add better generate

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>

vendor/github.com/genuinetools/reg/registry/authchallenge.go

@@ -0,0 +1,69 @@
+package registry
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"regexp"
+	"strings"
+)
+
+var (
+	bearerRegex = regexp.MustCompile(
+		`^\s*Bearer\s+(.*)$`)
+	basicRegex = regexp.MustCompile(`^\s*Basic\s+.*$`)
+)
+
+func parseAuthHeader(header http.Header) (*authService, error) {
+	ch, err := parseChallenge(header.Get("www-authenticate"))
+	if err != nil {
+		return nil, err
+	}
+
+	return ch, nil
+}
+
+func parseChallenge(challengeHeader string) (*authService, error) {
+	if basicRegex.MatchString(challengeHeader) {
+		return nil, nil
+	}
+
+	match := bearerRegex.FindAllStringSubmatch(challengeHeader, -1)
+	if d := len(match); d != 1 {
+		return nil, fmt.Errorf("malformed auth challenge header: '%s', %d", challengeHeader, d)
+	}
+	parts := strings.Split(strings.TrimSpace(match[0][1]), ",")
+
+	var realm, service string
+	var scope []string
+	for _, s := range parts {
+		p := strings.SplitN(s, "=", 2)
+		if len(p) != 2 {
+			return nil, fmt.Errorf("malformed auth challenge header: '%s'", challengeHeader)
+		}
+		key := p[0]
+		value := strings.TrimSuffix(strings.TrimPrefix(p[1], `"`), `"`)
+		switch key {
+		case "realm":
+			realm = value
+		case "service":
+			service = value
+		case "scope":
+			scope = strings.Fields(value)
+		default:
+			return nil, fmt.Errorf("unknown field in challege header %s: %v", key, challengeHeader)
+		}
+	}
+	parsedRealm, err := url.Parse(realm)
+	if err != nil {
+		return nil, err
+	}
+
+	a := &authService{
+		Realm:   parsedRealm,
+		Service: service,
+		Scope:   scope,
+	}
+
+	return a, nil
+}