Add Authenticator interface and Digest auth support

digestAuth.go

@@ -0,0 +1,83 @@
+package gowebdav
+
+import (
+	"crypto/md5"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+)
+
+// DigestAuth structure holds our credentials
+type DigestAuth struct {
+	user        string
+	pw          string
+	digestParts map[string]string
+}
+
+// Type identifies the DigestAuthenticator
+func (d *DigestAuth) Type() string {
+	return "DigestAuth"
+}
+
+// User holds the DigestAuth username
+func (d *DigestAuth) User() string {
+	return d.user
+}
+
+// Pass holds the DigestAuth password
+func (d *DigestAuth) Pass() string {
+	return d.pw
+}
+
+// Authorize the current request
+func (d *DigestAuth) Authorize(c *Client, method string, path string) {
+	d.digestParts["uri"] = path
+	d.digestParts["method"] = method
+	d.digestParts["username"] = d.user
+	d.digestParts["password"] = d.pw
+	c.headers.Set("Authorization", getDigestAuthorization(d.digestParts))
+}
+
+func digestParts(resp *http.Response) map[string]string {
+	result := map[string]string{}
+	if len(resp.Header["Www-Authenticate"]) > 0 {
+		wantedHeaders := []string{"nonce", "realm", "qop", "opaque"}
+		responseHeaders := strings.Split(resp.Header["Www-Authenticate"][0], ",")
+		for _, r := range responseHeaders {
+			for _, w := range wantedHeaders {
+				if strings.Contains(r, w) {
+					result[w] = strings.Split(r, `"`)[1]
+				}
+			}
+		}
+	}
+	return result
+}
+
+func getMD5(text string) string {
+	hasher := md5.New()
+	hasher.Write([]byte(text))
+	return hex.EncodeToString(hasher.Sum(nil))
+}
+
+func getCnonce() string {
+	b := make([]byte, 8)
+	io.ReadFull(rand.Reader, b)
+	return fmt.Sprintf("%x", b)[:16]
+}
+
+func getDigestAuthorization(digestParts map[string]string) string {
+	d := digestParts
+	// These are the correct ha1 and ha2 for qop=auth. We should probably check for other types of qop.
+	ha1 := getMD5(d["username"] + ":" + d["realm"] + ":" + d["password"])
+	ha2 := getMD5(d["method"] + ":" + d["uri"])
+	nonceCount := 00000001
+	cnonce := getCnonce()
+	response := getMD5(fmt.Sprintf("%s:%s:%v:%s:%s:%s", ha1, d["nonce"], nonceCount, cnonce, d["qop"], ha2))
+	authorization := fmt.Sprintf(`Digest username="%s", realm="%s", nonce="%s", uri="%s", cnonce="%s", nc="%v", qop="%s", response="%s", opaque="%s"`,
+		d["username"], d["realm"], d["nonce"], d["uri"], cnonce, nonceCount, d["qop"], response, d["opaque"])
+	return authorization
+}