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[bacula/docs] / docs / manuals / de / old / concepts / stunnel.tex

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\chapter{Using Stunnel to Encrypt Communications}
\label{StunnelChapter}
\index[general]{Using Stunnel to Encrypt Communications to Clients }

Prior to version 1.37, Bacula did not have built-in communications encryption.
Please see the \ilink {TLS chapter}{CommEncryption} if you are using Bacula
1.37 or greater.

Without too much effort, it is possible to encrypt the communications
between any of the daemons. This chapter will show you how to use {\bf
stunnel} to encrypt communications to your client programs. We assume the
Director and the Storage daemon are running on one machine that will be called
{\bf server} and the Client or File daemon is running on a different machine
called {\bf client}. Although the details may be slightly different, the same
principles apply whether you are encrypting between Unix, Linux, or Win32
machines. This example was developed between two Linux machines running
stunnel version 4.04-4 on a Red Hat Enterprise 3.0 system. 

\section{Communications Ports Used}
\index[general]{Used!Communications Ports }
\index[general]{Communications Ports Used }

First, you must know that with the standard Bacula configuration, the Director
will contact the File daemon on port 9102. The File daemon then contacts the
Storage daemon using the address and port parameters supplied by the Director.
The standard port used will be 9103. This is the typical server/client view of
the world, the File daemon is a server to the Director (i.e. listens for the
Director to contact it), and the Storage daemon is a server to the File
daemon.

\section{Encryption}
\index[general]{Encryption }

The encryption is accomplished between the Director and the File daemon by
using an stunnel on the Director's machine (server) to encrypt the data and to
contact an stunnel on the File daemon's machine (client), which decrypts the
data and passes it to the client. 

Between the File daemon and the Storage daemon, we use an stunnel on the File
daemon's machine to encrypt the data and another stunnel on the Storage
daemon's machine to decrypt the data. 

As a consequence, there are actually four copies of stunnel running, two on the
server and two on the client. This may sound a bit complicated, but it really
isn't. To accomplish this, we will need to construct four separate conf files
for stunnel, and we will need to make some minor modifications to the
Director's conf file. None of the other conf files need to be changed. 

\section{A Picture}
\index[general]{Picture }

Since pictures usually help a lot, here is an overview of what we will be
doing. Don't worry about all the details of the port numbers and such for the
moment. 

\footnotesize
\begin{verbatim}
  File daemon (client):
                 stunnel-fd1.conf
                   |===========|
  Port 29102  >----| Stunnel 1 |-----> Port 9102
                   |===========|
                 stunnel-fd2.conf
                   |===========|
  Port 9103   >----| Stunnel 2 |-----> server:29103
                   |===========|
  Director (server):
                 stunnel-dir.conf
                   |===========|
  Port 29102  >----| Stunnel 3 |-----> client:29102
                   |===========|
                 stunnel-sd.conf
                   |===========|
  Port 29103  >----| Stunnel 4 |-----> 9103
                   |===========|
\end{verbatim}
\normalsize

\section{Certificates}
\index[general]{Certificates }

In order for stunnel to function as a server, which it does in our diagram for
Stunnel 1 and Stunnel 4, you must have a certificate and the key. It is
possible to keep the two in separate files, but normally, you keep them in one
single .pem file. You may create this certificate yourself in which case, it
will be self-signed, or you may have it signed by a CA. 

If you want your clients to verify that the server is in fact valid (Stunnel 2
and Stunnel 3), you will need to have the server certificates signed by a CA
(Certificate Authority), and you will need to have the CA's public certificate
(contains the CA's public key). 

Having a CA signed certificate is {\bf highly} recommended if you are using
your client across the Internet, otherwise you are exposed to the man in the
middle attack and hence loss of your data. 

See below for how to create a self-signed certificate. 

\section{Securing the Data Channel}
\index[general]{Channel!Securing the Data }
\index[general]{Securing the Data Channel }

To simplify things a bit, let's for the moment consider only the data channel.
That is the connection between the File daemon and the Storage daemon, which
takes place on port 9103. In fact, in a minimalist solution, this is the only
connection that needs to be encrypted, because it is the one that transports your
data. The connection between the Director and the File daemon is simply a
control channel used to start the job and get the job status. 

Normally the File daemon will contact the Storage daemon on port 9103
(supplied by the Director), so we need an stunnel that listens on port 9103 on
the File daemon's machine, encrypts the data and sends it to the Storage
daemon. This is depicted by Stunnel 2 above. Note that this stunnel is
listening on port 9103 and sending to server:29103. We use port 29103 on the
server because if we would send the data to port 9103, it would go directly to the
Storage daemon, which doesn't understand encrypted data. On the server
machine, we run Stunnel 4, which listens on port 29103, decrypts the data and
sends it to the Storage daemon, which is listening on port 9103. 

\section{Data Channel Configuration}
\index[general]{Modification of bacula-dir.conf for the Data Channel }
\index[general]{baculoa-dir.conf!Modification for the Data Channel }

The Storage resource of the bacula-dir.conf normally looks something like the
following: 

\footnotesize
\begin{verbatim}
Storage {
  Name = File
  Address = server
  SDPort = 9103
  Password = storage_password
  Device = File
  Media Type = File
}
\end{verbatim}
\normalsize

Notice that this is running on the server machine, and it points the File
daemon back to server:9103, which is where our Storage daemon is listening. We
modify this to be: 

\footnotesize
\begin{verbatim}
Storage {
  Name = File
  Address = localhost
  SDPort = 9103
  Password = storage_password
  Device = File
  Media Type = File
}
\end{verbatim}
\normalsize

This causes the File daemon to send the data to the stunnel running on
localhost (the client machine). We could have used client as the address as
well. 

\section{Stunnel Configuration for the Data Channel}
\index[general]{Stunnel Configuration for the Data Channel }

In the diagram above, we see above Stunnel 2 that we use stunnel-fd2.conf on the
client. A pretty much minimal config file would look like the following: 

\footnotesize
\begin{verbatim}
client = yes
[29103]
accept = localhost:9103
connect = server:29103
\end{verbatim}
\normalsize

The above config file does encrypt the data but it does not require a
certificate, so it is subject to the man in the middle attack. The file I
actually used, stunnel-fd2.conf, looked like this: 

\footnotesize
\begin{verbatim}
#
# Stunnel conf for Bacula client -> SD
#
pid = /home/kern/bacula/bin/working/stunnel.pid
#
# A cert is not mandatory here. If verify=2, a
#  cert signed by a CA must be specified, and
#  either CAfile or CApath must point to the CA's
#  cert
#
cert = /home/kern/stunnel/stunnel.pem
CAfile = /home/kern/ssl/cacert.pem
verify = 2
client = yes
# debug = 7
# foreground = yes
[29103]
accept = localhost:9103
connect = server:29103
\end{verbatim}
\normalsize

You will notice that I specified a pid file location because I ran stunnel
under my own userid so I could not use the default, which requires root
permission. I also specified a certificate that I have as well as verify level
2 so that the certificate is required and verified, and I must supply the
location of the CA (Certificate Authority) certificate so that the stunnel
certificate can be verified. Finally, you will see that there are two lines
commented out, which when enabled, produce a lot of nice debug info in the
command window. 

If you do not have a signed certificate (stunnel.pem), you need to delete the
cert, CAfile, and verify lines. 

Note that the stunnel.pem, is actually a private key and a certificate in a
single file. These two can be kept and specified individually, but keeping
them in one file is more convenient. 

The config file, stunnel-sd.conf, needed for Stunnel 4 on the server machine
is: 

\footnotesize
\begin{verbatim}
#
# Bacula stunnel conf for Storage daemon
#
pid = /home/kern/bacula/bin/working/stunnel.pid
#
# A cert is mandatory here, it may be self signed
#  If it is self signed, the client may not use
#  verify
#
cert   = /home/kern/stunnel/stunnel.pem
client = no
# debug = 7
# foreground = yes
[29103]
accept = 29103
connect = 9103
\end{verbatim}
\normalsize

\section{Starting and Testing the Data Encryption}
\index[general]{Starting and Testing the Data Encryption }
\index[general]{Encryption!Starting and Testing the Data }

It will most likely be the simplest to implement the Data Channel encryption
in the following order: 

\begin{itemize}
\item Setup and run Bacula backing up some data on your  client machine
   without encryption.  
\item Stop Bacula.  
\item Modify the Storage resource in the Director's conf  file.  
\item Start Bacula  
\item Start stunnel on the server with:  

   \footnotesize
\begin{verbatim}
     stunnel stunnel-sd.conf
  
\end{verbatim}
\normalsize

\item Start stunnel on the client with:  

   \footnotesize
\begin{verbatim}
    stunnel stunnel-fd2.conf
  
\end{verbatim}
\normalsize

\item Run a job.  
\item If it doesn't work, turn debug on in both stunnel conf files,  restart
   the stunnels, rerun the job, repeat until it works. 
   \end{itemize}

\section{Encrypting the Control Channel}
\index[general]{Channel!Encrypting the Control }
\index[general]{Encrypting the Control Channel }

The Job control channel is between the Director and the File daemon, and as
mentioned above, it is not really necessary to encrypt, but it is good
practice to encrypt it as well. The two stunnels that are used in this case
will be Stunnel 1 and Stunnel 3 in the diagram above. Stunnel 3 on the server
might normally listen on port 9102, but if you have a local File daemon, this
will not work, so we make it listen on port 29102. It then sends the data to
client:29102. Again we use port 29102 so that the stunnel on the client
machine can decrypt the data before passing it on to port 9102 where the File
daemon is listening. 

\section{Control Channel Configuration}
\index[general]{Control Channel Configuration }

We need to modify the standard Client resource, which would normally look
something like: 

\footnotesize
\begin{verbatim}
Client {
  Name = client-fd
  Address = client
  FDPort = 9102
  Catalog = BackupDB
  Password = "xxx"
}
\end{verbatim}
\normalsize

to be: 

\footnotesize
\begin{verbatim}
Client {
  Name = client-fd
  Address = localhost
  FDPort = 29102
  Catalog = BackupDB
  Password = "xxx"
}
\end{verbatim}
\normalsize

This will cause the Director to send the control information to
localhost:29102 instead of directly to the client. 

\section{Stunnel Configuration for the Control Channel}
\index[general]{Config Files for stunnel to Encrypt the Control Channel }

The stunnel config file, stunnel-dir.conf, for the Director's machine would
look like the following: 

\footnotesize
\begin{verbatim}
#
# Bacula stunnel conf for the Directory to contact a client
#
pid = /home/kern/bacula/bin/working/stunnel.pid
#
# A cert is not mandatory here. If verify=2, a
#  cert signed by a CA must be specified, and
#  either CAfile or CApath must point to the CA's
#  cert
#
cert   = /home/kern/stunnel/stunnel.pem
CAfile = /home/kern/ssl/cacert.pem
verify = 2
client = yes
# debug = 7
# foreground = yes
[29102]
accept = localhost:29102
connect = client:29102
\end{verbatim}
\normalsize

and the config file, stunnel-fd1.conf, needed to run stunnel on the Client
would be: 

\footnotesize
\begin{verbatim}
#
# Bacula stunnel conf for the Directory to contact a client
#
pid = /home/kern/bacula/bin/working/stunnel.pid
#
# A cert is not mandatory here. If verify=2, a
#  cert signed by a CA must be specified, and
#  either CAfile or CApath must point to the CA's
#  cert
#
cert   = /home/kern/stunnel/stunnel.pem
CAfile = /home/kern/ssl/cacert.pem
verify = 2
client = yes
# debug = 7
# foreground = yes
[29102]
accept = localhost:29102
connect = client:29102
\end{verbatim}
\normalsize

\section{Starting and Testing the Control Channel}
\index[general]{Starting and Testing the Control Channel }
\index[general]{Channel!Starting and Testing the Control }

It will most likely be the simplest to implement the Control Channel
encryption in the following order: 

\begin{itemize}
\item Stop Bacula.  
\item Modify the Client resource in the Director's conf  file.  
\item Start Bacula  
\item Start stunnel on the server with:  

   \footnotesize
\begin{verbatim}
     stunnel stunnel-dir.conf
  
\end{verbatim}
\normalsize

\item Start stunnel on the client with:  

   \footnotesize
\begin{verbatim}
    stunnel stunnel-fd1.conf
  
\end{verbatim}
\normalsize

\item Run a job.  
\item If it doesn't work, turn debug on in both stunnel conf files,  restart
   the stunnels, rerun the job, repeat until it works. 
   \end{itemize}

\section{Using stunnel to Encrypt to a Second Client}
\index[general]{Using stunnel to Encrypt to a Second Client }
\index[general]{Client!Using stunnel to Encrypt to a Second }

On the client machine, you can just duplicate the setup that you have on the
first client file for file and it should work fine. 

In the bacula-dir.conf file, you will want to create a second client pretty
much identical to how you did for the first one, but the port number must be
unique. We previously used: 

\footnotesize
\begin{verbatim}
Client {
  Name = client-fd
  Address = localhost
  FDPort = 29102
  Catalog = BackupDB
  Password = "xxx"
}
\end{verbatim}
\normalsize

so for the second client, we will, of course, have a different name, and we
will also need a different port. Remember that we used port 29103 for the
Storage daemon, so for the second client, we can use port 29104, and the
Client resource would look like: 

\footnotesize
\begin{verbatim}
Client {
  Name = client2-fd
  Address = localhost
  FDPort = 29104
  Catalog = BackupDB
  Password = "yyy"
}
\end{verbatim}
\normalsize

Now, fortunately, we do not need a third stunnel to on the Director's machine,
we can just add the new port to the config file, stunnel-dir.conf, to make: 

\footnotesize
\begin{verbatim}
#
# Bacula stunnel conf for the Directory to contact a client
#
pid = /home/kern/bacula/bin/working/stunnel.pid
#
# A cert is not mandatory here. If verify=2, a
#  cert signed by a CA must be specified, and
#  either CAfile or CApath must point to the CA's
#  cert
#
cert   = /home/kern/stunnel/stunnel.pem
CAfile = /home/kern/ssl/cacert.pem
verify = 2
client = yes
# debug = 7
# foreground = yes
[29102]
accept = localhost:29102
connect = client:29102
[29104]
accept = localhost:29102
connect = client2:29102
\end{verbatim}
\normalsize

There are no changes necessary to the Storage daemon or the other stunnel so
that this new client can talk to our Storage daemon. 

\section{Creating a Self-signed Certificate}
\index[general]{Creating a Self-signed Certificate }
\index[general]{Certificate!Creating a Self-signed }

You may create a self-signed certificate for use with stunnel that will permit
you to make it function, but will not allow certificate validation. The .pem
file containing both the certificate and the key can be made with the
following, which I put in a file named {\bf makepem}: 

\footnotesize
\begin{verbatim}
#!/bin/sh
#
# Simple shell script to make a .pem file that can be used
# with stunnel and Bacula
#
OPENSSL=openssl
   umask 77
   PEM1="/bin/mktemp openssl.XXXXXX"
   PEM2="/bin/mktemp openssl.XXXXXX"
   ${OPENSSL} req -newkey rsa:1024 -keyout $PEM1 -nodes \
       -x509 -days 365 -out $PEM2
   cat $PEM1 > stunnel.pem
   echo ""   >>stunnel.pem
   cat $PEM2 >>stunnel.pem
   rm $PEM1 $PEM2
\end{verbatim}
\normalsize

The above script will ask you a number of questions. You may simply answer
each of them by entering a return, or if you wish you may enter your own data.


\section{Getting a CA Signed Certificate}
\index[general]{Certificate!Getting a CA Signed }
\index[general]{Getting a CA Signed Certificate }

The process of getting a certificate that is signed by a CA is quite a bit
more complicated. You can purchase one from quite a number of PKI vendors, but
that is not at all necessary for use with Bacula. 

To get a CA signed
certificate, you will either need to find a friend that has setup his own CA
or to become a CA yourself, and thus you can sign all your own certificates.
The book OpenSSL by John Viega, Matt Mesier \& Pravir Chandra from O'Reilly
explains how to do it, or you can read the documentation provided in the
Open-source PKI Book project at Source Forge: 
\elink{
http://ospkibook.sourceforge.net/docs/OSPKI-2.4.7/OSPKI-html/ospki-book.htm}
{http://ospkibook.sourceforge.net/docs/OSPKI-2.4.7/OSPKI-html/ospki-book.htm}.
Note, this link may change. 

\section{Using ssh to Secure the Communications}
\index[general]{Communications!Using ssh to Secure the }
\index[general]{Using ssh to Secure the Communications }

Please see the script {\bf ssh-tunnel.sh} in the {\bf examples} directory. It
was contributed by Stephan Holl.