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client.go
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client.go
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// client.go - mixnet PANDA client
// Copyright (C) 2018 David Stainton.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package client
import (
"bytes"
"encoding/base64"
"encoding/hex"
"fmt"
"time"
"github.com/katzenpost/client"
"github.com/katzenpost/panda/common"
"github.com/ugorji/go/codec"
"gopkg.in/op/go-logging.v1"
)
type Error string
func (e Error) Error() string { return string(e) }
const (
ShutdownError = Error("panda: shutdown requested")
SyntaxError = Error("panda failure, syntax error")
TagContendedError = Error("panda failure, tag contended error")
StorageError = Error("panda failure, storage error")
)
// Panda is a PANDA client that uses our mixnet client library
// to communicate with the PANDA kaetzchen service.
type Panda struct {
session *client.Session
log *logging.Logger
blobSize int
jsonHandle codec.JsonHandle
recipient string
provider string
}
// Padding returns the size of the ciphertext blobs
// to be exchanged.
func (p *Panda) Padding() int {
return p.blobSize
}
// Exchange performs a PANDA protocol message exchange
func (p *Panda) Exchange(id, message []byte, shutdown chan struct{}) ([]byte, error) {
delay := 15 * time.Second
for {
request := common.PandaRequest{
Version: common.PandaVersion,
Tag: hex.EncodeToString(id),
Message: base64.StdEncoding.EncodeToString(message),
}
var rawRequest []byte
enc := codec.NewEncoderBytes(&rawRequest, &p.jsonHandle)
enc.Encode(request)
p.log.Debugf("PANDA exchange sending kaetzchen query to %s@%s", p.recipient, p.provider)
reply, err := p.session.BlockingSendReliableMessage(p.recipient, p.provider, rawRequest)
if err != nil {
// do not abort loop on dropped messages
continue
}
response := new(common.PandaResponse)
dec := codec.NewDecoderBytes(bytes.TrimRight(reply, "\x00"), &p.jsonHandle)
if err := dec.Decode(response); err != nil {
p.log.Debugf("Failed to decode PANDA response: (%v)", err)
return nil, fmt.Errorf("Failed to decode PANDA response: (%v)", err)
}
if response.Version != common.PandaVersion {
p.log.Warning("warning, PANDA server version mismatch")
}
switch response.StatusCode {
case common.PandaStatusReceived1:
if len(response.Message) == 0 {
goto Sleep
}
decoded, err := base64.StdEncoding.DecodeString(response.Message)
if err != nil {
return nil, err
}
return decoded, nil
case common.PandaStatusReceived2:
if len(response.Message) == 0 {
goto Sleep
}
decoded, err := base64.StdEncoding.DecodeString(response.Message)
if err != nil {
return nil, err
}
return decoded, nil
case common.PandaStatusSyntaxError:
return nil, SyntaxError
case common.PandaStatusTagContendedError:
return nil, TagContendedError
case common.PandaStatusRequestRecordedError:
goto Sleep
case common.PandaStatusStorageError:
return nil, StorageError
}
Sleep:
select {
case <-shutdown:
return nil, ShutdownError
case <-time.After(delay):
delay *= 2
if delay > time.Hour {
delay = time.Hour
}
}
}
panic("unreachable")
}
// New creates a new Panda instance.
func New(blobSize int, s *client.Session, log *logging.Logger, recipient, provider string) *Panda {
p := &Panda{
session: s,
blobSize: blobSize,
log: log,
recipient: recipient,
provider: provider,
}
p.jsonHandle.Canonical = true
p.jsonHandle.ErrorIfNoField = true
return p
}