Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/platform/services/imageproxy/atmos_camo.go

@@ -0,0 +1,92 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package imageproxy
+
+import (
+	"crypto/hmac"
+	"crypto/sha1"
+	"encoding/hex"
+	"io"
+	"net/http"
+	"net/url"
+)
+
+type AtmosCamoBackend struct {
+	proxy     *ImageProxy
+	siteURL   *url.URL
+	remoteURL *url.URL
+	client    *http.Client
+}
+
+func makeAtmosCamoBackend(proxy *ImageProxy) *AtmosCamoBackend {
+	// We deliberately ignore the error because it's from config.json.
+	// The function returns a nil pointer in case of error, and we handle it when it's used.
+	siteURL, _ := url.Parse(*proxy.ConfigService.Config().ServiceSettings.SiteURL)
+	remoteURL, _ := url.Parse(*proxy.ConfigService.Config().ImageProxySettings.RemoteImageProxyURL)
+
+	return &AtmosCamoBackend{
+		proxy:     proxy,
+		siteURL:   siteURL,
+		remoteURL: remoteURL,
+		client:    proxy.HTTPService.MakeClient(false),
+	}
+}
+
+func (backend *AtmosCamoBackend) GetImage(w http.ResponseWriter, r *http.Request, imageURL string) {
+	http.Redirect(w, r, backend.getAtmosCamoImageURL(imageURL), http.StatusFound)
+}
+
+func (backend *AtmosCamoBackend) GetImageDirect(imageURL string) (io.ReadCloser, string, error) {
+	req, err := http.NewRequest("GET", backend.getAtmosCamoImageURL(imageURL), nil)
+	if err != nil {
+		return nil, "", Error{err}
+	}
+
+	resp, err := backend.client.Do(req)
+	if err != nil {
+		return nil, "", Error{err}
+	}
+
+	// Note that we don't do any additional validation of the received data since we expect the image proxy to do that
+	return resp.Body, resp.Header.Get("Content-Type"), nil
+}
+
+func (backend *AtmosCamoBackend) getAtmosCamoImageURL(imageURL string) string {
+	cfg := *backend.proxy.ConfigService.Config()
+	options := *cfg.ImageProxySettings.RemoteImageProxyOptions
+
+	if imageURL == "" || backend.siteURL == nil {
+		return imageURL
+	}
+
+	// Parse url, return siteURL in case of failure.
+	// Also if the URL is opaque.
+	parsedURL, err := url.Parse(imageURL)
+	if err != nil || parsedURL.Opaque != "" {
+		return backend.siteURL.String()
+	}
+
+	// If host is same as siteURL host/ remoteURL host, return.
+	if parsedURL.Host == backend.siteURL.Host || parsedURL.Host == backend.remoteURL.Host {
+		return parsedURL.String()
+	}
+
+	// Handle protocol-relative URLs.
+	if parsedURL.Scheme == "" {
+		parsedURL.Scheme = backend.siteURL.Scheme
+	}
+
+	// If it's a relative URL, fill up the hostname and scheme and return.
+	if parsedURL.Host == "" {
+		parsedURL.Host = backend.siteURL.Host
+		return parsedURL.String()
+	}
+
+	urlBytes := []byte(parsedURL.String())
+	mac := hmac.New(sha1.New, []byte(options))
+	mac.Write(urlBytes)
+	digest := hex.EncodeToString(mac.Sum(nil))
+
+	return backend.remoteURL.String() + "/" + digest + "/" + hex.EncodeToString(urlBytes)
+}