SenderID)); err != nil {
+		return
+	}
+	if err = binary.Read(buf, binary.BigEndian, &(ep.Mux)); err != nil {
+		return
+	}
+
+	if (buf.Len() - len(ep.AuthTag)) < 2 { // 2 bytes payload type + length of AuthTag must be left on buffer
+		return errors.New("Unable to unmarshal packet: too short")
+	}
+
+	ep.Payload = make([]byte, buf.Len()-len(ep.AuthTag))
+	buf.Read(ep.Payload)
+	buf.Read(ep.AuthTag)
+	return
+}