Package fallback

Variables

FallbackTLSConfigGRPC is a tls.Config used by the DefaultFallbackClientHandshakeFunc function. It supports GRPC use case, thus the alpn is set to 'h2'.

var FallbackTLSConfigGRPC = tls.Config{
    MinVersion:         tls.VersionTLS13,
    ClientSessionCache: nil,
    NextProtos:         []string{alpnProtoStrH2},
}

FallbackTLSConfigHTTP is a tls.Config used by the DefaultFallbackDialerAndAddress func. It supports the HTTP use case and the alpn is set to both 'http/1.1' and 'h2'.

var FallbackTLSConfigHTTP = tls.Config{
    MinVersion:         tls.VersionTLS13,
    ClientSessionCache: nil,
    NextProtos:         []string{alpnProtoStrH2, alpnProtoStrHTTP},
}

func DefaultFallbackDialerAndAddress ¶

func DefaultFallbackDialerAndAddress(fallbackAddr string) (*tls.Dialer, string, error)

DefaultFallbackDialerAndAddress returns a TLS dialer and the network address to dial. Example use:

    fallbackDialer, fallbackServerAddr := fallback.DefaultFallbackDialerAndAddress(fallbackAddr)
	dialTLSContext := s2a.NewS2aDialTLSContextFunc(&s2a.ClientOptions{
		S2AAddress:         s2aAddress, // required
		FallbackOpts: &s2a.FallbackOptions{
			FallbackDialer: &s2a.FallbackDialer{
				Dialer:     fallbackDialer,
				ServerAddr: fallbackServerAddr,
			},
		},
})

The fallback server's certificate should be verifiable using OS root store. The fallbackAddr is expected to be a network address, e.g. example.com:port. If port is not specified, it uses default port 443. In the returned function's TLS config, ClientSessionCache is explicitly set to nil to disable TLS resumption, and min TLS version is set to 1.3.

type ClientHandshake ¶

ClientHandshake establishes a TLS connection and returns it, plus its auth info. Inputs:

targetServer: the server attempted with S2A.
conn: the tcp connection to the server at address targetServer that was passed into S2A's ClientHandshake func.
            If fallback is successful, the `conn` should be closed.
err: the error encountered when performing the client-side TLS handshake with S2A.

type ClientHandshake func(ctx context.Context, targetServer string, conn net.Conn, err error) (net.Conn, credentials.AuthInfo, error)

func DefaultFallbackClientHandshakeFunc ¶

func DefaultFallbackClientHandshakeFunc(fallbackAddr string) (ClientHandshake, error)

DefaultFallbackClientHandshakeFunc returns a ClientHandshake function, which establishes a TLS connection to the provided fallbackAddr, returns the new connection and its auth info. Example use:

transportCreds, _ = s2a.NewClientCreds(&s2a.ClientOptions{
	S2AAddress: s2aAddress,
	FallbackOpts: &s2a.FallbackOptions{ // optional
		FallbackClientHandshakeFunc: fallback.DefaultFallbackClientHandshakeFunc(fallbackAddr),
	},
})

The fallback server's certificate must be verifiable using OS root store. The fallbackAddr is expected to be a network address, e.g. example.com:port. If port is not specified, it uses default port 443. In the returned function's TLS config, ClientSessionCache is explicitly set to nil to disable TLS resumption, and min TLS version is set to 1.3.