base_client module¶

class base_client.BaseClient(storage_server, public_key_server, crypto_object, username)¶

Bases: object

Base class to build a file store client off of.

You should build your secure client implementation in client.py, subclassing off of this base class.

download(name)¶

Returns the last value stored at name by the owner or anyone with whom it has been shared, or None if the file does not exist.

A secure client implementation of this method should meet all of the required properties listed in the project specification.

Parameters:	name (str) – The name of the file. You can assume file names are alphanumeric (that is, they match the regex [A-Za-z0-9]+).
Returns:	A string, the last value stored at name, or None if the file does not exist.

generate_public_key_pair()¶

Create a public key pair for this client.

Note

You should call this exactly once in the initialization of your client, passing the size of the key desired. This method will automatically put the key to the public key server, and save a copy of your private key to the filesystem. This is the only persistent state that your client can use (that is, you can assume that for the same username, a client will have the same public/private keys even if restarted).

If the key already exists, this will load it from the filesystem.

If the key does not exist, this will create a new key pair, upload the public key to the Public Key Server, and save a copy of the private key to the filesystem (as keys/<username>.pem).

This creates RSA keys with 2048-bit modulus. It returns an RSA key object which contains both the public and private key. You can pass this object to functions that take a public or private key.

Returns:	An RSA key object containing both the public and private key. For more details see the PyCrypto documentation for _RSAobj.

receive_share(from_username, message, newname)¶

Receive a share message generated by the share method of another client with username from_username. Once this is done, the client calling this method should now be able to access the shared file under the name newname.

A secure client implementation of this method should meet all of the required properties listed in the project specification.

share and receive_share work together as follows:

msg = alice.share("bob", filename)
bob.receive_share("alice", msg, newfilename)

Parameters:	from_username (str) – The username of the sharing client. message (str) – The message generated by the sharing client’s share method. newname (str) – The new filename under which this client will access the file.

revoke(user, name)¶

Revokes user‘s access to the file name.

user should not be able to observe new updated to name, and should not be able update it.

Anyone with whom user shared this file should also be revoked.

You may not send any messages during revocation.

A secure client implementation of this method should meet all of the required properties listed in the project specification.

Parameters:	user (str) – The username of the user whose access will be revoked name (str) – The name of the file

share(user, name)¶

Share a file name with user.

A secure client implementation of this method should meet all of the required properties listed in the project specification.

share and receive_share work together as follows:

msg = alice.share("bob", filename)
bob.receive_share("alice", msg, newfilename)

Parameters:	user (str) – The username of the user you are sharing with. name (str) – The name of the file you are sharing with user.
Returns:	A string, containing the message to give to user through an out-of-band channel that will let them access the file.

upload(name, value)¶

Places the string value at name so that future calls to download for name return value.

A secure client implementation of this method should meet all of the required properties listed in the project specification.

Parameters:	name (str) – The name of the file. You can assume file names are alphanumeric (that is, they match the regex [A-Za-z0-9]+). value (str) – The value to upload.

exception base_client.IntegrityError¶

Bases: RuntimeError

Error to raise whenever an integrity error is encountered.