aws_encryption_sdk.internal.utils¶

Helper utility functions for AWS Encryption SDK.

Functions

`content_type`(frame_length)	Returns the appropriate content type based on the frame length.
`extend_user_agent_suffix`(user_agent, suffix)	Adds a suffix to the provided user agent.
`get_aad_content_string`(content_type, …)	Prepares the appropriate Body AAD Value for a message body.
`message_id`()	Generates a new message ID.
`prep_stream_data`(data)	Takes an input str, bytes, io.IOBase, or file object and returns an appropriate stream for _EncryptionStream objects.
`prepare_data_keys`(primary_master_key, …)	Prepares a DataKey to be used for encrypting message and list of EncryptedDataKey objects to be serialized into header.
`source_data_key_length_check`(…)	Validates that the supplied source_data_key’s data_key is the correct length for the supplied algorithm’s kdf_input_len value.
`validate_frame_length`(frame_length, algorithm)	Validates that frame length is within the defined limits and is compatible with the selected algorithm.

Classes

ROStream

aws_encryption_sdk.internal.utils.content_type(frame_length)¶

Returns the appropriate content type based on the frame length.

Parameters:	frame_length (int) – Message frame length
Returns:	Appropriate content type based on frame length
Return type:	aws_encryption_sdk.identifiers.ContentType

aws_encryption_sdk.internal.utils.validate_frame_length(frame_length, algorithm)¶

Validates that frame length is within the defined limits and is compatible with the selected algorithm.

Parameters:	frame_length (int) – Frame size in bytes algorithm (aws_encryption_sdk.identifiers.Algorithm) – Algorithm to use for encryption
Raises:	SerializationError – if frame size is negative or not a multiple of the algorithm block size SerializationError – if frame size is larger than the maximum allowed frame size

aws_encryption_sdk.internal.utils.message_id()¶

Generates a new message ID.

Returns:	Message ID
Return type:	bytes

aws_encryption_sdk.internal.utils.get_aad_content_string(content_type, is_final_frame)¶

Prepares the appropriate Body AAD Value for a message body.

Parameters:	content_type (aws_encryption_sdk.identifiers.ContentType) – Defines the type of content for which to prepare AAD String is_final_frame (bool) – Boolean stating whether this is the final frame in a body
Returns:	Appropriate AAD Content String
Return type:	bytes
Raises:	UnknownIdentityError – if unknown content type

aws_encryption_sdk.internal.utils.prepare_data_keys(primary_master_key, master_keys, algorithm, encryption_context)¶

Prepares a DataKey to be used for encrypting message and list of EncryptedDataKey objects to be serialized into header.

Parameters:

primary_master_key (aws_encryption_sdk.key_providers.base.MasterKey) – Master key with which to generate the encryption data key
master_keys (list of aws_encryption_sdk.key_providers.base.MasterKey) – All master keys with which to encrypt data keys
algorithm (aws_encryption_sdk.identifiers.Algorithm) – Algorithm to use for encryption
encryption_context (dict) – Encryption context to use when generating data key

Return type:

aws_encryption_sdk.internal.utils.prep_stream_data(data)¶

Takes an input str, bytes, io.IOBase, or file object and returns an appropriate stream for _EncryptionStream objects.

Parameters:	data (str, bytes, io.IOBase, or file) – Input data
Returns:	Prepared stream
Return type:	io.BytesIO

aws_encryption_sdk.internal.utils.source_data_key_length_check(source_data_key, algorithm)¶

Validates that the supplied source_data_key’s data_key is the correct length for the supplied algorithm’s kdf_input_len value.

Parameters:	source_data_key (`aws_encryption_sdk.structures.RawDataKey` or `aws_encryption_sdk.structures.DataKey`) – Source data key object received from MasterKey decrypt or generate data_key methods algorithm (aws_encryption_sdk.identifiers.Algorithm) – Algorithm object which directs how this data key will be used
Raises:	InvalidDataKeyError – if data key length does not match required kdf input length

aws_encryption_sdk.internal.utils.extend_user_agent_suffix(user_agent, suffix)¶

Adds a suffix to the provided user agent.

Parameters:	user_agent (str) – Existing user agent (None == not yet defined) suffix (str) – Desired suffix to add to user agent
Returns:	User agent with suffix
Return type:	str