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README
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README
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TLS Module
Andrei Pelinescu-Onciul
iptelorg GmbH
Carsten Bock
ng-voice GmbH
Olle E. Johansson
Edvina AB
Copyright © 2007 iptelorg GmbH
Copyright © 2014 ng-voice GmbH
__________________________________________________________________
Table of Contents
1. Admin Guide
1. Overview
2. Quick Start
3. Important Notes
4. Compiling the TLS Module
5. TLS and Low Memory
6. TLS Debugging
7. Known Limitations
8. Quick Certificate Howto
9. Parameters
9.1. tls_method (string)
9.2. certificate (string)
9.3. private_key (string)
9.4. ca_list (string)
9.5. crl (string)
9.6. verify_certificate (boolean)
9.7. verify_depth (integer)
9.8. require_certificate (boolean)
9.9. cipher_list (string)
9.10. server_name (string)
9.11. send_timeout (int)
9.12. handshake_timeout (int)
9.13. connection_timeout (int)
9.14. tls_disable_compression (boolean)
9.15. ssl_release_buffers (integer)
9.16. ssl_freelist_max_len (integer)
9.17. ssl_max_send_fragment (integer)
9.18. ssl_read_ahead (boolean)
9.19. send_close_notify (boolean)
9.20. con_ct_wq_max (integer)
9.21. ct_wq_max (integer)
9.22. ct_wq_blk_size (integer)
9.23. tls_log (int)
9.24. tls_debug (int)
9.25. low_mem_threshold1 (integer)
9.26. low_mem_threshold2 (integer)
9.27. tls_force_run (boolean)
9.28. session_cache (boolean)
9.29. session_id (str)
9.30. renegotiation (boolean)
9.31. config (string)
9.32. xavp_cfg (string)
10. Functions
10.1. is_peer_verified()
11. RPC Commands
11.1. tls.info
11.2. tls.list
11.3. tls.options
11.4. tls.reload
12. Status
12.1. License
12.2. History
List of Examples
1.1. Quick start config
1.2. Compiling TLS with Debug Messages
1.3. Set tls_method parameter
1.4. Set certificate parameter
1.5. Set private_key parameter
1.6. Set ca_list parameter
1.7. Set crl parameter
1.8. Set verify_certificate parameter
1.9. Set verify_depth parameter
1.10. Set require_certificate parameter
1.11. Set cipher_list parameter
1.12. Set server_name parameter
1.13. Set connection_timeout parameter
1.14. Set tls.connection_timeout at runtime
1.15. Set tls_disable_compression parameter
1.16. Set ssl_release_buffers parameter
1.17. Set ssl_freelist_max_len parameter
1.18. Set ssl_max_send_fragment parameter
1.19. Set ssl_read_ahead parameter
1.20. Set send_close_notify parameter
1.21. Set tls.send_close_notify at runtime
1.22. Set con_ct_wq_max parameter
1.23. Set tls.con_ct_wq_max at runtime
1.24. Set ct_wq_max parameter
1.25. Set tls.ct_wq_max at runtime
1.26. Set ct_wq_blk_size parameter
1.27. Set tls.ct_wq_max at runtime
1.28. Set tls_log parameter
1.29. Set tls.log at runtime
1.30. Set tls_debug parameter
1.31. Set tls.debug at runtime
1.32. Set low_mem_threshold1 parameter
1.33. Set tls.low_mem_threshold1 at runtime
1.34. Set tls.low_mem_threshold2 parameter
1.35. Set tls.low_mem_threshold2 at runtime
1.36. Set tls_force_run parameter
1.37. Set session_cache parameter
1.38. Set session_id parameter
1.39. Set renegotiation parameter
1.40. Short config file
1.41. Set config parameter
1.42. Change and reload the TLS configuration at runtime
1.43. Set xavp_cfg parameter
1.44. is_peer_verified usage
Chapter 1. Admin Guide
Table of Contents
1. Overview
2. Quick Start
3. Important Notes
4. Compiling the TLS Module
5. TLS and Low Memory
6. TLS Debugging
7. Known Limitations
8. Quick Certificate Howto
9. Parameters
9.1. tls_method (string)
9.2. certificate (string)
9.3. private_key (string)
9.4. ca_list (string)
9.5. crl (string)
9.6. verify_certificate (boolean)
9.7. verify_depth (integer)
9.8. require_certificate (boolean)
9.9. cipher_list (string)
9.10. server_name (string)
9.11. send_timeout (int)
9.12. handshake_timeout (int)
9.13. connection_timeout (int)
9.14. tls_disable_compression (boolean)
9.15. ssl_release_buffers (integer)
9.16. ssl_freelist_max_len (integer)
9.17. ssl_max_send_fragment (integer)
9.18. ssl_read_ahead (boolean)
9.19. send_close_notify (boolean)
9.20. con_ct_wq_max (integer)
9.21. ct_wq_max (integer)
9.22. ct_wq_blk_size (integer)
9.23. tls_log (int)
9.24. tls_debug (int)
9.25. low_mem_threshold1 (integer)
9.26. low_mem_threshold2 (integer)
9.27. tls_force_run (boolean)
9.28. session_cache (boolean)
9.29. session_id (str)
9.30. renegotiation (boolean)
9.31. config (string)
9.32. xavp_cfg (string)
10. Functions
10.1. is_peer_verified()
11. RPC Commands
11.1. tls.info
11.2. tls.list
11.3. tls.options
11.4. tls.reload
12. Status
12.1. License
12.2. History
1. Overview
This module implements the TLS transport for Kamailio using the OpenSSL
library (http://www.openssl.org). To enable the Kamailio TLS support
this module must be loaded and enable_tls=yes core setting must be
added to the Kamailio config file.
IMPORTANT: the tls module must be loaded before any other Kamailio
module that uses libssl (OpenSSL library). A safe option is to have the
tls module loaded first (be in the first "loadmodule" in Kamailio.cfg).
2. Quick Start
Make sure you have a proper certificate and private key and either use
the certificate and private_key module parameters, or make sure the
certificate and key are in the same PEM file, named cert.pem an placed
in [your-cfg-install-prefix]/etc/kamailio/. Don't forget to load the
tls module and to enable TLS (add enable_tls=yes to your config).
Example 1.1. Quick start config
#...
loadmodule "modules/tls/tls.so"
modparam("tls", "private_key", "./andrei-test.pem")
modparam("tls", "certificate", "./andrei-test.pem")
modparam("tls", "ca_list", "./calist.pem")
enable_tls=yes
route{
# ....
}
3. Important Notes
The TLS module needs some special options enabled when compiling
Kamailio. These options are enabled by default, however in case you're
using a modified Kamailio version or Makefile, make sure that you
enable -DUSE_TLS and -DTLS_HOOKS (or compile with make TLS_HOOKS=1
which will take care of both options).
To quickly check if your Kamailio version was compiled with these
options, run kamailio -V and look for USE_TLS and TLS_HOOKS among the
flags.
This module includes several workarounds for various Openssl bugs (like
compression and Kerberos using the wrong memory allocations functions,
low memory problems a.s.o). On startup it will try to enable the needed
workarounds based on the OpenSSL library version. Each time a known
problem is detected and a workaround is enabled, a message will be
logged. In general it is recommended to compile this module on the same
machine or a similar machine to where kamailio will be run or to link
it statically with libssl. For example if on the compile machine
OpenSSL does not have the Kerberos support enabled, but on the target
machine a Kerberos enabled OpenSSL library is installed, Kamailio
cannot apply the needed workarounds and will refuse to start. The same
thing will happen if the OpenSSL versions are too different (to force
Kamailio startup anyway, see the tls_force_run module parameter).
Compression is fully supported if you have a new enough OpenSSL version
(starting with 0.9.8). Although there are some problems with zlib
compression in currently deployed OpenSSL versions (up to and including
0.9.8d, see openssl bug #1468), the TLS module will automatically
switch to its own fixed version. Note however that starting with
Kamailio 3.1 compression is not enabled by default, due to the huge
extra memory consumption that it causes (about 10x more memory). To
enable it use modparam("tls", "tls_disable_compression", 0) (see
tls_disable_compression).
The TLS module includes workarounds for the following known openssl
bugs:
* openssl #1204 (disable SS_OP_TLS_BLOCK_PADDING_BUG if compression
is enabled, for versions between 0.9.8 and 0.9.8c),
* openssl #1468 (fix zlib compression memory allocation),
* openssl #1467 (kerberos support will be disabled if the openssl
version is less than 0.9.8e-beta1)
* openssl #1491 (stop using tls in low memory situations due to the
very high risk of openssl crashing or leaking memory).
The bug reports can be viewed at http://rt.openssl.org/.
4. Compiling the TLS Module
In most case compiling the TLS module is as simple as:
make -C modules/tls
or
make modules modules=modules/tls
or (compiling whole Kamailio and the tls module)
make all include_modules=tls
.
However in some cases the OpenSSL library requires linking with other
libraries. For example compiling the OpenSSL library with Kerberos and
zlib-shared support will require linking the TLS module with libkrb5
and libz. In this case just add TLS_EXTRA_LIBS="library list" to make's
command line. E.g.:
make TLS_EXTRA_LIBS="-lkrb5 -lz" all include_modules=tls
In general, if Kamailio fails to start with a symbol not found error
when trying to load the TLS module (check the log), it means some
needed library was not linked and it must be added to TLS_EXTRA_LIBS
Elliptic Curve Diffie-Hellman (EDCH)-Ciphers are only supported in
OpenSSL 1.0.0e and later.
5. TLS and Low Memory
The Openssl library doesn't handle low memory situations very well. If
memory allocations start to fail (due to memory shortage), Openssl can
crash or cause memory leaks (making the memory shortage even worse). As
of this writing all Openssl versions were affected (including 0.9.8e),
see Openssl bug #1491. The TLS module has some workarounds for
preventing this problem (see low_mem_treshold1 and low_mem_threshold2),
however starting Kamailio with enough shared memory is higly
recommended. When this is not possible a quick way to significantly
reduce Openssl memory usage it to disable compression (see
tls_disable_compression).
6. TLS Debugging
Debugging messages can be selectively enabled by recompiling the TLS
module with a combination of the following defines:
* TLS_WR_DEBUG - debug messages for the write/send part.
* TLS_RD_DEBUG - debug messages for the read/receive part.
* TLS_BIO_DEBUG - debug messages for the custom BIO.
Example 1.2. Compiling TLS with Debug Messages
make -C modules/tls extra_defs="-DTLS_WR_DEBUG -DTLS_RD_DEBUG"
To change the level at which the debug messages are logged, change the
tls_debug module parameter.
7. Known Limitations
The private key must not be encrypted (Kamailio cannot ask you for a
password on startup).
The TLS certificate verifications ignores the certificate name, Subject
Altname and IP extensions, it just checks if the certificate is signed
by a recognized CA. One can use the select framework to try to overcome
this limitation (check in the script for the contents of various
certificate fields), but this is not only slow, but also not exactly
standard conforming (the verification should happen during TLS
connection establishment and not after).
TLS specific config reloading is not safe, so for now better don't use
it, especially under heavy traffic.
This documentation is incomplete. The provided selects are not
documented. A list with all the ones implemented by the TLS module can
be seen under doc/select_list/select_tls.txt or or
http://sip-router.org/docbook/sip-router/branch/master/select_list/sele
ct_list.html#select_list.tls.
8. Quick Certificate Howto
There are various ways to create, sign certificates and manage small
CAs (Certificate Authorities). If you are in a hurry and everything you
have are the installed OpenSSL libraries and utilities, read on.
Assumptions: we run our own CA.
Warning: in this example no key is encrypted. The client and server
private keys must not be encrypted (Kamailio doesn't support encrypted
keys), so make sure the corresponding files are readable only by
trusted people. You should use a password to protect your CA private
key.
Assumptions
------------
The default openssl configuration (usually /etc/ssl/openssl.cnf)
default_ca section is the one distributed with openssl and uses the default
directories:
...
default_ca = CA_default # The default ca section
[ CA_default ]
dir = ./demoCA # Where everything is kept
certs = $dir/certs # Where the issued certs are kept
crl_dir = $dir/crl # Where the issued crl are kept
database = $dir/index.txt # database index file.
#unique_subject = no # Set to 'no' to allow creation of
# several ctificates with same subject.
new_certs_dir = $dir/newcerts # default place for new certs.
certificate = $dir/cacert.pem # The CA certificate
serial = $dir/serial # The current serial number
crlnumber = $dir/crlnumber # the current CRL number
crl = $dir/crl.pem # The current CRL
private_key = $dir/private/cakey.pem# The private key
RANDFILE = $dir/private/.rand # private random number file
...
If this is not the case create a new OpenSSL config file that uses the above
paths for the default CA and add to all the openssl commands:
-config filename. E.g.:
openssl ca -config my_openssl.cnf -in kamailio1_cert_req.pem -out kamail
io1_cert.pem
Creating the CA certificate
---------------------------
1. Create the CA directory
mkdir ca
cd ca
2. Create the CA directory structure and files (see ca(1))
mkdir demoCA #default CA name, edit /etc/ssl/openssl.cnf
mkdir demoCA/private
mkdir demoCA/newcerts
touch demoCA/index.txt
echo 01 >demoCA/serial
echo 01 >demoCA/crlnumber
2. Create CA private key
openssl genrsa -out demoCA/private/cakey.pem 2048
chmod 600 demoCA/private/cakey.pem
3. Create CA self-signed certificate
openssl req -out demoCA/cacert.pem -x509 -new -key demoCA/private/cake
y.pem
Creating a server/client TLS certificate
----------------------------------------
1. Create a certificate request (and its private key in privkey.pem)
openssl req -out kamailio1_cert_req.pem -new -nodes
WARNING: the organization name should be the same as in the CA certifica
te.
2. Sign it with the CA certificate
openssl ca -in kamailio1_cert_req.pem -out kamailio1_cert.pem
3. Copy kamailio1_cert.pem to your Kamailio configuration dir
Setting Kamailio to use the TLS certificate
---------------------------------------------
1. Create the CA list file:
for each of your CA certificates that you intend to use do:
cat cacert.pem >>calist.pem
2. Copy your Kamailio certificate, private key and ca list file to your
intended machine (preferably in your Kamailio configuration directory,
this is the default place Kamailio searches for).
3. Set up Kamailio.cfg to use the certificate
if your Kamailio certificate name is different from cert.pem or it is no
t
placed in Kamailio cfg. directory, add to your kamailio.cfg:
modparam("tls", "certificate", "/path/cert_file_name")
4. Set up Kamailio to use the private key
if your private key is not contained in the same file as the certificate
(or the certificate name is not the default cert.pem), add to your
Kamailio.cfg:
modparam("tls", "private_key", "/path/private_key_file")
5. Set up Kamailio to use the CA list (optional)
The CA list is not used for your server certificate - it's used to approve ot
her servers
and clients connecting to your server with a client certificate or for approv
ing
a certificate used by a server your server connects to.
add to your Kamailio.cfg:
modparam("tls", "ca_list", "/path/ca_list_file")
6. Set up TLS authentication options:
modparam("tls", "verify_certificate", 1)
modparam("tls", "require_certificate", 1)
(for more information see the module parameters documentation)
Revoking a certificate and using a CRL
--------------------------------------
1. Revoking a certificate:
openssl ca -revoke bad_cert.pem
2. Generate/update the certificate revocation list:
openssl ca -gencrl -out my_crl.pem
3. Copy my_crl.pem to your Kamailio config. dir
4. Set up Kamailio to use the CRL:
modparam("tls", "crl", "path/my_crl.pem")
9. Parameters
9.1. tls_method (string)
9.2. certificate (string)
9.3. private_key (string)
9.4. ca_list (string)
9.5. crl (string)
9.6. verify_certificate (boolean)
9.7. verify_depth (integer)
9.8. require_certificate (boolean)
9.9. cipher_list (string)
9.10. server_name (string)
9.11. send_timeout (int)
9.12. handshake_timeout (int)
9.13. connection_timeout (int)
9.14. tls_disable_compression (boolean)
9.15. ssl_release_buffers (integer)
9.16. ssl_freelist_max_len (integer)
9.17. ssl_max_send_fragment (integer)
9.18. ssl_read_ahead (boolean)
9.19. send_close_notify (boolean)
9.20. con_ct_wq_max (integer)
9.21. ct_wq_max (integer)
9.22. ct_wq_blk_size (integer)
9.23. tls_log (int)
9.24. tls_debug (int)
9.25. low_mem_threshold1 (integer)
9.26. low_mem_threshold2 (integer)
9.27. tls_force_run (boolean)
9.28. session_cache (boolean)
9.29. session_id (str)
9.30. renegotiation (boolean)
9.31. config (string)
9.32. xavp_cfg (string)
9.1. tls_method (string)
Sets the TLS protocol method. Possible values are:
* TLSv1.2 - only TLSv1.2 connections are accepted (available starting
with openssl/libssl v1.0.1e)
* TLSv1.1+ - TLSv1.1 or newer (TLSv1.2, ...) connections are accepted
(available starting with openssl/libssl v1.0.1)
* TLSv1.1 - only TLSv1.1 connections are accepted (available starting
with openssl/libssl v1.0.1)
* TLSv1+ - TLSv1.0 or newer (TLSv1.1, TLSv1.2, ...) connections are
accepted.
* TLSv1 - only TLSv1 (TLSv1.0) connections are accepted. This is the
default value.
* SSLv3 - only SSLv3 connections are accepted. Note: you shouldn't
use SSLv3 for anything which should be secure.
* SSLv2 - only SSLv2 connections, for old clients. Note: you
shouldn't use SSLv2 for anything which should be secure. Newer
versions of libssl don't include support for it anymore.
* SSLv23 - any of the SSLv2, SSLv3 and TLSv1 or newer methods will be
accepted.
From the OpenSSL manual: "A TLS/SSL connection established with
these methods may understand the SSLv3, TLSv1, TLSv1.1 and TLSv1.2
protocols. If extensions are required (for example server name) a
client will send out TLSv1 client hello messages including
extensions and will indicate that it also understands TLSv1.1,
TLSv1.2 and permits a fallback to SSLv3. A server will support
SSLv3, TLSv1, TLSv1.1 and TLSv1.2 protocols. This is the best
choice when compatibility is a concern."
Note: For older libssl version, this option allows SSLv2, with
hello messages done over SSLv2. You shouldn't use SSLv2 or SSLv3
for anything which should be secure.
If RFC 3261 conformance is desired, at least TLSv1 must be used. For
compatibility with older clients SSLv23 is the option, but again, be
aware of security concerns, SSLv2/3 being considered very insecure by
2014. For current information about what's considered secure, please
consult, IETF BCP 195, currently RFC 7525 - "Recommendations for Secure
Use of Transport Layer Security (TLS) and Datagram Transport Layer
Security (DTLS)"
Example 1.3. Set tls_method parameter
...
modparam("tls", "tls_method", "TLSv1")
...
9.2. certificate (string)
Sets the certificate file name. The certificate file can also contain
the private key in PEM format.
If the file name starts with a '.' the path will be relative to the
working directory (at runtime). If it starts with a '/' it will be an
absolute path and if it starts with anything else the path will be
relative to the main config file directory (e.g.: for kamailio -f
/etc/kamailio/kamailio.cfg it will be relative to /etc/kamailio/).
The default value is /usr/local/etc/kamailio/cert.pem
Example 1.4. Set certificate parameter
...
modparam("tls", "certificate", "/usr/local/etc/kamailio/my_certificate.pem")
...
9.3. private_key (string)
Sets the private key file name. The private key can be in the same file
as the certificate or in a separate file, specified by this
configuration parameter.
If the file name starts with a '.' the path will be relative to the
working directory (at runtime). If it starts with a '/' it will be an
absolute path and if it starts with anything else the path will be
relative to the main config file directory (e.g.: for kamailio -f
/etc/kamailio/kamailio.cfg it will be relative to /etc/kamailio/).
Note: the private key can be contained in the same file as the
certificate (just append it to the certificate file, e.g.: cat pkey.pem
>> cert.pem)
The default value is /usr/local/etc/kamailio/cert.pem
Example 1.5. Set private_key parameter
...
modparam("tls", "private", "/usr/local/etc/kamailio/my_pkey.pem")
...
9.4. ca_list (string)
Sets the CA list file name. This file contains a list of all the
trusted CAs certificates used when connecting to other SIP
implementations. If a signature in a certificate chain belongs to one
of the listed CAs, the verification of that certificate will succeed.
If the file name starts with a '.' the path will be relative to the
working directory (at runtime). If it starts with a '/' it will be an
absolute path and if it starts with anything else the path will be
relative to the main config file directory (e.g.: for kamailio -f
/etc/kamailio/kamailio.cfg it will be relative to /etc/kamailio/).
By default the CA file is not set.
An easy way to create the CA list is to append each trusted trusted CA
certificate in the PEM format to one file, e.g.:
for f in trusted_cas/*.pem ; do cat "$f" >> ca_list.pem ; done
See also verify_certificate, verify_depth, require_certificate and crl.
Example 1.6. Set ca_list parameter
...
modparam("tls", "ca_list", "/usr/local/etc/kamailio/ca_list.pem")
...
9.5. crl (string)
Sets the certificate revocation list (CRL) file name. This file
contains a list of revoked certificates. Any attempt to verify a
revoked certificate will fail.
If not set, no CRL list will be used.
If the file name starts with a '.' the path will be relative to the
working directory (at runtime). If it starts with a '/' it will be an
absolute path and if it starts with anything else the path will be
relative to the main config file directory (e.g.: for kamailio -f
/etc/kamailio/kamailio.cfg it will be relative to /etc/kamailio/).
Note
If set, require_certificate should also be set or it will not have any
effect.
By default the CRL file name is not set.
To update the CRL in a running Kamailio, make sure you configure TLS
via a separate TLS config file (the config modparam) and issue a
tls.reload RPC call, e.g.:
$ kamcmd tls.reload
A quick way to create the CRL in PEM format, using OpenSSL is:
$ openssl ca -gencrl -keyfile cacert.key -cert cacert.pem -out my_crl.pem
my_crl.pem will contain the signed list of the revoked certificates.
To revoke a TLS certificate use something like:
$ openssl ca -revoke bad_cert.pem -keyfile cacert.key -cert cacert.pem
and then refresh the crl file using the command above.
To display the CRL contents use:
$ openssl crl -in crl.pem -noout -text
See also ca_list, verify_certificate, verify_depth and
require_certificate.
Example 1.7. Set crl parameter
...
modparam("tls", "crl", "/usr/local/etc/kamailio/crl.pem")
...
9.6. verify_certificate (boolean)
If enabled it will force certificate verification when connecting to
other SIP servers.. For more information see the verify(1) OpenSSL man
page.
Note: the certificate verification will always fail if the ca_list is
empty.
See also: ca_list, require_certificate, verify_depth.
By default the certificate verification is off.
Example 1.8. Set verify_certificate parameter
...
modparam("tls", "verify_certificate", 1)
...
9.7. verify_depth (integer)
Sets how far up the certificate chain will the certificate verification
go in the search for a trusted CA.
See also: ca_list, require_certificate, verify_certificate,
The default value is 9.
Example 1.9. Set verify_depth parameter
...
modparam("tls", "verify_depth", 9)
...
9.8. require_certificate (boolean)
When enabled Kamailio will require a certificate from a client
connecting to the TLS port. If the client does not offer a certificate
and verify_certificate is on, certificate verification will fail.
The default value is off.
Example 1.10. Set require_certificate parameter
...
modparam("tls", "require_certificate", 1)
...
9.9. cipher_list (string)
Sets the list of accepted ciphers. The list consists of cipher strings
separated by colons. For more information on the cipher list format see
the cipher(1) OpenSSL man page.
The default value is not set (all the OpenSSL supported ciphers are
enabled).
Example 1.11. Set cipher_list parameter
...
modparam("tls", "cipher_list", "HIGH")
...
9.10. server_name (string)
Sets the Server Name Indication (SNI) value.
This is a TLS extension enabling one TLS server to serve multiple host
names with unique certificates.
The default value is empty (not set).
Example 1.12. Set server_name parameter
...
modparam("tls", "server_name", "kamailio.org")
...
9.11. send_timeout (int)
This parameter is obsolete and cannot be used in newer TLS versions (>
Kamailio 3.0). In these versions the send_timeout is replaced by
tcp_send_timeout (common with all the tcp connections).
9.12. handshake_timeout (int)
This parameter is obsolete and cannot be used in newer TLS versions (>
Kamailio 3.0). In these versions the handshake_timeout is replaced by
tcp_connect_timeout (common with all the tcp connections).
9.13. connection_timeout (int)
Sets the amount of time after which an idle TLS connection will be
closed, if no I/O ever occurred after the initial open. If an I/O event
occurs, the timeout will be extended with tcp_connection_lifetime. The
value is expressed in seconds.
The default value is 10 min.
If the value set is -1, the connection will never be close on idle.
This setting can be changed also at runtime, via the RPC interface and
config framework. The config variable name is tls.connection_timeout.
Example 1.13. Set connection_timeout parameter
...
modparam("tls", "connection_timeout", 60)
...
Example 1.14. Set tls.connection_timeout at runtime
$ kamcmd cfg.set_now_int tls connection_timeout 180
9.14. tls_disable_compression (boolean)
If set compression over TLS will be disabled. Note that compression
uses a lot of memory (about 10x more then with the compression
disabled), so if you want to minimize memory usage is a good idea to
disable it. TLS compression also expose you for the CRIME security
vulnerability.
By default TLS compression is disabled.
Example 1.15. Set tls_disable_compression parameter
...
modparam("tls", "tls_disable_compression", 0) # enable
...
9.15. ssl_release_buffers (integer)
Release internal OpenSSL read or write buffers as soon as they are no
longer needed. Combined with ssl_freelist_max_len has the potential of
saving a lot of memory ( ~ 32k per connection in the default
configuration, or 16k + ssl_max_send_fragment). For Kamailio versions >
3.0 it makes little sense to disable it (0) since the tls module
already has its own internal buffering.
A value of -1 would not change this option from its openssl default.
Use 0 or 1 for enable/disable.
By default the value is 1 (enabled).
Note
This option is supported only for OpenSSL versions >= 1.0.0. On all the
other versions attempting to change the default will trigger an error.
Example 1.16. Set ssl_release_buffers parameter
modparam("tls", "ssl_release_buffers", 1)
9.16. ssl_freelist_max_len (integer)
Sets the maximum number of free memory chunks, that OpenSSL will keep
per connection. Setting it to 0 would cause any unused memory chunk to
be immediately freed, reducing the memory footprint. A too large value
would result in extra memory consumption.
Should be combined with ssl_release_buffers.
A value of -1 has a special meaning: the OpenSSL default will be used
(no attempt on changing the value will be made). For OpenSSL 1.0 the
internal default is 32.
By default the value is 0 (no freelist).
Note
This option is supported only for OpenSSL versions >= 1.0.0. On all the
other versions attempting to change the default will trigger an error.
Example 1.17. Set ssl_freelist_max_len parameter
modparam("tls", "ssl_freelist_max_len", 0)
9.17. ssl_max_send_fragment (integer)
Sets the maximum number of bytes (from the clear text) sent into one
TLS record. Valid values are between 512 and 16384. Note however that
even valid low values might not be big enough to allow a succesfull
handshake (try minimum 1024).
Lower values would lead to less memory usage, but values lower then the
typical Kamailio write size would incur a slight performance penalty.
Good values are bigger then the size of the biggest SIP packet one
normally expects to forward. For example in most setups 2048 would be a
good value.
Note
Values on the lower side, even if valid (> 512), might not allow for a
succesfull initial handshake. This happens if the certificate does not
fit inside one send fragment. Values lower then 1024 should not be
used. Even with higher values, if the handshake fails, try increasing
the value.
A value of -1 has a special meaning: the OpenSSL default will be used
(no attempt on changing the value will be made).
By default the value is -1 (the OpenSSL default, which at least in
OpenSSL 1.0.0 is ~ 16k).
Note
This option is supported only for OpenSSL versions >= 0.9.9. On all the
other versions attempting to change the default will trigger an error.
Example 1.18. Set ssl_max_send_fragment parameter
modparam("tls", "ssl_max_send_fragment", 4096)
9.18. ssl_read_ahead (boolean)
Enables read ahead, reducing the number of internal OpenSSL BIO read()
calls. This option has only debugging value, in normal circumstances it
should not be changed from the default.
When disabled OpenSSL will make at least 2 BIO read() calls per
received record: one to get the record header and one to get the rest
of the record.
The TLS module buffers internally all read()s and defines its own fast
BIO so enabling this option would only cause more memory consumption
and a minor slow-down (extra memcpy).
A value of -1 has a special meaning: the OpenSSL default will be used
(no attempt on changing the value will be made).
By default the value is 0 (disabled).
Example 1.19. Set ssl_read_ahead parameter
modparam("tls", "ssl_read_ahead", 1)
9.19. send_close_notify (boolean)
Enables/disables sending close notify alerts prior to closing the
corresponding TCP connection. Sending the close notify prior to TCP
shutdown is "nicer" from a TLS point of view, but it has a measurable
performance impact. Default: off. Can be set at runtime
(tls.send_close_notify).
The default value is 0 (off).
It can be changed also at runtime, via the RPC interface and config
framework. The config variable name is tls.send_close_notify.
Example 1.20. Set send_close_notify parameter
...
modparam("tls", "send_close_notify", 1)
...
Example 1.21. Set tls.send_close_notify at runtime
$ kamcmd cfg.set_now_int tls send_close_notify 1
9.20. con_ct_wq_max (integer)
Sets the maximum allowed per connection clear-text send queue size in
bytes. This queue is used when data cannot be encrypted and sent
immediately because of an ongoing TLS level renegotiation.
The default value is 65536 (64 Kb).
It can be changed also at runtime, via the RPC interface and config
framework. The config variable name is tls.con_ct_wq_max.
Example 1.22. Set con_ct_wq_max parameter
...
modparam("tls", "con_ct_wq_max", 1048576)
...
Example 1.23. Set tls.con_ct_wq_max at runtime
$ kamcmd cfg.set_now_int tls con_ct_wq_max 1048576
9.21. ct_wq_max (integer)
Sets the maximum total number of bytes queued in all the clear-text
send queues. These queues are used when data cannot be encrypted and
sent immediately because of an ongoing TLS level renegotiation.
The default value is 10485760 (10 Mb).
It can be changed also at runtime, via the RPC interface and config
framework. The config variable name is tls.ct_wq_max.
Example 1.24. Set ct_wq_max parameter
...
modparam("tls", "ct_wq_max", 4194304)
...
Example 1.25. Set tls.ct_wq_max at runtime
$ kamcmd cfg.set_now_int tls ct_wq_max 4194304
9.22. ct_wq_blk_size (integer)
Minimum block size for the internal clear-text send queues (debugging /
advanced tunning). Good values are multiple of typical datagram sizes.
The default value is 4096.
It can be changed also at runtime, via the RPC interface and config
framework. The config variable name is tls.ct_wq_blk_size.
Example 1.26. Set ct_wq_blk_size parameter
...
modparam("tls", "ct_wq_blk_size", 2048)
...
Example 1.27. Set tls.ct_wq_max at runtime
$ kamcmd cfg.set_now_int tls ct_wq_blk_size 2048
9.23. tls_log (int)
Sets the log level at which TLS related messages will be logged.
The default value is 3 (L_DBG).
It can be changed also at runtime, via the RPC interface and config
framework. The config variable name is tls.log.
Example 1.28. Set tls_log parameter
...
# ignore TLS messages if Kamailio is started with debug less than 10
modparam("tls", "tls_log", 10)
...
Example 1.29. Set tls.log at runtime
$ kamcmd cfg.set_now_int tls log 10