in workmail-upstream-gateway-filter/src/app.py [0:0]
def upstream_gateway_handler(email_summary, context):
"""
Upstream Gateway Filtering for Amazon WorkMail
Parameters
----------
email_summary: dict, required
Amazon WorkMail Message Summary Input Format
For more information, see https://docs.aws.amazon.com/workmail/latest/adminguide/lambda.html
{
"summaryVersion": "2019-07-28", # AWS WorkMail Message Summary Version
"envelope": {
"mailFrom" : {
"address" : "from@domain.test" # String containing from email address
},
"recipients" : [ # List of all recipient email addresses
{ "address" : "recipient1@domain.test" },
{ "address" : "recipient2@domain.test" }
]
},
"sender" : {
"address" : "sender@domain.test" # String containing sender email address
},
"subject" : "Hello From Amazon WorkMail!", # String containing email subject (Truncated to first 256 chars)"
"messageId": "00000000-0000-0000-0000-000000000000", # String containing message id for retrieval using workmail flow API
"invocationId": "00000000000000000000000000000000", # String containing the id of this lambda invocation. Useful for detecting retries and avoiding duplication
"flowDirection": "INBOUND", # String indicating direction of email flow. Value is either "INBOUND" or "OUTBOUND"
"truncated": false # boolean indicating if any field in message was truncated due to size limitations
}
context: object, required
Lambda Context runtime methods and attributes
Attributes
----------
context.aws_request_id: str
Lambda request ID
context.client_context: object
Additional context when invoked through AWS Mobile SDK
context.function_name: str
Lambda function name
context.function_version: str
Function version identifier
context.get_remaining_time_in_millis: function
Time in milliseconds before function times out
context.identity:
Cognito identity provider context when invoked through AWS Mobile SDK
context.invoked_function_arn: str
Function ARN
context.log_group_name: str
Cloudwatch Log group name
context.log_stream_name: str
Cloudwatch Log stream name
context.memory_limit_in_mb: int
Function memory
https://docs.aws.amazon.com/lambda/latest/dg/python-context-object.html
Returns
-------
Amazon WorkMail Sync Lambda Response Format
For more information, see https://docs.aws.amazon.com/workmail/latest/adminguide/lambda.html#synchronous-schema
return {
'actions': [ # Required, should contain at least 1 list element
{
'action' : { # Required
'type': 'string', # Required. Can be "BOUNCE", "DROP", "DEFAULT", BYPASS_SPAM_CHECK, or MOVE_TO_JUNK
'parameters': { <various> } # Optional. For bounce, <various> can be {"bounceMessage": "message that goes in bounce mail"}
},
'recipients': list of strings, # Optional. Indicates list of recipients for which this action applies
'default': boolean # Optional. Indicates whether this action applies to all recipients
}
]}
"""
logger.info(email_summary)
# get the environment variables containing the header name and regex to match
filter_header_name = os.getenv('FILTER_HEADER_NAME')
if not filter_header_name:
error_msg = 'FILTER_HEADER_NAME not set in environment. Please follow https://docs.aws.amazon.com/lambda/latest/dg/env_variables.html to set it.'
logger.error(error_msg)
raise ValueError(error_msg)
filter_header_regex = os.getenv('FILTER_HEADER_REGEX')
if not filter_header_regex:
error_msg = 'FILTER_HEADER_REGEX not set in environment. Please follow https://docs.aws.amazon.com/lambda/latest/dg/env_variables.html to set it.'
logger.error(error_msg)
raise ValueError(error_msg)
regexp = re.compile(filter_header_regex)
# get the value of the message header
workmail = boto3.client('workmailmessageflow')
msg_id = email_summary['messageId']
raw_msg = workmail.get_raw_message_content(messageId=msg_id)
parsed_msg = email.message_from_bytes(raw_msg['messageContent'].read())
filter_header_value = parsed_msg.get(filter_header_name)
flow_direction = email_summary['flowDirection']
if flow_direction == 'INBOUND' and filter_header_value:
logger.info(filter_header_name + ": " + filter_header_value)
if regexp.search(filter_header_value):
return {
'actions': [
{
'allRecipients': True, # For all recipients
'action' : { 'type': 'MOVE_TO_JUNK' }
}
]
}
else:
return {
'actions': [
{
'allRecipients': True, # For all recipients
'action' : { 'type': 'BYPASS_SPAM_CHECK' }
}
]
}
logger.info("Default action. Nothing to do.")
return {
'actions': [
{
'allRecipients': True, # For all recipients
'action' : { 'type' : 'DEFAULT' } # let the email be sent normally
}
]
}