isabella232 / keyspace

Capability-based secure key management and credential storage

Keyspace

End-to-end (i.e. client-side) encryption for key/value stores, using RbNaCl for security and Moneta for persistence.

About

Keyspace is an encrypted name/value store which emphasizes a "least authority" philosophy for information sharing. All data is stored as encrypted name/value pairs, and data can be organized into "vaults" which each have independent encryption tokens and access control.

Keyspace uses capability-based security to manage access to vaults. Each capability takes the form of cryptographic tokens which are unique to a particular vault. Knowledge of these tokens is necessary and sufficient to gain access to a particular vault. Such an access scheme is known as "capabilities as keys" or "cryptographic capabilities". This approach provides secure sharing of access to vaults.

This means there is no access control system (e.g. RBAC) other than the capability tokens themselves. Authorization is handled completely by whether or not you have the necessary cryptographic tokens to carry out a desired action. This straightforward approach leaves little room for error and reduces the entire attack surface to vulnerabilities in the cryptographic code or leaked capability tokens.

Keyspace is built on Moneta, an abstract API to many kinds of key/value stores including all ActiveRecord compatible databases, Redis, Riak, Cassandra, CouchDB, MongoDB, and many others. If there's a key/value store you would like to persist to, Moneta probably supports it.

Cryptography in Keyspace is handled by RbNaCl, a Ruby wrapper to the Networking and Cryptography library by Daniel J. Bernstein.

Status

Keyspace is still experimental and the design is subject to change.

Mailing List

If you're interested in using Keyspace, join the mailing list by sending a message to:

• [email protected]

Capabilities

Capabilities are (relatively) short tokens which grant a specific type of authority within Keyspace. Knowledge of a capability is necessary and sufficient to gain a particular type of access. Capabilities can also be "degraded", so that a capability holder can grant others a limited subset of the authority granted to them by the capability they hold.

A capability token looks like the following:

ks.write:foobar@d2hotnrmcxsqgibpszqoj6mowovsmmq4ajgy626qavbtk74tsbk5bqjypkhjlmbsqy7266umric6vn7iasaa6ccljqzrr7d35dqrh7i

There are 3 parts to the capability token:

• "ks.write": URI scheme indicating this is a Keyspace (i.e. "ks") writecap There are three capability levels (see below)
• "foobar": the name of the vault this writecap provides access to
• "d2hotnrmcxsqgibpsz...": A Base32-encoded string containing the cryptographic keys which control access to this vault.

There are three capability levels for each vault:

• verifycap (ks.verify): Can determine a value is authentic, but can't decrypt it
• readcap (ks.read): Can read values from within the vault, but cannot write to it
• writecap (ks.write): Can write new values into the vault

Each set of capabilities builds upon the last: users with the read capability can also verify, and users with the write capability can also read. Users who have access to a vault can delegate access to other users simply by sharing their capability token. Users can also degrade capabilities, i.e. they can produce read-verify tokens from a write-read-verify token, and verify only tokens from a read-verify token (or write-read-verify token).

Data Flow

Keyspace provides a separation between the powers of system administrators to alter the system configuration, system users who want to consume and verify the authenticity of configuration data, and the server, which is a dumb datastore which will save any values it can verify.

Server

Keyspace provides a Sinatra service for writing to and reading from vaults. The Sinatra service itself has only the verify capability, meaning that if it is ever compromised, the attacker cannot read the contents of the Keyspace. Furthermore, they cannot alter the system configuration, because they will be unable to sign new values without the writecap.

All encryption of plaintext happens client-side via a command line tool which runs on a computer under the control of a trusted administrator. Data is encrypted using NaCl's "SecretBox" primitive (i.e. XSalsa20 + Poly1305) and signed with the Ed25519 digital signature algorithm prior to transmission to the server, and remains encrypted until accessed by another client with the read (or verify) capabilities.

Ruby Client

Keyspace provides a simple Ruby client for storing and retrieving encrypted data from the server. In this example, a system operator creates a vault, puts a value inside of it, and then saves the vault to the server:

>> vault = Keyspace::Client::Vault.create("myvault")
 => #<Keyspace::Client::Vault ks.write:[email protected]>
>> vault[:foobar] = "baz"
 => "baz"
>> vault.save!
 => true

The system administrator can then degrade the capability for this vault to a readcap prior to disseminating it to a system user:

>> vault.capability.degrade(:readcap).to_s
 => "ks.read:myvault@d4u5qekdyezqlugxmhtuerytyyjp4fqjqsgbqjhfgm5mnw...daokugjdi"

We'll now switch to the perspective of a system user who has been given the readcap created above. First, they'll set the server URL and create a new vault object from the readcap. They'll then be able to access values from this vault by key, but they cannot make changes:

>> Keyspace::Client.url = "http://127.0.0.1:4567"
 => "http://127.0.0.1:4567"
>> vault = Keyspace::Client::Vault.new("ks.read:myvault@d4u5qekdyezqlugxmhtuerytyyjp4fqjqsgbqjhfgm5mnw...daokugjdi")
 => #<Keyspace::Client::Vault "ks.read:myvault@d4u5qekdyezqlugxmhtuerytyyjp4fqjqsgbqjhfgm5mnw...daokugjdi">
>> vault[:foobar]
 => "baz"
>> vault[:foobar] = "can't touch this"
Keyspace::InvalidCapabilityError: don't have write capability for this vault: myvault
        from /Users/tony/dev/keyspace/lib/keyspace/client/vault.rb:56:in `put'
        from (irb):9
        from /Users/tony/.rvm/rubies/ruby-1.9.3-p194/bin/irb:16:in `<main>'

Security Notes

Keyspace is built on state-of-the-art cryptographic primitives, but that alone does not make for a secure system. It is yet to be audited by an expert cryptographer, and for that reason alone should be somewhat suspect in the eyes of anyone interested in its security.

For that reason alone, Keyspace should be experimental until audited by cryptographic experts.

Reporting Security Problems

If you have discovered a bug in Keyspace of a sensitive nature, i.e. one which can compromise the security of Keyspace users, you can report it securely by sending a GPG encrypted message. Please use the following key:

https://raw.github.com/livingsocial/keyspace/master/keyspace.gpg

The key fingerprint is (or should be):

190E 42D6 8327 A515 BFDF AAE0 B210 269D BB2D 8787

Suggested Reading

Keyspace is inspired by the cryptographic capabilities system implemented in Tahoe: The Least Authority Filesystem.

License

This software is released under the MIT license:

Copyright (C) 2013, LivingSocial, Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.