VPP/HostStack/TLS

TLS App

TLS service is offered by the stack to other client applications via a custom builtin application. The TLS application implements a special transport type that allows it to behave as an application, from the underlying TCP transport perspective, but also as a transport, from the client application perspective. We refer to this shim layer as a TLS context. The app does not directly implement the TLS protocol, i.e., the record layer, handshaking protocols and the cryptographic computations and suites [1], instead it relies on the mbedtls library [2]. A high level view of the architecture can be seen lower:

Because encryption and decryption operations result in the increase and decrease of number of bytes, respectively, a single client session requires four fifos. That is, in each direction encrypted and unencrypted data is buffered in distinct fifos.

To establish a client session, the following steps are typically taken:

• Client app requests a TLS connection to a remote session endpoint
• The TLS app, acting as a transport, is notified of the connections request. A TLS context is allocated and then, acting as an application, the TLS app opens a TCP connection to the remote transport endpoint.
• Once the TCP connection is established and the TLS app is notified, the context is initialized as a TLS client and the handshake

References

[1] RFC5246 The Transport Layer Security (TLS) Protocol Version 1.2

[2] mbedtls library