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// Package ctlsock implements the control socket interface that can be
// activated by passing "-ctlsock" on the command line.
package ctlsock
import (
"encoding/json"
"errors"
"fmt"
"io"
"net"
"os"
"syscall"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// Interface should be implemented by fusefrontend[_reverse]
type Interface interface {
EncryptPath(string) (string, error)
DecryptPath(string) (string, error)
}
// RequestStruct is sent by a client
type RequestStruct struct {
EncryptPath string
DecryptPath string
}
// ResponseStruct is sent by us as response to a request
type ResponseStruct struct {
// Result is the resulting decrypted or encrypted path. Empty on error.
Result string
// ErrNo is the error number as defined in errno.h.
// 0 means success and -1 means that the error number is not known
// (look at ErrText in this case).
ErrNo int32
// ErrText is a detailed error message.
ErrText string
// WarnText contains warnings that may have been encountered while
// processing the message.
WarnText string
}
type ctlSockHandler struct {
fs Interface
socket *net.UnixListener
}
// Serve serves incoming connections on "sock". This call blocks so you
// probably want to run it in a new goroutine.
func Serve(sock net.Listener, fs Interface) {
handler := ctlSockHandler{
fs: fs,
socket: sock.(*net.UnixListener),
}
handler.acceptLoop()
}
func (ch *ctlSockHandler) acceptLoop() {
for {
conn, err := ch.socket.Accept()
if err != nil {
// TODO Can this warning trigger when the socket it closed on
// program exit? I have never observed it, but the documentation
// says that Close() unblocks Accept().
tlog.Warn.Printf("ctlsock: Accept error: %v", err)
break
}
go ch.handleConnection(conn.(*net.UnixConn))
}
}
// ReadBufSize is the size of the request read buffer.
// The longest possible path is 4096 bytes on Linux and 1024 on Mac OS X so
// 5000 bytes should be enough to hold the whole JSON request. This
// assumes that the path does not contain too many characters that had to be
// be escaped in JSON (for example, a null byte blows up to "\u0000").
// We abort the connection if the request is bigger than this.
const ReadBufSize = 5000
// handleConnection reads and parses JSON requests from "conn"
func (ch *ctlSockHandler) handleConnection(conn *net.UnixConn) {
buf := make([]byte, ReadBufSize)
for {
n, err := conn.Read(buf)
if err == io.EOF {
conn.Close()
return
} else if err != nil {
tlog.Warn.Printf("ctlsock: Read error: %#v", err)
conn.Close()
return
}
if n == ReadBufSize {
tlog.Warn.Printf("ctlsock: request too big (max = %d bytes)", ReadBufSize-1)
conn.Close()
return
}
buf = buf[:n]
var in RequestStruct
err = json.Unmarshal(buf, &in)
if err != nil {
tlog.Warn.Printf("ctlsock: JSON Unmarshal error: %#v", err)
err = errors.New("JSON Unmarshal error: " + err.Error())
sendResponse(conn, err, "", "")
continue
}
ch.handleRequest(&in, conn)
// Restore original size.
buf = buf[:cap(buf)]
}
}
// handleRequest handles an already-unmarshaled JSON request
func (ch *ctlSockHandler) handleRequest(in *RequestStruct, conn *net.UnixConn) {
var err error
var inPath, outPath, clean, warnText string
// You cannot perform both decryption and encryption in one request
if in.DecryptPath != "" && in.EncryptPath != "" {
err = errors.New("Ambiguous")
sendResponse(conn, err, "", "")
return
}
// Neither encryption nor encryption has been requested, makes no sense
if in.DecryptPath == "" && in.EncryptPath == "" {
err = errors.New("Empty input")
sendResponse(conn, err, "", "")
return
}
// Canonicalize input path
if in.EncryptPath != "" {
inPath = in.EncryptPath
} else {
inPath = in.DecryptPath
}
clean = SanitizePath(inPath)
// Warn if a non-canonical path was passed
if inPath != clean {
warnText = fmt.Sprintf("Non-canonical input path '%s' has been interpreted as '%s'.", inPath, clean)
}
// Error out if the canonical path is now empty
if clean == "" {
err = errors.New("Empty input after canonicalization")
sendResponse(conn, err, "", warnText)
return
}
// Actual encrypt or decrypt operation
if in.EncryptPath != "" {
outPath, err = ch.fs.EncryptPath(clean)
} else {
outPath, err = ch.fs.DecryptPath(clean)
}
sendResponse(conn, err, outPath, warnText)
}
// sendResponse sends a JSON response message
func sendResponse(conn *net.UnixConn, err error, result string, warnText string) {
msg := ResponseStruct{
Result: result,
WarnText: warnText,
}
if err != nil {
msg.ErrText = err.Error()
msg.ErrNo = -1
// Try to extract the actual error number
if pe, ok := err.(*os.PathError); ok {
if se, ok := pe.Err.(syscall.Errno); ok {
msg.ErrNo = int32(se)
}
}
}
jsonMsg, err := json.Marshal(msg)
if err != nil {
tlog.Warn.Printf("ctlsock: Marshal failed: %v", err)
return
}
// For convenience for the user, add a newline at the end.
jsonMsg = append(jsonMsg, '\n')
_, err = conn.Write(jsonMsg)
if err != nil {
tlog.Warn.Printf("ctlsock: Write failed: %v", err)
}
}
|
