From 4ec4f4ddae4285adf0a40618360ec5cea02d85c3 Mon Sep 17 00:00:00 2001 From: Rainer Gerhards Date: Tue, 6 May 2008 10:23:35 +0200 Subject: updated doc set to reflect TLS support --- doc/Makefile.am | 1 + doc/features.html | 35 ++- doc/rsyslog_ng_comparison.html | 33 +-- doc/rsyslog_stunnel.html | 488 ++++++++++++++++++++--------------------- doc/rsyslog_tls.html | 170 ++++++++++++++ 5 files changed, 452 insertions(+), 275 deletions(-) create mode 100644 doc/rsyslog_tls.html diff --git a/doc/Makefile.am b/doc/Makefile.am index 6eb82b81..90be2725 100644 --- a/doc/Makefile.am +++ b/doc/Makefile.am @@ -21,6 +21,7 @@ html_files = \ rsyslog_high_database_rate.html \ rsyslog_php_syslog_ng.html \ rsyslog_recording_pri.html \ + rsyslog_tls.html \ rsyslog_stunnel.html \ syslog-protocol.html \ version_naming.html \ diff --git a/doc/features.html b/doc/features.html index f9d17818..9fbebedf 100644 --- a/doc/features.html +++ b/doc/features.html @@ -1,5 +1,7 @@ -rsyslog features +rsyslog features + +

RSyslog - Features

This page lists both current features as well as @@ -23,13 +25,18 @@ to MySQL databases

native support for writing to Postgres databases

direct support for Firebird/Interbase, OpenTDS (MS SQL, Sybase), SQLLite, Ingres, Oracle, and mSQL via libdbi, -a database abstraction layer (almost as good as native)
native support for sending mail messages (first seen in 3.17.0)
+a database abstraction layer (almost as good as native) +
native support for sending +mail messages (first seen in 3.17.0)

support for (plain) tcp based syslog - much better reliability

support for sending and receiving compressed syslog messages

support for on-demand on-disk spooling of messages that can not be processed fast enough (a great feature for writing massive -amounts of syslog messages to a database)
support for selectively processing messages only during specific timeframes and spooling them to disk otherwise
+amounts of syslog messages to a database) +
support for selectively processing +messages only during specific timeframes and spooling them to +disk otherwise

ability to monitor text files and convert their contents into syslog messages (one per line)

ability to configure backup syslog/database servers - if @@ -49,8 +56,9 @@ substrings
command execution
support for running multiple rsyslogd instances on a single machine
-
support for -ssl-protected syslog (via stunnel)
+
support for TLS-protected +syslog (both natively +and via stunnel)

ability to filter on any part of the message, not just facility and severity

ability to use regular expressions in filters
@@ -70,8 +78,7 @@ high log volume on multicore machines) compliant messages (it is volatile because standardization is currently underway and this is a proof-of-concept implementation to aid this effort) -
experimental support for syslog-transport-tls based -framing on syslog/tcp connections
+
world's first implementation of syslog-transport-tls

the sysklogd's klogd functionality is implemented as the imklog input plug-in. So rsyslog is a full replacement for the sysklogd package

support for IPv6
@@ -90,7 +97,13 @@ via custom plugins
support for arbitrary complex boolean, string and arithmetic expressions in message filters
-

+
World's first
+Rsyslog has an interesting number of "world's firsts" - things that +were implemented for the first time ever in rsyslog. Some of them are still features not available elsewhere.
+
world's first implementation of IETF I-D syslog-protocol (February 2006, version 1.12.2 and above)
world's first implementation of dynamic syslog on-the-wire compression (Deceber 2006, version 1.13.0 and above)
world's first open-source implementation of a disk-queueing syslogd (January 2008, version 3.11.0 and above)
+
world's first implementation of IETF I-D +syslog-transport-tls (May 2008, version 3.19.0 and above)
+

Upcoming Features

The list below is something like a repository of ideas we'd like to implement. Features on this list are typically NOT scheduled @@ -105,11 +118,9 @@ to the bugzilla tracker.

port it to more *nix variants (eg AIX and HP UX) - this needs volunteers with access to those machines and knowledge
-
support for native SSL enryption of plain tcp syslog -sessions. This will most probably happen based on syslog-transport-tls.

pcre filtering - maybe (depending on feedback) - simple regex already partly added. So far, this seems sufficient so -that there is no urgent need to do pcre
+that there is no urgent need to do pcre. If done, it will be a loadable RainerScript function.
support for RFC 3195 as a sender - this is currently unlikely to happen, because there is no real demand for it. Any work on RFC 3195 has been @@ -122,4 +133,4 @@ future of RFC 3195 in rsyslog.

To see when each feature was added, see the rsyslog change log (online only).
- + \ No newline at end of file diff --git a/doc/rsyslog_ng_comparison.html b/doc/rsyslog_ng_comparison.html index 0d57a374..72fee210 100644 --- a/doc/rsyslog_ng_comparison.html +++ b/doc/rsyslog_ng_comparison.html @@ -1,11 +1,9 @@ -rsyslog vs. syslog-ng - a comparison - - +rsyslog vs. syslog-ng - a comparison
rsyslog vs. syslog-ng

Written by Rainer Gerhards -(2008-04-08)
+(2008-05-06)

We have often been asked about a comparison sheet between rsyslog and syslog-ng. Unfortunately, I do not know much about syslog-ng, I did not even use it once. Also, there seems to be no @@ -101,7 +99,7 @@ Network (Protocol) Support
support for GSS-API yes -no (?) +no ability to limit the allowed @@ -141,20 +139,24 @@ reliable RFC no -support for ssl-protected +support for TLS/SSL-protected syslog -via +natively (since 3.19.0)
via stunnel via stunnel
paid edition natively -support for IETF's new -syslog-protocol draft +support for IETF's new syslog-protocol draft yes no +support for IETF's new syslog-transport-tls draft +yes
(since 3.19.0 - world's first implementation) +no + + support for IPv6 yes yes @@ -162,7 +164,7 @@ syslog-protocol draft native ability to send SNMP traps yes -? +no ability to preserve the original @@ -426,8 +428,10 @@ including ability to present channel and priority as visible log data yes not sure... -native ability to send mail messages -yes (ommail, introduced in 3.17.0) + +native ability to send mail messages +yes (ommail, +introduced in 3.17.0) not sure... @@ -578,6 +582,5 @@ feature sheet. I have not yet been able to fully work through it. In the mean time, you may want to read it in parallel. It is available at Balabit's site.

This document is current as of 2008-04-08 and definitely -incomplete (I did not yet manage to complete it!).

SSL Encrypting syslog with stunnel

SSL Encrypting Syslog with Stunnel

Written by - Rainer - Gerhards (2005-07-22)

Abstract

In this paper, I describe how to encrypt syslog -messages on the network. Encryption -is vital to keep the confidiental content of syslog messages secure. I describe the overall -approach and provide an HOWTO do it with the help of -rsyslogd and stunnel.

Background

Syslog is a -clear-text protocol. That means anyone with a sniffer can have -a peek at your data. In some environments, this is no problem at all. In -others, it is a huge setback, probably even preventing deployment of syslog -solutions. Thankfully, there is an easy way to encrypt syslog communication. I -will describe one approach in this paper.

The most straigthforward solution would be that the syslogd itself encrypts -messages. Unfortuantely, encryption is only standardized in -RFC 3195. But there -is currently no syslogd that implements RFC 3195's encryption features, -so this route leads to nothing. Another approach would be to use vendor- or -project-specific syslog extensions. There are a few around, but the problem here -is that they have compatibility issues. However, there is one surprisingly easy -and interoperable solution: though not standardized, many vendors and projects -implement plain tcp syslog. In a nutshell, plain tcp syslog is a mode where -standard syslog messages are transmitted via tcp and records are separated by -newline characters. This mode is supported by all major syslogd's (both on Linux/Unix -and Windows) as well as log sources (for example, -EventReporter for Windows -Event Log forwarding). Plain tcp syslog offers reliability, but it does not -offer encryption in itself. However, since it operates on a tcp stream, it is now easy -to add encryption. There are various ways to do that. In this paper, I will -describe how it is done with stunnel (an -other alternative would be IPSec, for example).

Stunnel is open source and it is available both for Unix/Linux and Windows. -It provides a way to - use ssl communication for any non-ssl aware client and server - in this case, - our syslogd.

Stunnel works much like a wrapper. Both on the client and on the server machine, - tunnel portals are created. The non-ssl aware client and server software is - configured to not directly talk to the remote partner, but to the local - (s)tunnel portal instead. Stunnel, in turn, takes the data received from the - client, encrypts it via ssl, sends it to the remote tunnel portal and that - remote portal sends it to the recipient process on the remote machine. The - transfer to the portals is done via unencrypted communication. As such, - it is vital that - the portal and the respective program that is talking to it are on the same - machine, otherwise data would travel partly unencrypted. Tunneling, as done by stunnel, - requires connection oriented communication. This is why you need to use - tcp-based syslog. As a side-note, you can also encrypt a plain-text RFC - 3195 session via stunnel, though this definitely is not what the - protocol designers had on their mind ;)

In the rest of this document, I assume that you use rsyslog on both the -client and the server. For the samples, I use Debian. -Interestingly, there are -some annoying differences between stunnel implementations. For example, on -Debian a comment line starts with a semicolon (';'). On -Red Hat, it starts with -a hash sign ('#'). So you need to watch out for subtle issues when setting up -your system.

Overall System Setup

In ths paper, I assume two machines, one named "client" and the other named "server". -It is obvious that, in practice, you will probably have multiple clients but -only one server. Syslog traffic shall be transmitted via stunnel over the -network. Port 60514 is to be used for that purpose. The machines are set up as -follows:

Client

rsyslog forwards message to stunnel local portal at port 61514
local stunnel forwards data via the network to port 60514 to its remote - peer

Server

stunnel listens on port 60514 to connections from its client peers
all connections are forwarded to the locally-running rsyslog listening - at port 61514

Setting up the system

For Debian, you need the "stunnel4" package. The "stunnel" package is the -older 3.x release, which will not support the configuration I describe below. -Other distributions might have other names. For example, on Red Hat it is just "stunnel". -Make sure that you install the appropriate package on both the client and the -server. It is also a good idea to check if there are updates for either stunnel -or openssl (which stunnel uses) - there are often security fixes available and -often the latest fixes are not included in the default package.

In my sample setup, I use only the bare minimum of options. For example, I do -not make the server check client cerficiates. Also, I do not talk much about -certificates at all. If you intend to really secure your system, you should -probably learn about certificates and how to manage and deploy them. This is -beyond the scope of this paper. For additional information, - -http://www.stunnel.org/faq/certs.html is a good starting point.

You also need to install rsyslogd on both machines. Do this before starting -with the configuration. You should also familarize yourself with its -configuration file syntax, so that you know which actions you can trigger with -it. Rsyslogd can work as a drop-in replacement for stock -sysklogd. So if you know -the standard syslog.conf syntax, you do not need to learn any more to follow -this paper.

Server Setup

At the server, you need to have a digital certificate. That certificate -enables SSL operation, as it provides the necessary crypto keys being used to -secure the connection. Many versions of stunnel come with a default certificate, -often found in /etc/stunnel/stunnel.pem. If you have it, it is good for testing -only. If you use it in production, it is very easy to break into your secure -channel as everybody is able to get hold of your private key. I didn't find an -stunnel.pem on my Debian machine. I guess the Debian folks removed it because of -its insecurity.

You can create your own certificate with a simple openssl tool - you need to -do it if you have none and I highly recommend to create one in any case. To -create it, cd to /etc/stunnel and type:

openssl req -new -x509 -days 3650 -nodes -out -stunnel.pem -keyout stunnel.pem

That command will ask you a number of questions. Provide some answer for -them. If you are unsure, read - -http://www.stunnel.org/faq/certs.html. After the command has finished, you -should have a usable stunnel.pem in your working directory.

Next is to create a configuration file for stunnel. It will direct stunnel -what to do. You can used the following basic file:

; Certificate/key is needed in server mode
-cert = /etc/stunnel/stunnel.pem
-
-; Some debugging stuff useful for troubleshooting
-debug = 7
-foreground=yes
-
-[ssyslog]
-accept  = 60514
-connect = 61514
-

Save this file to e.g. /etc/stunnel/syslog-server.conf. Please note that the -settings in italics are for debugging only. They run stunnel -with a lot of debug information in the foreground. This is very valuable while -you setup the system - and very useless once everything works well. So be sure -to remove these lines when going to production.

Finally, you need to start the stunnel daemon. Under Debian, this is done via -"stunnel /etc/stunnel/syslog.server.conf". If you have enabled the debug -settings, you will immediately see a lot of nice messages.

Now you have stunnel running, but it obviously unable to talk to rsyslog - -because it is not yet running. If not already done, configure it so that it does -everything you want. If in doubt, you can simply copy /etc/syslog.conf to /etc/rsyslog.conf -and you probably have what you want. The really important thing in rsyslogd -configuration is that you must make it listen to tcp port 61514 (remember: this -is where stunnel send the messages to). Thankfully, this is easy to achive: just -add "-t 61514" to the rsyslogd startup options in your system startup script. -After done so, start (or restart) rsyslogd.

The server should now be fully operational.

Client Setup

The client setup is simpler. Most importantly, you do not need a certificate -(of course, you can use one if you would like to authenticate the client, but -this is beyond the scope of this paper). So the basic thing you need to do is -create the stunnel configuration file.

; Some debugging stuff useful for troubleshooting
-debug = 7
-foreground=yes
-
-client=yes
-
-[ssyslog]
-accept  = 127.0.0.1:61514
-connect = 192.0.2.1:60514
-
-

Again, the text in italics is for debugging purposes only. I suggest -you leave it in during your initial testing and then remove it. The most -important difference to the server configuration outlined above is the "client=yes" -directive. It is what makes this stunnel behave like a client. The accept -directive binds stunnel only to the local host, so that it is protected from -receiving messages from the network (somebody might fake to be the local sender). -The address "192.0.2.1" is the address of the server machine. You must change it -to match your configuration. Save this file to /etc/stunnel/syslog-client.conf.

Then, start stunnel via "stunnel4 /etc/stunnel/syslog-client.conf". Now -you should see some startup messages. If no errors appear, you have a running -client stunnel instance.

Finally, you need to tell rsyslogd to send data to the remote host. In stock -syslogd, you do this via the "@host" forwarding directive. The same works with -rsyslog, but it suppports extensions to use tcp. Add the following line to your -/etc/rsyslog.conf:

*.*      @@127.0.0.1:61514
-
-

- -

Please note the double at-sign (@@). This is no typo. It tells rsyslog to use -tcp instead of udp delivery. In this sample, all messages are forwarded to the -remote host. Obviously, you may want to limit this via the usual rsyslog.conf -settings (if in doubt, use man rsyslog.con).

You do not need to add any special startup settings to rsyslog on the client. -Start or restart rsyslog so that the new configuration setting takes place.

Done

After following these steps, you should have a working secure syslog -forwarding system. To verify, you can type "logger test" or a similar smart -command on the client. It should show up in the respective server log file. If -you dig out you sniffer, you should see that the traffic on the wire is actually -protected. In the configuration use above, the two stunnel endpoints should be -quite chatty, so that you can follow the action going on on your system.

If you have only basic security needs, you can probably just remove the debug -settings and take the rest of the configuration to production. If you are -security-sensitve, you should have a look at the various stunnel settings that -help you further secure the system.

Preventing Systems from talking directly to the rsyslog Server

It is possible that remote systems (or attackers) talk to the rsyslog server -by directly connecting to its port 61514. Currently (July of 2005), rsyslog does -not offer the ability to bind to the local host, only. This feature is planned, -but as long as it is missing, rsyslog must be protected via a firewall. This can -easily be done via e.g iptables. Just be sure not to forget it.

Conclusion

With minumal effort, you can set up a secure logging infrastructure employing -ssl encrypted syslog message transmission. As a side note, you also have the -benefit of reliable tcp delivery which is far less prone to message loss than -udp.

Feedback requested

I would appreciate feedback on this tutorial. If you have additional ideas, -comments or find bugs (I *do* bugs - no way... ;)), please -let me know.

Revision History

2005-07-22 * - Rainer Gerhards * Initial Version created
2005-07-26 * - Rainer Gerhards * Some text brush-up, hyperlinks added
2005-08-03 * - Rainer Gerhards - * license added

Copyright

Permission is granted to copy, distribute and/or modify this document - under the terms of the GNU Free Documentation License, Version 1.2 - or any later version published by the Free Software Foundation; - with no Invariant Sections, no Front-Cover Texts, and no Back-Cover - Texts. A copy of the license can be viewed at - -http://www.gnu.org/copyleft/fdl.html.

SSL Encrypting syslog with stunnel

SSL Encrypting Syslog with Stunnel

Written by + Rainer + Gerhards (2005-07-22)

Abstract

In this paper, I describe how to encrypt syslog +messages on the network. Encryption +is vital to keep the confidiental content of syslog messages secure. I describe the overall +approach and provide an HOWTO do it with the help of +rsyslogd and stunnel.

Please note that starting with rsyslog 3.19.0, rsyslog provides native TLS/SSL encryption without the need of stunnel. I +strongly recomend to use that feature instead of stunnel. The stunnel +documentation here is mostly provided for backwards compatibility. New +deployments are advised to use native TLS mode.

Background

Syslog is a +clear-text protocol. That means anyone with a sniffer can have +a peek at your data. In some environments, this is no problem at all. In +others, it is a huge setback, probably even preventing deployment of syslog +solutions. Thankfully, there is an easy way to encrypt syslog communication. I +will describe one approach in this paper.

The most straigthforward solution would be that the syslogd itself encrypts +messages. Unfortuantely, encryption is only standardized in +RFC 3195. But there +is currently no syslogd that implements RFC 3195's encryption features, +so this route leads to nothing. Another approach would be to use vendor- or +project-specific syslog extensions. There are a few around, but the problem here +is that they have compatibility issues. However, there is one surprisingly easy +and interoperable solution: though not standardized, many vendors and projects +implement plain tcp syslog. In a nutshell, plain tcp syslog is a mode where +standard syslog messages are transmitted via tcp and records are separated by +newline characters. This mode is supported by all major syslogd's (both on Linux/Unix +and Windows) as well as log sources (for example, +EventReporter for Windows +Event Log forwarding). Plain tcp syslog offers reliability, but it does not +offer encryption in itself. However, since it operates on a tcp stream, it is now easy +to add encryption. There are various ways to do that. In this paper, I will +describe how it is done with stunnel (an +other alternative would be IPSec, for example).

Stunnel is open source and it is available both for Unix/Linux and Windows. +It provides a way to + use ssl communication for any non-ssl aware client and server - in this case, + our syslogd.

Stunnel works much like a wrapper. Both on the client and on the server machine, + tunnel portals are created. The non-ssl aware client and server software is + configured to not directly talk to the remote partner, but to the local + (s)tunnel portal instead. Stunnel, in turn, takes the data received from the + client, encrypts it via ssl, sends it to the remote tunnel portal and that + remote portal sends it to the recipient process on the remote machine. The + transfer to the portals is done via unencrypted communication. As such, + it is vital that + the portal and the respective program that is talking to it are on the same + machine, otherwise data would travel partly unencrypted. Tunneling, as done by stunnel, + requires connection oriented communication. This is why you need to use + tcp-based syslog. As a side-note, you can also encrypt a plain-text RFC + 3195 session via stunnel, though this definitely is not what the + protocol designers had on their mind ;)

In the rest of this document, I assume that you use rsyslog on both the +client and the server. For the samples, I use Debian. +Interestingly, there are +some annoying differences between stunnel implementations. For example, on +Debian a comment line starts with a semicolon (';'). On +Red Hat, it starts with +a hash sign ('#'). So you need to watch out for subtle issues when setting up +your system.

Overall System Setup

In ths paper, I assume two machines, one named "client" and the other named "server". +It is obvious that, in practice, you will probably have multiple clients but +only one server. Syslog traffic shall be transmitted via stunnel over the +network. Port 60514 is to be used for that purpose. The machines are set up as +follows:

Client

rsyslog forwards message to stunnel local portal at port 61514
local stunnel forwards data via the network to port 60514 to its remote + peer

Server

stunnel listens on port 60514 to connections from its client peers
all connections are forwarded to the locally-running rsyslog listening + at port 61514

Setting up the system

For Debian, you need the "stunnel4" package. The "stunnel" package is the +older 3.x release, which will not support the configuration I describe below. +Other distributions might have other names. For example, on Red Hat it is just "stunnel". +Make sure that you install the appropriate package on both the client and the +server. It is also a good idea to check if there are updates for either stunnel +or openssl (which stunnel uses) - there are often security fixes available and +often the latest fixes are not included in the default package.

In my sample setup, I use only the bare minimum of options. For example, I do +not make the server check client cerficiates. Also, I do not talk much about +certificates at all. If you intend to really secure your system, you should +probably learn about certificates and how to manage and deploy them. This is +beyond the scope of this paper. For additional information, + +http://www.stunnel.org/faq/certs.html is a good starting point.

You also need to install rsyslogd on both machines. Do this before starting +with the configuration. You should also familarize yourself with its +configuration file syntax, so that you know which actions you can trigger with +it. Rsyslogd can work as a drop-in replacement for stock +sysklogd. So if you know +the standard syslog.conf syntax, you do not need to learn any more to follow +this paper.

Server Setup

At the server, you need to have a digital certificate. That certificate +enables SSL operation, as it provides the necessary crypto keys being used to +secure the connection. Many versions of stunnel come with a default certificate, +often found in /etc/stunnel/stunnel.pem. If you have it, it is good for testing +only. If you use it in production, it is very easy to break into your secure +channel as everybody is able to get hold of your private key. I didn't find an +stunnel.pem on my Debian machine. I guess the Debian folks removed it because of +its insecurity.

You can create your own certificate with a simple openssl tool - you need to +do it if you have none and I highly recommend to create one in any case. To +create it, cd to /etc/stunnel and type:

openssl req -new -x509 -days 3650 -nodes -out +stunnel.pem -keyout stunnel.pem

That command will ask you a number of questions. Provide some answer for +them. If you are unsure, read + +http://www.stunnel.org/faq/certs.html. After the command has finished, you +should have a usable stunnel.pem in your working directory.

Next is to create a configuration file for stunnel. It will direct stunnel +what to do. You can used the following basic file:

; Certificate/key is needed in server mode
cert = /etc/stunnel/stunnel.pem

; Some debugging stuff useful for troubleshooting
debug = 7
foreground=yes
+
+[ssyslog]
+accept  = 60514
+connect = 61514

Save this file to e.g. /etc/stunnel/syslog-server.conf. Please note that the +settings in italics are for debugging only. They run stunnel +with a lot of debug information in the foreground. This is very valuable while +you setup the system - and very useless once everything works well. So be sure +to remove these lines when going to production.

Finally, you need to start the stunnel daemon. Under Debian, this is done via +"stunnel /etc/stunnel/syslog.server.conf". If you have enabled the debug +settings, you will immediately see a lot of nice messages.

Now you have stunnel running, but it obviously unable to talk to rsyslog - +because it is not yet running. If not already done, configure it so that it does +everything you want. If in doubt, you can simply copy /etc/syslog.conf to /etc/rsyslog.conf +and you probably have what you want. The really important thing in rsyslogd +configuration is that you must make it listen to tcp port 61514 (remember: this +is where stunnel send the messages to). Thankfully, this is easy to achive: just +add "-t 61514" to the rsyslogd startup options in your system startup script. +After done so, start (or restart) rsyslogd.

The server should now be fully operational.

Client Setup

The client setup is simpler. Most importantly, you do not need a certificate +(of course, you can use one if you would like to authenticate the client, but +this is beyond the scope of this paper). So the basic thing you need to do is +create the stunnel configuration file.

; Some debugging stuff useful for troubleshooting
debug = 7
foreground=yes
+
+client=yes
+
+[ssyslog]
+accept  = 127.0.0.1:61514
+connect = 192.0.2.1:60514

Again, the text in italics is for debugging purposes only. I suggest +you leave it in during your initial testing and then remove it. The most +important difference to the server configuration outlined above is the "client=yes" +directive. It is what makes this stunnel behave like a client. The accept +directive binds stunnel only to the local host, so that it is protected from +receiving messages from the network (somebody might fake to be the local sender). +The address "192.0.2.1" is the address of the server machine. You must change it +to match your configuration. Save this file to /etc/stunnel/syslog-client.conf.

Then, start stunnel via "stunnel4 /etc/stunnel/syslog-client.conf". Now +you should see some startup messages. If no errors appear, you have a running +client stunnel instance.

Finally, you need to tell rsyslogd to send data to the remote host. In stock +syslogd, you do this via the "@host" forwarding directive. The same works with +rsyslog, but it suppports extensions to use tcp. Add the following line to your +/etc/rsyslog.conf:

*.*      @@127.0.0.1:61514

+ +

Please note the double at-sign (@@). This is no typo. It tells rsyslog to use +tcp instead of udp delivery. In this sample, all messages are forwarded to the +remote host. Obviously, you may want to limit this via the usual rsyslog.conf +settings (if in doubt, use man rsyslog.con).

You do not need to add any special startup settings to rsyslog on the client. +Start or restart rsyslog so that the new configuration setting takes place.

Done

After following these steps, you should have a working secure syslog +forwarding system. To verify, you can type "logger test" or a similar smart +command on the client. It should show up in the respective server log file. If +you dig out you sniffer, you should see that the traffic on the wire is actually +protected. In the configuration use above, the two stunnel endpoints should be +quite chatty, so that you can follow the action going on on your system.

If you have only basic security needs, you can probably just remove the debug +settings and take the rest of the configuration to production. If you are +security-sensitve, you should have a look at the various stunnel settings that +help you further secure the system.

Preventing Systems from talking directly to the rsyslog Server

It is possible that remote systems (or attackers) talk to the rsyslog server +by directly connecting to its port 61514. Currently (July of 2005), rsyslog does +not offer the ability to bind to the local host, only. This feature is planned, +but as long as it is missing, rsyslog must be protected via a firewall. This can +easily be done via e.g iptables. Just be sure not to forget it.

Conclusion

With minumal effort, you can set up a secure logging infrastructure employing +ssl encrypted syslog message transmission. As a side note, you also have the +benefit of reliable tcp delivery which is far less prone to message loss than +udp.

Feedback requested

I would appreciate feedback on this tutorial. If you have additional ideas, +comments or find bugs (I *do* bugs - no way... ;)), please +let me know.

Revision History

2005-07-22 * + Rainer Gerhards * Initial Version created
2005-07-26 * + Rainer Gerhards * Some text brush-up, hyperlinks added
2005-08-03 * + Rainer Gerhards + * license added
2008-05-05 * Rainer Gerhards + * updated to reflect native TLS capability of rsyslog 3.19.0 and above

Copyright

Permission is granted to copy, distribute and/or modify this document + under the terms of the GNU Free Documentation License, Version 1.2 + or any later version published by the Free Software Foundation; + with no Invariant Sections, no Front-Cover Texts, and no Back-Cover + Texts. A copy of the license can be viewed at + +http://www.gnu.org/copyleft/fdl.html.

TLS (SSL) Encrypting syslog

Encrypting Syslog Traffic with TLS (SSL)

Written by Rainer +Gerhards (2008-05-06)

Abstract

In this paper, I describe how to encrypt syslog +messages on the network. Encryption +is vital to keep the confidiental content of syslog messages secure. I +describe the overall +approach and provide an HOWTO do it with rsyslog's TLS +features.

Please +note that TLS is the more secure successor of SSL. While people often +talk about "SSL encryption" they actually mean "TLS encryption". So +don't look any further if you look for how to SSL-encrypt syslog. You +have found the right spot.

Background

Traditional syslog is a clear-text protocol. That +means anyone with a sniffer can have a peek at your data. In +some environments, this is no problem at all. In others, it is a huge +setback, probably even preventing deployment of syslog solutions. +Thankfully, there are easy ways to encrypt syslog +communication.

running +a wrapper like stunnel around the syslog session

total +loss of syslog messages due to stunnel mode

unreliability +of TCP syslog

Rsyslog supports syslog via +GSSAPI since long to overcome these limitatinos. However, +syslog via GSSAPI is a rsyslog-exclusive transfer mode and it requires +a proper Kerberos environment. As such, it isn't a really universal +solution. The IETF has begun standardizing syslog over plain tcp over +TLS for a while now. While I am not fully satisfied with the results so +far, this obviously has the potential to become the long-term +solution. The Internet Draft in question, syslog-transport-tls has been +dormant for some time but is now (May of 2008) again being worked on. I +expect it to turn into a RFC within the next 12 month (but don't take +this for granted ;)). I didn't want to wait for it, because there +obviously is need for TLS syslog right now (and, honestly, I have waited long enough...). Consequently, I have +implemented the current draft, with some interpretations I made (there +will be a compliance doc soon). So in essence, a TLS-protected syslog +transfer mode is available right now. As a side-note, Rsyslog is the world's first +implementation of syslog-transport-tls.

Please note that in theory it should be compatible with other, +non IETF syslog-transport-tls implementations. If you would like to run +it with something else, please let us know so that we can create a +compatibility list (and implement compatbility where it doesn't yet +exist).

Overall System Setup

Encryption requires a reliable stream. So It will not work +over UDP syslog. In rsyslog, network transports utilize a so-called +"network stream layer" (netstream for short). This layer provides a +unified view of the transport to the application layer. The plain TCP +syslog sender and receiver are the upper layer. The driver layer +currently consists of the "ptcp" and "gtls" library plugins. "ptcp" +stands for "plain tcp" and is used for unencrypted message transfer. It +is also used internally by the gtls driver, so it must always be +present on a system. The "gtls" driver is for GnutTLS, a TLS library. +It is used for encrypted message transfer. In the future, additional +drivers will become available (most importantly, we would like to +include a driver for NSS).

What you need to do to build an encrypted syslog channel is to +simply use the proper netstream drivers on both the client and the +server. Client, in the sense of this document, is the rsyslog system +that is sending syslog messages to a remote (central) loghost, which is +called the server. In short, the setup is as follows:

Client

forwards messages via plain tcp syslog using gtls netstream +driver to central sever on port 10514
+

Server

accept incoming messages via plain tcp syslog using gtls +netstream driver on port 10514

Setting up the system

Server Setup

At the server, you need to have a digital certificate. That +certificate enables SSL operation, as it provides the necessary crypto +keys being used to secure the connection. There is a set of default +certificates in ./contrib/gnutls. These are key.pem and cert.pem. These +are good for testing. If you use it in production, +it is very easy to break into your secure channel as everybody is able +to get hold of your private key. So it is a good idea to +generate the key and certificate yourself.

You also need a root CA certificate. Again, there is a sample +CA certificate in ./contrib/gnutls, named ca.cert. It is suggested to +generate your own.

To configure the server, you need to tell it where are its +certificate files, to use the gtls driver and start up a listener. This +is done as follows:
+

# make gtls driver the default
$DefaultNetstreamDriver gtls

# certificate files
$DefaultNetstreamDriverCAFile /path/to/contrib/gnutls/ca.pem
$DefaultNetstreamDriverCertFile /path/to/contrib/gnutls/cert.pem
$DefaultNetstreamDriverKeyFile /path/to/contrib/gnutls/key.pem

$ModLoad /home/rger/proj/rsyslog/plugins/imtcp/.libs/imtcp # load listener

$InputTCPServerStreamDriverMode 1 # run driver in TLS-only mode
$InputTCPServerRun 10514 # start up listener at port 10514

Restart (or HUP) rsyslogd. The server should now be fully +operational.

Client Setup

The client setup is equally simple. You need less +certificates, just the CA cert.

# certificate files - just CA for a client
$DefaultNetstreamDriverCAFile /path/to/contrib/gnutls/ca.pem

# set up the action
$DefaultNetstreamDriver gtls # use gtls netstream driver
$ActionSendStreamDriverMode 1 # require TLS for the connection
*.* @@(o)server.example.net:10514 # send (all) messages

Note that we use the regular TCP forwarding syntax (@@) here. +There is nothing special, because the encryption is handled by the +netstream driver. So I have just forwarded every message (*.*) for +simplicity - you can use any of rsyslog's filtering capabilities (like +epxression-based filters or regular expressions). Note that the "(o)" +part is not strictly necessary. It selects octet-based framing, which +provides compatiblity to IETF's syslog-transport-tls draft. Besides +compatibility, this is also a more reliable transfer mode, so I suggest +to always use it.

Done

After +following these steps, you should have a working secure +syslog forwarding system. To verify, you can type "logger test" or a +similar "smart" command on the client. It should show up in the +respective server log file. If you dig out your sniffer, you should see +that the traffic on the wire is actually protected.

Limitations

The current implementation has a number of limitations. These are +being worked on. Most importantly, neither the client nor the server +are authenticated. So while the message transfer is encrypted, you can +not be sure which peer you are talking to. Please note that this is a +limitation found in most real-world SSL syslog systems. Of course, that +is not an excuse for not yet providing this feature - but it tells you +that it is acceptable and can be worked around by proper firewalling, +ACLs and other organizational measures. Mutual authentication will be +added shortly to rsyslog.

Secondly, the plain tcp syslog listener +can currently listen to a single port, in a single mode. So if you use +a TLS-based listener, you can not run unencrypted syslog on the same +instance at the same time. A work-around is to run a second rsyslogd +instance. This limitation, too, is scheduled to be removed soon.

The +RELP transport can currently not be protected by TLS. A work-around is +to use stunnel. TLS support for RELP will be added once plain TCP +syslog has sufficiently matured.

Conclusion

With minumal effort, you can set up a secure logging +infrastructure employing TLS encrypted syslog message transmission.

Feedback requested

I would appreciate feedback on this tutorial. If you have +additional ideas, comments or find bugs (I *do* bugs - no way... ;)), +please +let me know.

Revision History

2008-05-06 * Rainer +Gerhards * Initial Version created

Copyright

Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version +1.2 or any later version published by the Free Software Foundation; +with no Invariant Sections, no Front-Cover Texts, and no Back-Cover +Texts. A copy of the license can be viewed at +http://www.gnu.org/copyleft/fdl.html.