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auth.go
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package main
import (
"bytes"
"fmt"
"net"
"os"
"strconv"
"strings"
"text/template"
"time"
)
const (
authRealm = "cow proxy"
authRawBodyTmpl = `<!DOCTYPE html>
<html>
<head> <title>COW Proxy</title> </head>
<body>
<h1>407 Proxy authentication required</h1>
<hr />
Generated by <i>COW</i>
</body>
</html>
`
)
type netAddr struct {
ip net.IP
mask net.IPMask
}
var auth struct {
required bool
user string
passwd string
ha1 string // used in request digest
allowedClient []netAddr
authed *TimeoutSet // cache authentication based on client i
template *template.Template
}
func parseAllowedClient(val string) {
if val == "" {
return
}
auth.required = true
arr := strings.Split(val, ",")
auth.allowedClient = make([]netAddr, len(arr))
for i, v := range arr {
s := strings.TrimSpace(v)
ipAndMask := strings.Split(s, "/")
if len(ipAndMask) > 2 {
fmt.Println("allowedClient syntax error: client should be the form ip/nbitmask")
os.Exit(1)
}
ip := net.ParseIP(ipAndMask[0])
if ip == nil {
fmt.Printf("allowedClient syntax error %s: ip address not valid\n", s)
os.Exit(1)
}
var mask net.IPMask
if len(ipAndMask) == 2 {
nbit, err := strconv.Atoi(ipAndMask[1])
if err != nil {
fmt.Printf("allowedClient syntax error %s: %v\n", s, err)
os.Exit(1)
}
if nbit > 32 {
fmt.Println("allowedClient error: mask number should <= 32")
os.Exit(1)
}
mask = NewNbitIPv4Mask(nbit)
} else {
mask = NewNbitIPv4Mask(32)
}
auth.allowedClient[i] = netAddr{ip.Mask(mask), mask}
}
}
func parseUserPasswd(val string) {
if val == "" {
return
}
auth.required = true
arr := strings.SplitN(val, ":", 2)
if len(arr) != 2 || arr[0] == "" || arr[1] == "" {
fmt.Println("User password syntax wrong, should be in the form of user:passwd")
os.Exit(1)
}
auth.user, auth.passwd = arr[0], arr[1]
}
func initAuth() {
parseUserPasswd(config.UserPasswd)
parseAllowedClient(config.AllowedClient)
if !auth.required {
return
}
auth.authed = NewTimeoutSet(time.Duration(config.AuthTimeout) * time.Hour)
if auth.user == "" {
return
}
auth.ha1 = md5sum(auth.user + ":" + authRealm + ":" + auth.passwd)
rawTemplate := "HTTP/1.1 407 Proxy Authentication Required\r\n" +
"Proxy-Authenticate: Digest realm=\"" + authRealm + "\", nonce=\"{{.Nonce}}\", qop=\"auth\"\r\n" +
"Content-Type: text/html\r\n" +
"Cache-Control: no-cache\r\n" +
"Content-Length: " + fmt.Sprintf("%d", len(authRawBodyTmpl)) + "\r\n\r\n" + authRawBodyTmpl
var err error
if auth.template, err = template.New("auth").Parse(rawTemplate); err != nil {
errl.Println("Internal error generating auth template:", err)
os.Exit(1)
}
}
// Return err = nil if authentication succeed. nonce would be not empty if
// authentication is needed, and should be passed back on subsequent call.
func Authenticate(conn *clientConn, r *Request) (err error) {
clientIP, _ := splitHostPort(conn.RemoteAddr().String())
if auth.authed.has(clientIP) {
debug.Printf("%s has already authed\n", clientIP)
return
}
if authIP(clientIP) { // IP is allowed
return
}
err = authUserPasswd(conn, r)
if err == nil {
auth.authed.add(clientIP)
}
return
}
// authIP checks whether the client ip address matches one in allowedClient.
// It uses a sequential search.
func authIP(clientIP string) bool {
ip := net.ParseIP(clientIP)
if ip == nil {
panic("authIP should always get IP address")
}
for _, na := range auth.allowedClient {
if ip.Mask(na.mask).Equal(na.ip) {
debug.Printf("client ip %s allowed\n", clientIP)
return true
}
}
return false
}
func genNonce() string {
buf := new(bytes.Buffer)
fmt.Fprintf(buf, "%x", time.Now().Unix())
return buf.String()
}
func calcRequestDigest(kv map[string]string, ha1, method string) string {
// Refer to rfc2617 section 3.2.2.1 Request-Digest
buf := bytes.NewBufferString(ha1)
buf.WriteByte(':')
buf.WriteString(kv["nonce"])
buf.WriteByte(':')
buf.WriteString(kv["nc"])
buf.WriteByte(':')
buf.WriteString(kv["cnonce"])
buf.WriteByte(':')
buf.WriteString("auth") // qop value
buf.WriteByte(':')
buf.WriteString(md5sum(method + ":" + kv["uri"]))
return md5sum(buf.String())
}
func checkProxyAuthorization(r *Request) error {
debug.Println("authorization:", r.ProxyAuthorization)
arr := strings.SplitN(r.ProxyAuthorization, " ", 2)
if len(arr) != 2 {
errl.Println("auth: malformed ProxyAuthorization header:", r.ProxyAuthorization)
return errBadRequest
}
if strings.ToLower(strings.TrimSpace(arr[0])) != "digest" {
errl.Println("auth: client using unsupported authenticate method:", arr[0])
return errBadRequest
}
authHeader := parseKeyValueList(arr[1])
if len(authHeader) == 0 {
errl.Println("auth: empty authorization list")
return errBadRequest
}
nonceTime, err := strconv.ParseInt(authHeader["nonce"], 16, 64)
if err != nil {
return err
}
// If nonce time too early, reject. iOS will create a new connection to do
// authenticate.
if time.Now().Sub(time.Unix(nonceTime, 0)) > time.Minute {
return errAuthRequired
}
if authHeader["username"] != auth.user {
errl.Println("auth: username mismatch:", authHeader["username"])
return errAuthRequired
}
if authHeader["qop"] != "auth" {
errl.Println("auth: qop wrong:", authHeader["qop"])
return errBadRequest
}
response, ok := authHeader["response"]
if !ok {
errl.Println("auth: no request-digest")
return errBadRequest
}
digest := calcRequestDigest(authHeader, auth.ha1, r.Method)
if response == digest {
return nil
}
errl.Println("auth: digest not match, maybe password wrong")
return errAuthRequired
}
func authUserPasswd(conn *clientConn, r *Request) (err error) {
if r.ProxyAuthorization != "" {
// client has sent authorization header
err = checkProxyAuthorization(r)
if err == nil {
return
} else if err != errAuthRequired {
sendErrorPage(conn, errCodeBadReq, "Bad authorization request", "")
return
}
}
nonce := genNonce()
data := struct {
Nonce string
}{
nonce,
}
buf := new(bytes.Buffer)
if err := auth.template.Execute(buf, data); err != nil {
errl.Println("Error generating auth response:", err)
return errInternal
}
if debug {
debug.Println("authorization response:", buf.String())
}
if _, err := conn.Write(buf.Bytes()); err != nil {
errl.Println("Sending auth response error:", err)
return errShouldClose
}
return errAuthRequired
}