4 \chapter{Using Stunnel to Encrypt Communications}
6 \index[general]{Using Stunnel to Encrypt Communications to Clients }
8 Prior to version 1.37, Bacula did not have built-in communications encryption.
9 Please see the \ilink {TLS chapter}{CommEncryption} if you are using Bacula
12 Without too much effort, it is possible to encrypt the communications
13 between any of the daemons. This chapter will show you how to use {\bf
14 stunnel} to encrypt communications to your client programs. We assume the
15 Director and the Storage daemon are running on one machine that will be called
16 {\bf server} and the Client or File daemon is running on a different machine
17 called {\bf client}. Although the details may be slightly different, the same
18 principles apply whether you are encrypting between Unix, Linux, or Win32
19 machines. This example was developed between two Linux machines running
20 stunnel version 4.04-4 on a Red Hat Enterprise 3.0 system.
22 \section{Communications Ports Used}
23 \index[general]{Used!Communications Ports }
24 \index[general]{Communications Ports Used }
26 First, you must know that with the standard Bacula configuration, the Director
27 will contact the File daemon on port 9102. The File daemon then contacts the
28 Storage daemon using the address and port parameters supplied by the Director.
29 The standard port used will be 9103. This is the typical server/client view of
30 the world, the File daemon is a server to the Director (i.e. listens for the
31 Director to contact it), and the Storage daemon is a server to the File
35 \index[general]{Encryption }
37 The encryption is accomplished between the Director and the File daemon by
38 using an stunnel on the Director's machine (server) to encrypt the data and to
39 contact an stunnel on the File daemon's machine (client), which decrypts the
40 data and passes it to the client.
42 Between the File daemon and the Storage daemon, we use an stunnel on the File
43 daemon's machine to encrypt the data and another stunnel on the Storage
44 daemon's machine to decrypt the data.
46 As a consequence, there are actually four copies of stunnel running, two on the
47 server and two on the client. This may sound a bit complicated, but it really
48 isn't. To accomplish this, we will need to construct four separate conf files
49 for stunnel, and we will need to make some minor modifications to the
50 Director's conf file. None of the other conf files need to be changed.
53 \index[general]{Picture }
55 Since pictures usually help a lot, here is an overview of what we will be
56 doing. Don't worry about all the details of the port numbers and such for the
64 Port 29102 >----| Stunnel 1 |-----> Port 9102
68 Port 9103 >----| Stunnel 2 |-----> server:29103
73 Port 29102 >----| Stunnel 3 |-----> client:29102
77 Port 29103 >----| Stunnel 4 |-----> 9103
82 \section{Certificates}
83 \index[general]{Certificates }
85 In order for stunnel to function as a server, which it does in our diagram for
86 Stunnel 1 and Stunnel 4, you must have a certificate and the key. It is
87 possible to keep the two in separate files, but normally, you keep them in one
88 single .pem file. You may create this certificate yourself in which case, it
89 will be self-signed, or you may have it signed by a CA.
91 If you want your clients to verify that the server is in fact valid (Stunnel 2
92 and Stunnel 3), you will need to have the server certificates signed by a CA
93 (Certificate Authority), and you will need to have the CA's public certificate
94 (contains the CA's public key).
96 Having a CA signed certificate is {\bf highly} recommended if you are using
97 your client across the Internet, otherwise you are exposed to the man in the
98 middle attack and hence loss of your data.
100 See below for how to create a self-signed certificate.
102 \section{Securing the Data Channel}
103 \index[general]{Channel!Securing the Data }
104 \index[general]{Securing the Data Channel }
106 To simplify things a bit, let's for the moment consider only the data channel.
107 That is the connection between the File daemon and the Storage daemon, which
108 takes place on port 9103. In fact, in a minimalist solution, this is the only
109 connection that needs to be encrypted, because it is the one that transports your
110 data. The connection between the Director and the File daemon is simply a
111 control channel used to start the job and get the job status.
113 Normally the File daemon will contact the Storage daemon on port 9103
114 (supplied by the Director), so we need an stunnel that listens on port 9103 on
115 the File daemon's machine, encrypts the data and sends it to the Storage
116 daemon. This is depicted by Stunnel 2 above. Note that this stunnel is
117 listening on port 9103 and sending to server:29103. We use port 29103 on the
118 server because if we would send the data to port 9103, it would go directly to the
119 Storage daemon, which doesn't understand encrypted data. On the server
120 machine, we run Stunnel 4, which listens on port 29103, decrypts the data and
121 sends it to the Storage daemon, which is listening on port 9103.
123 \section{Data Channel Configuration}
124 \index[general]{Modification of bacula-dir.conf for the Data Channel }
125 \index[general]{baculoa-dir.conf!Modification for the Data Channel }
127 The Storage resource of the bacula-dir.conf normally looks something like the
136 Password = storage_password
143 Notice that this is running on the server machine, and it points the File
144 daemon back to server:9103, which is where our Storage daemon is listening. We
153 Password = storage_password
160 This causes the File daemon to send the data to the stunnel running on
161 localhost (the client machine). We could have used client as the address as
164 \section{Stunnel Configuration for the Data Channel}
165 \index[general]{Stunnel Configuration for the Data Channel }
167 In the diagram above, we see above Stunnel 2 that we use stunnel-fd2.conf on the
168 client. A pretty much minimal config file would look like the following:
174 accept = localhost:9103
175 connect = server:29103
179 The above config file does encrypt the data but it does not require a
180 certificate, so it is subject to the man in the middle attack. The file I
181 actually used, stunnel-fd2.conf, looked like this:
186 # Stunnel conf for Bacula client -> SD
188 pid = /home/kern/bacula/bin/working/stunnel.pid
190 # A cert is not mandatory here. If verify=2, a
191 # cert signed by a CA must be specified, and
192 # either CAfile or CApath must point to the CA's
195 cert = /home/kern/stunnel/stunnel.pem
196 CAfile = /home/kern/ssl/cacert.pem
202 accept = localhost:9103
203 connect = server:29103
207 You will notice that I specified a pid file location because I ran stunnel
208 under my own userid so I could not use the default, which requires root
209 permission. I also specified a certificate that I have as well as verify level
210 2 so that the certificate is required and verified, and I must supply the
211 location of the CA (Certificate Authority) certificate so that the stunnel
212 certificate can be verified. Finally, you will see that there are two lines
213 commented out, which when enabled, produce a lot of nice debug info in the
216 If you do not have a signed certificate (stunnel.pem), you need to delete the
217 cert, CAfile, and verify lines.
219 Note that the stunnel.pem, is actually a private key and a certificate in a
220 single file. These two can be kept and specified individually, but keeping
221 them in one file is more convenient.
223 The config file, stunnel-sd.conf, needed for Stunnel 4 on the server machine
229 # Bacula stunnel conf for Storage daemon
231 pid = /home/kern/bacula/bin/working/stunnel.pid
233 # A cert is mandatory here, it may be self signed
234 # If it is self signed, the client may not use
237 cert = /home/kern/stunnel/stunnel.pem
247 \section{Starting and Testing the Data Encryption}
248 \index[general]{Starting and Testing the Data Encryption }
249 \index[general]{Encryption!Starting and Testing the Data }
251 It will most likely be the simplest to implement the Data Channel encryption
252 in the following order:
255 \item Setup and run Bacula backing up some data on your client machine
258 \item Modify the Storage resource in the Director's conf file.
260 \item Start stunnel on the server with:
264 stunnel stunnel-sd.conf
269 \item Start stunnel on the client with:
273 stunnel stunnel-fd2.conf
279 \item If it doesn't work, turn debug on in both stunnel conf files, restart
280 the stunnels, rerun the job, repeat until it works.
283 \section{Encrypting the Control Channel}
284 \index[general]{Channel!Encrypting the Control }
285 \index[general]{Encrypting the Control Channel }
287 The Job control channel is between the Director and the File daemon, and as
288 mentioned above, it is not really necessary to encrypt, but it is good
289 practice to encrypt it as well. The two stunnels that are used in this case
290 will be Stunnel 1 and Stunnel 3 in the diagram above. Stunnel 3 on the server
291 might normally listen on port 9102, but if you have a local File daemon, this
292 will not work, so we make it listen on port 29102. It then sends the data to
293 client:29102. Again we use port 29102 so that the stunnel on the client
294 machine can decrypt the data before passing it on to port 9102 where the File
297 \section{Control Channel Configuration}
298 \index[general]{Control Channel Configuration }
300 We need to modify the standard Client resource, which would normally look
329 This will cause the Director to send the control information to
330 localhost:29102 instead of directly to the client.
332 \section{Stunnel Configuration for the Control Channel}
333 \index[general]{Config Files for stunnel to Encrypt the Control Channel }
335 The stunnel config file, stunnel-dir.conf, for the Director's machine would
336 look like the following:
341 # Bacula stunnel conf for the Directory to contact a client
343 pid = /home/kern/bacula/bin/working/stunnel.pid
345 # A cert is not mandatory here. If verify=2, a
346 # cert signed by a CA must be specified, and
347 # either CAfile or CApath must point to the CA's
350 cert = /home/kern/stunnel/stunnel.pem
351 CAfile = /home/kern/ssl/cacert.pem
357 accept = localhost:29102
358 connect = client:29102
362 and the config file, stunnel-fd1.conf, needed to run stunnel on the Client
368 # Bacula stunnel conf for the Directory to contact a client
370 pid = /home/kern/bacula/bin/working/stunnel.pid
372 # A cert is not mandatory here. If verify=2, a
373 # cert signed by a CA must be specified, and
374 # either CAfile or CApath must point to the CA's
377 cert = /home/kern/stunnel/stunnel.pem
378 CAfile = /home/kern/ssl/cacert.pem
384 accept = localhost:29102
385 connect = client:29102
389 \section{Starting and Testing the Control Channel}
390 \index[general]{Starting and Testing the Control Channel }
391 \index[general]{Channel!Starting and Testing the Control }
393 It will most likely be the simplest to implement the Control Channel
394 encryption in the following order:
398 \item Modify the Client resource in the Director's conf file.
400 \item Start stunnel on the server with:
404 stunnel stunnel-dir.conf
409 \item Start stunnel on the client with:
413 stunnel stunnel-fd1.conf
419 \item If it doesn't work, turn debug on in both stunnel conf files, restart
420 the stunnels, rerun the job, repeat until it works.
423 \section{Using stunnel to Encrypt to a Second Client}
424 \index[general]{Using stunnel to Encrypt to a Second Client }
425 \index[general]{Client!Using stunnel to Encrypt to a Second }
427 On the client machine, you can just duplicate the setup that you have on the
428 first client file for file and it should work fine.
430 In the bacula-dir.conf file, you will want to create a second client pretty
431 much identical to how you did for the first one, but the port number must be
432 unique. We previously used:
446 so for the second client, we will, of course, have a different name, and we
447 will also need a different port. Remember that we used port 29103 for the
448 Storage daemon, so for the second client, we can use port 29104, and the
449 Client resource would look like:
463 Now, fortunately, we do not need a third stunnel to on the Director's machine,
464 we can just add the new port to the config file, stunnel-dir.conf, to make:
469 # Bacula stunnel conf for the Directory to contact a client
471 pid = /home/kern/bacula/bin/working/stunnel.pid
473 # A cert is not mandatory here. If verify=2, a
474 # cert signed by a CA must be specified, and
475 # either CAfile or CApath must point to the CA's
478 cert = /home/kern/stunnel/stunnel.pem
479 CAfile = /home/kern/ssl/cacert.pem
485 accept = localhost:29102
486 connect = client:29102
488 accept = localhost:29102
489 connect = client2:29102
493 There are no changes necessary to the Storage daemon or the other stunnel so
494 that this new client can talk to our Storage daemon.
496 \section{Creating a Self-signed Certificate}
497 \index[general]{Creating a Self-signed Certificate }
498 \index[general]{Certificate!Creating a Self-signed }
500 You may create a self-signed certificate for use with stunnel that will permit
501 you to make it function, but will not allow certificate validation. The .pem
502 file containing both the certificate and the key can be made with the
503 following, which I put in a file named {\bf makepem}:
509 # Simple shell script to make a .pem file that can be used
510 # with stunnel and Bacula
514 PEM1="/bin/mktemp openssl.XXXXXX"
515 PEM2="/bin/mktemp openssl.XXXXXX"
516 ${OPENSSL} req -newkey rsa:1024 -keyout $PEM1 -nodes \
517 -x509 -days 365 -out $PEM2
518 cat $PEM1 > stunnel.pem
519 echo "" >>stunnel.pem
520 cat $PEM2 >>stunnel.pem
525 The above script will ask you a number of questions. You may simply answer
526 each of them by entering a return, or if you wish you may enter your own data.
529 \section{Getting a CA Signed Certificate}
530 \index[general]{Certificate!Getting a CA Signed }
531 \index[general]{Getting a CA Signed Certificate }
533 The process of getting a certificate that is signed by a CA is quite a bit
534 more complicated. You can purchase one from quite a number of PKI vendors, but
535 that is not at all necessary for use with Bacula.
538 certificate, you will either need to find a friend that has setup his own CA
539 or to become a CA yourself, and thus you can sign all your own certificates.
540 The book OpenSSL by John Viega, Matt Mesier \& Pravir Chandra from O'Reilly
541 explains how to do it, or you can read the documentation provided in the
542 Open-source PKI Book project at Source Forge:
544 http://ospkibook.sourceforge.net/docs/OSPKI-2.4.7/OSPKI-html/ospki-book.htm}
545 {http://ospkibook.sourceforge.net/docs/OSPKI-2.4.7/OSPKI-html/ospki-book.htm}.
546 Note, this link may change.
548 \section{Using ssh to Secure the Communications}
549 \index[general]{Communications!Using ssh to Secure the }
550 \index[general]{Using ssh to Secure the Communications }
552 Please see the script {\bf ssh-tunnel.sh} in the {\bf examples} directory. It
553 was contributed by Stephan Holl.