[MM-26812] Add support for resumable file uploads (#15252)

* Implement AppendFile for FileBackend

* Split test into subtests

* [MM-26812] Add support for resumable file uploads (#15252)

* Implement UploadSession

* Implement UploadSessionStore

* Add error strings

* Implement resumable file uploads

* Add UploadType

* Fix retry layer tests

* Regenerate store layers

* Fix store error handling

* Use base for filename

* Prevent concurrent uploads on the same upload session

* Fix erroneus error string

* Improve error handling

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

* Fix translations

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/upload.go

@@ -0,0 +1,123 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package api4
+
+import (
+	"net/http"
+
+	"github.com/mattermost/mattermost-server/v5/audit"
+	"github.com/mattermost/mattermost-server/v5/model"
+)
+
+func (api *API) InitUpload() {
+	api.BaseRoutes.Uploads.Handle("", api.ApiSessionRequired(createUpload)).Methods("POST")
+	api.BaseRoutes.Upload.Handle("", api.ApiSessionRequired(getUpload)).Methods("GET")
+	api.BaseRoutes.Upload.Handle("", api.ApiSessionRequired(uploadData)).Methods("POST")
+}
+
+func createUpload(c *Context, w http.ResponseWriter, r *http.Request) {
+	if !*c.App.Config().FileSettings.EnableFileAttachments {
+		c.Err = model.NewAppError("createUpload",
+			"api.file.attachments.disabled.app_error",
+			nil, "", http.StatusNotImplemented)
+		return
+	}
+
+	us := model.UploadSessionFromJson(r.Body)
+	if us == nil {
+		c.SetInvalidParam("upload")
+		return
+	}
+
+	auditRec := c.MakeAuditRecord("createUpload", audit.Fail)
+	defer c.LogAuditRec(auditRec)
+	auditRec.AddMeta("upload", us)
+
+	if !c.App.SessionHasPermissionToChannel(*c.App.Session(), us.ChannelId, model.PERMISSION_UPLOAD_FILE) {
+		c.SetPermissionError(model.PERMISSION_UPLOAD_FILE)
+		return
+	}
+
+	us.Id = model.NewId()
+	us.Type = model.UploadTypeAttachment
+	us.UserId = c.App.Session().UserId
+	us, err := c.App.CreateUploadSession(us)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	auditRec.Success()
+	w.WriteHeader(http.StatusCreated)
+	w.Write([]byte(us.ToJson()))
+}
+
+func getUpload(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequireUploadId()
+	if c.Err != nil {
+		return
+	}
+
+	us, err := c.App.GetUploadSession(c.Params.UploadId)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	if us.UserId != c.App.Session().UserId {
+		c.Err = model.NewAppError("getUpload", "api.upload.get_upload.forbidden.app_error", nil, "", http.StatusForbidden)
+		return
+	}
+
+	w.Write([]byte(us.ToJson()))
+}
+
+func uploadData(c *Context, w http.ResponseWriter, r *http.Request) {
+	if !*c.App.Config().FileSettings.EnableFileAttachments {
+		c.Err = model.NewAppError("uploadData", "api.file.attachments.disabled.app_error",
+			nil, "", http.StatusNotImplemented)
+		return
+	}
+
+	c.RequireUploadId()
+	if c.Err != nil {
+		return
+	}
+
+	auditRec := c.MakeAuditRecord("uploadData", audit.Fail)
+	defer c.LogAuditRec(auditRec)
+	auditRec.AddMeta("upload_id", c.Params.UploadId)
+
+	us, err := c.App.GetUploadSession(c.Params.UploadId)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	if r.ContentLength > (us.FileSize - us.FileOffset) {
+		c.Err = model.NewAppError("uploadData", "api.upload.upload_data.invalid_content_length",
+			nil, "", http.StatusBadRequest)
+		return
+	}
+
+	if us.UserId != c.App.Session().UserId || !c.App.SessionHasPermissionToChannel(*c.App.Session(), us.ChannelId, model.PERMISSION_UPLOAD_FILE) {
+		c.SetPermissionError(model.PERMISSION_UPLOAD_FILE)
+		return
+	}
+
+	info, err := c.App.UploadData(us, r.Body)
+	if err != nil {
+		c.Err = err
+		return
+	}
+
+	auditRec.Success()
+
+	if info == nil {
+		w.WriteHeader(http.StatusNoContent)
+		return
+	}
+
+	w.Write([]byte(info.ToJson()))
+}