c7n-mailer: Custodian Mailer

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A mailer implementation for Custodian. Outbound mail delivery is still somewhat organization-specific, so this at the moment serves primarily as an example implementation.

The Cloud Custodian Mailer can now be easily run in a Docker container. Click here for details.

Message Relay

Custodian Mailer subscribes to an SQS queue, looks up users, and sends emails via SES, Slack messages, and/or notifications to DataDog or Splunk. Custodian Lambda and instance policies can send messages to the SQS queue. SQS queues should be cross-account enabled for sending between accounts.

Tutorial

Our goal in starting out with the Custodian mailer is to install the mailer, and run a policy that triggers an email to your inbox.

1. Install the mailer on your laptop (if you are not running as a Docker container
   • or use pip install c7n-mailer
2. In your text editor, create a mailer.yml file to hold your mailer config.
3. In the AWS console, create a new standard SQS queue (quick create is fine). Copy the queue URL to queue_url in mailer.yml.
4. In AWS, locate or create a role that has read access to the queue. Grab the role ARN and set it as role in mailer.yml.

There are different notification endpoints options, you can combine both.

Email:

Make sure your email address is verified in SES, and set it as from_address in mailer.yml. By default SES is in sandbox mode where you must verify every individual recipient of emails. If need be, make an AWS support ticket to be taken out of SES sandbox mode.

Your mailer.yml should now look something like this:

queue_url: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test
role: arn:aws:iam::123456790:role/c7n-mailer-test
from_address: you@example.com

You can also set region if you are in a region other than us-east-1 as well as lambda_tags to give the mailer tags.

region: us-east-2
lambda_tags:
  owner: ops

Now let's make a Custodian policy to populate your mailer queue. Create a test-policy.yml file with this content (update to and queue to match your environment)

  policies:
  - name: c7n-mailer-test
    resource: sqs
    filters:
      - "tag:MailerTest": absent
    actions:
      - type: notify
        template: default
        priority_header: '2'
        subject: testing the c7n mailer
        to:
          - you@example.com
        transport:
          type: sqs
          queue: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test

DataDog:

The standard way to do a DataDog integration is use the c7n integration with AWS CloudWatch and use the DataDog integration with AWS to collect CloudWatch metrics. The mailer/messenger integration is only for the case you don't want or you can't use AWS CloudWatch, e.g. in Azure or GCP.

Note this integration requires the additional dependency of Datadog Python bindings:

pip install datadog

Your mailer.yml should now look something like this:

queue_url: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test
role: arn:aws:iam::123456790:role/c7n-mailer-test
datadog_api_key: XXXXXXXXXXXXXXXXXXXXXXXXXXXXX
datadog_application_key: YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

(Also set region if you are in a region other than us-east-1.)

Now, let's make a Custodian policy to populate your mailer queue. Create a test-policy.yml:

policies:
  - name: c7n-mailer-test
    resource: ebs
    filters:
     - Attachments: []
    actions:
      - type: notify
        to:
          - datadog://?metric_name=datadog.metric.name&metric_value_tag=Size
        transport:
          type: sqs
          queue: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test

There is a special to format that specifies Datadog delivery and it includes the Datadog configuration via URL parameters:

• metric_name: is the name of the metrics send to DataDog.
• metric_value_tag: by default the metric value to send to DataDog is 1, but if you want to use one of the tags returned in the policy, you can set it with the attribute metric_value_tag. For example, in the test-policy.yml policy, the value used is the size of the EBS volume. The value must be a number and it will be transformed to a float value.

Slack:

The Custodian mailer supports Slack messaging as a separate notification mechanism for the SQS transport method. To enable Slack integration, you must specify a Slack token in the slack_token field in your mailer.yml file. For example:

queue_url: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test
role: arn:aws:iam::123456790:role/c7n-mailer-test
slack_token: xoxo-token123

To enable Slack messaging, several unique fields are evaluated in the policy, as shown in the below example:

policies:
  - name: c7n-mailer-test
    resource: ebs
    filters:
     - Attachments: []
    actions:
      - type: notify
        slack_template: slack
        slack_msg_color: danger
        to:
          - slack://owners
          - slack://foo@bar.com
          - slack://#custodian-test
          - slack://webhook/#c7n-webhook-test
          - slack://tag/resource_tag
          - https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX
        transport:
          type: sqs
          queue: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test

Slack messages support the use of a unique template field specified in slack_template. This field is unique and usage will not break existing functionality for messages also specifying an email template in the template field. This field is optional, however, and if not specified, the mailer will use the default value slack_default.

The unique template field slack_msg_color can be used to specify a color border for the Slack message. This accepts the Slack presets of danger (red), warning (yellow) and good (green). It can also accept an HTML hex code. See the Slack documentation for details.

Note: if you are using a hex color code, it will need to be wrapped in quotes like so: slack_msg_color: '#4287f51'. Otherwise, the YAML interpreter will consider it a comment.

The Slack integration for c7n-mailer supports several flavors of messaging, listed below. These are not mutually exclusive and any combination of the types can be used, but the preferred method is incoming webhooks.

Slack delivery can also be set via a resource's tag name. For example, using slack://tag/slack_channel will look for a tag name of slack_channel, and if matched on a resource will deliver the message to the value of that resource's tag:

slack_channel:https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX slack_channel:custodian-test owner:foo@bar

Delivery via tag has been tested with webhooks, but it should support all delivery methods.

Splunk HTTP Event Collector (HEC)

The Custodian mailer supports delivery to the HTTP Event Collector (HEC) endpoint of a Splunk instance as a separate notification mechanism for the SES transport method. To enable Splunk HEC integration, you must specify the URL to the HEC endpoint as well as a valid username and token:

queue_url: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test
role: arn:aws:iam::123456790:role/c7n-mailer-test
splunk_hec_url: https://http-inputs-foo.splunkcloud.com/services/collector/event
splunk_hec_token: 268b3cc2-f32e-4a19-a1e8-aee08d86ca7f

To send events for a policy to the Splunk HEC endpoint, add a to address notify action specifying the name of the Splunk index to send events to in the form splunkhec://indexName:

policies:
  - name: c7n-mailer-test
    resource: ebs
    filters:
     - Attachments: []
    actions:
      - type: notify
        to:
          - splunkhec://myIndexName
        transport:
          type: sqs
          queue: https://sqs.us-east-1.amazonaws.com/1234567890/c7n-mailer-test

The splunkhec://indexName address type can be combined in the same notify action with other destination types (e.g. email, Slack, DataDog, etc).

Now run:

c7n-mailer --config mailer.yml --update-lambda && custodian run -c test-policy.yml -s .

Note: You can set the profile via environment variable e.g. export AWS_DEFAULT_PROFILE=foo

You should see output similar to the following:

(env) $ c7n-mailer --config mailer.yml --update-lambda && custodian run -c test-policy.yml -s .
DEBUG:custodian.lambda:Created custodian lambda archive size: 3.01mb
2017-01-12 07:55:16,227: custodian.policy:INFO Running policy c7n-mailer-test resource: sqs region:default c7n:0.8.22.0
2017-01-12 07:55:16,229: custodian.policy:INFO policy: c7n-mailer-test resource:sqs has count:1 time:0.00
2017-01-12 07:55:18,017: custodian.actions:INFO sent message:dead-beef policy:c7n-mailer-test template:default count:1
2017-01-12 07:55:18,017: custodian.policy:INFO policy: c7n-mailer-test action: notify resources: 1 execution_time: 1.79
(env) $

Check the AWS console for a new Lambda named cloud-custodian-mailer. The mailer runs every five minutes, so wait a bit and then look for an email in your inbox. If it doesn't appear, look in the lambda's logs for debugging information. If it does, congratulations! You are off and running with the Custodian mailer.

Usage & Configuration

Once installed you should have a c7n-mailer executable on your path:

(env) $ c7n-mailer
usage: c7n-mailer [-h] -c CONFIG
c7n-mailer: error: argument -c/--config is required
(env) $

Fundamentally, what c7n-mailer does is it deploys a Lambda function (using Mu) based on the configuration you specify in a YAML file. Here is the schema to which the file must conform and here is a description of the options:

Standard Lambda Function Config

Standard Azure Functions Config

Mailer Infrastructure Config

SMTP Config

If smtp_server is unset, c7n_mailer will use AWS SES or Azure SendGrid.

DataDog Config

These fields are not necessary if c7n_mailer is run in a instance/lambda/etc with the DataDog agent.

Slack Config

SendGrid Config

Microsoft Graph Config

Splunk HEC Config

The following configuration items are all optional. The ones marked "Required for Splunk" are only required if you're sending notifications to splunkhec:// destinations.

SDK Config

Secured String

In order to ensure sensitive data is not stored plaintext in a policy, c7n-mailer supports secured strings. You can treat it as a regular string or use secured string features.

AWS

You can use KMS to encrypt your secrets and use encrypted secret in mailer policy. Custodian tries to decrypt the string using KMS, if it fails c7n treats it as a plaintext secret.

 plaintext_secret: <raw_secret>
 secured_string: <encrypted_secret>

Azure

You can store your secrets in Azure Key Vault secrets and reference them from the policy.

  plaintext_secret: <raw_secret>
  secured_string:
    type: azure.keyvault
    secret: https://your-vault.vault.azure.net/secrets/your-secret

Note: secrets.get permission on the KeyVault for the Service Principal is required.

GCP

You can store your secrets as GCP Secret Manager secrets and reference them from the policy.

  plaintext_secret: <raw_secret>
  secured_string:
    type: gcp.secretmanager
    secret: projects/12345678912/secrets/your-secret

An example of an SMTP password set as a secured string:

  smtp_password:
    type: gcp.secretmanager
    secret: projects/59808015552/secrets/smtp_pw

Note: If you do not specify a version, /versions/latest will be appended to your secret location.

Configuring a policy to send email

Outbound email can be added to any policy by including the notify action.

policies:
  - name: bad-apples
    resource: asg
    filters:
     - "tag:ASV": absent
    actions:
      - type: notify
        template: default
        template_format: 'html'
        priority_header: '1'
        subject: fix your tags
        to:
          - resource-owner
        owner_absent_contact:
          - foo@example.com
        transport:
          type: sqs
          queue: https://sqs.us-east-1.amazonaws.com/80101010101/cloud-custodian-message-relay

So breaking it down, you add an action of type notify. You can specify a template that's used to format the email; customizing templates is described below.

The to list specifies the intended recipient for the email. You can specify either an email address, an SNS topic, a Datadog Metric, or a special value. The special values are either

• resource-owner, in which case the email will be sent to the listed OwnerContact tag on the resource that matched the policy, or
• event-owner for push-based/realtime policies that will send to the user that was responsible for the underlying event.
• priority_header to indicate the importance of an email with headers. Different emails clients will display stars, exclamation points or flags depending on the value. Should be an string from 1 to 5.

Both of these special values are best effort, i.e., if no OwnerContact tag is specified then resource-owner email will not be delivered, and in the case of event-owner an instance role or system account will not result in an email.

The optional owner_absent_contact list specifies email addresses to notify only if the resource-owner special option was unable to find any matching owner contact tags.

In addition, you may choose to use a custom tag instead of the default OwnerContact. In order to configure this, the mailer.yaml must be modified to include the contact_tags and the custom tag. The resource-owner will now email the custom tag instead of OwnerContact.

contact_tags:
  - "custom_tag"

For reference purposes, the JSON Schema of the notify action:

{
  "type": "object",
  "required": ["type", "transport", "to"],
  "properties": {
    "type": {"enum": ["notify"]},
    "to": {"type": "array", "items": {"type": "string"}},
    "owner_absent_contact": {"type": "array", "items": {"type": "string"}},
    "subject": {"type": "string"},
    "priority_header": {"type": "string"},
    "template": {"type": "string"},
    "transport": {
      "type": "object",
      "required": ["type", "queue"],
      "properties": {
        "queue": {"type": "string"},
        "region": {"type": "string"},
        "type": {"enum": ["sqs"]}
      }
    }
  }
}

Using on Azure

Requires:

• c7n_azure package. See Installing Azure Plugin
• SendGrid account. See Using SendGrid with Azure
• Azure Storage Queue

The mailer supports an Azure Storage Queue transport and SendGrid delivery on Azure. Configuration for this scenario requires only minor changes from AWS deployments.

You will need to grant Storage Queue Data Contributor role on the Queue for the identity mailer is running under.

The notify action in your policy will reflect transport type asq with the URL to an Azure Storage Queue. For example:

policies:
  - name: azure-notify
    resource: azure.resourcegroup
    description: send a message to a mailer instance
    actions:
      - type: notify
        template: default
        priority_header: '2'
        subject: Hello from C7N Mailer
        to:
          - you@youremail.com
        transport:
          type: asq
          queue: https://storageaccount.queue.core.windows.net/queuename

In your mailer configuration, you'll need to provide your SendGrid API key as well as prefix your queue URL with asq:// to let mailer know what type of queue it is:

queue_url: asq://storageaccount.queue.core.windows.net/queuename
from_address: you@youremail.com
sendgrid_api_key: SENDGRID_API_KEY

The mailer will transmit all messages found on the queue on each execution, and will retry sending 3 times in the event of a failure calling SendGrid. After the retries the queue message will be discarded.

In addition, SendGrid delivery on Azure supports using resource tags to send emails. For example, in the to field:

to:
  - tag:OwnerEmail

This will find the email address associated with the resource's OwnerEmail tag, and send an email to the specified address. If no tag is found, or the associated email address is invalid, no email will be sent.

Deploying Azure Functions

The --update-lambda CLI option will also deploy Azure Functions if you have an Azure mailer configuration.

c7n-mailer --config mailer.yml --update-lambda

where a simple mailer.yml using Consumption functions may look like:

queue_url: asq://storage.queue.core.windows.net/custodian
from_address: foo@mail.com
sendgrid_api_key: <key>
function_properties:
  servicePlan:
    name: 'testmailer1'

Configuring Function Identity

You can configure the service principal used for api calls made by the mailer azure function by specifying an identity configuration under function properties. Mailer supports User Assigned Identities, System Managed Identities, defaulting to an embedding of the cli user's service principals credentials.

When specifying a user assigned identity, unlike in a custodian function policy where simply providing an name is sufficient, the uuid/id and client id of the identity must be provided. You can retrieve this information on the cli using the az identity list.

function_properties:
  identity:
    type: UserAssigned
    id: "/subscriptions/333fd504-7f11-2270-88c8-7325a27f7222/resourcegroups/c7n/providers/Microsoft.ManagedIdentity/userAssignedIdentities/mailer"
    client_id: "b9cb06fa-dfb8-4342-add3-aab5acb2abbc"

A system managed identity can also be used, and the Azure platform will create an identity when the function is provisoned, however the function's identity then needs to be retrieved and mapped to rbac permissions post provisioning, this user management activity must be performed manually.

function_properties:
  identity:
    type: SystemAssigned

Using on GCP

Requires:

• c7n_gcp package. See GCP Getting Started
• google-cloud-secret-manager package, for pulling in secured string values.
• A working SMTP Account.
• GCP Pubsub Subscription

The mailer supports GCP Pubsub transports and SMTP/Email delivery, as well as Datadog and Splunk. Configuration for this scenario requires only minor changes from AWS deployments.

The notify action in your policy will reflect transport type projects with the URL to a GCP Pub/Sub Topic. For example:

policies:
  - name: gcp-notify
    resource: gcp.compute
    description: example policy
    actions:
      - type: notify
        template: default
        priority_header: '2'
        subject: Hello from C7N Mailer
        to:
          - you@youremail.com
        transport:
          type: pubsub
          topic: projects/myproject/topics/mytopic

In your mailer configuration, you'll need to provide your SMTP account information as well as your topic subscription path in the queue_url variable. Please note that the subscription you specify should be subscribed to the topic you assign in your policies' notify action for GCP resources.

queue_url: projects/myproject/subscriptions/mysubscription
from_address: you@youremail.com
# c7n-mailer currently requires a role be present, even if it's empty
role: ""

smtp_server: my.smtp.add.ress
smtp_port: 25
smtp_ssl: true
smtp_username: smtpuser
smtp_password:
  type: gcp.secretmanager
  secret: projects/12345678912/secrets/smtppassword

The mailer will transmit all messages found on the queue on each execution using SMTP/Email delivery.

Deploying GCP Functions

GCP Cloud Functions for c7n-mailer are currently not supported.

Writing an email template

Templates are authored in jinja2. Drop a file with the .j2 extension into the a templates directory, and send a pull request to this repo. You can then reference it in the notify action as the template variable by file name minus extension. Templates ending with .html.j2 are sent as HTML-formatted emails, all others are sent as plain text.

You can use -t or --templates cli argument to pass custom folder with your templates.

The following variables are available when rendering templates:

The following extra global functions are available:

The following extra jinja filters are available:

Developer Install (OS X El Capitan)

Clone the repository:

$ git clone https://github.com/cloud-custodian/cloud-custodian

Install dependencies (with virtualenv):

$ virtualenv c7n_mailer
$ source c7n_mailer/bin/activate
$ cd tools/c7n_mailer
$ pip install -r requirements.txt

Install the extensions:

python setup.py develop

Testing Templates and Recipients

A c7n-mailer-replay entrypoint is provided to assist in testing email notifications and templates. This script operates on an actual SQS message from cloud-custodian itself, which you can either retrieve from the SQS queue or replicate locally. By default it expects the message file to be base64-encoded, gzipped JSON, just like c7n sends to SQS. With the -p | --plain argument, it will expect the message file to contain plain JSON.

c7n-mailer-replay has three main modes of operation:

• With no additional arguments, it will render the template specified by the policy the message is for, and actually send mail from the local machine as c7n-mailer would. This only works with SES, not SMTP.
• With the -T | --template-print argument, it will log the email addresses that would receive mail, and print the rendered message body template to STDOUT.
• With the -d | --dry-run argument, it will print the actual email body (including headers) that would be sent, for each message that would be sent, to STDOUT.

Testing Templates for Azure

The c7n-mailer-replay entrypoint can be used to test templates for Azure with either of the arguments:

• -T | --template-print
• -d | --dry-run

Running c7n-mailer-replay without either of these arguments will throw an error as it will attempt to authorize with AWS.

The following is an example for retrieving a sample message to test against templates:

• Run a policy with the notify action, providing the name of the template to test, to populate the queue.

• Using the azure cli, save the message locally:

$ az storage message get --queue-name <queuename> --account-name <storageaccountname> --query '[].content' > test_message.gz

• The example message can be provided to c7n-mailer-replay by running:

$ c7n-mailer-replay test_message.gz -T --config mailer.yml