/
basic.go
65 lines (58 loc) · 1.99 KB
/
basic.go
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package main
import (
"encoding/base64"
"./martini"
"net/http"
"strings"
"crypto/sha256"
"crypto/subtle"
)
// SecureCompare performs a constant time compare of two strings to limit timing attacks.
func auth_SecureCompare(given string, actual string) bool {
givenSha := sha256.Sum256([]byte(given))
actualSha := sha256.Sum256([]byte(actual))
return subtle.ConstantTimeCompare(givenSha[:], actualSha[:]) == 1
}
// User is the authenticated username that was extracted from the request.
type User string
// BasicRealm is used when setting the WWW-Authenticate response header.
var BasicRealm = "Authorization Required"
// Basic returns a Handler that authenticates via Basic Auth. Writes a http.StatusUnauthorized
// if authentication fails.
func Basic(username string, password string) martini.Handler {
var siteAuth = base64.StdEncoding.EncodeToString([]byte(username + ":" + password))
return func(res http.ResponseWriter, req *http.Request, c martini.Context) {
auth := req.Header.Get("Authorization")
if !auth_SecureCompare(auth, "Basic "+siteAuth) {
unauthorized(res)
return
}
c.Map(User(username))
}
}
// BasicFunc returns a Handler that authenticates via Basic Auth using the provided function.
// The function should return true for a valid username/password combination.
func auth_BasicFunc(authfn func(string, string) bool) martini.Handler {
return func(res http.ResponseWriter, req *http.Request, c martini.Context) {
auth := req.Header.Get("Authorization")
if len(auth) < 6 || auth[:6] != "Basic " {
unauthorized(res)
return
}
b, err := base64.StdEncoding.DecodeString(auth[6:])
if err != nil {
unauthorized(res)
return
}
tokens := strings.SplitN(string(b), ":", 2)
if len(tokens) != 2 || !authfn(tokens[0], tokens[1]) {
unauthorized(res)
return
}
c.Map(User(tokens[0]))
}
}
func unauthorized(res http.ResponseWriter) {
res.Header().Set("WWW-Authenticate", "Basic realm=\""+BasicRealm+"\"")
http.Error(res, "Not Authorized", http.StatusUnauthorized)
}