Move registry package into handler package

The goal is to free up the distribution/registry package to include common
registry types. This moves the webapp definitions out of the way to allow for
this change in the future.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

docs/handlers/basicauth_prego14.go

@@ -0,0 +1,41 @@
+// +build !go1.4
+
+package handlers
+
+import (
+	"encoding/base64"
+	"net/http"
+	"strings"
+)
+
+// NOTE(stevvooe): This is basic auth support from go1.4 present to ensure we
+// can compile on go1.3 and earlier.
+
+// BasicAuth returns the username and password provided in the request's
+// Authorization header, if the request uses HTTP Basic Authentication.
+// See RFC 2617, Section 2.
+func basicAuth(r *http.Request) (username, password string, ok bool) {
+	auth := r.Header.Get("Authorization")
+	if auth == "" {
+		return
+	}
+	return parseBasicAuth(auth)
+}
+
+// parseBasicAuth parses an HTTP Basic Authentication string.
+// "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==" returns ("Aladdin", "open sesame", true).
+func parseBasicAuth(auth string) (username, password string, ok bool) {
+	if !strings.HasPrefix(auth, "Basic ") {
+		return
+	}
+	c, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(auth, "Basic "))
+	if err != nil {
+		return
+	}
+	cs := string(c)
+	s := strings.IndexByte(cs, ':')
+	if s < 0 {
+		return
+	}
+	return cs[:s], cs[s+1:], true
+}