source: code/trunk/vendor/github.com/emersion/go-sasl/plain.go@ 822

package sasl

import (
        "bytes"
        "errors"
)

// The PLAIN mechanism name.
const Plain = "PLAIN"

type plainClient struct {
        Identity string
        Username string
        Password string
}

func (a *plainClient) Start() (mech string, ir []byte, err error) {
        mech = "PLAIN"
        ir = []byte(a.Identity + "\x00" + a.Username + "\x00" + a.Password)
        return
}

func (a *plainClient) Next(challenge []byte) (response []byte, err error) {
        return nil, ErrUnexpectedServerChallenge
}

// A client implementation of the PLAIN authentication mechanism, as described
// in RFC 4616. Authorization identity may be left blank to indicate that it is
// the same as the username.
func NewPlainClient(identity, username, password string) Client {
        return &plainClient{identity, username, password}
}

// Authenticates users with an identity, a username and a password. If the
// identity is left blank, it indicates that it is the same as the username.
// If identity is not empty and the server doesn't support it, an error must be
// returned.
type PlainAuthenticator func(identity, username, password string) error

type plainServer struct {
        done         bool
        authenticate PlainAuthenticator
}

func (a *plainServer) Next(response []byte) (challenge []byte, done bool, err error) {
        if a.done {
                err = ErrUnexpectedClientResponse
                return
        }

        // No initial response, send an empty challenge
        if response == nil {
                return []byte{}, false, nil
        }

        a.done = true

        parts := bytes.Split(response, []byte("\x00"))
        if len(parts) != 3 {
                err = errors.New("Invalid response")
                return
        }

        identity := string(parts[0])
        username := string(parts[1])
        password := string(parts[2])

        err = a.authenticate(identity, username, password)
        done = true
        return
}

// A server implementation of the PLAIN authentication mechanism, as described
// in RFC 4616.
func NewPlainServer(authenticator PlainAuthenticator) Server {
        return &plainServer{authenticate: authenticator}
}