github.com/olljanat/moby@v1.13.1/api/server/middleware/debug.go

package middleware

import (
	"bufio"
	"encoding/json"
	"io"
	"net/http"
	"strings"

	"github.com/Sirupsen/logrus"
	"github.com/docker/docker/api/server/httputils"
	"github.com/docker/docker/pkg/ioutils"
	"golang.org/x/net/context"
)

// DebugRequestMiddleware dumps the request to logger
func DebugRequestMiddleware(handler func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error) func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
	return func(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
		logrus.Debugf("Calling %s %s", r.Method, r.RequestURI)

		if r.Method != "POST" {
			return handler(ctx, w, r, vars)
		}
		if err := httputils.CheckForJSON(r); err != nil {
			return handler(ctx, w, r, vars)
		}
		maxBodySize := 4096 // 4KB
		if r.ContentLength > int64(maxBodySize) {
			return handler(ctx, w, r, vars)
		}

		body := r.Body
		bufReader := bufio.NewReaderSize(body, maxBodySize)
		r.Body = ioutils.NewReadCloserWrapper(bufReader, func() error { return body.Close() })

		b, err := bufReader.Peek(maxBodySize)
		if err != io.EOF {
			// either there was an error reading, or the buffer is full (in which case the request is too large)
			return handler(ctx, w, r, vars)
		}

		var postForm map[string]interface{}
		if err := json.Unmarshal(b, &postForm); err == nil {
			maskSecretKeys(postForm)
			formStr, errMarshal := json.Marshal(postForm)
			if errMarshal == nil {
				logrus.Debugf("form data: %s", string(formStr))
			} else {
				logrus.Debugf("form data: %q", postForm)
			}
		}

		return handler(ctx, w, r, vars)
	}
}

func maskSecretKeys(inp interface{}) {
	if arr, ok := inp.([]interface{}); ok {
		for _, f := range arr {
			maskSecretKeys(f)
		}
		return
	}
	if form, ok := inp.(map[string]interface{}); ok {
	loop0:
		for k, v := range form {
			for _, m := range []string{"password", "secret", "jointoken", "unlockkey"} {
				if strings.EqualFold(m, k) {
					form[k] = "*****"
					continue loop0
				}
			}
			maskSecretKeys(v)
		}
	}
}