def validate_remote_usernames_against_iam_groups(config: BlessConfig, request: BlessUserRequest):
requested_remotes = request.remote_usernames.split(',')
if config.getboolean(bless_config.BLESS_OPTIONS_SECTION,
bless_config.REMOTE_USERNAMES_AGAINST_IAM_GROUPS_OPTION):
iam = boto3.client('iam')
user_groups = iam.list_groups_for_user(UserName=request.bastion_user)
iam_group_with_full_access = config.get(bless_config.BLESS_OPTIONS_SECTION,
bless_config.FULL_ACCESS_IAM_GROUP_NAME_OPTION)
# if full access iam group is set then check if the user belongs to the group
if iam_group_with_full_access != bless_config.FULL_ACCESS_IAM_GROUP_NAME_DEFAULT:
for group in user_groups['Groups']:
if group['GroupName'] == iam_group_with_full_access:
return None
group_name_template = config.get(bless_config.BLESS_OPTIONS_SECTION,
bless_config.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('ValidationError',
'user {} is not in the {} iam group'.format(
request.bastion_user,
required_group_name))
return None
def __init__(self, ca_private_key_password=None, config_file=None):
"""
:param ca_private_key_password: For local testing, if the password is provided, skip the KMS
decrypt.
:param config_file: The config file to load the SSH CA private key from, and additional settings.
"""
# AWS Region determines configs related to KMS
if 'AWS_REGION' in os.environ:
self.region = os.environ['AWS_REGION']
else:
self.region = 'us-west-2'
# Load the deployment config values
self.config = BlessConfig(self.region, config_file=config_file)
password_ciphertext_b64 = self.config.getpassword()
# decrypt ca private key password
if ca_private_key_password is None:
kms_client = boto3.client('kms', region_name=self.region)
try:
ca_password = kms_client.decrypt(
CiphertextBlob=base64.b64decode(password_ciphertext_b64))
self.ca_private_key_password = ca_password['Plaintext']
except ClientError as e:
self.ca_private_key_password_error = str(e)
else:
self.ca_private_key_password = ca_private_key_password
def test_config_no_password():
with pytest.raises(ValueError) as e:
BlessConfig('bogus-region',
config_file=os.path.join(os.path.dirname(__file__), 'full.cfg'))
assert 'No Region Specific And No Default Password Provided.' == e.value.message
config = BlessConfig('bogus-region',
config_file=os.path.join(os.path.dirname(__file__), 'full-with-default.cfg'))
assert '<INSERT_DEFAULT_KMS_ENCRYPTED_BASE64_ENCODED_PEM_PASSWORD_HERE>' == config.getpassword()
def test_config_no_password():
with pytest.raises(ValueError) as e:
BlessConfig(
"bogus-region",
config_file=os.path.join(os.path.dirname(__file__), "full.cfg"),
)
assert "No Region Specific And No Default Password Provided." == str(
e.value)
config = BlessConfig(
"bogus-region",
config_file=os.path.join(os.path.dirname(__file__),
"full-with-default.cfg"),
)
assert ("<INSERT_DEFAULT_KMS_ENCRYPTED_BASE64_ENCODED_PEM_PASSWORD_HERE>"
== config.getpassword())
def __init__(self, ca_private_key_password=None,
config_file=None):
"""
:param ca_private_key_password: For local testing, if the password is provided, skip the KMS
decrypt.
:param config_file: The config file to load the SSH CA private key from, and additional settings.
"""
# AWS Region determines configs related to KMS
if 'AWS_REGION' in os.environ:
self.region = os.environ['AWS_REGION']
else:
self.region = 'us-west-2'
# Load the deployment config values
self.config = BlessConfig(self.region, config_file=config_file)
password_ciphertext_b64 = self.config.getpassword()
# decrypt ca private key password
if ca_private_key_password is None:
kms_client = boto3.client('kms', region_name=self.region)
try:
ca_password = kms_client.decrypt(
CiphertextBlob=base64.b64decode(password_ciphertext_b64))
self.ca_private_key_password = ca_password['Plaintext']
except ClientError as e:
self.ca_private_key_password_error = str(e)
else:
self.ca_private_key_password = ca_private_key_password
def test_zlib_compression_env_with_uncompressed_key(monkeypatch):
extra_environment_variables = {
'bless_ca_default_password':
'******',
'bless_ca_ca_private_key_compression':
'zlib',
'bless_ca_ca_private_key':
base64.b64encode(b'<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>'),
}
for k, v in extra_environment_variables.items():
monkeypatch.setenv(k, v)
# Create an empty config, everything is set in the environment
config = BlessConfig('us-east-1', config_file='')
with pytest.raises(zlib.error) as e:
config.getprivatekey()
def test_none_compression_env_key(monkeypatch):
extra_environment_variables = {
'bless_ca_default_password':
'******',
'bless_ca_ca_private_key_compression':
'none',
'bless_ca_ca_private_key':
str(base64.b64encode(b'<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>'),
encoding='ascii')
}
for k, v in extra_environment_variables.items():
monkeypatch.setenv(k, v)
# Create an empty config, everything is set in the environment
config = BlessConfig('us-east-1', config_file='')
assert b'<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>' == config.getprivatekey(
)
def test_configs(config, region, expected_cert_valid, expected_entropy_min,
expected_rand_seed, expected_log_level, expected_password,
expected_username_validation, expected_key_compression):
config = BlessConfig(region, config_file=config)
assert expected_cert_valid == config.getint(
BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert expected_cert_valid == config.getint(
BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert expected_entropy_min == config.getint(BLESS_OPTIONS_SECTION,
ENTROPY_MINIMUM_BITS_OPTION)
assert expected_rand_seed == config.getint(BLESS_OPTIONS_SECTION,
RANDOM_SEED_BYTES_OPTION)
assert expected_log_level == config.get(BLESS_OPTIONS_SECTION,
LOGGING_LEVEL_OPTION)
assert expected_password == config.getpassword()
assert expected_username_validation == config.get(
BLESS_OPTIONS_SECTION, USERNAME_VALIDATION_OPTION)
assert expected_key_compression == config.get(
BLESS_CA_SECTION, CA_PRIVATE_KEY_COMPRESSION_OPTION)
def test_wrong_compression_env_key(monkeypatch):
extra_environment_variables = {
'bless_ca_default_password':
'******',
'bless_ca_ca_private_key_compression':
'lzh',
'bless_ca_ca_private_key':
str(base64.b64encode(b'<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>'),
encoding='ascii')
}
for k, v in extra_environment_variables.items():
monkeypatch.setenv(k, v)
# Create an empty config, everything is set in the environment
config = BlessConfig('us-east-1', config_file='')
with pytest.raises(ValueError) as e:
config.getprivatekey()
assert "Compression lzh is not supported." == str(e.value)
def test_none_compression_env_key(monkeypatch):
extra_environment_variables = {
"bless_ca_default_password":
"******",
"bless_ca_ca_private_key_compression":
"none",
"bless_ca_ca_private_key":
str(
base64.b64encode(b"<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>"),
encoding="ascii",
),
}
for k, v in extra_environment_variables.items():
monkeypatch.setenv(k, v)
# Create an empty config, everything is set in the environment
config = BlessConfig("us-east-1", config_file="")
assert b"<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>" == config.getprivatekey(
)
def test_configs(config, region, expected_cert_valid, expected_entropy_min, expected_rand_seed,
expected_log_level, expected_password):
config = BlessConfig(region, config_file=config)
assert expected_cert_valid == config.getint(BLESS_OPTIONS_SECTION,
CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert expected_cert_valid == config.getint(BLESS_OPTIONS_SECTION,
CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert expected_entropy_min == config.getint(BLESS_OPTIONS_SECTION,
ENTROPY_MINIMUM_BITS_OPTION)
assert expected_rand_seed == config.getint(BLESS_OPTIONS_SECTION,
RANDOM_SEED_BYTES_OPTION)
assert expected_log_level == config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
assert expected_password == config.getpassword()
def test_configs(config, region, expected_cert_valid, expected_entropy_min, expected_rand_seed,
expected_log_level, expected_password, expected_username_validation):
config = BlessConfig(region, config_file=config)
assert expected_cert_valid == config.getint(BLESS_OPTIONS_SECTION,
CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert expected_cert_valid == config.getint(BLESS_OPTIONS_SECTION,
CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert expected_entropy_min == config.getint(BLESS_OPTIONS_SECTION,
ENTROPY_MINIMUM_BITS_OPTION)
assert expected_rand_seed == config.getint(BLESS_OPTIONS_SECTION,
RANDOM_SEED_BYTES_OPTION)
assert expected_log_level == config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
assert expected_password == config.getpassword()
assert expected_username_validation == config.get(BLESS_OPTIONS_SECTION,
USERNAME_VALIDATION_OPTION)
def test_kms_config_opts(monkeypatch):
# Default option
config = BlessConfig("us-east-1",
config_file=os.path.join(os.path.dirname(__file__),
'full.cfg'))
assert config.getboolean(KMSAUTH_SECTION,
KMSAUTH_USEKMSAUTH_OPTION) is False
# Config file value
config = BlessConfig("us-east-1",
config_file=os.path.join(os.path.dirname(__file__),
'full-with-kmsauth.cfg'))
assert config.getboolean(KMSAUTH_SECTION,
KMSAUTH_USEKMSAUTH_OPTION) is True
assert config.getboolean(
KMSAUTH_SECTION,
VALIDATE_REMOTE_USERNAMES_AGAINST_IAM_GROUPS_OPTION) is False
def test_empty_config():
with pytest.raises(ValueError):
BlessConfig('us-west-2', config_file='')
def test_empty_config():
with pytest.raises(ValueError):
BlessConfig("us-west-2", config_file="")
def test_configs(config, region, expected_cert_valid, expected_entropy_min,
expected_rand_seed, expected_host_cert_before_valid,
expected_host_cert_after_valid, expected_log_level,
expected_password, expected_username_validation,
expected_hostname_validation, expected_iam_groups_validation,
expected_iam_groups_validation_format,
expected_key_compression):
config = BlessConfig(region, config_file=config)
assert expected_cert_valid == config.getint(
BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert expected_cert_valid == config.getint(
BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert expected_entropy_min == config.getint(BLESS_OPTIONS_SECTION,
ENTROPY_MINIMUM_BITS_OPTION)
assert expected_rand_seed == config.getint(BLESS_OPTIONS_SECTION,
RANDOM_SEED_BYTES_OPTION)
assert expected_host_cert_before_valid == config.getint(
BLESS_OPTIONS_SECTION, SERVER_CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert expected_host_cert_after_valid == config.getint(
BLESS_OPTIONS_SECTION, SERVER_CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert expected_log_level == config.get(BLESS_OPTIONS_SECTION,
LOGGING_LEVEL_OPTION)
assert expected_password == config.getpassword()
assert expected_username_validation == config.get(
BLESS_OPTIONS_SECTION, USERNAME_VALIDATION_OPTION)
assert expected_hostname_validation == config.get(
BLESS_OPTIONS_SECTION, HOSTNAME_VALIDATION_OPTION)
assert expected_iam_groups_validation == config.get(
BLESS_OPTIONS_SECTION, REMOTE_USERNAMES_AGAINST_IAM_GROUPS_OPTION)
assert expected_iam_groups_validation_format == config.get(
BLESS_OPTIONS_SECTION, IAM_GROUP_NAME_VALIDATION_FORMAT_OPTION)
assert expected_key_compression == config.get(
BLESS_CA_SECTION, CA_PRIVATE_KEY_COMPRESSION_OPTION)
def test_config_environment_override(monkeypatch):
extra_environment_variables = {
"bless_options_certificate_validity_after_seconds":
"1",
"bless_options_certificate_validity_before_seconds":
"1",
"bless_options_server_certificate_validity_after_seconds":
"1",
"bless_options_server_certificate_validity_before_seconds":
"1",
"bless_options_hostname_validation":
"disabled",
"bless_options_entropy_minimum_bits":
"2",
"bless_options_random_seed_bytes":
"3",
"bless_options_logging_level":
"DEBUG",
"bless_options_certificate_extensions":
"permit-X11-forwarding",
"bless_options_username_validation":
"debian",
"bless_options_remote_usernames_validation":
"useradd",
"bless_ca_us_east_1_password":
"******",
"bless_ca_default_password":
"******",
"bless_ca_ca_private_key_file":
"<INSERT_YOUR_ENCRYPTED_PEM_FILE_NAME>",
"bless_ca_ca_private_key":
str(
base64.b64encode(b"<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>"),
encoding="ascii",
),
"kms_auth_use_kmsauth":
"True",
"kms_auth_kmsauth_key_id":
"<INSERT_ARN>",
"kms_auth_kmsauth_serviceid":
"bless-test",
}
for k, v in extra_environment_variables.items():
monkeypatch.setenv(k, v)
# Create an empty config, everything is set in the environment
config = BlessConfig("us-east-1", config_file="")
assert 1 == config.getint(BLESS_OPTIONS_SECTION,
CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert 1 == config.getint(BLESS_OPTIONS_SECTION,
CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert 1 == config.getint(BLESS_OPTIONS_SECTION,
SERVER_CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert 1 == config.getint(BLESS_OPTIONS_SECTION,
SERVER_CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert 2 == config.getint(BLESS_OPTIONS_SECTION,
ENTROPY_MINIMUM_BITS_OPTION)
assert 3 == config.getint(BLESS_OPTIONS_SECTION, RANDOM_SEED_BYTES_OPTION)
assert "DEBUG" == config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
assert "permit-X11-forwarding" == config.get(
BLESS_OPTIONS_SECTION, CERTIFICATE_EXTENSIONS_OPTION)
assert "debian" == config.get(BLESS_OPTIONS_SECTION,
USERNAME_VALIDATION_OPTION)
assert "disabled" == config.get(BLESS_OPTIONS_SECTION,
HOSTNAME_VALIDATION_OPTION)
assert "useradd" == config.get(BLESS_OPTIONS_SECTION,
REMOTE_USERNAMES_VALIDATION_OPTION)
assert ("<INSERT_US-EAST-1_KMS_ENCRYPTED_BASE64_ENCODED_PEM_PASSWORD_HERE>"
== config.getpassword())
assert "<INSERT_YOUR_ENCRYPTED_PEM_FILE_NAME>" == config.get(
BLESS_CA_SECTION, CA_PRIVATE_KEY_FILE_OPTION)
assert b"<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>" == config.getprivatekey(
)
assert config.getboolean(KMSAUTH_SECTION, KMSAUTH_USEKMSAUTH_OPTION)
assert "<INSERT_ARN>" == config.get(KMSAUTH_SECTION, KMSAUTH_KEY_ID_OPTION)
assert "bless-test" == config.get(KMSAUTH_SECTION,
KMSAUTH_SERVICE_ID_OPTION)
config.aws_region = "invalid"
assert ("<INSERT_DEFAULT_KMS_ENCRYPTED_BASE64_ENCODED_PEM_PASSWORD_HERE>"
== config.getpassword())
def lambda_handler(event,
context=None,
ca_private_key_password=None,
entropy_check=True,
config_file=os.path.join(os.path.dirname(__file__),
'bless_deploy.cfg')):
"""
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.
"""
# AWS Region determines configs related to KMS
region = os.environ['AWS_REGION']
# Load the deployment config values
config = BlessConfig(region, config_file=config_file)
logging_level = config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
numeric_level = getattr(logging, logging_level.upper(), None)
if not isinstance(numeric_level, int):
raise ValueError('Invalid log level: {}'.format(logging_level))
logger = logging.getLogger()
logger.setLevel(numeric_level)
certificate_validity_window_seconds = config.getint(
BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_WINDOW_SEC_OPTION)
entropy_minimum_bits = config.getint(BLESS_OPTIONS_SECTION,
ENTROPY_MINIMUM_BITS_OPTION)
random_seed_bytes = config.getint(BLESS_OPTIONS_SECTION,
RANDOM_SEED_BYTES_OPTION)
ca_private_key_file = config.get(BLESS_CA_SECTION,
CA_PRIVATE_KEY_FILE_OPTION)
password_ciphertext_b64 = config.getpassword()
# read the private key .pem
with open(os.path.join(os.path.dirname(__file__), ca_private_key_file),
'r') as f:
ca_private_key = f.read()
# decrypt ca private key password
if ca_private_key_password is None:
kms_client = boto3.client('kms', region_name=region)
ca_password = kms_client.decrypt(
CiphertextBlob=base64.b64decode(password_ciphertext_b64))
ca_private_key_password = ca_password['Plaintext']
# if running as a Lambda, we can check the entropy pool and seed it with KMS if desired
if entropy_check:
with open('/proc/sys/kernel/random/entropy_avail', 'r') as f:
entropy = int(f.read())
logger.debug(entropy)
if entropy < entropy_minimum_bits:
logger.info(
'System entropy was {}, which is lower than the entropy_'
'minimum {}. Using KMS to seed /dev/urandom'.format(
entropy, entropy_minimum_bits))
response = kms_client.generate_random(
NumberOfBytes=random_seed_bytes)
random_seed = response['Plaintext']
with open('/dev/urandom', 'w') as urandom:
urandom.write(random_seed)
# Process cert request
schema = BlessSchema(strict=True)
request = schema.load(event).data
# cert values determined only by lambda and its configs
current_time = int(time.time())
valid_before = current_time + certificate_validity_window_seconds
valid_after = current_time - certificate_validity_window_seconds
# 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)
cert_builder.add_valid_principal(request.remote_username)
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[{}] 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_address(request.bastion_ip)
cert_builder.set_key_id(key_id)
cert = cert_builder.get_cert_file()
logger.info(
'Issued a cert to bastion_ip[{}] for the remote_username of [{}] with the key_id[{}] and '
'valid_from[{}])'.format(
request.bastion_ip, request.remote_username, key_id,
time.strftime("%Y/%m/%d %H:%M:%S", time.gmtime(valid_after))))
return cert
def lambda_handler(event, context=None, ca_private_key_password=None,
entropy_check=True,
config_file=os.path.join(os.path.dirname(__file__), 'bless_deploy.cfg')):
"""
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.
"""
# AWS Region determines configs related to KMS
region = os.environ['AWS_REGION']
# Load the deployment config values
config = BlessConfig(region,
config_file=config_file)
logging_level = config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
numeric_level = getattr(logging, logging_level.upper(), None)
if not isinstance(numeric_level, int):
raise ValueError('Invalid log level: {}'.format(logging_level))
logger = logging.getLogger()
logger.setLevel(numeric_level)
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)
entropy_minimum_bits = config.getint(BLESS_OPTIONS_SECTION, ENTROPY_MINIMUM_BITS_OPTION)
random_seed_bytes = config.getint(BLESS_OPTIONS_SECTION, RANDOM_SEED_BYTES_OPTION)
ca_private_key = config.getprivatekey()
password_ciphertext_b64 = config.getpassword()
certificate_extensions = config.get(BLESS_OPTIONS_SECTION, CERTIFICATE_EXTENSIONS_OPTION)
# Process cert request
schema = BlessSchema(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)
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))
# decrypt ca private key password
if ca_private_key_password is None:
kms_client = boto3.client('kms', region_name=region)
try:
ca_password = kms_client.decrypt(
CiphertextBlob=base64.b64decode(password_ciphertext_b64))
ca_private_key_password = ca_password['Plaintext']
except ClientError as e:
return error_response('ClientError', str(e))
# if running as a Lambda, we can check the entropy pool and seed it with KMS if desired
if entropy_check:
with open('/proc/sys/kernel/random/entropy_avail', 'r') as f:
entropy = int(f.read())
logger.debug(entropy)
if entropy < entropy_minimum_bits:
logger.info(
'System entropy was {}, which is lower than the entropy_'
'minimum {}. Using KMS to seed /dev/urandom'.format(
entropy, entropy_minimum_bits))
response = kms_client.generate_random(
NumberOfBytes=random_seed_bytes)
random_seed = response['Plaintext']
with open('/dev/urandom', 'w') as urandom:
urandom.write(random_seed)
# 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.get(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))
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(event, context=None, ca_private_key_password=None, okta_api_token=None,
entropy_check=True,
config_file=os.path.join(os.path.dirname(__file__), 'bless_deploy.cfg')):
"""
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.
"""
# AWS Region determines configs related to KMS
region = os.environ['AWS_REGION']
# Load the deployment config values
config = BlessConfig(region, config_file=config_file)
logger = logging.getLogger(__name__)
logging_level = config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
numeric_level = getattr(logging, logging_level.upper(), None)
if not isinstance(numeric_level, int):
raise ValueError('Invalid log level: {}'.format(logging_level))
logger.setLevel(numeric_level)
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)
certificate_breakglass_validity_before_seconds = config.getint(
BLESS_OPTIONS_SECTION,
CERTIFICATE_BREAKGLASS_BEFORE_SEC_OPTION
)
certificate_breakglass_validity_after_seconds = config.getint(
BLESS_OPTIONS_SECTION,
CERTIFICATE_BREAKGLASS_AFTER_SEC_OPTION
)
breakglass_user = config.get(BLESS_OPTIONS_SECTION, BREAKGLASS_USER_OPTION)
entropy_minimum_bits = config.getint(BLESS_OPTIONS_SECTION, ENTROPY_MINIMUM_BITS_OPTION)
random_seed_bytes = config.getint(BLESS_OPTIONS_SECTION, RANDOM_SEED_BYTES_OPTION)
ca_private_key_file = config.get(BLESS_CA_SECTION, CA_PRIVATE_KEY_FILE_OPTION)
password_ciphertext_b64 = config.getpassword()
certificate_extensions = config.get(BLESS_OPTIONS_SECTION, CERTIFICATE_EXTENSIONS_OPTION)
encrypted_okta_api_token = config.get(OKTA_OPTIONS_SECTION, ENCRYPTED_OKTA_API_TOKEN_OPTION)
okta_base_url = config.get(OKTA_OPTIONS_SECTION, OKTA_BASE_URL_OPTION)
okta_allowed_groups = config.get(OKTA_OPTIONS_SECTION, OKTA_ALLOWED_GROUPS_OPTION)
if okta_allowed_groups:
okta_allowed_groups = set(okta_allowed_groups.split(','))
logger.debug("Allowed okta groups: {}".format(okta_allowed_groups))
# Process cert request
schema = BlessSchema(strict=True)
try:
request = schema.load(event).data
except ValidationError as e:
return error_response('InputValidationError', str(e))
logger.info('Bless lambda invoked by okta user: {}@{}, bastion user: {}, kmsauth_token: {}]'.format(
request.okta_user,
request.bastion_user_ip,
request.bastion_user,
request.kmsauth_token)
)
# read the private key .pem
with open(os.path.join(os.path.dirname(__file__), ca_private_key_file), 'r') as f:
ca_private_key = f.read()
kms_client = boto3.client('kms', region_name=region)
# decrypt ca private key password
if ca_private_key_password is None:
try:
ca_password = kms_client.decrypt(
CiphertextBlob=base64.b64decode(password_ciphertext_b64))
ca_private_key_password = ca_password['Plaintext']
except ClientError as e:
return error_response('ClientError', str(e))
# decrypt okta api token
if okta_api_token is None:
try:
decrypted_okta_api_token = kms_client.decrypt(
CiphertextBlob=base64.b64decode(encrypted_okta_api_token))
okta_api_token = decrypted_okta_api_token['Plaintext']
except ClientError as e:
return error_response('ClientError', str(e))
'''
Fetch user context from Okta
* Username
* Groups
* SSH key
'''
# add extra property to Okta user profile schema
OktaUserProfile.types['public_key'] = str
okta_users_client = okta.UsersClient(okta_base_url, okta_api_token)
user = okta_users_client.get_user(request.okta_user)
groups_info = okta_users_client.get_user_groups(request.okta_user)
groups = set()
for group_info in groups_info:
# Encode unicode response from okta json api as a byte string to ease comparisons
groups.add(group_info.profile.name.encode('utf-8'))
logger.debug('User groups: {}'.format(groups))
allowed_groups = okta_allowed_groups
logger.debug('Whitelist groups: {}'.format(allowed_groups))
logger.debug('Matched groups: {}'.format(groups.intersection(allowed_groups)))
# If the len is greater than 0, breakglass will be false.
breakglass = not len(groups.intersection(allowed_groups))
public_key_to_sign = user.profile.public_key
if public_key_to_sign.startswith(VALID_SSH_RSA_PUBLIC_KEY_HEADER):
pass
else:
raise ValidationError('Invalid SSH Public Key.')
# if running as a Lambda, we can check the entropy pool and seed it with KMS if desired
if entropy_check:
with open('/proc/sys/kernel/random/entropy_avail', 'r') as f:
entropy = int(f.read())
logger.debug(entropy)
if entropy < entropy_minimum_bits:
logger.info(
'System entropy was {}, which is lower than the entropy_'
'minimum {}. Using KMS to seed /dev/urandom'.format(
entropy, entropy_minimum_bits))
response = kms_client.generate_random(
NumberOfBytes=random_seed_bytes)
random_seed = response['Plaintext']
with open('/dev/urandom', 'w') as urandom:
urandom.write(random_seed)
# 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: # Normal user flow
bypass_time_validity_check = False
valid_before = current_time + certificate_validity_after_seconds
valid_after = current_time - certificate_validity_before_seconds
# Authenticate the user with KMS, if key is setup
if config.get(KMSAUTH_SECTION, KMSAUTH_USEKMSAUTH_OPTION):
if request.kmsauth_token:
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.remote_usernames.split(',')[0]),
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,
public_key_to_sign)
# Handle breakglass certificate modifications
if breakglass:
logger.critical('Breakglass access for okta user: {}@{}, bastion user: {}'.format(
request.okta_user,
request.bastion_user_ip,
request.bastion_user)
)
valid_before = current_time + certificate_breakglass_validity_before_seconds
valid_after = current_time - certificate_breakglass_validity_after_seconds
cert_builder.add_valid_principal(breakglass_user)
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 = 'AWS Request ID: {}, User: {}, Source IP: {}, Command: {}, ' \
'Fingerprint: {}, Bless CA: {}, Expires: {}'\
.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 the remote_usernames of [{}] with the 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 test_config_environment_override(monkeypatch):
extra_environment_variables = {
'bless_options_certificate_validity_after_seconds': '1',
'bless_options_certificate_validity_before_seconds': '1',
'bless_options_entropy_minimum_bits': '2',
'bless_options_random_seed_bytes': '3',
'bless_options_logging_level': 'DEBUG',
'bless_options_certificate_extensions': 'permit-X11-forwarding',
'bless_ca_us_east_1_password': '******',
'bless_ca_default_password': '******',
'bless_ca_ca_private_key_file': '<INSERT_YOUR_ENCRYPTED_PEM_FILE_NAME>',
'bless_ca_ca_private_key': base64.b64encode('<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>'),
'kms_auth_use_kmsauth': 'True',
'kms_auth_kmsauth_key_id': '<INSERT_ARN>',
'kms_auth_kmsauth_serviceid': 'bless-test',
}
for k,v in extra_environment_variables.items():
monkeypatch.setenv(k, v)
# Create an empty config, everything is set in the environment
config = BlessConfig('us-east-1', config_file='')
assert 1 == config.getint(BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_AFTER_SEC_OPTION)
assert 1 == config.getint(BLESS_OPTIONS_SECTION, CERTIFICATE_VALIDITY_BEFORE_SEC_OPTION)
assert 2 == config.getint(BLESS_OPTIONS_SECTION, ENTROPY_MINIMUM_BITS_OPTION)
assert 3 == config.getint(BLESS_OPTIONS_SECTION, RANDOM_SEED_BYTES_OPTION)
assert 'DEBUG' == config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
assert 'permit-X11-forwarding' == config.get(BLESS_OPTIONS_SECTION, CERTIFICATE_EXTENSIONS_OPTION)
assert '<INSERT_US-EAST-1_KMS_ENCRYPTED_BASE64_ENCODED_PEM_PASSWORD_HERE>' == config.getpassword()
assert '<INSERT_YOUR_ENCRYPTED_PEM_FILE_NAME>' == config.get(BLESS_CA_SECTION, CA_PRIVATE_KEY_FILE_OPTION)
assert '<INSERT_YOUR_ENCRYPTED_PEM_FILE_CONTENT>' == config.getprivatekey()
assert config.getboolean(KMSAUTH_SECTION, KMSAUTH_USEKMSAUTH_OPTION)
assert '<INSERT_ARN>' == config.get(KMSAUTH_SECTION, KMSAUTH_KEY_ID_OPTION)
assert 'bless-test' == config.get(KMSAUTH_SECTION, KMSAUTH_SERVICE_ID_OPTION)
config.aws_region = 'invalid'
assert '<INSERT_DEFAULT_KMS_ENCRYPTED_BASE64_ENCODED_PEM_PASSWORD_HERE>' == config.getpassword()
def test_config_no_password():
with pytest.raises(ValueError) as e:
BlessConfig('bogus-region',
config_file=os.path.join(os.path.dirname(__file__),
'full.cfg'))
assert 'No Region Specific Password Provided.' == e.value.message
def lambda_handler(event,
context=None,
ca_private_key_password=None,
entropy_check=True,
config_file=os.path.join(os.path.dirname(__file__),
'bless_deploy.cfg')):
"""
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.
"""
# AWS Region determines configs related to KMS
region = os.environ['AWS_REGION']
# Load the deployment config values
config = BlessConfig(region, config_file=config_file)
logging_level = config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
numeric_level = getattr(logging, logging_level.upper(), None)
if not isinstance(numeric_level, int):
raise ValueError('Invalid log level: {}'.format(logging_level))
logger = logging.getLogger()
logger.setLevel(numeric_level)
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)
entropy_minimum_bits = config.getint(BLESS_OPTIONS_SECTION,
ENTROPY_MINIMUM_BITS_OPTION)
random_seed_bytes = config.getint(BLESS_OPTIONS_SECTION,
RANDOM_SEED_BYTES_OPTION)
ca_private_key = config.getprivatekey()
password_ciphertext_b64 = config.getpassword()
certificate_extensions = config.get(BLESS_OPTIONS_SECTION,
CERTIFICATE_EXTENSIONS_OPTION)
# Process cert request
schema = BlessSchema(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)
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))
# decrypt ca private key password
if ca_private_key_password is None:
kms_client = boto3.client('kms', region_name=region)
try:
ca_password = kms_client.decrypt(
CiphertextBlob=base64.b64decode(password_ciphertext_b64))
ca_private_key_password = ca_password['Plaintext']
except ClientError as e:
return error_response('ClientError', str(e))
# if running as a Lambda, we can check the entropy pool and seed it with KMS if desired
if entropy_check:
with open('/proc/sys/kernel/random/entropy_avail', 'r') as f:
entropy = int(f.read())
logger.debug(entropy)
if entropy < entropy_minimum_bits:
logger.info(
'System entropy was {}, which is lower than the entropy_'
'minimum {}. Using KMS to seed /dev/urandom'.format(
entropy, entropy_minimum_bits))
response = kms_client.generate_random(
NumberOfBytes=random_seed_bytes)
random_seed = response['Plaintext']
with open('/dev/urandom', 'w') as urandom:
urandom.write(random_seed)
# 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.get(KMSAUTH_SECTION, KMSAUTH_USEKMSAUTH_OPTION):
if request.kmsauth_token:
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.remote_usernames),
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(event, context=None, ca_private_key_password=None,
entropy_check=True,
config_file=os.path.join(os.path.dirname(__file__), 'bless_deploy.cfg')):
"""
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.
"""
# AWS Region determines configs related to KMS
region = os.environ['AWS_REGION']
# Load the deployment config values
config = BlessConfig(region,
config_file=config_file)
logging_level = config.get(BLESS_OPTIONS_SECTION, LOGGING_LEVEL_OPTION)
numeric_level = getattr(logging, logging_level.upper(), None)
if not isinstance(numeric_level, int):
raise ValueError('Invalid log level: {}'.format(logging_level))
logger = logging.getLogger()
logger.setLevel(numeric_level)
certificate_validity_window_seconds = config.getint(BLESS_OPTIONS_SECTION,
CERTIFICATE_VALIDITY_WINDOW_SEC_OPTION)
entropy_minimum_bits = config.getint(BLESS_OPTIONS_SECTION, ENTROPY_MINIMUM_BITS_OPTION)
random_seed_bytes = config.getint(BLESS_OPTIONS_SECTION, RANDOM_SEED_BYTES_OPTION)
ca_private_key_file = config.get(BLESS_CA_SECTION, CA_PRIVATE_KEY_FILE_OPTION)
password_ciphertext_b64 = config.getpassword()
# read the private key .pem
with open(os.path.join(os.path.dirname(__file__), ca_private_key_file), 'r') as f:
ca_private_key = f.read()
# decrypt ca private key password
if ca_private_key_password is None:
kms_client = boto3.client('kms', region_name=region)
ca_password = kms_client.decrypt(
CiphertextBlob=base64.b64decode(password_ciphertext_b64))
ca_private_key_password = ca_password['Plaintext']
# if running as a Lambda, we can check the entropy pool and seed it with KMS if desired
if entropy_check:
with open('/proc/sys/kernel/random/entropy_avail', 'r') as f:
entropy = int(f.read())
logger.debug(entropy)
if entropy < entropy_minimum_bits:
logger.info(
'System entropy was {}, which is lower than the entropy_'
'minimum {}. Using KMS to seed /dev/urandom'.format(
entropy, entropy_minimum_bits))
response = kms_client.generate_random(
NumberOfBytes=random_seed_bytes)
random_seed = response['Plaintext']
with open('/dev/urandom', 'w') as urandom:
urandom.write(random_seed)
# Process cert request
schema = BlessSchema(strict=True)
request = schema.load(event).data
# cert values determined only by lambda and its configs
current_time = int(time.time())
valid_before = current_time + certificate_validity_window_seconds
valid_after = current_time - certificate_validity_window_seconds
# 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)
cert_builder.add_valid_principal(request.remote_username)
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[{}] 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_address(request.bastion_ip)
cert_builder.set_key_id(key_id)
cert = cert_builder.get_cert_file()
logger.info(
'Issued a cert to bastion_ip[{}] for the remote_username of [{}] with the key_id[{}] and '
'valid_from[{}])'.format(
request.bastion_ip, request.remote_username, key_id,
time.strftime("%Y/%m/%d %H:%M:%S", time.gmtime(valid_after))))
return cert
