audit.go

package audit

import (
	"bytes"
	"encoding/json"
	"io/ioutil"
	"net/http"
	"time"

	"github.com/pborman/uuid"

	k8stypes "k8s.io/apimachinery/pkg/types"
)

const (
	contentTypeJSON = "application/json"
)

const (
	levelNull = iota
	levelMetadata
	levelRequest
	levelRequestResponse
)

var (
	bodyMethods = map[string]bool{
		http.MethodPut:  true,
		http.MethodPost: true,
	}
	sensitiveRequestHeader  = []string{"Cookie", "Authorization"}
	sensitiveResponseHeader = []string{"Cookie", "Set-Cookie"}
)

type auditLog struct {
	log     *log
	writer  *LogWriter
	reqBody []byte
}

type log struct {
	AuditID           k8stypes.UID `json:"auditID,omitempty"`
	RequestURI        string       `json:"requestURI,omitempty"`
	User              *userInfo    `json:"user,omitempty"`
	Method            string       `json:"method,omitempty"`
	RemoteAddr        string       `json:"remoteAddr,omitempty"`
	RequestTimestamp  string       `json:"requestTimestamp,omitempty"`
	ResponseTimestamp string       `json:"responseTimestamp,omitempty"`
	ResponseCode      int          `json:"responseCode,omitempty"`
	RequestHeader     http.Header  `json:"requestHeader,omitempty"`
	ResponseHeader    http.Header  `json:"responseHeader,omitempty"`
	RequestBody       []byte       `json:"requestBody,omitempty"`
	ResponseBody      []byte       `json:"responseBody,omitempty"`
}

type userInfo struct {
	Name  string `json:"name,omitempty"`
	Group string `json:"group,omitempty"`
}

func new(writer *LogWriter, req *http.Request) (*auditLog, error) {
	auditLog := &auditLog{
		writer: writer,
		log: &log{
			AuditID:          k8stypes.UID(uuid.NewRandom().String()),
			RequestURI:       req.RequestURI,
			Method:           req.Method,
			RemoteAddr:       req.RemoteAddr,
			RequestTimestamp: time.Now().Format(time.RFC3339),
		},
	}

	contentType := req.Header.Get("Content-Type")
	if writer.Level >= levelRequest && bodyMethods[req.Method] && contentType == contentTypeJSON {
		reqBody, err := readBodyWithoutLosingContent(req)
		if err != nil {
			return nil, err
		}
		auditLog.reqBody = reqBody
	}
	return auditLog, nil
}

func (a *auditLog) write(reqHeaders, resHeaders http.Header, resCode int, resBody []byte) error {
	userInfo := &userInfo{
		Name:  reqHeaders.Get("Impersonate-User"),
		Group: reqHeaders.Get("Impersonate-Group"),
	}
	a.log.User = userInfo
	a.log.ResponseTimestamp = time.Now().Format(time.RFC3339)
	a.log.RequestHeader = filterOutHeaders(reqHeaders, sensitiveRequestHeader)
	a.log.ResponseHeader = filterOutHeaders(resHeaders, sensitiveResponseHeader)
	a.log.ResponseCode = resCode

	var buffer bytes.Buffer
	alByte, err := json.Marshal(a.log)
	if err != nil {
		return err
	}

	buffer.Write(bytes.TrimSuffix(alByte, []byte("}")))

	if a.writer.Level >= levelRequest && a.reqBody != nil {
		buffer.WriteString(`,"requestBody":`)
		buffer.Write(bytes.TrimSuffix(a.reqBody, []byte("\n")))
	}
	if a.writer.Level >= levelRequestResponse && resHeaders.Get("Content-Type") == contentTypeJSON && resBody != nil {
		buffer.WriteString(`,"responseBody":`)
		buffer.Write(bytes.TrimSuffix(resBody, []byte("\n")))
	}
	buffer.WriteString("}\n")
	_, err = a.writer.Output.Write(buffer.Bytes())
	return err
}

func readBodyWithoutLosingContent(req *http.Request) ([]byte, error) {
	if !bodyMethods[req.Method] {
		return nil, nil
	}

	bodyBytes, err := ioutil.ReadAll(req.Body)
	if err != nil {
		return nil, err
	}
	req.Body = ioutil.NopCloser(bytes.NewBuffer(bodyBytes))

	return bodyBytes, nil
}

func filterOutHeaders(headers http.Header, filterKeys []string) map[string][]string {
	newHeader := make(map[string][]string)
	for k, v := range headers {
		if isExist(filterKeys, k) {
			continue
		}
		newHeader[k] = v
	}
	return newHeader
}

func isExist(array []string, key string) bool {
	for _, v := range array {
		if v == key {
			return true
		}
	}
	return false
}