def lambda_handler_user(event,
context=None,
ca_private_key_password=None,
entropy_check=True,
config_file=None):
"""
This is the function that will be called when the lambda function starts.
:param event: Dictionary of the json request.
:param context: AWS LambdaContext Object
http://docs.aws.amazon.com/lambda/latest/dg/python-context-object.html
:param ca_private_key_password: For local testing, if the password is provided, skip the KMS
decrypt.
:param entropy_check: For local testing, if set to false, it will skip checking entropy and
won't try to fetch additional random from KMS.
:param config_file: The config file to load the SSH CA private key from, and additional settings.
:return: the SSH Certificate that can be written to id_rsa-cert.pub or similar file.
"""
bless_cache = setup_lambda_cache(ca_private_key_password, config_file)
# AWS Region determines configs related to KMS
region = bless_cache.region
# Load the deployment config values
config = bless_cache.config
logger = set_logger(config)
certificate_validity_before_seconds = config.getint(
BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
certificate_validity_after_seconds = config.getint(
BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
ca_private_key = config.getprivatekey()
certificate_extensions = config.get(BLESS_OPTIONS_SECTION,
CERTIFICATE_EXTENSIONS_OPTION)
# Process cert request
schema = BlessUserSchema(strict=True)
schema.context[USERNAME_VALIDATION_OPTION] = config.get(
BLESS_OPTIONS_SECTION, USERNAME_VALIDATION_OPTION)
schema.context[REMOTE_USERNAMES_VALIDATION_OPTION] = config.get(
BLESS_OPTIONS_SECTION, REMOTE_USERNAMES_VALIDATION_OPTION)
schema.context[REMOTE_USERNAMES_BLACKLIST_OPTION] = config.get(
BLESS_OPTIONS_SECTION, REMOTE_USERNAMES_BLACKLIST_OPTION)
try:
request = schema.load(event).data
except ValidationError as e:
return error_response('InputValidationError', str(e))
logger.info(
'Bless lambda invoked by [user: {0}, bastion_ips:{1}, public_key: {2}, kmsauth_token:{3}]'
.format(request.bastion_user, request.bastion_user_ip,
request.public_key_to_sign, request.kmsauth_token))
# Make sure we have the ca private key password
if bless_cache.ca_private_key_password is None:
return error_response('ClientError',
bless_cache.ca_private_key_password_error)
else:
ca_private_key_password = bless_cache.ca_private_key_password
# if running as a Lambda, we can check the entropy pool and seed it with KMS if desired
if entropy_check:
check_entropy(config, logger)
# cert values determined only by lambda and its configs
current_time = int(time.time())
test_user = config.get(BLESS_OPTIONS_SECTION, TEST_USER_OPTION)
if test_user and (request.bastion_user == test_user
or request.remote_usernames == test_user):
# This is a test call, the lambda will issue an invalid
# certificate where valid_before < valid_after
valid_before = current_time
valid_after = current_time + 1
bypass_time_validity_check = True
else:
valid_before = current_time + certificate_validity_after_seconds
valid_after = current_time - certificate_validity_before_seconds
bypass_time_validity_check = False
# Authenticate the user with KMS, if key is setup
if config.getboolean(KMSAUTH_SECTION, KMSAUTH_USEKMSAUTH_OPTION):
if request.kmsauth_token:
# Allow bless to sign the cert for a different remote user than the name of the user who signed it
allowed_remotes = config.get(
KMSAUTH_SECTION, KMSAUTH_REMOTE_USERNAMES_ALLOWED_OPTION)
if allowed_remotes:
allowed_users = allowed_remotes.split(',')
requested_remotes = request.remote_usernames.split(',')
if allowed_users != ['*'] and not all(
[u in allowed_users for u in requested_remotes]):
return error_response(
'KMSAuthValidationError',
'unallowed remote_usernames [{}]'.format(
request.remote_usernames))
# Check if the user is in the required IAM groups
if config.getboolean(
KMSAUTH_SECTION,
VALIDATE_REMOTE_USERNAMES_AGAINST_IAM_GROUPS_OPTION):
iam = boto3.client('iam')
user_groups = iam.list_groups_for_user(
UserName=request.bastion_user)
group_name_template = config.get(
KMSAUTH_SECTION,
IAM_GROUP_NAME_VALIDATION_FORMAT_OPTION)
for requested_remote in requested_remotes:
required_group_name = group_name_template.format(
requested_remote)
user_is_in_group = any(
group for group in user_groups['Groups']
if group['GroupName'] == required_group_name)
if not user_is_in_group:
return error_response(
'KMSAuthValidationError',
'user {} is not in the {} iam group'.format(
request.bastion_user, required_group_name))
elif request.remote_usernames != request.bastion_user:
return error_response(
'KMSAuthValidationError',
'remote_usernames must be the same as bastion_user')
try:
validator = KMSTokenValidator(
None, config.getkmsauthkeyids(),
config.get(KMSAUTH_SECTION, KMSAUTH_SERVICE_ID_OPTION),
region)
# decrypt_token will raise a TokenValidationError if token doesn't match
validator.decrypt_token(
"2/user/{}".format(request.bastion_user),
request.kmsauth_token)
except TokenValidationError as e:
return error_response('KMSAuthValidationError', str(e))
else:
return error_response('InputValidationError',
'Invalid request, missing kmsauth token')
# Build the cert
ca = get_ssh_certificate_authority(ca_private_key, ca_private_key_password)
cert_builder = get_ssh_certificate_builder(ca, SSHCertificateType.USER,
request.public_key_to_sign)
for username in request.remote_usernames.split(','):
cert_builder.add_valid_principal(username)
cert_builder.set_valid_before(valid_before)
cert_builder.set_valid_after(valid_after)
if certificate_extensions:
for e in certificate_extensions.split(','):
if e:
cert_builder.add_extension(e)
else:
cert_builder.clear_extensions()
# cert_builder is needed to obtain the SSH public key's fingerprint
key_id = 'request[{}] for[{}] from[{}] command[{}] ssh_key[{}] ca[{}] valid_to[{}]'.format(
context.aws_request_id, request.bastion_user, request.bastion_user_ip,
request.command, cert_builder.ssh_public_key.fingerprint,
context.invoked_function_arn,
time.strftime("%Y/%m/%d %H:%M:%S", time.gmtime(valid_before)))
cert_builder.set_critical_option_source_addresses(request.bastion_ips)
cert_builder.set_key_id(key_id)
cert = cert_builder.get_cert_file(bypass_time_validity_check)
logger.info(
'Issued a cert to bastion_ips[{}] for remote_usernames[{}] with key_id[{}] and '
'valid_from[{}])'.format(
request.bastion_ips, request.remote_usernames, key_id,
time.strftime("%Y/%m/%d %H:%M:%S", time.gmtime(valid_after))))
return success_response(cert)
def lambda_handler_host(
event,
context=None,
ca_private_key_password=None,
entropy_check=True,
config_file=None,
):
"""
This is the function that will be called when the lambda function starts.
:param event: Dictionary of the json request.
:param context: AWS LambdaContext Object
http://docs.aws.amazon.com/lambda/latest/dg/python-context-object.html
:param ca_private_key_password: For local testing, if the password is provided, skip the KMS
decrypt.
:param entropy_check: For local testing, if set to false, it will skip checking entropy and
won't try to fetch additional random from KMS.
:param config_file: The config file to load the SSH CA private key from, and additional settings.
:return: the SSH Certificate that can be written to id_rsa-cert.pub or similar file.
"""
bless_cache = setup_lambda_cache(ca_private_key_password, config_file)
# Load the deployment config values
config = bless_cache.config
logger = set_logger(config)
certificate_validity_before_seconds = config.getint(
BLESS_OPTIONS_SECTION, SERVER_CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
certificate_validity_after_seconds = config.getint(
BLESS_OPTIONS_SECTION, SERVER_CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
ca_private_key = config.getprivatekey()
# Process cert request
schema = BlessHostSchema(strict=True)
schema.context[HOSTNAME_VALIDATION_OPTION] = config.get(
BLESS_OPTIONS_SECTION, HOSTNAME_VALIDATION_OPTION)
try:
request = schema.load(event).data
except ValidationError as e:
return error_response("InputValidationError", str(e))
# todo: You'll want to bring your own hostnames validation.
logger.info(
"Bless lambda invoked by [public_key: {}] for hostnames[{}]".format(
request.public_key_to_sign, request.hostnames))
# Make sure we have the ca private key password
if bless_cache.ca_private_key_password is None:
return error_response("ClientError",
bless_cache.ca_private_key_password_error)
else:
ca_private_key_password = bless_cache.ca_private_key_password
# if running as a Lambda, we can check the entropy pool and seed it with KMS if desired
if entropy_check:
check_entropy(config, logger)
# cert values determined only by lambda and its configs
current_time = int(time.time())
valid_before = current_time + certificate_validity_after_seconds
valid_after = current_time - certificate_validity_before_seconds
# Build the cert
ca = get_ssh_certificate_authority(ca_private_key, ca_private_key_password)
cert_builder = get_ssh_certificate_builder(ca, SSHCertificateType.HOST,
request.public_key_to_sign)
for hostname in request.hostnames.split(","):
cert_builder.add_valid_principal(hostname)
cert_builder.set_valid_before(valid_before)
cert_builder.set_valid_after(valid_after)
# cert_builder is needed to obtain the SSH public key's fingerprint
key_id = "request[{}] ssh_key[{}] ca[{}] valid_to[{}]".format(
context.aws_request_id,
cert_builder.ssh_public_key.fingerprint,
context.invoked_function_arn,
time.strftime("%Y/%m/%d %H:%M:%S", time.gmtime(valid_before)),
)
cert_builder.set_key_id(key_id)
cert = cert_builder.get_cert_file()
logger.info("Issued a server cert to hostnames[{}] with key_id[{}] and "
"valid_from[{}])".format(
request.hostnames,
key_id,
time.strftime("%Y/%m/%d %H:%M:%S",
time.gmtime(valid_after)),
))
return success_response(cert)