digest implementation for http digest authentication

digest.go

package main

import (
	"crypto/md5"
	"fmt"
	"strings"
)

type digest struct {
	username string
	password string
	realm    string
	uri      string
	method   string
	nonce    string
	nc       int
	cnonce   string
	qop      string
	opaque   string
}

func (d *digest) ha1() string {
	s := strings.Join([]string{d.username, d.realm, d.password}, ":")
	return fmt.Sprintf("%x", md5.Sum([]byte(s)))
}

func (d *digest) ha2() string {
	s := strings.Join([]string{d.method, d.uri}, ":")
	return fmt.Sprintf("%x", md5.Sum([]byte(s)))
}

func (d *digest) response() string {
	s := strings.Join([]string{d.ha1(), d.nonce, fmt.Sprintf("%08x", d.nc), d.cnonce, d.qop, d.ha2()}, ":")
	return fmt.Sprintf("%x", md5.Sum([]byte(s)))
}

func (d *digest) String() string {
	params := map[string]string{
		"username": fmt.Sprintf("%q", d.username),
		"realm":    fmt.Sprintf("%q", d.realm),
		"nonce":    fmt.Sprintf("%q", d.nonce),
		"uri":      fmt.Sprintf("%q", d.uri),
		"qop":      d.qop,
		"nc":       fmt.Sprintf("%08x", d.nc),
		"cnonce":   fmt.Sprintf("%q", d.cnonce),
		"response": fmt.Sprintf("%q", d.response()),
		"opaque":   fmt.Sprintf("%q", d.opaque),
	}

	values := []string{}
	for k, v := range params {
		values = append(values, fmt.Sprintf("%s=%s", k, v))
	}

	return strings.Join(values, ", ")
}

func (d *digest) Header() string {
	return fmt.Sprintf("Digest %s", d.String())
}

func parseDigest(v string) map[string]string {
	params := map[string]string{}

	t := strings.SplitN(v, " ", 2)
	if len(t) < 2 {
		return params
	}

	for _, p := range strings.Split(t[1], ",") {
		t := strings.SplitN(p, "=", 2)
		if len(t) == 2 {
			params[strings.TrimSpace(t[0])] = strings.Trim(t[1], "\" ")
		}
	}

	return params
}