mirror of
https://github.com/ergochat/ergo.git
synced 2024-11-25 05:19:25 +01:00
150 lines
4.0 KiB
Go
150 lines
4.0 KiB
Go
// Copyright 2018 by David A. Golden. All rights reserved.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License"); you may
|
|
// not use this file except in compliance with the License. You may obtain
|
|
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
package scram
|
|
|
|
import (
|
|
"crypto/hmac"
|
|
"encoding/base64"
|
|
"errors"
|
|
"fmt"
|
|
"strings"
|
|
)
|
|
|
|
type clientState int
|
|
|
|
const (
|
|
clientStarting clientState = iota
|
|
clientFirst
|
|
clientFinal
|
|
clientDone
|
|
)
|
|
|
|
// ClientConversation implements the client-side of an authentication
|
|
// conversation with a server. A new conversation must be created for
|
|
// each authentication attempt.
|
|
type ClientConversation struct {
|
|
client *Client
|
|
nonceGen NonceGeneratorFcn
|
|
hashGen HashGeneratorFcn
|
|
minIters int
|
|
state clientState
|
|
valid bool
|
|
gs2 string
|
|
nonce string
|
|
c1b string
|
|
serveSig []byte
|
|
}
|
|
|
|
// Step takes a string provided from a server (or just an empty string for the
|
|
// very first conversation step) and attempts to move the authentication
|
|
// conversation forward. It returns a string to be sent to the server or an
|
|
// error if the server message is invalid. Calling Step after a conversation
|
|
// completes is also an error.
|
|
func (cc *ClientConversation) Step(challenge string) (response string, err error) {
|
|
switch cc.state {
|
|
case clientStarting:
|
|
cc.state = clientFirst
|
|
response, err = cc.firstMsg()
|
|
case clientFirst:
|
|
cc.state = clientFinal
|
|
response, err = cc.finalMsg(challenge)
|
|
case clientFinal:
|
|
cc.state = clientDone
|
|
response, err = cc.validateServer(challenge)
|
|
default:
|
|
response, err = "", errors.New("Conversation already completed")
|
|
}
|
|
return
|
|
}
|
|
|
|
// Done returns true if the conversation is completed or has errored.
|
|
func (cc *ClientConversation) Done() bool {
|
|
return cc.state == clientDone
|
|
}
|
|
|
|
// Valid returns true if the conversation successfully authenticated with the
|
|
// server, including counter-validation that the server actually has the
|
|
// user's stored credentials.
|
|
func (cc *ClientConversation) Valid() bool {
|
|
return cc.valid
|
|
}
|
|
|
|
func (cc *ClientConversation) firstMsg() (string, error) {
|
|
// Values are cached for use in final message parameters
|
|
cc.gs2 = cc.gs2Header()
|
|
cc.nonce = cc.client.nonceGen()
|
|
cc.c1b = fmt.Sprintf("n=%s,r=%s", encodeName(cc.client.username), cc.nonce)
|
|
|
|
return cc.gs2 + cc.c1b, nil
|
|
}
|
|
|
|
func (cc *ClientConversation) finalMsg(s1 string) (string, error) {
|
|
msg, err := parseServerFirst(s1)
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
|
|
// Check nonce prefix and update
|
|
if !strings.HasPrefix(msg.nonce, cc.nonce) {
|
|
return "", errors.New("server nonce did not extend client nonce")
|
|
}
|
|
cc.nonce = msg.nonce
|
|
|
|
// Check iteration count vs minimum
|
|
if msg.iters < cc.minIters {
|
|
return "", fmt.Errorf("server requested too few iterations (%d)", msg.iters)
|
|
}
|
|
|
|
// Create client-final-message-without-proof
|
|
c2wop := fmt.Sprintf(
|
|
"c=%s,r=%s",
|
|
base64.StdEncoding.EncodeToString([]byte(cc.gs2)),
|
|
cc.nonce,
|
|
)
|
|
|
|
// Create auth message
|
|
authMsg := cc.c1b + "," + s1 + "," + c2wop
|
|
|
|
// Get derived keys from client cache
|
|
dk := cc.client.getDerivedKeys(KeyFactors{Salt: string(msg.salt), Iters: msg.iters})
|
|
|
|
// Create proof as clientkey XOR clientsignature
|
|
clientSignature := computeHMAC(cc.hashGen, dk.StoredKey, []byte(authMsg))
|
|
clientProof := xorBytes(dk.ClientKey, clientSignature)
|
|
proof := base64.StdEncoding.EncodeToString(clientProof)
|
|
|
|
// Cache ServerSignature for later validation
|
|
cc.serveSig = computeHMAC(cc.hashGen, dk.ServerKey, []byte(authMsg))
|
|
|
|
return fmt.Sprintf("%s,p=%s", c2wop, proof), nil
|
|
}
|
|
|
|
func (cc *ClientConversation) validateServer(s2 string) (string, error) {
|
|
msg, err := parseServerFinal(s2)
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
|
|
if len(msg.err) > 0 {
|
|
return "", fmt.Errorf("server error: %s", msg.err)
|
|
}
|
|
|
|
if !hmac.Equal(msg.verifier, cc.serveSig) {
|
|
return "", errors.New("server validation failed")
|
|
}
|
|
|
|
cc.valid = true
|
|
return "", nil
|
|
}
|
|
|
|
func (cc *ClientConversation) gs2Header() string {
|
|
if cc.client.authzID == "" {
|
|
return "n,,"
|
|
}
|
|
return fmt.Sprintf("n,%s,", encodeName(cc.client.authzID))
|
|
}
|