Microsoft Azure Sentinel (om_azure)
This module forwards logs to Azure services that support the Azure Monitor HTTP Data Collector API. It has been tested with Azure Log Analytics Workspace and Azure Sentinel. It will connect to the URL specified in the configuration in either plain HTTP or HTTPS mode. Event data is sent in batches, reducing the latency caused by the HTTP responses, thus improving Microsoft Azure’s server performance.
Output log format
om_azure forwards log records over HTTP(S) as JSON payload.
The JSON format depends on the value of the $raw_event field.
The module checks if the value of $raw_event is valid JSON and applies the following rules:
-
If it is valid JSON, the value is forwarded as is.
-
If it is not valid JSON, the log record is converted to JSON in the following format:
{ "raw_event": "<json_escaped_raw_event>" }
Additional metadata, including the NXLog-specific fields EventReceivedTime, SourceModuleName, and SourceModuleType, will not be included in the output unless these values have been written to the $raw_event field.
The processing required to achieve this depends on the format of the input data, but generally it means you need to:
-
Parse the log record according to the data format.
-
If the input data is already in JSON format, use parse_json() to parse
$raw_eventinto fields. -
If the input is unstructured plain text data, copy the value of
$raw_eventto a custom field.
-
-
Create and populate any additional custom fields.
-
Use to_json() to convert the fields to JSON format and update the value of
$raw_event.
See the Examples section for NXLog configuration examples of the above.
Configuration
The om_azure module accepts the following directives in addition to the common module directives. The SharedKey, TableName, WorkspaceID and URL directives are required.
Required directives
The following directives are required for the module to start.
This mandatory directive specifies the either the Primary key or the Secondary key (referred to as the shared key in most of the code examples in the Authorization section of the HTTP Data Collector API) of the Microsoft Azure Sentinel. |
|
This mandatory directive specifies the name of Custom Table to which module will be sending log messages.
Azure automatically appends |
|
This mandatory directive specifies the URL for the module to POST the event data. If multiple URL directives are specified on new lines, the module works in a failover configuration. If a destination becomes unavailable, the module automatically fails over to the next one. If the last destination becomes unavailable, the module fails over to the first destination. The module operates in plain HTTP or HTTPS mode depending on the URL provided. If the port number is not explicitly defined in the URL, it defaults to port 80 for HTTP and port 443 for HTTPS. |
|
This mandatory directive specifies the Workspace ID of the Microsoft Azure Sentinel. |
TLS/SSL directives
The following directives are for configuring secure data transfer via TLS/SSL.
This boolean directive specifies whether the connection should be allowed with an expired certificate.
If set to |
|||
This boolean directive specifies that the connection should be allowed regardless of the certificate verification results.
If set to |
|||
HTTP basic authorization username. |
|||
HTTP basic authorization password.
|
|||
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 server. 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 A remote server’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. The default operating system root certificate store will be used if this directive is not specified.
Unix-like operating systems commonly store root certificates in |
|||
This specifies the path of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote server. A remote server’s self-signed certificate (which is not signed by a CA) can be trusted by specifying the remote server certificate itself. In case of certificates signed by an intermediate CA, the certificate specified must contain the complete certificate chain (certificate bundle). |
|||
This optional directive specifies the thumbprint of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote server. The hexadecimal fingerprint string can be copied from Windows Certificate Manager (certmgr.msc). Whitespaces are automatically removed. The certificate must be added to a Windows certificate store that is accessible by NXLog. This directive is only supported on Windows and is mutually exclusive with the HTTPSCADir and HTTPSCAFile directives. |
|||
This specifies the path of the certificate file that will be presented to the remote server during the HTTPS handshake. |
|||
This specifies the path of the private key file that was used to generate the certificate specified by the HTTPSCertFile directive. This is used for the HTTPS handshake. |
|||
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 This directive is only supported on Windows and is mutually exclusive with the HTTPSCertFile and HTTPSCertKeyFile 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 |
|||
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 optional directive specifies file with dh-parameters for Diffie-Hellman key exchange. These parameters can be generated with dhparam(1ssl). If no directive is specified, default parameters will be used. See OpenSSL Wiki for further details. |
|||
This directive specifies the passphrase of the private key specified by the HTTPSCertKeyFile 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 optional boolean directive, when set to |
|||
This optional directive can be used to set the permitted SSL cipher list, overriding the default.
Use the format described in the ciphers(1ssl) man page.
For example specify
|
|||
This optional directive can be used to set the permitted cipher list for TLSv1.3. Use the same format as in the HTTPSSSLCipher directive. Refer to the OpenSSL documentation for a list of valid TLS v1.3 cipher suites. The default value is:
|
|||
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
|
|||
This directive can be used to set the allowed SSL/TLS protocol(s).
It takes a comma-separated list of values which can be any of the following: |
|||
This optional directive specifies the local port number of the connection. If this is not specified, a random high port number will be used, which is not always ideal in firewalled network environments.
|
|||
This optional directive is used to specify the IP address (or hostname) and port number of the HTTP proxy server to be used.
The format is
|
|||
This optional directive sets the reconnect interval in seconds. If it is set, the module attempts to reconnect in every defined second. If it is not set, the reconnect interval will start at 1 second and doubles on every attempt. If the duration of the successful connection is greater than the current reconnect interval, then the reconnect interval will be reset to 1 sec. |
Examples
This configuration reads log messages from file and forwards them via HTTPS. No further processing is done on the log records.
<Input file>
Module im_file
File 'log.txt'
</Input>
define WORKSPACE DUMMY_WORKSPACE
define SHAREDKEY DUMMY_SHAREDKEY
define SUBDOMAIN ods.opinsights.azure.com
define RESOURCE api/logs
define APIVER api-version=2016-04-01
<Output azure>
Module om_azure
URL https://%WORKSPACE%.%SUBDOMAIN%/%RESOURCE%?%APIVER%
WorkspaceID %WORKSPACE%
SharedKey %SHAREDKEY%
TableName "CustomLogs"
HTTPSCAFile %CERTDIR%/ca.pem
AddHeader X-Custom : custom-value
Exec add_http_header("Y-Dynamic", "dynamic value");
</Output>The following is a log record sample read by NXLog.
Mar 24 15:58:53 pc1 systemd[1452]: tracker-store.service: Succeeded.The following is the JSON-formatted log record that will be sent to Microsoft Azure.
{
"raw_event": "Mar 24 15:58:53 pc1 systemd[1452]: tracker-store.service: Succeeded."
}This configuration reads log records from file and adds a $Hostname metadata field.
Log records are converted to JSON using the to_json() procedure of the xm_json module before they are forwarded to Microsoft Azure.
<Extension json>
Module xm_json
</Extension>
<Input file>
Module im_file
File '/path/to/log/file'
Exec $Hostname = hostname();
Exec $Message = $raw_event;
</Input>
define WORKSPACE DUMMY_WORKSPACE
define SHAREDKEY DUMMY_SHAREDKEY
define SUBDOMAIN ods.opinsights.azure.com
define RESOURCE api/logs
define APIVER api-version=2016-04-01
<Output azure>
Module om_azure
URL https://%WORKSPACE%.%SUBDOMAIN%/%RESOURCE%?%APIVER%
HTTPSCAFile %CERTDIR%/ca.pem
WorkspaceID %WORKSPACE%
SharedKey %SHAREDKEY%
TableName "testImFileNative_dir"
Exec to_json();
</Output>The following is a log record sample read by NXLog.
Mar 24 15:58:53 pc1 systemd[1452]: tracker-store.service: Succeeded.The following is the JSON-formatted log record that will be sent to Microsoft Azure.
{
"EventReceivedTime": "2021-03-24T16:52:20.457348+01:00",
"SourceModuleName": "file",
"SourceModuleType": "im_file",
"Hostname": "pc1",
"Message": "Mar 24 15:58:53 pc1 systemd[1452]: tracker-store.service: Succeeded."
}This configuration reads syslog records from file. It uses the parse_syslog() procedure of the xm_syslog module to parse logs into structured data. Log records are then converted to JSON using the to_json() procedure of the xm_json module before they are forwarded to Microsoft Azure.
<Extension syslog>
Module xm_syslog
</Extension>
<Extension json>
Module xm_json
</Extension>
<Input file>
Module im_file
File '/path/to/log/file'
Exec parse_syslog();
</Input>
define WORKSPACE DUMMY_WORKSPACE
define SHAREDKEY DUMMY_SHAREDKEY
define SUBDOMAIN ods.opinsights.azure.com
define RESOURCE api/logs
define APIVER api-version=2016-04-01
<Output azure>
Module om_azure
URL https://%WORKSPACE%.%SUBDOMAIN%/%RESOURCE%?%APIVER%
HTTPSCAFile %CERTDIR%/ca.pem
WorkspaceID %WORKSPACE%
SharedKey %SHAREDKEY%
TableName "testImFileNative_dir"
Exec to_json();
</Output>The following is a log record sample read by NXLog.
Mar 24 15:58:53 pc1 systemd[1452]: tracker-store.service: Succeeded.The following is the JSON-formatted log record that will be sent to Microsoft Azure.
{
"EventReceivedTime": "2021-03-24T16:30:18.920342+01:00",
"SourceModuleName": "file",
"SourceModuleType": "im_file",
"SyslogFacilityValue": 1,
"SyslogFacility": "USER",
"SyslogSeverityValue": 5,
"SyslogSeverity": "NOTICE",
"SeverityValue": 2,
"Severity": "INFO",
"Hostname": "pc1",
"EventTime": "2021-03-24T15:58:53.000000+01:00",
"SourceName": "systemd",
"ProcessID": 1452,
"Message": "tracker-store.service: Succeeded."
}This configuration reads JSON-formatted log records from file.
It uses the parse_json() procedure of the xm_json module to parse logs into structured data and adds an $EventType metadata field.
Log records are then converted back to JSON using the to_json()procedure before they are forwarded to Microsoft Azure.
<Extension json>
Module xm_json
</Extension>
<Input file>
Module im_file
File '/path/to/log/file'
Exec parse_json();
Exec $EventType = "browser-history";
</Input>
define WORKSPACE DUMMY_WORKSPACE
define SHAREDKEY DUMMY_SHAREDKEY
define SUBDOMAIN ods.opinsights.azure.com
define RESOURCE api/logs
define APIVER api-version=2016-04-01
<Output azure>
Module om_azure
URL https://%WORKSPACE%.%SUBDOMAIN%/%RESOURCE%?%APIVER%
HTTPSCAFile %CERTDIR%/ca.pem
WorkspaceID %WORKSPACE%
SharedKey %SHAREDKEY%
TableName "testImFileNative_dir"
Exec to_json();
</Output>The following is a log record sample read by NXLog.
{
"AccessTime": "2021-03-24T16:30:43.000000+01:00",
"URL": "https://nxlog.co",
"Title": "High Performance Log Collection Solutions",
"Username": "user1"
}The following is the JSON-formatted log record that will be sent to the Microsoft Azure Sentinel server.
{
"EventReceivedTime": "2021-03-24T17:14:23.908155+01:00",
"SourceModuleName": "file",
"SourceModuleType": "im_file",
"AccessTime": "2021-03-24T16:30:43.000000+01:00",
"URL": "https://nxlog.co",
"Title": "High Performance Log Collection Solutions",
"Username": "user1",
"EventType": "browser-history"
}
