Adding http basic authentication middleware

Signed-off-by: Vishal Rana <vr@labstack.com>

middleware/auth.go

@@ -0,0 +1,64 @@
+package middleware
+
+import (
+	"encoding/base64"
+	"github.com/labstack/echo"
+	"net/http"
+)
+
+type (
+	AuthFunc func(string, string) bool
+)
+
+const (
+	Basic = "Basic"
+)
+
+// BasicAuth provides HTTP basic authentication middleware.
+func BasicAuth(fn AuthFunc) echo.HandlerFunc {
+	return func(c *echo.Context) (he *echo.HTTPError) {
+		auth := c.Request.Header.Get(echo.Authorization)
+		i := 0
+		l := len(Basic)
+		he = &echo.HTTPError{Code: http.StatusUnauthorized}
+
+		for ; i < len(auth); i++ {
+			c := auth[i]
+			// Ignore empty spaces
+			if c == ' ' {
+				continue
+			}
+
+			// Check scheme
+			if i < l {
+				// Ignore case
+				if i == 0 {
+					if c != Basic[i] && c != 'b' {
+						return
+					}
+				} else {
+					if c != Basic[i] {
+						return
+					}
+				}
+			} else {
+				// Extract credentials
+				b, err := base64.StdEncoding.DecodeString(auth[i:])
+				if err != nil {
+					return
+				}
+				cred := string(b)
+				for i := 0; i < len(cred); i++ {
+					if cred[i] == ':' {
+						// Verify credentials
+						if !fn(cred[:i], cred[i+1:]) {
+							return
+						}
+						return nil
+					}
+				}
+			}
+		}
+		return nil
+	}
+}