# gtls Network Stream Driver

This network stream driver implements a TLS protected transport via the GnuTLS library.

Available since: 3.19.0 (suggested minimum 3.19.8 and above)

# Supported Driver Modes

- 0 - unencrypted transmission (just like ptcp driver)
- 1 - TLS-protected operation

Note

Mode 0 does not provide any benefit over the ptcp driver. This mode exists for technical reasons, but should not be used. It may be removed in the future.

# Supported Authentication Modes

- anon - anonymous authentication as described in IETF’s draft-ietf-syslog-transport-tls-12 Internet draft
- x509/fingerprint - certificate fingerprint authentication as described in IETF’s draft-ietf-syslog-transport-tls-12 Internet draft
- x509/certvalid - certificate validation only
- x509/name - certificate validation and subject name authentication as described in IETF’s draft-ietf-syslog-transport-tls-12 Internet draft

Note

“anon” does not permit to authenticate the remote peer. As such, this mode is vulnerable to man in the middle attacks as well as unauthorized access. It is recommended NOT to use this mode. A certificate/key does not need to be configured in this authmode.

Note

Anon mode changes in: v8.190 (or above)

- Anonymous Ciphers (DH and ECDH) are available in ANON mode.
    Note: ECDH is not available on GnuTLS Version below 3.x.
- Server does not require a certificate anymore in anon mode.
- If Server has a certificate and the Client does not, the highest possible ciphers will be selected.
- If both Server and Client do not have a certificate, the highest available anon cipher will be used.

x509/certvalid is a nonstandard mode. It validates the remote peers certificate, but does not check the subject name. This is weak authentication that may be useful in scenarios where multiple devices are deployed and it is sufficient proof of authenticity when their certificates are signed by the CA the server trusts. This is better than anon authentication, but still not recommended. Known Problems

Even in x509/fingerprint mode, both the client and server certificate currently must be signed by the same root CA. This is an artifact of the underlying GnuTLS library and the way we use it. It is expected that we can resolve this issue in the future.

# CheckExtendedKeyPurpose

- off - by default this binary argument is turned off, which means that Extended Key Usage extension of GNUTls certificates is ignored in cert validation.
- on - if you turn this option on, it will check that peer’s certificate contains the value for GNUTLS_KP_TLS_WWW_SERVER or GNUTLS_KP_TLS_WWW_CLIENT respectively, depending whether we are on sending or receiving end of a connection.

# PrioritizeSAN

- off - by default this binary argument is turned off, which means that validation of names in certificates goes per older RFC 5280 and either Subject Alternative Name or Common Name match is good and connection is allowed.
- on - if you turn this option on, it will perform stricter name checking as per newer RFC 6125, where, if any SAN is found, contents of CN are completely ignored and name validity is decided based on SAN only.

See also

Help with configuring/using `Rsyslog`:

- Mailing list - best route for general questions
- GitHub: rsyslog source project - detailed questions, reporting issues that are believed to be bugs with `Rsyslog`
- Stack Exchange (View, Ask) - experimental support from rsyslog community

See also

Contributing to `Rsyslog`:

- Source project: rsyslog project README.
- Documentation: rsyslog-doc project README

Copyright 2008-2020 Rainer Gerhards (Großrinderfeld), and Others.