fix(go.sum): update ResolveSpec dependency to v1.0.87

vendor/mellium.im/sasl/plain.go

@@ -0,0 +1,52 @@
+// Copyright 2016 The Mellium Contributors.
+// Use of this source code is governed by the BSD 2-clause
+// license that can be found in the LICENSE file.
+
+package sasl
+
+import (
+	"bytes"
+)
+
+var plainSep = []byte{0}
+
+var plain = Mechanism{
+	Name: "PLAIN",
+	Start: func(m *Negotiator) (more bool, resp []byte, _ interface{}, err error) {
+		username, password, identity := m.credentials()
+		payload := make([]byte, 0, len(identity)+len(username)+len(password)+2)
+		payload = append(payload, identity...)
+		payload = append(payload, '\x00')
+		payload = append(payload, username...)
+		payload = append(payload, '\x00')
+		payload = append(payload, password...)
+		return false, payload, nil, nil
+	},
+	Next: func(m *Negotiator, challenge []byte, _ interface{}) (more bool, resp []byte, _ interface{}, err error) {
+		// If we're a client, or we're a server that's past the AuthTextSent step,
+		// we should never actually hit this step.
+		if m.State()&Receiving != Receiving || m.State()&StepMask != AuthTextSent {
+			err = ErrTooManySteps
+			return
+		}
+
+		// If we're a server, validate that the challenge looks like:
+		// "Identity\x00Username\x00Password"
+		parts := bytes.Split(challenge, plainSep)
+		if len(parts) != 3 {
+			err = ErrInvalidChallenge
+			return
+		}
+
+		if m.Permissions(Credentials(func() (Username, Password, Identity []byte) {
+			return parts[1], parts[2], parts[0]
+		})) {
+			// Everything checks out as far as we know and the server should continue
+			// to authenticate the user.
+			return
+		}
+
+		err = ErrAuthn
+		return
+	},
+}