caddyhttp: {http.request.body_base64} placeholder

modules/caddyhttp/app.go

@@ -51,6 +51,7 @@ func init() {
 // Placeholder | Description
 // ------------|---------------
 // `{http.request.body}` | The request body (⚠️ inefficient; use only for debugging)
+// `{http.request.body_base64}` | The request body, base64-encoded (⚠️ for debugging)
 // `{http.request.cookie.*}` | HTTP request cookie
 // `{http.request.duration}` | Time up to now spent handling the request (after decoding headers from client)
 // `{http.request.duration_ms}` | Same as 'duration', but in milliseconds.

modules/caddyhttp/replacer.go

@@ -229,6 +229,21 @@ func addHTTPVarsToReplacer(repl *caddy.Replacer, req *http.Request, w http.Respo
 				req.Body = io.NopCloser(buf)  // replace real body with buffered data
 				return buf.String(), true
 
+			case "http.request.body_base64":
+				if req.Body == nil {
+					return "", true
+				}
+				// normally net/http will close the body for us, but since we
+				// are replacing it with a fake one, we have to ensure we close
+				// the real body ourselves when we're done
+				defer req.Body.Close()
+				// read the request body into a buffer (can't pool because we
+				// don't know its lifetime and would have to make a copy anyway)
+				buf := new(bytes.Buffer)
+				_, _ = io.Copy(buf, req.Body) // can't handle error, so just ignore it
+				req.Body = io.NopCloser(buf)  // replace real body with buffered data
+				return base64.StdEncoding.EncodeToString(buf.Bytes()), true
+
 			// original request, before any internal changes
 			case "http.request.orig_method":
 				or, _ := req.Context().Value(OriginalRequestCtxKey).(http.Request)