TLS/SSL (im_ssl)

This directive specifies a path to a directory containing certificate authority (CA) certificates. These certificates will be used to verify the certificate presented by the remote client. The certificate files must be named using the OpenSSL hashed format, i.e. the hash of the certificate followed by .0, .1 etc. To find the hash of a certificate using OpenSSL:

For example, if the certificate hash is e2f14e4a, then the certificate filename should be e2f14e4a.0. If there is another certificate with the same hash then it should be named e2f14e4a.1 and so on.

A remote client’s self-signed certificate (which is not signed by a CA) can also be trusted by including a copy of the certificate in this directory.

NXLog Agent uses the operating system root certificate store if this directive is not specified. Unix-like operating systems commonly store root certificates in /etc/ssl/certs. Windows operating systems use the Windows Certificate Store, while macOS uses the Keychain Access Application as the default certificate store. See Certification Authority (CA) certificates in the NXLog Platform User Guide for more information on using this directive.

This optional directive, supported only on Windows, defines a pattern for locating a suitable CA (Certificate Authority) certificate and its thumbprint in the native Windows Certificate Storage. The pattern must follow PCRE2 rules and use the format "SUBJECT=, CN=, DN=, SAN=" where DN is "CN=, O=, OU=, L=, ST=, C=". During configuration, this directive resolves into the corresponding CAThumbprint value. If multiple matching certificates are found, the first encountered thumbprint is selected. We recommend ensuring that the used certificate storage is well-maintained for optimal performance. This feature is not dynamic; the agent must be restarted if the certificate changes. This directive is mutually exclusive with the CAThumbprint directive.

Configuration examples:

or

A normal log output example would look like as follows:

This optional directive, supported only on Windows, defines a pattern for identifying a corresponding certificate and its thumbprint within the native Windows Certificate Storage. The pattern must follow PCRE2 rules and use the format "SUBJECT=, CN=, DN=, SAN=" where DN is "CN=, O=, OU=, L=, ST=, C=". The certificate must be imported in PFX format into the Local Computer\Personal certificate store for NXLog Agent to locate it. During configuration, this directive is resolved into the corresponding CertThumbprint value. The first found thumbprint will be chosen if multiple certificates match the pattern. We recommend ensuring that the used certificate storage is well-maintained for optimal performance. This feature is not dynamic; the agent must be restarted if the certificate changes. This directive is mutually exclusive with the CertThumbprint directive.

Configuration examples:

or

A normal log output example would look like as follows:

This optional directive specifies the thumbprint of the certificate that will be presented to the remote server during the HTTPS handshake. The hexadecimal fingerprint string can be copied from Windows Certificate Manager (certmgr.msc). Whitespaces are automatically removed. The certificate must be imported to the Local Computer\Personal certificate store in PFX format for NXLog Agent to find it. Run the following command to create a PFX file from the certificate and private key using OpenSSL:

When the global directive UseCNGCertificates is set to FALSE the private key associated with the certificate must be exportable.

On the contrary, when the global directive UseCNGCertificates is set to TRUE the private key associated with the certificate does not have to be exportable. In cases like TPM modules, the private key is always nonexportable.

The usage of the directive is the same in all cases:

This directive is only supported on Windows and is mutually exclusive with the CertFile and CertKeyFile directives.

This directive specifies a path to a directory containing certificate revocation list (CRL) files. These CRL files will be used to check for certificates that were revoked and should no longer be accepted. The files must be named using the OpenSSL hashed format, i.e. the hash of the issuer followed by .r0, .r1 etc. To find the hash of the issuer of a CRL file using OpenSSL:

For example if the hash is e2f14e4a, then the filename should be e2f14e4a.r0. If there is another file with the same hash then it should be named e2f14e4a.r1 and so on.

This specifies the path of the certificate revocation list (CRL) which will be used to check for certificates that have been revoked and should no longer be accepted. Example to generate a CRL file using OpenSSL:

This directive specifies the passphrase of the private key specified by the CertKeyFile directive. A passphrase is required when the private key is encrypted. Example to generate a private key with Triple DES encryption using OpenSSL:

This directive is not needed for passwordless private keys.

This boolean value specifies that the remote client must present a certificate. If set to TRUE and a certificate is not presented during the SSL handshake, the connection will be refused. The default value is TRUE: each connection must use a certificate.

This optional directive enables the logging of the TLS protocol version and cipher suite upon a successful SSL/TLS handshake. Setting this directive to TRUE includes the protocol and cipher used in the log output, which can be helpful for debugging, security audits, and ensuring compliance with encryption standards.

This optional directive can be used to set the permitted cipher list for TLSv1.2 and below, overriding the default. Use the format described in the ciphers(1ssl) man page. For example specify RSA:!COMPLEMENTOFALL to include all ciphers with RSA authentication but leave out ciphers without encryption.

This optional directive can be used to set the permitted cipher list for TLSv1.3. Use the same format as in the SSLCipher directive. Refer to the OpenSSL documentation for a list of valid TLS v1.3 cipher suites. The default value is:

TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256

This boolean directive allows you to enable data compression when sending data over the network. The compression mechanism is based on the zlib compression library. If the directive is not specified, it defaults to FALSE: compression is disabled.

The module accepts connections on the IP address or hostname and port defined here. The default address is localhost and the default port is 514. The port number can be defined by appending it at the end of the hostname or IP address using a colon as a separator (host:port). IPv6 addresses must be enclosed in square brackets ([host]:port). The port section of this directive and the Port directive are mutually exclusive. In case both are defined, the port number defined here takes precedence over a port defined in the Port directive. In case none of them is defined, the default port is used.

To listen on multiple addresses or ports in a single module instance, this directive can be repeated multiple times. Both IPv4 and IPv6 addresses are supported. If a DNS name is used, the number of addresses or cnames should be kept below 16 to avoid potential issues caused by DNS response size limits.

This optional directive can be used to allow IP addresses and/or networks to connect. The directive can be set multiple times to add different IPs or networks to allow. This directive is only active when the ListenAddr directive is present. In the absence of this directive, the BlockIP directive is considered. If both AllowIP and BlockIP are absent, then hosts are not restricted from connecting to a listening module.

The following formats may be used for the AllowIP directive:

This optional directive can be used to deny IP addresses and/or networks to connect. The directive can be set multiple times to add different IPs or networks to deny. This directive is only active when the ListenAddr directive is present. In the absence of this directive, the AllowIP directive is considered. If both AllowIP and BlockIP are absent, then hosts are not restricted from connecting to a listening module.

The following formats may be used for the BlockIP directive:

With this optional directive it is possible to set the maximum number of allowed concurrent/active connections for a listening TCP socket. If not specified, the default value is 4294967295, unlimited. When the limit is reached, the incoming connection will be rejected and an error message is shown in the selflog

This optional directive defines the maximum time in seconds before NXLog Agent closes TCP connections without traffic. The minimum timeout value is 15 seconds. If this directive is not specified, NXLog Agent does not close idle TCP connections.

This optional boolean directive specifies whether the module instance should exclusively bind to the specified port. The default value is FALSE; multiple module instances can bind to the same port.

This optional boolean directive specifies whether multiple im_ssl module instances can listen on the same port. When you enable this directive, multiple instances run in a separate thread, allowing NXLog Agent to process incoming logs simultaneously. See the examples below. The default value is FALSE; multiple instances cannot bind to the same port.