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minio/cmd/generic-handlers.go

668 lines
19 KiB

/*
* Minio Cloud Storage, (C) 2015, 2016, 2017 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cmd
import (
"bufio"
"context"
"net"
"net/http"
"strings"
"time"
humanize "github.com/dustin/go-humanize"
"github.com/minio/minio/cmd/logger"
"github.com/minio/minio/pkg/sys"
"github.com/rs/cors"
"golang.org/x/time/rate"
)
// HandlerFunc - useful to chain different middleware http.Handler
type HandlerFunc func(http.Handler) http.Handler
func registerHandlers(h http.Handler, handlerFns ...HandlerFunc) http.Handler {
for _, hFn := range handlerFns {
h = hFn(h)
}
return h
}
// Adds limiting body size middleware
// Maximum allowed form data field values. 64MiB is a guessed practical value
// which is more than enough to accommodate any form data fields and headers.
const requestFormDataSize = 64 * humanize.MiByte
// For any HTTP request, request body should be not more than 16GiB + requestFormDataSize
// where, 16GiB is the maximum allowed object size for object upload.
const requestMaxBodySize = globalMaxObjectSize + requestFormDataSize
type requestSizeLimitHandler struct {
handler http.Handler
maxBodySize int64
}
func setRequestSizeLimitHandler(h http.Handler) http.Handler {
return requestSizeLimitHandler{handler: h, maxBodySize: requestMaxBodySize}
}
func (h requestSizeLimitHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// Restricting read data to a given maximum length
r.Body = http.MaxBytesReader(w, r.Body, h.maxBodySize)
h.handler.ServeHTTP(w, r)
}
const (
// Maximum size for http headers - See: https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html
maxHeaderSize = 8 * 1024
// Maximum size for user-defined metadata - See: https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html
maxUserDataSize = 2 * 1024
)
type requestHeaderSizeLimitHandler struct {
http.Handler
}
func setRequestHeaderSizeLimitHandler(h http.Handler) http.Handler {
return requestHeaderSizeLimitHandler{h}
}
// ServeHTTP restricts the size of the http header to 8 KB and the size
// of the user-defined metadata to 2 KB.
func (h requestHeaderSizeLimitHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if isHTTPHeaderSizeTooLarge(r.Header) {
writeErrorResponse(w, ErrMetadataTooLarge, r.URL)
return
}
h.Handler.ServeHTTP(w, r)
}
// isHTTPHeaderSizeTooLarge returns true if the provided
// header is larger than 8 KB or the user-defined metadata
// is larger than 2 KB.
func isHTTPHeaderSizeTooLarge(header http.Header) bool {
var size, usersize int
for key := range header {
length := len(key) + len(header.Get(key))
size += length
for _, prefix := range userMetadataKeyPrefixes {
if strings.HasPrefix(key, prefix) {
usersize += length
break
}
}
if usersize > maxUserDataSize || size > maxHeaderSize {
return true
}
}
return false
}
// ReservedMetadataPrefix is the prefix of a metadata key which
// is reserved and for internal use only.
const ReservedMetadataPrefix = "X-Minio-Internal-"
type reservedMetadataHandler struct {
http.Handler
}
func filterReservedMetadata(h http.Handler) http.Handler {
return reservedMetadataHandler{h}
}
// ServeHTTP fails if the request contains at least one reserved header which
// would be treated as metadata.
func (h reservedMetadataHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if containsReservedMetadata(r.Header) {
writeErrorResponse(w, ErrUnsupportedMetadata, r.URL)
return
}
h.Handler.ServeHTTP(w, r)
}
// containsReservedMetadata returns true if the http.Header contains
// keys which are treated as metadata but are reserved for internal use
// and must not set by clients
func containsReservedMetadata(header http.Header) bool {
for key := range header {
if strings.HasPrefix(key, ReservedMetadataPrefix) {
return true
}
}
return false
}
// Reserved bucket.
const (
minioReservedBucket = "minio"
minioReservedBucketPath = "/" + minioReservedBucket
)
// Adds redirect rules for incoming requests.
type redirectHandler struct {
handler http.Handler
}
func setBrowserRedirectHandler(h http.Handler) http.Handler {
return redirectHandler{handler: h}
}
// Fetch redirect location if urlPath satisfies certain
// criteria. Some special names are considered to be
// redirectable, this is purely internal function and
// serves only limited purpose on redirect-handler for
// browser requests.
func getRedirectLocation(urlPath string) (rLocation string) {
if urlPath == minioReservedBucketPath {
rLocation = minioReservedBucketPath + "/"
}
if contains([]string{
"/",
"/webrpc",
"/login",
"/favicon.ico",
}, urlPath) {
rLocation = minioReservedBucketPath + urlPath
}
return rLocation
}
// guessIsBrowserReq - returns true if the request is browser.
// This implementation just validates user-agent and
// looks for "Mozilla" string. This is no way certifiable
// way to know if the request really came from a browser
// since User-Agent's can be arbitrary. But this is just
// a best effort function.
func guessIsBrowserReq(req *http.Request) bool {
if req == nil {
return false
}
return strings.Contains(req.Header.Get("User-Agent"), "Mozilla")
}
// guessIsHealthCheckReq - returns true if incoming request looks
// like healthcheck request
func guessIsHealthCheckReq(req *http.Request) bool {
if req == nil {
return false
}
aType := getRequestAuthType(req)
return aType == authTypeAnonymous && (req.Method == http.MethodGet || req.Method == http.MethodHead) &&
(req.URL.Path == healthCheckPathPrefix+healthCheckLivenessPath ||
req.URL.Path == healthCheckPathPrefix+healthCheckReadinessPath)
}
// guessIsMetricsReq - returns true if incoming request looks
// like metrics request
func guessIsMetricsReq(req *http.Request) bool {
if req == nil {
return false
}
aType := getRequestAuthType(req)
return aType == authTypeAnonymous &&
req.URL.Path == minioReservedBucketPath+prometheusMetricsPath
}
// guessIsRPCReq - returns true if the request is for an RPC endpoint.
func guessIsRPCReq(req *http.Request) bool {
if req == nil {
return false
}
return req.Method == http.MethodConnect && req.Proto == "HTTP/1.0"
}
func (h redirectHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
aType := getRequestAuthType(r)
// Re-direct only for JWT and anonymous requests from browser.
if aType == authTypeJWT || aType == authTypeAnonymous {
// Re-direction is handled specifically for browser requests.
if guessIsBrowserReq(r) && globalIsBrowserEnabled {
// Fetch the redirect location if any.
redirectLocation := getRedirectLocation(r.URL.Path)
if redirectLocation != "" {
// Employ a temporary re-direct.
http.Redirect(w, r, redirectLocation, http.StatusTemporaryRedirect)
return
}
}
}
h.handler.ServeHTTP(w, r)
}
// Adds Cache-Control header
type cacheControlHandler struct {
handler http.Handler
}
func setBrowserCacheControlHandler(h http.Handler) http.Handler {
return cacheControlHandler{h}
}
func (h cacheControlHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if r.Method == http.MethodGet && guessIsBrowserReq(r) && globalIsBrowserEnabled {
// For all browser requests set appropriate Cache-Control policies
if hasPrefix(r.URL.Path, minioReservedBucketPath+"/") {
if hasSuffix(r.URL.Path, ".js") || r.URL.Path == minioReservedBucketPath+"/favicon.ico" {
// For assets set cache expiry of one year. For each release, the name
// of the asset name will change and hence it can not be served from cache.
w.Header().Set("Cache-Control", "max-age=31536000")
} else {
// For non asset requests we serve index.html which will never be cached.
w.Header().Set("Cache-Control", "no-store")
}
}
}
h.handler.ServeHTTP(w, r)
}
Move admin APIs to new path and add redesigned heal APIs (#5351) - Changes related to moving admin APIs - admin APIs now have an endpoint under /minio/admin - admin APIs are now versioned - a new API to server the version is added at "GET /minio/admin/version" and all API operations have the path prefix /minio/admin/v1/<operation> - new service stop API added - credentials change API is moved to /minio/admin/v1/config/credential - credentials change API and configuration get/set API now require TLS so that credentials are protected - all API requests now receive JSON - heal APIs are disabled as they will be changed substantially - Heal API changes Heal API is now provided at a single endpoint with the ability for a client to start a heal sequence on all the data in the server, a single bucket, or under a prefix within a bucket. When a heal sequence is started, the server returns a unique token that needs to be used for subsequent 'status' requests to fetch heal results. On each status request from the client, the server returns heal result records that it has accumulated since the previous status request. The server accumulates upto 1000 records and pauses healing further objects until the client requests for status. If the client does not request any further records for a long time, the server aborts the heal sequence automatically. A heal result record is returned for each entity healed on the server, such as system metadata, object metadata, buckets and objects, and has information about the before and after states on each disk. A client may request to force restart a heal sequence - this causes the running heal sequence to be aborted at the next safe spot and starts a new heal sequence.
7 years ago
// Check to allow access to the reserved "bucket" `/minio` for Admin
// API requests.
func isAdminReq(r *http.Request) bool {
return strings.HasPrefix(r.URL.Path, adminAPIPathPrefix+"/")
}
// Adds verification for incoming paths.
type minioReservedBucketHandler struct {
handler http.Handler
}
func setReservedBucketHandler(h http.Handler) http.Handler {
return minioReservedBucketHandler{h}
}
func (h minioReservedBucketHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
Move admin APIs to new path and add redesigned heal APIs (#5351) - Changes related to moving admin APIs - admin APIs now have an endpoint under /minio/admin - admin APIs are now versioned - a new API to server the version is added at "GET /minio/admin/version" and all API operations have the path prefix /minio/admin/v1/<operation> - new service stop API added - credentials change API is moved to /minio/admin/v1/config/credential - credentials change API and configuration get/set API now require TLS so that credentials are protected - all API requests now receive JSON - heal APIs are disabled as they will be changed substantially - Heal API changes Heal API is now provided at a single endpoint with the ability for a client to start a heal sequence on all the data in the server, a single bucket, or under a prefix within a bucket. When a heal sequence is started, the server returns a unique token that needs to be used for subsequent 'status' requests to fetch heal results. On each status request from the client, the server returns heal result records that it has accumulated since the previous status request. The server accumulates upto 1000 records and pauses healing further objects until the client requests for status. If the client does not request any further records for a long time, the server aborts the heal sequence automatically. A heal result record is returned for each entity healed on the server, such as system metadata, object metadata, buckets and objects, and has information about the before and after states on each disk. A client may request to force restart a heal sequence - this causes the running heal sequence to be aborted at the next safe spot and starts a new heal sequence.
7 years ago
switch {
case guessIsRPCReq(r), guessIsBrowserReq(r), guessIsHealthCheckReq(r), guessIsMetricsReq(r), isAdminReq(r):
Move admin APIs to new path and add redesigned heal APIs (#5351) - Changes related to moving admin APIs - admin APIs now have an endpoint under /minio/admin - admin APIs are now versioned - a new API to server the version is added at "GET /minio/admin/version" and all API operations have the path prefix /minio/admin/v1/<operation> - new service stop API added - credentials change API is moved to /minio/admin/v1/config/credential - credentials change API and configuration get/set API now require TLS so that credentials are protected - all API requests now receive JSON - heal APIs are disabled as they will be changed substantially - Heal API changes Heal API is now provided at a single endpoint with the ability for a client to start a heal sequence on all the data in the server, a single bucket, or under a prefix within a bucket. When a heal sequence is started, the server returns a unique token that needs to be used for subsequent 'status' requests to fetch heal results. On each status request from the client, the server returns heal result records that it has accumulated since the previous status request. The server accumulates upto 1000 records and pauses healing further objects until the client requests for status. If the client does not request any further records for a long time, the server aborts the heal sequence automatically. A heal result record is returned for each entity healed on the server, such as system metadata, object metadata, buckets and objects, and has information about the before and after states on each disk. A client may request to force restart a heal sequence - this causes the running heal sequence to be aborted at the next safe spot and starts a new heal sequence.
7 years ago
// Allow access to reserved buckets
default:
// For all other requests reject access to reserved
// buckets
bucketName, _ := urlPath2BucketObjectName(r.URL.Path)
if isMinioReservedBucket(bucketName) || isMinioMetaBucket(bucketName) {
writeErrorResponse(w, ErrAllAccessDisabled, r.URL)
return
}
}
h.handler.ServeHTTP(w, r)
}
type timeValidityHandler struct {
handler http.Handler
}
// setTimeValidityHandler to validate parsable time over http header
func setTimeValidityHandler(h http.Handler) http.Handler {
return timeValidityHandler{h}
}
// Supported Amz date formats.
var amzDateFormats = []string{
time.RFC1123,
time.RFC1123Z,
iso8601Format,
// Add new AMZ date formats here.
}
// Supported Amz date headers.
var amzDateHeaders = []string{
"x-amz-date",
"date",
}
// parseAmzDate - parses date string into supported amz date formats.
func parseAmzDate(amzDateStr string) (amzDate time.Time, apiErr APIErrorCode) {
for _, dateFormat := range amzDateFormats {
amzDate, err := time.Parse(dateFormat, amzDateStr)
if err == nil {
return amzDate, ErrNone
}
}
return time.Time{}, ErrMalformedDate
}
// parseAmzDateHeader - parses supported amz date headers, in
// supported amz date formats.
func parseAmzDateHeader(req *http.Request) (time.Time, APIErrorCode) {
for _, amzDateHeader := range amzDateHeaders {
amzDateStr := req.Header.Get(http.CanonicalHeaderKey(amzDateHeader))
if amzDateStr != "" {
return parseAmzDate(amzDateStr)
}
}
// Date header missing.
return time.Time{}, ErrMissingDateHeader
}
func (h timeValidityHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
aType := getRequestAuthType(r)
if aType == authTypeSigned || aType == authTypeSignedV2 || aType == authTypeStreamingSigned {
// Verify if date headers are set, if not reject the request
amzDate, apiErr := parseAmzDateHeader(r)
if apiErr != ErrNone {
// All our internal APIs are sensitive towards Date
// header, for all requests where Date header is not
// present we will reject such clients.
writeErrorResponse(w, apiErr, r.URL)
return
}
// Verify if the request date header is shifted by less than globalMaxSkewTime parameter in the past
// or in the future, reject request otherwise.
curTime := UTCNow()
if curTime.Sub(amzDate) > globalMaxSkewTime || amzDate.Sub(curTime) > globalMaxSkewTime {
writeErrorResponse(w, ErrRequestTimeTooSkewed, r.URL)
return
}
}
h.handler.ServeHTTP(w, r)
}
type resourceHandler struct {
handler http.Handler
}
// List of default allowable HTTP methods.
var defaultAllowableHTTPMethods = []string{
http.MethodGet,
http.MethodPut,
http.MethodHead,
http.MethodPost,
http.MethodDelete,
http.MethodOptions,
}
// setCorsHandler handler for CORS (Cross Origin Resource Sharing)
func setCorsHandler(h http.Handler) http.Handler {
commonS3Headers := []string{
"Date",
"ETag",
"Server",
"Connection",
"Accept-Ranges",
"Content-Range",
"Content-Encoding",
"Content-Length",
"Content-Type",
"x-amz-request-id",
}
c := cors.New(cors.Options{
AllowedOrigins: []string{"*"},
AllowedMethods: defaultAllowableHTTPMethods,
AllowedHeaders: []string{"*"},
ExposedHeaders: commonS3Headers,
AllowCredentials: true,
})
return c.Handler(h)
}
// setIgnoreResourcesHandler -
// Ignore resources handler is wrapper handler used for API request resource validation
// Since we do not support all the S3 queries, it is necessary for us to throw back a
// valid error message indicating that requested feature is not implemented.
func setIgnoreResourcesHandler(h http.Handler) http.Handler {
return resourceHandler{h}
10 years ago
}
// Checks requests for not implemented Bucket resources
func ignoreNotImplementedBucketResources(req *http.Request) bool {
for name := range req.URL.Query() {
// Enable GetBucketACL dummy call specifically.
if name == "acl" && req.Method == http.MethodGet {
return false
}
if notimplementedBucketResourceNames[name] {
return true
}
}
return false
}
// Checks requests for not implemented Object resources
func ignoreNotImplementedObjectResources(req *http.Request) bool {
for name := range req.URL.Query() {
// Enable GetObjectACL dummy call specifically.
if name == "acl" && req.Method == http.MethodGet {
return false
}
if notimplementedObjectResourceNames[name] {
return true
}
}
return false
}
// List of not implemented bucket queries
var notimplementedBucketResourceNames = map[string]bool{
"acl": true,
"cors": true,
"lifecycle": true,
"logging": true,
"replication": true,
"tagging": true,
"versions": true,
"requestPayment": true,
"versioning": true,
"website": true,
"inventory": true,
"metrics": true,
"accelerate": true,
}
// List of not implemented object queries
var notimplementedObjectResourceNames = map[string]bool{
"torrent": true,
"acl": true,
"policy": true,
"tagging": true,
"restore": true,
"select": true,
}
// Resource handler ServeHTTP() wrapper
func (h resourceHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
bucketName, objectName := urlPath2BucketObjectName(r.URL.Path)
// If bucketName is present and not objectName check for bucket level resource queries.
if bucketName != "" && objectName == "" {
if ignoreNotImplementedBucketResources(r) {
writeErrorResponse(w, ErrNotImplemented, r.URL)
return
}
}
// If bucketName and objectName are present check for its resource queries.
if bucketName != "" && objectName != "" {
if ignoreNotImplementedObjectResources(r) {
writeErrorResponse(w, ErrNotImplemented, r.URL)
return
}
}
Move admin APIs to new path and add redesigned heal APIs (#5351) - Changes related to moving admin APIs - admin APIs now have an endpoint under /minio/admin - admin APIs are now versioned - a new API to server the version is added at "GET /minio/admin/version" and all API operations have the path prefix /minio/admin/v1/<operation> - new service stop API added - credentials change API is moved to /minio/admin/v1/config/credential - credentials change API and configuration get/set API now require TLS so that credentials are protected - all API requests now receive JSON - heal APIs are disabled as they will be changed substantially - Heal API changes Heal API is now provided at a single endpoint with the ability for a client to start a heal sequence on all the data in the server, a single bucket, or under a prefix within a bucket. When a heal sequence is started, the server returns a unique token that needs to be used for subsequent 'status' requests to fetch heal results. On each status request from the client, the server returns heal result records that it has accumulated since the previous status request. The server accumulates upto 1000 records and pauses healing further objects until the client requests for status. If the client does not request any further records for a long time, the server aborts the heal sequence automatically. A heal result record is returned for each entity healed on the server, such as system metadata, object metadata, buckets and objects, and has information about the before and after states on each disk. A client may request to force restart a heal sequence - this causes the running heal sequence to be aborted at the next safe spot and starts a new heal sequence.
7 years ago
// A put method on path "/" doesn't make sense, ignore it.
if r.Method == http.MethodPut && r.URL.Path == "/" {
writeErrorResponse(w, ErrNotImplemented, r.URL)
return
}
// Serve HTTP.
h.handler.ServeHTTP(w, r)
}
// httpResponseRecorder wraps http.ResponseWriter
// to record some useful http response data.
type httpResponseRecorder struct {
http.ResponseWriter
respStatusCode int
}
// Wraps ResponseWriter's Write()
func (rww *httpResponseRecorder) Write(b []byte) (int, error) {
return rww.ResponseWriter.Write(b)
}
// Wraps ResponseWriter's Flush()
func (rww *httpResponseRecorder) Flush() {
rww.ResponseWriter.(http.Flusher).Flush()
}
// Wraps ResponseWriter's WriteHeader() and record
// the response status code
func (rww *httpResponseRecorder) WriteHeader(httpCode int) {
rww.respStatusCode = httpCode
rww.ResponseWriter.WriteHeader(httpCode)
}
func (rww *httpResponseRecorder) Hijack() (net.Conn, *bufio.ReadWriter, error) {
return rww.ResponseWriter.(http.Hijacker).Hijack()
}
// httpStatsHandler definition: gather HTTP statistics
type httpStatsHandler struct {
handler http.Handler
}
// setHttpStatsHandler sets a http Stats Handler
func setHTTPStatsHandler(h http.Handler) http.Handler {
return httpStatsHandler{handler: h}
}
func (h httpStatsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// Wraps w to record http response information
ww := &httpResponseRecorder{ResponseWriter: w}
// Time start before the call is about to start.
tBefore := UTCNow()
// Execute the request
h.handler.ServeHTTP(ww, r)
// Time after call has completed.
tAfter := UTCNow()
// Time duration in secs since the call started.
//
// We don't need to do nanosecond precision in this
// simply for the fact that it is not human readable.
durationSecs := tAfter.Sub(tBefore).Seconds()
// Update http statistics
globalHTTPStats.updateStats(r, ww, durationSecs)
}
// pathValidityHandler validates all the incoming paths for
// any bad components and rejects them.
type pathValidityHandler struct {
handler http.Handler
}
func setPathValidityHandler(h http.Handler) http.Handler {
return pathValidityHandler{handler: h}
}
// Bad path components to be rejected by the path validity handler.
const (
dotdotComponent = ".."
dotComponent = "."
)
// Check if the incoming path has bad path components,
// such as ".." and "."
func hasBadPathComponent(path string) bool {
path = strings.TrimSpace(path)
for _, p := range strings.Split(path, slashSeparator) {
switch strings.TrimSpace(p) {
case dotdotComponent:
return true
case dotComponent:
return true
}
}
return false
}
func (h pathValidityHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// Check for bad components in URL path.
if hasBadPathComponent(r.URL.Path) {
writeErrorResponse(w, ErrInvalidResourceName, r.URL)
return
}
// Check for bad components in URL query values.
for _, vv := range r.URL.Query() {
for _, v := range vv {
if hasBadPathComponent(v) {
writeErrorResponse(w, ErrInvalidResourceName, r.URL)
return
}
}
}
h.handler.ServeHTTP(w, r)
}
// setRateLimitHandler middleware limits the throughput to h using a
// rate.Limiter token bucket configured with maxOpenFileLimit and
// burst set to 1. The request will idle for up to 1*time.Second.
// If the limiter detects the deadline will be exceeded, the request is
// cancelled immediately.
func setRateLimitHandler(h http.Handler) http.Handler {
_, maxLimit, err := sys.GetMaxOpenFileLimit()
logger.CriticalIf(context.Background(), err)
// Burst value is set to 1 to allow only maxOpenFileLimit
// requests to happen at once.
l := rate.NewLimiter(rate.Limit(maxLimit), 1)
return rateLimit{l, h}
}
type rateLimit struct {
*rate.Limiter
handler http.Handler
}
func (l rateLimit) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// create a new context from the request with the wait timeout
ctx, cancel := context.WithTimeout(r.Context(), 1*time.Second)
defer cancel() // always cancel the context!
// Wait errors out if the request cannot be processed within
// the deadline. time/rate tries to reserve a slot if possible
// with in the given duration if it's not possible then Wait(ctx)
// returns an error and we cancel the request with ErrSlowDown
// error message to the client. This context wait also ensures
// requests doomed to fail are terminated early, preventing a
// potential pileup on the server.
if err := l.Wait(ctx); err != nil {
// Send an S3 compatible error, SlowDown.
writeErrorResponse(w, ErrSlowDown, r.URL)
return
}
l.handler.ServeHTTP(w, r)
}
type securityHeaderHandler struct {
handler http.Handler
}
func addSecurityHeaders(h http.Handler) http.Handler {
return securityHeaderHandler{handler: h}
}
func (s securityHeaderHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
header := w.Header()
header.Set("X-XSS-Protection", "\"1; mode=block\"") // Prevents against XSS attacks
header.Set("Content-Security-Policy", "block-all-mixed-content") // prevent mixed (HTTP / HTTPS content)
s.handler.ServeHTTP(w, r)
}