add CSRF checking

1 files changed, 50 insertions, 0 deletions

diff --git a/srv/api/csrf.go b/srv/api/csrf.go
new file mode 100644
index 0000000..d705adb
--- /dev/null
+++ b/srv/api/csrf.go
@@ -0,0 +1,50 @@
+package api
+
+import (
+	"errors"
+	"net/http"
+)
+
+const (
+	csrfTokenCookieName = "csrf_token"
+	csrfTokenHeaderName = "X-CSRF-Token"
+)
+
+func setCSRFMiddleware(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+
+		csrfTok, err := getCookie(r, csrfTokenCookieName, "")
+
+		if err != nil {
+			internalServerError(rw, r, err)
+			return
+
+		} else if csrfTok == "" {
+			http.SetCookie(rw, &http.Cookie{
+				Name:   csrfTokenCookieName,
+				Value:  randStr(32),
+				Secure: true,
+			})
+		}
+
+		h.ServeHTTP(rw, r)
+	})
+}
+
+func checkCSRFMiddleware(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+
+		csrfTok, err := getCookie(r, csrfTokenCookieName, "")
+
+		if err != nil {
+			internalServerError(rw, r, err)
+			return
+
+		} else if csrfTok == "" || r.Header.Get(csrfTokenHeaderName) != csrfTok {
+			badRequest(rw, r, errors.New("invalid CSRF token"))
+			return
+		}
+
+		h.ServeHTTP(rw, r)
+	})
+}