Microsoft Azure (im_azure)

This module can be used to collect logs from Microsoft Azure applications. It can operate in three different modes to connect to the following data sources:

Azure Table Storage
Azure Blob Storage
Azure Log Analytics workspace

To examine the supported platforms, see the list of installation packages.

Storage setup

For Blob or Table modes, Azure web application logging and storage can be configured from the Azure Management Portal by following these steps:

After logging in to the Portal, open the left portal menu, select Storage accounts, and then select Create.
Create the new storage account, providing a storage account name, region, and redundancy type. Take note of the storage name, you will need to specify this value in the NXLog Agent configuration. More information on the storage settings can be found in the Microsoft documentation on how to Create a storage account.
On the Review + create tab, click Create and wait for storage setup to complete.
Navigate to your app and select App Service logs.
Select On for Application Logging (Blob).
Configure Storage Settings corresponding with the storage account created above. More information on the configuration settings can be found in the Microsoft documentation on how to Enable diagnostic logging for apps.
Confirm the changes by clicking Save, then restart the service. Note that it may take a while for Azure to create the table and/or blob in the storage.

Log Analytics workspace setup

For Analytics mode, an application needs to be registered and granted the necessary permissions to read from the Log Analytics workspace. Follow these steps to create and configure the app from the Azure Management Portal.

After logging in to the Portal, open the left portal menu, and select Azure Active Directory.
Select App registrations and then + New registration.
Provide an app name and select who can use the application, then click Register.
Open the settings for your new app and take note of the Application (client) ID. You will need to specify this value for the ClientID directive.

Grant the app permission to use the Log Analytics API and create a client secret:

From the left menu, select API permissions and then + Add a permission. Select APIs my organization uses and choose Log Analytics API.
Select Application permissions for the type of permission required, and Data.Read for the permission.
Click Add permissions to create the permission.
From the left menu, select Certificates & secrets and then + New client secret. Enter a description and expiration period, then click Add.
Take note of the Value of the new secret, you will need to specify this for the SharedKey directive.

Add the app to your Log Analytics workspace:

Go to your Log Analytics workspace and take note of the Workspace ID. You will need to specify this value for the WorkspaceID directive.
From the left menu, select Access control (IAM). Click + Add and select Add role assignments.
Choose Log Analytics Reader for role, select the application registered above, and click Save.

For more information on the configuration settings see How to: Use the portal to create an Azure AD application in the Microsoft documentation, and the Microsoft Tech Community blog post on how to Access Azure Sentinel Log Analytics via API.

Configuration

The im_azure module accepts the following directives in addition to the common module directives.

Required directives

The following directives are required for the module to start.

Mode

This mandatory directive specifies the type of service the module should connect to. It accepts one of the following values: Table, Blob, Analytics. Each mode requires a corresponding set of mandatory directives.

Table mode directives

The following are mandatory directives when using Table mode.

SharedKey

This directive specifies the authentication key to use for connecting to the Azure Storage account.

StorageName

This directive specifies the name of the storage account to connect to.

TableName

This directive specifies the storage table from which to collect logs.

Blob mode directives

The following are mandatory directives when using Blob mode.

BlobName

This directive specifies either the name of the blob container or the path of a single blob (formatted as container/blob) from which to collect logs.

SharedKey

This directive specifies the authentication key to connect to the Azure Storage account.

StorageName

This directive specifies the name of the storage account to connect to.

Analytics mode directives

The following are mandatory directives when using Analytics mode.

ClientID

This directive specifies the ID of the Microsoft Azure Active Directory application that will be used to authenticate with Azure Active Directory.

SharedKey

This directive specifies the client secret to authenticate with Azure Active Directory.

TableName

This directive specifies the storage table from which to collect logs.

TenantID

This directive specifies the ID of the Azure Active Directory tenant to connect to.

WorkspaceID

This directive specifies the workspace ID of the Log Analytics account from which to collect logs.

HTTPS directives

The following directives configure secure data transfer via HTTPS.

HTTPSAllowExpired

Specifies if the connection should be allowed with an expired certificate. If set to TRUE, the remote host will be able to connect with an expired certificate. The default is FALSE: the certificate must not be expired. This directive is only valid if HTTPSRequireCert is set to TRUE.

HTTPSAllowHostnameValidation

Specifies if the certificate FQDN should be validated against the server hostname or not. If set to TRUE, the connection will only be allowed if the certificate FQDN corresponds to the server hostname. The default value is FALSE: the remote server hostname is not validated.

HTTPSAllowUntrusted

Specifies if the connection should be allowed without certificate verification. If set to TRUE, the connection will be allowed even if the remote host presents an unknown or self-signed certificate. The default value is FALSE: the remote host must present a trusted certificate.

HTTPSCADir

The path to a directory containing certificate authority (CA) certificates. These certificates will be used to verify the certificate presented by the remote host. 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:

$ openssl x509 -hash -noout -in ca.crt

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 host’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 /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.

In addition, Microsoft’s PKI repository contains root certificates for Microsoft services.

HTTPSCAFile

The path of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote host. A remote host’s self-signed certificate (which is not signed by a CA) can be trusted by specifying the remote host certificate itself. In case of certificates signed by an intermediate CA, the certificate specified must contain the complete certificate chain (certificate bundle).

HTTPSCAPattern

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 HTTPSCAThumbprint directive.

Configuration examples:

CAPattern    'Test' + ' ' + 'Root'

CAPattern    $domain

A normal log output example would look like as follows:

matching pattern [DN=CN=Client\.example\.com;.*?SAN=DNS:Client\.example\.com] to certificate [SUBJECT=US, ClientState, ClientCity, ClientCompany, ClientUnit, Client.example.com, CN=Client.example.com; DN=CN=Client.example.com, O=ClientCompany, OU=ClientUnit, L=ClientCity, ST=ClientState, C=US; SAN=DNS:Client.example.com; DNS:www.Client.example.com; IP:127.0.0.3; ]

HTTPSCAThumbprint

This optional directive, supported only on Windows, specifies the thumbprint of the certificate authority (CA) certificate that will be used to verify the certificate presented by the remote host. 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 Agent. This directive is mutually exclusive with the HTTPSCADir and HTTPSCAFile directives.

HTTPSCertFile

The path of the certificate file that will be presented to the remote host during the HTTPS handshake.

HTTPSCertKeyFile

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.

HTTPSCertPattern

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 HTTPSCertThumbprint directive.

Configuration examples:

CertPattern    $hostname + 'Cert'

CertPattern    DN=CN=Client\.example\.com;.*?SAN=DNS:Client\.example\.com

A normal log output example would look like as follows:

matching pattern [DN=CN=Client\.example\.com;.*?SAN=DNS:Client\.example\.com] to certificate [SUBJECT=US, ClientState, ClientCity, ClientCompany, ClientUnit, Client.example.com, CN=Client.example.com; DN=CN=Client.example.com, O=ClientCompany, OU=ClientUnit, L=ClientCity, ST=ClientState, C=US; SAN=DNS:Client.example.com; DNS:www.Client.example.com; IP:127.0.0.3; ]

HTTPSCertThumbprint

This optional directive, supported only on Windows, specifies the thumbprint of the certificate that will be presented to the remote host 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:

$ openssl pkcs12 -export -out server.pfx -inkey server.key -in server.pem

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

If you generate the certificate request using Windows Certificate Manager, enable the Make private key exportable option from the certificate properties.
If you import the certificate with the Windows Certificate Import Wizard, make sure that the Mark this key as exportable option is enabled.
If you migrate the certificate and associated private key from one Windows machine to another, select Yes, export the private key when exporting from the source machine.

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:

HTTPSCertThumbprint    7c2cc5a5fb59d4f46082a510e74df17da95e2152

HTTPSCRLDir

The 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:

$ openssl crl -hash -noout -in crl.pem

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.

HTTPSCRLFile

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:

$ openssl ca -gencrl -out crl.pem

HTTPSDHFile

This optional directive specifies a 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.

HTTPSKeyPass

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:

$ openssl genrsa -des3 -out server.key 2048

This directive is not needed for passwordless private keys.

HTTPSLoadCertificateChains

If set to TRUE, try to load higher-level certificates from the referenced PEM file which may contain only one certificate or the whole chain. The default value is FALSE: certificates will be instead loaded from the operating system certification storage.

This directive is only supported on Windows.

HTTPSRequireCert

Specifies if the remote HTTPS host must present a certificate. If set to TRUE and there is no certificate presented during the connection handshake, the connection will be refused. The default value is TRUE: each connection must use a certificate.

HTTPSSearchAllCertStores

This optional directive, if set to TRUE, enables the loading of all available Windows certificates into NXLog Agent, for use during remote certificate verification. Any required certificates must be added to a Windows certificate store that NXLog Agent can access. This directive is mutually exclusive with the HTTPSCAThumbprint, HTTPSCADir and HTTPSCAFile directives.

This directive is only supported on Windows.

HTTPSSSLCipher

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 RSA:!COMPLEMENTOFALL to include all ciphers with RSA authentication but leave out ciphers without encryption.

If RSA or DSA ciphers with Diffie-Hellman key exchange are used, DHFile can be set for specifying custom dh-parameters.

HTTPSSSLCiphersuites

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:

TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256

HTTPSSSLCompression

If set to TRUE, enables 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 (the compression is disabled).

Some Linux packages (for example, Debian) use the OpenSSL library provided by the OS and may not support the zlib compression mechanism. The module will emit a warning on startup if the compression support is missing. The generic deb/rpm packages are bundled with a zlib-enabled libssl library.

HTTPSSSLProtocol

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: SSLv2, SSLv3, TLSv1, TLSv1.1, TLSv1.2 and TLSv1.3. By default, the TLSv1.2 and TLSv1.3 protocols are allowed. Note that the OpenSSL library shipped by Linux distributions may not support SSLv2 and SSLv3, and these will not work even if enabled with this directive.

Sigalgs

The signature algorithm parameter that is being sent to the Windows SSL library. Allowed values depend on the available encryption providers.

This directive is only supported on Windows.

SNI

This optional directive specifies the hostname used for Server Name Indication (SNI) in HTTPS mode. If not specified, it defaults to the hostname in the URL directive.

UseCNGCertificates

If set to TRUE, the module uses the Windows Cryptography API: Next Generation (CNG) to access the private keys associated with certificates identified by a thumbprint.

This directive is only supported on Windows.

Optional directives

LocalPort

This optional directive specifies the local port number of the connection. If not specified, a random high port number will be used, which may be unsuitable for firewalled network environments.

PollInterval

This directive specifies how frequently the module will check for new events, in seconds. If this directive is not specified, it defaults to 1 second. Fractional seconds may be specified (PollInterval 0.5 will check twice every second).

ReadFromLast

This optional boolean directive instructs the module to only read logs that arrive after NXLog Agent is started. This directive comes into effect if a saved position is not found, for example, on the first start, or when the SavePos directive is FALSE. When the SavePos directive is TRUE, and a previously saved position is found, the module will always resume reading from the saved position. If ReadFromLast is FALSE, the module will read all logs from the beginning of the file. This can result in a lot of messages and is usually not the expected behavior. If this directive is not specified, it defaults to TRUE.

The following matrix shows the outcome of this directive in conjunction with the SavePos directive:

ReadFromLast SavePos SavedPosition Outcome

TRUE

Reads events that are logged after NXLog Agent is started.

TRUE

Yes

Reads events from the saved position.

TRUE

FALSE

Reads events that are logged after NXLog Agent is started.

TRUE

FALSE

Yes

Reads events that are logged after NXLog Agent is started.

FALSE

TRUE

Reads all events.

FALSE

TRUE

Yes

Reads events from the saved position.

FALSE

Reads all events.

FALSE

Yes

Reads all events.

SavePos

If this boolean directive is set to TRUE, the file position will be saved when NXLog Agent exits. The file position will be read from the cache file upon startup. The default is TRUE; the file position will be saved if this directive is not specified. This directive affects the outcome of the ReadFromLast directive. The SavePos directive can be overridden by the global NoCache directive.

URL

This directive specifies the URL for connecting to the storage account. The module works in a failover configuration if additional URL directives are specified on new lines. If the first URL is unreachable, the module automatically fails over to the next one. If the last URL is unreachable, the module fails over to the first URL.

If this directive is not specified, it defaults to http://<storagename>.<table|blob>.core.windows.net or to https://api.loganalytics.io depending on the mode. If defined, the value must start with http:// or https://.

HTTP is only supported for table or blob storage and the storage account must have the Require secure transfer for REST API operations security setting disabled. Log Analytics workspaces require HTTPS.

Examples

Example 1. Collecting logs from Azure Table Storage

When in Table mode, im_azure expects a table containing a Message field. The value of this field is made available in the $raw_event field.

This configuration collects logs from a table and converts the data to JSON format using the xm_json extension module. Since the configuration uses a secure URL, the HTTPSCADir is specified and points to a folder that contains the Trusted Root CA certificates on the machine. Alternatively, the HTTPSCAFile directive can be used to specify a file containing the complete certificate chain for the Azure server, or the HTTPSAllowUntrusted directive to accept all certificates.

nxlog.conf

<Extension json>
    Module         xm_json
</Extension>

<Input azure_table>
    Module         im_azure
    Mode           Table

    URL            https://<storage_name>.table.core.windows.net/
    HTTPSCADir     /path/to/trusted/ca/cert/store

    SharedKey      storage_access_key
    StorageName    storage_name
    TableName      storage_table_name

    Exec           $Message = $raw_event; to_json();
</Input>

Input sample

The following is a log record stored in an Azure table. It contains a Message field and thus conforms to im_azure's data format requirements.

PartitionKey	RowKey	Tiestamp	Message
PK1	RK1	2021-08-10T14:14:59.0689266Z	This is test message 1

PartitionKey

RowKey

Tiestamp

Message

PK1

RK1

2021-08-10T14:14:59.0689266Z

This is test message 1

Output sample

The following is the same log message in JSON format after it was processed by NXLog Agent.

{
  "ProcessID": 0,
  "ThreadID": 0,
  "EventTime": "2021-08-10T16:14:59.068926+02:00",
  "EventReceivedTime": "2021-08-18T16:01:59.531635+02:00",
  "SourceModuleName": "azure_table",
  "SourceModuleType": "im_azure",
  "Message": "This is test message 1"
}

Example 2. Collecting logs from Azure Blob Storage

When in Blob mode, im_azure expects data to be in CSV format and contain the following header:

date,level,applicationName,instanceId,eventTickCount,eventId,pid,tid,message,activityId

This configuration collects logs from a blob container and converts the data to JSON format using the xm_json extension module. Since the configuration uses a secure URL, the HTTPSCADir is specified and points to a folder which contains the Trusted Root CA certificates on the machine. Alternatively, the HTTPSCAFile directive can be used to specify a file containing the complete certificate chain for the Azure server, or the HTTPSAllowUntrusted directive to accept all certifcates.

nxlog.conf

<Extension json>
    Module         xm_json
</Extension>

<Input azure_blob>
    Module         im_azure
    Mode           Blob

    URL            https://<storage_name>.blob.core.windows.net/
    HTTPSCADir     /path/to/trusted/ca/cert/store

    BlobName       blob_container_name
    SharedKey      storage_access_key
    StorageName    storage_name

    Exec           $Message = $raw_event; to_json();
</Input>

Input sample

The following is a log record conforming to the CSV data format expected by im_azure.

2021-08-17T18:44:23.369931,2,MyWebApp,003,2,405,1001,1009,This is test message 1,3131

Output sample

The following is the same log record in JSON format after it was processed by NXLog Agent.

{
  "SourceName": "MyWebApp",
  "SeverityValue": 4,
  "Severity": "ERROR",
  "ProcessID": 1001,
  "ThreadID": 1009,
  "EventTime": "2021-08-17T20:44:23.369931+02:00",
  "EventReceivedTime": "2021-08-18T15:30:42.290532+02:00",
  "SourceModuleName": "azure_blob",
  "SourceModuleType": "im_azure",
  "Message": "This is test message 1"
}

Example 3. Collecting logs from Azure Log Analytics workspace

This configuration collects logs from an AuditLogs table in Azure Log Analytics workspace. im_azure receives records from the Log Analytics API in JSON format, which it then parses into structured data and writes each record as a list of key-value pairs to the $raw_event field.

nxlog.conf

<Input azure_workspace>
    Module                 im_azure
    Mode                   Analytics

    # Since the API uses HTTPS, SSL must be configured
    HTTPSAllowUntrusted    TRUE

    ClientID               azure_ad_app_id
    SharedKey              azure_ad_app_secret
    TenantID               azure_ad_tenant_id
    WorkspaceID            workspace_id
    TableName              AuditLogs
</Input>

Output sample

The following is a record from the AuditLog table after it was processed by NXLog Agent.

2021-08-19 12:23:15 nxlog-server INFO TenantId="c1580b88-581a-4cd0-a5c8-a3dd46241740" SourceSystem="Azure AD" TimeGenerated="2021-08-11 18:30:30" ResourceId="/tenants/50fc51f4-477d-4a3c-8ea2-d9306b08461f/providers/Microsoft.aadiam" OperationName="Update application" OperationVersion="1.0" Category="ApplicationManagement" ResultType="" ResultSignature="None" ResultDescription="" DurationMs="0" CorrelationId="947f8943-691f-4393-833f-e64ca47dfd49" Resource="Microsoft.aadiam" ResourceGroup="Microsoft.aadiam" ResourceProvider="" Identity="" Level="4" Location="" AdditionalDetails="[{\"key\":\"User-Agent\",\"value\":\"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.131 Safari/537.36 Edg/92.0.902.67\"}]" Id="Directory_947f8943-691f-4393-833f-e64ca47dfd49_H1F9O_140032957" InitiatedBy="{\"user\":{\"id\":\"f6385f8d-9c20-4235-a2df-17b76774f75f\",\"displayName\":null,\"userPrincipalName\":\"admin@example.com\",\"ipAddress\":null,\"roles\":[]}}" LoggedByService="Core Directory" Result="success" ResultReason="" TargetResources="[{\"id\":\"c118f7ea-f476-478a-9b7a-e6ad2d7b6d77\",\"displayName\":\"nxlog-agent\",\"type\":\"Application\",\"modifiedProperties\":[],\"administrativeUnits\":[]}]" AADTenantId="50fc51f4-477d-4a3c-8ea2-d9306b08461f" ActivityDisplayName="Update application" ActivityDateTime="2021-08-11 18:30:30" AADOperationType="Update" Type="AuditLogs"