scram – Go implementation of RFC-5802

Description

Package scram provides client and server implementations of the Salted Challenge Response Authentication Mechanism (SCRAM) described in

• RFC-5802
• RFC-5929
• RFC-7677
• RFC-9266

It includes both client and server side support.

Channel binding is supported for SCRAM-PLUS variants, including:

• tls-unique (RFC 5929) - insecure, but required
• tls-server-end-point (RFC 5929) - works with all TLS versions
• tls-exporter (RFC 9266) - recommended for TLS 1.3+

SCRAM message extensions are not supported.

Examples

Client side

package main

import "github.com/xdg-go/scram"

func main() {
    // Get Client with username, password and (optional) authorization ID.
    clientSHA1, err := scram.SHA1.NewClient("mulder", "trustno1", "")
    if err != nil {
        panic(err)
    }

    // Prepare the authentication conversation. Use the empty string as the
    // initial server message argument to start the conversation.
    conv := clientSHA1.NewConversation()
    var serverMsg string

    // Get the first message, send it and read the response.
    firstMsg, err := conv.Step(serverMsg)
    if err != nil {
        panic(err)
    }
    serverMsg = sendClientMsg(firstMsg)

    // Get the second message, send it, and read the response.
    secondMsg, err := conv.Step(serverMsg)
    if err != nil {
        panic(err)
    }
    serverMsg = sendClientMsg(secondMsg)

    // Validate the server's final message.  We have no further message to
    // send so ignore that return value.
    _, err = conv.Step(serverMsg)
    if err != nil {
        panic(err)
    }

    return
}

func sendClientMsg(s string) string {
    // A real implementation would send this to a server and read a reply.
    return ""
}

Client side with channel binding (SCRAM-PLUS)

package main

import (
    "crypto/tls"
    "github.com/xdg-go/scram"
)

func main() {
    // Establish TLS connection
    tlsConn, err := tls.Dial("tcp", "server:port", &tls.Config{MinVersion: tls.VersionTLS13})
    if err != nil {
        panic(err)
    }
    defer tlsConn.Close()

    // Get Client with username, password
    client, err := scram.SHA256.NewClient("mulder", "trustno1", "")
    if err != nil {
        panic(err)
    }

    // Create channel binding from TLS connection (TLS 1.3 example)
    // Use NewTLSExporterBinding for TLS 1.3+, NewTLSServerEndpointBinding for all TLS versions
    channelBinding, err := scram.NewTLSExporterBinding(&tlsConn.ConnectionState())
    if err != nil {
        panic(err)
    }

    // Create conversation with channel binding for SCRAM-SHA-256-PLUS
    conv := client.NewConversationWithChannelBinding(channelBinding)
    // ... rest of authentication conversation
}

Copyright and License

Copyright 2018 by David A. Golden. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License"). You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0