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syslog-ng Premium Edition 7.0.12 - Administration Guide

Preface Introduction to syslog-ng The concepts of syslog-ng Installing syslog-ng The syslog-ng PE quick-start guide The syslog-ng PE configuration file Collecting log messages — sources and source drivers
How sources work default-network-drivers: Receive and parse common syslog messages internal: Collecting internal messages file: Collecting messages from text files wildcard-file: Collecting messages from multiple text files network: Collecting messages using the RFC3164 protocol (network() driver) osquery: Collect and parse osquery result logs pipe: Collecting messages from named pipes program: Receiving messages from external applications python: writing server-style Python sources python-fetcher: writing fetcher-style Python sources snmptrap: Read Net-SNMP traps sun-streams: Collecting messages on Sun Solaris syslog: Collecting messages using the IETF syslog protocol (syslog() driver) system: Collecting the system-specific log messages of a platform systemd-journal: Collecting messages from the systemd-journal system log storage systemd-syslog: Collecting systemd messages using a socket tcp, tcp6, udp, udp6: Collecting messages from remote hosts using the BSD syslog protocol unix-stream, unix-dgram: Collecting messages from UNIX domain sockets windowsevent: Collecting Windows event logs
Sending and storing log messages — destinations and destination drivers
elasticsearch: Sending messages directly to Elasticsearch version 1.x elasticsearch2: Sending messages directly to Elasticsearch version 2.0 or higher file: Storing messages in plain-text files hdfs: Storing messages on the Hadoop Distributed File System (HDFS) http: Posting messages over HTTP kafka: Publishing messages to Apache Kafka logstore: Storing messages in encrypted files mongodb: Storing messages in a MongoDB database network: Sending messages to a remote log server using the RFC3164 protocol (network() driver) pipe: Sending messages to named pipes program: Sending messages to external applications python: writing custom Python destinations smtp: Generating SMTP messages (e-mail) from logs splunk-hec: Sending messages to Splunk HTTP Event Collector sql: Storing messages in an SQL database syslog: Sending messages to a remote logserver using the IETF-syslog protocol syslog-ng: Forwarding messages and tags to another syslog-ng node tcp, tcp6, udp, udp6: Sending messages to a remote log server using the legacy BSD-syslog protocol (tcp(), udp() drivers) unix-stream, unix-dgram: Sending messages to UNIX domain sockets usertty: Sending messages to a user terminal — usertty() destination Client-side failover
Routing messages: log paths, flags, and filters Global options of syslog-ng PE TLS-encrypted message transfer Advanced Log Transfer Protocol Reliability and minimizing the loss of log messages Manipulating messages parser: Parse and segment structured messages Processing message content with a pattern database Correlating log messages Enriching log messages with external data Monitoring statistics and metrics of syslog-ng Multithreading and scaling in syslog-ng PE Troubleshooting syslog-ng Best practices and examples The syslog-ng manual pages About us

Configuring TLS on the syslog-ng server

Purpose:

Complete the following steps on the syslog-ng server:

To configure TLS on the syslog-ng clients

  1. Copy the certificate (for example syslog-ng.cert) of the syslog-ng server to the syslog-ng server host, for example into the /opt/syslog-ng/etc/syslog-ng/cert.d directory. The certificate must be a valid X.509 certificate in PEM format.

  2. Copy the CA certificate (for example cacert.pem) of the Certificate Authority that issued the certificate of the syslog-ng clients to the syslog-ng server, for example into the /opt/syslog-ng/etc/syslog-ng/ca.d directory.

    Issue the following command on the certificate: openssl x509 -noout -hash -in cacert.pem The result is a hash (for example, 6d2962a8), a series of alphanumeric characters based on the Distinguished Name of the certificate.

    Issue the following command to create a symbolic link to the certificate that uses the hash returned by the previous command and the .0 suffix.

    ln -s cacert.pem 6d2962a8.0

  3. Copy the private key (for example syslog-ng.key) matching the certificate of the syslog-ng server to the syslog-ng server host, for example into the /opt/syslog-ng/etc/syslog-ng/key.d directory. The key must be in PEM format. If you want to use a password-protected key, see Password-protected keys.

  4. Add a source statement to the syslog-ng configuration file that uses the tls( key-file(key_file_fullpathname) cert-file(cert_file_fullpathname) ) option and specify the key and certificate files. The source must use the source driver (network() or syslog()) matching the destination driver used by the syslog-ng client. Also specify the directory storing the certificate of the CA that issued the client's certificate.

    For the details of the available tls() options, see TLS options.

    Example: A source statement using TLS

    The following source receives log messages encrypted using TLS, arriving to the 1999/TCP port of any interface of the syslog-ng server.

    source demo_tls_source {
        network(ip(0.0.0.0) port(1999)
            transport("tls")
                   tls( key-file("/opt/syslog-ng/etc/syslog-ng/key.d/syslog-ng.key")
                        cert-file("/opt/syslog-ng/etc/syslog-ng/cert.d/syslog-ng.cert")
                        ca-dir("/opt/syslog-ng/etc/syslog-ng/ca.d")) ); };

    A similar source for receiving messages using the IETF-syslog protocol:

    source demo_tls_syslog_source {
                            syslog(ip(0.0.0.0) port(1999)
                            transport("tls")
                            tls( key-file("/opt/syslog-ng/etc/syslog-ng/key.d/syslog-ng.key")
                            cert-file("/opt/syslog-ng/etc/syslog-ng/cert.d/syslog-ng.cert")
                            ca-dir("/opt/syslog-ng/etc/syslog-ng/ca.d")) ); };

    Caution:

    Do not forget to update the certificate and key files when they expire.

Password-protected keys

Starting with syslog-ng PE version 7.0.7, you can use password-protected private keys in the network() and syslog() source and destination drivers.

Restrictions and limitations:
  • Hazard of data loss! If you use password-protected keys, you must provide the passphrase of the password-protected keys every time syslog-ng PE is restarted (syslog-ng PE keeps the passphrases over reloads). The sources and destinations that use these keys will not work until you provide the passwords. Other parts of the syslog-ng PE configuration will be unaffected.

    This means that if you use a password-protected key in a destination, and you use this destination in a log path that has multiple destinations, neither destinations will receive log messages until you provide the password. In such cases, always use disk-based buffering to avoid data loss.

  • The path and the filename of the private key cannot contain whitespaces.

  • Depending on your platform, the number of passwords syslog-ng PE can use at the same time might be limited (for example, on Ubuntu 16.04 you can store 16 passwords if you are running syslog-ng PE as a non-root user). If you use lots of password-protected private keys in your syslog-ng PE configuration, increase this limit using the following command: sudo ulimit -l unlimited

Providing the passwords

The syslog-ng-ctl credentials status command allows you to query the status of the private keys that syslog-ng PE uses in the network() and syslog() drivers. The command returns the list of private keys used, and their status. For example:

syslog-ng-ctl credentials status
Secret store status:
/home/user/ssl_test/client-1/client-encrypted.key SUCCESS

If the status of a key is PENDING, you must provide the passphrase for the key, otherwise syslog-ng PE cannot use it. The sources and destinations that use these keys will not work until you provide the passwords. Other parts of the syslog-ng PE configuration will be unaffected. You must provide the passphrase of the password-protected keys every time syslog-ng PE is restarted.

The following log message also notifies you of PENDING passphrases:

Waiting for password; keyfile='private.key'

You can add the passphrase to a password-protected private key file using the following command. syslog-ng PE will display a prompt for you to enter the passphrase. We recommend that you use this method.

syslog-ng-ctl credentials add --id=<path-to-the-key>

Alternatively, you can include the passphrase in the --secret parameter:

syslog-ng-ctl credentials add --id=<path-to-the-key> --secret=<passphrase-of-the-key>

Or you can pipe the passphrase to the syslog-ng-ctl command, for example:

echo "<passphrase-of-the-key>" | syslog-ng-ctl credentials add --id=<path-to-the-key>

For details on the syslog-ng-ctl credentials command, see The syslog-ng control tool manual page.

TLS options

The syslog-ng application can encrypt incoming and outgoing syslog message flows using TLS if you use the network() or syslog() drivers.

NOTE:

The format of the TLS connections used by syslog-ng is similar to using syslog-ng and stunnel, but the source IP information is not lost.

To encrypt connections, use the transport("tls") and tls() options in the source and destination statements.

The tls() option can include the following settings:

allow-compress()
Accepted values: yes | no
Default: no

Description: Enable on-the-wire compression in TLS communication. Note that this option must be enabled both on the server and the client to have any effect. Enabling compression can significantly reduce the bandwidth required to transport the messages, but can slightly decrease the performance of syslog-ng PE, reducing the number of transferred messages during a given period.

Available in version 7.0.12 and later.

ca-dir()
Accepted values: Directory name
Default: none

Description: Name of a directory, that contains a set of trusted CA certificates in PEM format. The CA certificate files have to be named after the 32-bit hash of the subject's name. This naming can be created using the c_rehash utility in openssl. For an example, see Configuring TLS on the syslog-ng clients. The syslog-ng PE application uses the CA certificates in this directory to validate the certificate of the peer.

cert-file()
Accepted values: Filename
Default: none

Description: Name of a file, that contains an X.509 certificate (or a certificate chain) in PEM format, suitable as a TLS certificate, matching the private key set in the key-file() option. The syslog-ng PE application uses this certificate to authenticate the syslog-ng PE client on the destination server. If the file contains a certificate chain, the file must begin with the certificate of the host, followed by the CA certificate that signed the certificate of the host, and any other signing CAs in order.

cipher-suite()
Accepted values: Name of a cipher, or a colon-separated list
Default: Depends on the OpenSSL version that syslog-ng PE uses

Description: Specifies the cipher, hash, and key-exchange algorithms used for the encryption, for example, ECDHE-ECDSA-AES256-SHA384. The list of available algorithms depends on the version of OpenSSL used to compile syslog-ng PE. To specify multiple ciphers, separate the cipher names with a colon, and enclose the list between double-quotes, for example:

cipher-suite("ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384")
crl-dir()
Accepted values: Directory name
Default: none

Description: Name of a directory that contains the Certificate Revocation Lists for trusted CAs. Similarly to ca-dir() files, use the 32-bit hash of the name of the issuing CAs as filenames. The extension of the files must be .r0.

If the crl-dir() is set, and the peer certificate has been revoked, syslog-ng PE rejects the connection. If the peer certificate has not been revoked, or syslog-ng PE cannot access the CRL, syslog-ng PE accepts the connection.

dhparam-file()
Accepted values: string (filename)
Default: none

Description: Specifies a file containing Diffie-Hellman parameters, generated using the openssl dhparam utility. Note that syslog-ng PE supports only DH parameter files in the PEM format. If you do not set this parameter, syslog-ng PE uses the 2048-bit MODP Group, as described in RFC 3526.

ecdh-curve-list()
Accepted values: string [colon-separated list]
Default: none

Description: A colon-separated list that specifies the curves that are permitted in the connection when using Elliptic Curve Cryptography (ECC).

The syslog-ng PE application automatically uses the highest preference curve that both peers support. If not specified, the list includes every supported curve.

Example:

ecdh-curve-list("prime256v1:secp384r1")

The syslog-ng Premium Edition application currently supports the following curves: sect163k1, sect163r1, sect163r2, sect193r1, sect193r2,, sect233k1, sect233r1, sect239k1, sect283k1, sect283r1,, sect409k1, sect409r1, sect571k1, sect571r1, secp160k1,, secp160r1, secp160r2, secp192k1, prime192v1, secp224k1,, secp224r1, secp256k1, prime256v1, secp384r1, secp521r1,, brainpoolP256r1, brainpoolP384r1, brainpoolP512r1.

key-file()
Accepted values: Filename
Default: none

Description: Path and name of a file that contains a private key in PEM format, suitable as a TLS key. If properly configured, the syslog-ng PE application uses this private key and the matching certificate (set in the cert-file() option) to authenticate the syslog-ng PE client on the destination server.

Starting with syslog-ng PE version 7.0.7, you can use password-protected private keys in the network() and syslog() source and destination drivers. The path and the filename cannot contain whitespaces. For details, see Password-protected keys.

peer-verify()
Accepted values: optional-trusted | optional-untrusted | required-trusted | required-untrusted
Default: required-trusted

Description: Verification method of the peer, the four possible values is a combination of two properties of validation:

  • whether the peer is required to provide a certificate (required or optional prefix), and

  • whether the certificate provided needs to be valid or not.

The following table summarizes the possible options and their results depending on the certificate of the peer.

The remote peer has:
no certificate invalid certificate valid certificate
Local peer-verify() setting optional-untrusted TLS-encryption TLS-encryption TLS-encryption
optional-trusted TLS-encryption rejected connection TLS-encryption
required-untrusted rejected connection TLS-encryption TLS-encryption
required-trusted rejected connection rejected connection TLS-encryption

For untrusted certificates only the existence of the certificate is checked, but it does not have to be valid — syslog-ng accepts the certificate even if it is expired, signed by an unknown CA, or its CN and the name of the machine mismatches.

Caution:

When validating a certificate, the entire certificate chain must be valid, including the CA certificate. If any certificate of the chain is invalid, syslog-ng PE will reject the connection.

ssl-options()
Accepted values: comma-separated list of the following options: no-sslv2, no-sslv3, no-tlsv1, no-tlsv11, no-tlsv12, none
Default: no-sslv2

Description: Sets the specified options of the SSL/TLS protocols. Currently, you can use it to disable specific protocol versions. Note that disabling a newer protocol version (for example, TLSv1.1) does not automatically disable older versions of the same protocol (for example, TLSv1.0). For example, use the following option to permit using only TLSv1.1 or newer:

ssl-options(no-sslv2, no-sslv3, no-tlsv1)

Using ssl-options(none) means that syslog-ng PE does not specify any restrictions on the protocol used. However, in this case, the underlying OpenSSL library can restrict the available protocols, for example, certain OpenSSL versions automatically disable SSLv2.

This option is available in syslog-ng PE 7.0 and newer.

Example: Using ssl-options

The following destination explicitly disables SSL and TLSv1.0

destination demo_tls_destination {
    network("172.16.177.147" port(6514)
    transport("tls")
    tls( ca-dir("/etc/syslog-ng/ca.d")
         key-file("/etc/syslog-ng/cert.d/clientkey.pem")
         cert-file("/etc/syslog-ng/cert.d/clientcert.pem")
         ssl-options(no-sslv2, no-sslv3, no-tlsv1) )
    ); };
trusted-dn()
Accepted values: list of accepted distinguished names
Default: none

Description: To accept connections only from hosts using certain certificates signed by the trusted CAs, list the distinguished names of the accepted certificates in this parameter. For example using trusted-dn("*, O=Example Inc, ST=Some-State, C=*") will accept only certificates issued for the Example Inc organization in Some-State state.

trusted-keys()
Accepted values: list of accepted SHA-1 fingerprints
Default: none

Description: To accept connections only from hosts using certain certificates having specific SHA-1 fingerprints, list the fingerprints of the accepted certificates in this parameter. For example trusted-keys("SHA1:00:EF:ED:A4:CE:00:D1:14:A4:AB:43:00:EF:00:91:85:FF:89:28:8F", "SHA1:0C:42:00:3E:B2:60:36:64:00:E2:83:F0:80:46:AD:00:A8:9D:00:15").

To find the fingerprint of a certificate, you can use the following command: openssl x509 -in <certificate-filename> -sha1 -noout -fingerprint

NOTE:

When using the trusted-keys() and trusted-dn() parameters, note the following:

  • First, the trusted-keys() parameter is checked. If the fingerprint of the peer is listed, the certificate validation is performed.

  • If the fingerprint of the peer is not listed in the trusted-keys() parameter, the trusted-dn() parameter is checked. If the DN of the peer is not listed in the trusted-dn() parameter, the authentication of the peer fails and the connection is closed.

Advanced Log Transfer Protocol

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