libemail

README

A Drop in Replacement for Geneos libemail.so

libemail.so is intended as a drop-in replacement for standard libemail.so with the following extras:

• For e-mail notifications
  • Enhanced, modern SMTP support
  • TLS
  • Authentication
  • Go templates for both text and HTML
  • HTML and CSS support
  • EMail meta parameters are removed from list available to formats
• For other notifications
  • Added function to send a notification message to a msTeams channel

Building

If you do not download a ready compiled binary then you can build from source.

You must have Go 1.17 or later installed as well as make and any other tools required by the CGo toolchain.

git clone https://github.com/itrs-group/cordial.git
cd cordial/libraries/libemail
make

If you do not have make installed you can build using:

go build -buildmode c-shared -o libemail.so *.go

Then copy the resulting libemail.so to a suitable location and add the path to the Gateway configuration. You can replace the libemail.so file in the official distribution but you should probably backup the original file by renaming it:

mv libemail.so libemail.so.orig

Note that the Gateway does not reload any shared libraries it has already loaded and so a Gateway restart may be required to pick up the new library.

Using

As a replacement for libemail.so

The official libemail.so is documented here and all of the parameters are supported.

Note that if you are using this as a literal drop-in replacement you may need to restart the Gateway process to load the new library, if the old one was already loaded from the same location.

New features

The following additional parameters are supported by the SendMail function:

• _SMTP_USERNAME
• _SMTP_PASSWORD
• _SMTP_PASSWORD_FILE Deprecated
• _SMTP_TLS

If _SMTP_USERNAME is set then authentication is attempted. As the Gateway writes all parameters to it's log file, the password should either be encoded using ExpandString or placed in a file with restrictive permissions that can be read by the Gateway process. The _SMTP_PASSWORD_FILE is either and absolute path or a path to a file relative to the working directory of the Gateway. If defined then _SMTP_PASSWORD overrides the value in any file referenced by _SMTP_PASSWORD_FILE.

To use an encoded password it must be in the format ${enc:KEYFILE:CIPHERTEXT}. This is the format supported by ExpandString and can be created using the geneos program or manually by following the instructions in Secure Passwords. Assuming you have created a keyfile and saved it to the default location (e.g. geneos aes new -k ~/.config/geneos/keyfile.aes) then you can generate the value like this:

# first, create a keyfile, if one does not exist
$ geneos aes new -D
$ geneos aes encode -e
Password: [ENTER PASSWORD HERE]
${enc:~/.config/geneos/keyfile.aes:+encs+02554ABDB5474D9FC604CAF63E50918C}

Copy the entire output line to the value for _SMTP_PASSWORD and ensure that the keyfile is accessible to the Gateway process. You can copy the keyfile to a new location, such as the Gateway's working directory, but remember to update the path in the ${enc:...} setting.

Note: Another benefit of using ExpandString encoding is that the Gateway automatically redacts any string that starts +encs+ in it's output, so all the log will show is (literally) _SMTP_PASSWORD=${enc:~/.config/geneos/keyfile.aes:XXX} which can serve as an extra layer of protection against casual viewing of the logs and configuration files.

_SMTP_TLS can be one of default, force or none (case insensitive). default is to try TLS but fall back to plain text depending on the SMTP server.

If you use this library with authentication and connect to a public server, such as GMail or Outlook, then you should always create and use a unique "app password" and never use the real password for the sender account.

GoSendMail function

This is a forward compatible function that accepts almost the standard parameters (except those with FORMAT in the name) above but will also add an HTML part to the EMail.

Go templates

The following new parameters are used to support Go templates - both text and HTML:

• _TEMPLATE_TEXT

  Override the built-in text template. This is now a single block of configurable text and uses Go templates to embed the logic to evaluate different Alert types that was previously performed in code and with multiple formats.

• _TEMPLATE_TEXT_FILE

  Override the build-in text template with the contents of the named file. This takes precedence over _TEMPLATE_TEXT

• _TEMPLATE_TEXT_ONLY

  If this is set (to any value) then the function will send a text-only EMail and not process any HTML or CSS settings

• _TEMPLATE_HTML and _TEMPLATE_HTML_FILE

  Similar to the above, these settings override the default HTML template. The default HTML template is almost identical to the text one except all parameter values are rendered in bold.

• _TEMPLATE_HTML_ONLY

  Not yet implemented This option will send HTML only email and avoids a multipart MIME message.

• _TEMPLATE_CSS and _TEMPLATE_CSS_FILE

  Similar to the above, these settings override the default CSS template. The CSS template is included in the HTML template, whether default or user defined, using the following syntax and should be enclosed in <style type="text/css>...</style> tags:

  {{template "css"}}
  

• _TEMPLATE_LOGO_FILE

  Override the default embedded logo, which is a Material notification icon. This should be a PNG file and is referenced in the HTML as:

  <img src="cid:logo.png" />
  

Note: If you use any of the non-FILE settings then the Gateway will log the full template text in the log each time the GoSendMail function is invoked. This may result is very large log lines. It is suggested you use the _FILE suffixed settings for anything other than very simple templates.

In a future version it is expected that multiple files will be loadable using Go's embed FS features.

Debug

There is one built in _DEBUG parameter but you can also add your own to the template logic and _TEMPLATE_DEBUG has been included in the built-in templates to demonstrate this.

• _DEBUG

  If set to true (case insensitive) prevents EMail meta parameters (e.g. _FROM, _SMTP_SERVER etc.) from being removed from the parameters passed to formats or templates. This includes the plain text password, if provided, so beware. You can then output these values in your custom formats and templates for review.

• _TEMPLATE_DEBUG

  This example parameter outputs a text and HTML table of all parameters, unsorted, which may or may not include the EMail meta-parameters, depending on _DEBUG above. In the built-in templates this has to be either TRUE or true and will not work for True, for example.

GoSendToMsTeamsChannel function

This is a function that sends notification messages to one or multiple Microsoft Teams channels, using the incoming webhook API. A pre-requisite for using this function is to create an incoming webhook for each target channel in Microsoft Teams. See following refs for details:

• https://docs.microsoft.com/en-us/microsoftteams/platform/webhooks-and-connectors/how-to/add-incoming-webhook
• https://techcommunity.microsoft.com/t5/microsoft-365-pnp-blog/how-to-configure-and-use-incoming-webhooks-in-microsoft-teams/ba-p/2051118
• https://docs.microsoft.com/en-us/microsoftteams/platform/webhooks-and-connectors/how-to/connectors-using?tabs=cURL

The following parameters are used to send messages to Microsoft Teams chanela with support for Go templates (both text & HTML):

• _TO

  List of Microsoft Teams incoming webhook URLs, separated by | (pipe) character.

• _SUBJECT

  Similar to the legacy parameter used by the SendMail function. This parameter supports both the Go template & the legacy Geneos formatting.

• _TEMPLATE_HTML_FILE

  Override the built-in template (default) with the contents of the Go HTML template file whose path is defined in this parameter. This takes precedence over _TEMPLATE_HTML, _TEMPLATE_TEXT_FILE, _TEMPLATE_TEXT & _FORMAT.

• _TEMPLATE_HTML

  Override the built-in template (default) with a single block of configurable text using a Go HTML template format. This takes precedence over _TEMPLATE_TEXT_FILE, _TEMPLATE_TEXT & _FORMAT.

• _TEMPLATE_TEXT_FILE Override the built-in template (default) with the contents of the Go text template file whose path is defined in this parameter. This takes precedence over _TEMPLATE_TEXT & _FORMAT.

• _TEMPLATE_TEXT

  Override the built-in template (default) with a single block of configurable text using a Go text template format. This takes precedence over _FORMAT.

• _FORMAT

  Override the built-in template (default) with a single block of configurable text using either a Go template format or a Geneos legacy format.