mattermost/api/file.go

// Copyright (c) 2015 Mattermost, Inc. All Rights Reserved.
// See License.txt for license information.

package api

import (
	"bytes"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"image"
	"image/color"
	"image/draw"
	_ "image/gif"
	"image/jpeg"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	l4g "github.com/alecthomas/log4go"
	"github.com/disintegration/imaging"
	"github.com/goamz/goamz/aws"
	"github.com/goamz/goamz/s3"
	"github.com/gorilla/mux"
	"github.com/mattermost/platform/model"
	"github.com/mattermost/platform/utils"
	"github.com/mssola/user_agent"
	"github.com/rwcarlsen/goexif/exif"
	_ "golang.org/x/image/bmp"
)

const (
	/*
	  EXIF Image Orientations
	  1        2       3      4         5            6           7          8

	  888888  888888      88  88      8888888888  88                  88  8888888888
	  88          88      88  88      88  88      88  88          88  88      88  88
	  8888      8888    8888  8888    88          8888888888  8888888888          88
	  88          88      88  88
	  88          88  888888  888888
	*/
	Upright            = 1
	UprightMirrored    = 2
	UpsideDown         = 3
	UpsideDownMirrored = 4
	RotatedCWMirrored  = 5
	RotatedCCW         = 6
	RotatedCCWMirrored = 7
	RotatedCW          = 8

	MaxImageSize = 6048 * 4032 // 24 megapixels, roughly 36MB as a raw image
)

func InitFile() {
	l4g.Debug(utils.T("api.file.init.debug"))

	BaseRoutes.TeamFiles.Handle("/upload", ApiUserRequired(uploadFile)).Methods("POST")

	BaseRoutes.NeedFile.Handle("/get", ApiUserRequiredTrustRequester(getFile)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_thumbnail", ApiUserRequiredTrustRequester(getFileThumbnail)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_preview", ApiUserRequiredTrustRequester(getFilePreview)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_info", ApiUserRequired(getFileInfo)).Methods("GET")
	BaseRoutes.NeedFile.Handle("/get_public_link", ApiUserRequired(getPublicLink)).Methods("GET")

	BaseRoutes.Public.Handle("/files/{file_id:[A-Za-z0-9]+}/get", ApiAppHandlerTrustRequesterIndependent(getPublicFile)).Methods("GET")
	BaseRoutes.Public.Handle("/files/get/{team_id:[A-Za-z0-9]+}/{channel_id:[A-Za-z0-9]+}/{user_id:[A-Za-z0-9]+}/{filename:([A-Za-z0-9]+/)?.+(\\.[A-Za-z0-9]{3,})?}", ApiAppHandlerTrustRequesterIndependent(getPublicFileOld)).Methods("GET")
}

func uploadFile(c *Context, w http.ResponseWriter, r *http.Request) {
	if len(utils.Cfg.FileSettings.DriverName) == 0 {
		c.Err = model.NewLocAppError("uploadFile", "api.file.upload_file.storage.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	if r.ContentLength > *utils.Cfg.FileSettings.MaxFileSize {
		c.Err = model.NewLocAppError("uploadFile", "api.file.upload_file.too_large.app_error", nil, "")
		c.Err.StatusCode = http.StatusRequestEntityTooLarge
		return
	}

	if err := r.ParseMultipartForm(*utils.Cfg.FileSettings.MaxFileSize); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	m := r.MultipartForm

	props := m.Value
	if len(props["channel_id"]) == 0 {
		c.SetInvalidParam("uploadFile", "channel_id")
		return
	}
	channelId := props["channel_id"][0]
	if len(channelId) == 0 {
		c.SetInvalidParam("uploadFile", "channel_id")
		return
	}

	if !HasPermissionToChannelContext(c, channelId, model.PERMISSION_UPLOAD_FILE) {
		return
	}

	resStruct := &model.FileUploadResponse{
		FileInfos: []*model.FileInfo{},
		ClientIds: []string{},
	}

	previewPathList := []string{}
	thumbnailPathList := []string{}
	imageDataList := [][]byte{}

	for i, fileHeader := range m.File["files"] {
		file, fileErr := fileHeader.Open()
		defer file.Close()
		if fileErr != nil {
			http.Error(w, fileErr.Error(), http.StatusInternalServerError)
			return
		}

		buf := bytes.NewBuffer(nil)
		io.Copy(buf, file)
		data := buf.Bytes()

		info, err := doUploadFile(c.TeamId, channelId, c.Session.UserId, fileHeader.Filename, data)
		if err != nil {
			c.Err = err
			return
		}

		if info.PreviewPath != "" || info.ThumbnailPath != "" {
			previewPathList = append(previewPathList, info.PreviewPath)
			thumbnailPathList = append(thumbnailPathList, info.ThumbnailPath)
			imageDataList = append(imageDataList, data)
		}

		resStruct.FileInfos = append(resStruct.FileInfos, info)

		if len(m.Value["client_ids"]) > 0 {
			resStruct.ClientIds = append(resStruct.ClientIds, m.Value["client_ids"][i])
		}
	}

	handleImages(previewPathList, thumbnailPathList, imageDataList)

	w.Write([]byte(resStruct.ToJson()))
}

func doUploadFile(teamId string, channelId string, userId string, rawFilename string, data []byte) (*model.FileInfo, *model.AppError) {
	filename := filepath.Base(rawFilename)

	info, err := model.GetInfoForBytes(filename, data)
	if err != nil {
		err.StatusCode = http.StatusBadRequest
		return nil, err
	}

	info.Id = model.NewId()
	info.CreatorId = userId

	pathPrefix := "teams/" + teamId + "/channels/" + channelId + "/users/" + userId + "/" + info.Id + "/"
	info.Path = pathPrefix + filename

	if info.IsImage() {
		// Check dimensions before loading the whole thing into memory later on
		if info.Width*info.Height > MaxImageSize {
			err := model.NewLocAppError("uploadFile", "api.file.upload_file.large_image.app_error", nil, "")
			err.StatusCode = http.StatusBadRequest
			return nil, err
		}

		nameWithoutExtension := filename[:strings.LastIndex(filename, ".")]
		info.PreviewPath = pathPrefix + nameWithoutExtension + "_preview.jpg"
		info.ThumbnailPath = pathPrefix + nameWithoutExtension + "_thumb.jpg"
	}

	if err := WriteFile(data, info.Path); err != nil {
		return nil, err
	}

	if result := <-Srv.Store.FileInfo().Save(info); result.Err != nil {
		return nil, result.Err
	}

	return info, nil
}

func handleImages(previewPathList []string, thumbnailPathList []string, fileData [][]byte) {
	for i := range fileData {
		go func() {
			// Decode image bytes into Image object
			img, imgType, err := image.Decode(bytes.NewReader(fileData[i]))
			if err != nil {
				l4g.Error(utils.T("api.file.handle_images_forget.decode.error"), err)
				return
			}

			width := img.Bounds().Dx()
			height := img.Bounds().Dy()

			// Fill in the background of a potentially-transparent png file as white
			if imgType == "png" {
				dst := image.NewRGBA(img.Bounds())
				draw.Draw(dst, dst.Bounds(), image.NewUniform(color.White), image.Point{}, draw.Src)
				draw.Draw(dst, dst.Bounds(), img, img.Bounds().Min, draw.Over)
				img = dst
			}

			// Flip the image to be upright
			orientation, _ := getImageOrientation(fileData[i])

			switch orientation {
			case UprightMirrored:
				img = imaging.FlipH(img)
			case UpsideDown:
				img = imaging.Rotate180(img)
			case UpsideDownMirrored:
				img = imaging.FlipV(img)
			case RotatedCWMirrored:
				img = imaging.Transpose(img)
			case RotatedCCW:
				img = imaging.Rotate270(img)
			case RotatedCCWMirrored:
				img = imaging.Transverse(img)
			case RotatedCW:
				img = imaging.Rotate90(img)
			}

			go generateThumbnailImage(img, thumbnailPathList[i], width, height)
			go generatePreviewImage(img, previewPathList[i], width)
		}()
	}
}

func getImageOrientation(imageData []byte) (int, error) {
	if exifData, err := exif.Decode(bytes.NewReader(imageData)); err != nil {
		return Upright, err
	} else {
		if tag, err := exifData.Get("Orientation"); err != nil {
			return Upright, err
		} else {
			orientation, err := tag.Int(0)
			if err != nil {
				return Upright, err
			} else {
				return orientation, nil
			}
		}
	}
}

func generateThumbnailImage(img image.Image, thumbnailPath string, width int, height int) {
	thumbWidth := float64(utils.Cfg.FileSettings.ThumbnailWidth)
	thumbHeight := float64(utils.Cfg.FileSettings.ThumbnailHeight)
	imgWidth := float64(width)
	imgHeight := float64(height)

	var thumbnail image.Image
	if imgHeight < thumbHeight && imgWidth < thumbWidth {
		thumbnail = img
	} else if imgHeight/imgWidth < thumbHeight/thumbWidth {
		thumbnail = imaging.Resize(img, 0, utils.Cfg.FileSettings.ThumbnailHeight, imaging.Lanczos)
	} else {
		thumbnail = imaging.Resize(img, utils.Cfg.FileSettings.ThumbnailWidth, 0, imaging.Lanczos)
	}

	buf := new(bytes.Buffer)
	if err := jpeg.Encode(buf, thumbnail, &jpeg.Options{Quality: 90}); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.encode_jpeg.error"), thumbnailPath, err)
		return
	}

	if err := WriteFile(buf.Bytes(), thumbnailPath); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.upload_thumb.error"), thumbnailPath, err)
		return
	}
}

func generatePreviewImage(img image.Image, previewPath string, width int) {
	var preview image.Image
	if width > int(utils.Cfg.FileSettings.PreviewWidth) {
		preview = imaging.Resize(img, utils.Cfg.FileSettings.PreviewWidth, utils.Cfg.FileSettings.PreviewHeight, imaging.Lanczos)
	} else {
		preview = img
	}

	buf := new(bytes.Buffer)

	if err := jpeg.Encode(buf, preview, &jpeg.Options{Quality: 90}); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.encode_preview.error"), previewPath, err)
		return
	}

	if err := WriteFile(buf.Bytes(), previewPath); err != nil {
		l4g.Error(utils.T("api.file.handle_images_forget.upload_preview.error"), previewPath, err)
		return
	}
}

func getFile(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if data, err := ReadFile(info.Path); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFileThumbnail(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if info.ThumbnailPath == "" {
		c.Err = model.NewLocAppError("getFileThumbnail", "api.file.get_file_thumbnail.no_thumbnail.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := ReadFile(info.ThumbnailPath); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFilePreview(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if info.PreviewPath == "" {
		c.Err = model.NewLocAppError("getFilePreview", "api.file.get_file_preview.no_preview.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := ReadFile(info.PreviewPath); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFileInfo(c *Context, w http.ResponseWriter, r *http.Request) {
	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	w.Header().Set("Cache-Control", "max-age=2592000, public")

	w.Write([]byte(info.ToJson()))
}

func getPublicFile(c *Context, w http.ResponseWriter, r *http.Request) {
	if !utils.Cfg.FileSettings.EnablePublicLink {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_disabled.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	info, err := getFileInfoForRequest(c, r, false)
	if err != nil {
		c.Err = err
		return
	}

	hash := r.URL.Query().Get("h")

	if len(hash) > 0 {
		correctHash := generatePublicLinkHash(info.Id, *utils.Cfg.FileSettings.PublicLinkSalt)

		if hash != correctHash {
			c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
			c.Err.StatusCode = http.StatusBadRequest
			return
		}
	} else {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := ReadFile(info.Path); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func getFileInfoForRequest(c *Context, r *http.Request, requireFileVisible bool) (*model.FileInfo, *model.AppError) {
	if len(utils.Cfg.FileSettings.DriverName) == 0 {
		err := model.NewLocAppError("getFileInfoForRequest", "api.file.get_file_info_for_request.storage.app_error", nil, "")
		err.StatusCode = http.StatusNotImplemented
		return nil, err
	}

	params := mux.Vars(r)

	fileId := params["file_id"]
	if len(fileId) != 26 {
		return nil, NewInvalidParamError("getFileInfoForRequest", "file_id")
	}

	var info *model.FileInfo
	if result := <-Srv.Store.FileInfo().Get(fileId); result.Err != nil {
		return nil, result.Err
	} else {
		info = result.Data.(*model.FileInfo)
	}

	// only let users access files visible in a channel, unless they're the one who uploaded the file
	if info.CreatorId != c.Session.UserId {
		if len(info.PostId) == 0 {
			err := model.NewLocAppError("getFileInfoForRequest", "api.file.get_file_info_for_request.no_post.app_error", nil, "file_id="+fileId)
			err.StatusCode = http.StatusBadRequest
			return nil, err
		}

		if requireFileVisible {
			if !HasPermissionToChannelByPostContext(c, info.PostId, model.PERMISSION_READ_CHANNEL) {
				return nil, c.Err
			}
		}
	}

	return info, nil
}

func getPublicFileOld(c *Context, w http.ResponseWriter, r *http.Request) {
	if len(utils.Cfg.FileSettings.DriverName) == 0 {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_public_file_old.storage.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	} else if !utils.Cfg.FileSettings.EnablePublicLink {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_disabled.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	params := mux.Vars(r)

	teamId := params["team_id"]
	channelId := params["channel_id"]
	userId := params["user_id"]
	filename := params["filename"]

	hash := r.URL.Query().Get("h")

	if len(hash) > 0 {
		correctHash := generatePublicLinkHash(filename, *utils.Cfg.FileSettings.PublicLinkSalt)

		if hash != correctHash {
			c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
			c.Err.StatusCode = http.StatusBadRequest
			return
		}
	} else {
		c.Err = model.NewLocAppError("getPublicFile", "api.file.get_file.public_invalid.app_error", nil, "")
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	path := "teams/" + teamId + "/channels/" + channelId + "/users/" + userId + "/" + filename

	var info *model.FileInfo
	if result := <-Srv.Store.FileInfo().GetByPath(path); result.Err != nil {
		c.Err = result.Err
		return
	} else {
		info = result.Data.(*model.FileInfo)
	}

	if len(info.PostId) == 0 {
		c.Err = model.NewLocAppError("getPublicFileOld", "api.file.get_public_file_old.no_post.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	if data, err := ReadFile(info.Path); err != nil {
		c.Err = err
		c.Err.StatusCode = http.StatusNotFound
	} else if err := writeFileResponse(info.Name, data, w, r); err != nil {
		c.Err = err
		return
	}
}

func writeFileResponse(filename string, bytes []byte, w http.ResponseWriter, r *http.Request) *model.AppError {
	w.Header().Set("Cache-Control", "max-age=2592000, public")
	w.Header().Set("Content-Length", strconv.Itoa(len(bytes)))
	w.Header().Del("Content-Type") // Content-Type will be set automatically by the http writer

	// attach extra headers to trigger a download on IE, Edge, and Safari
	ua := user_agent.New(r.UserAgent())
	bname, _ := ua.Browser()

	w.Header().Set("Content-Disposition", "attachment;filename=\""+filename+"\"")

	if bname == "Edge" || bname == "Internet Explorer" || bname == "Safari" {
		w.Header().Set("Content-Type", "application/octet-stream")
	}

	// prevent file links from being embedded in iframes
	w.Header().Set("X-Frame-Options", "DENY")
	w.Header().Set("Content-Security-Policy", "Frame-ancestors 'none'")

	w.Write(bytes)

	return nil
}

func getPublicLink(c *Context, w http.ResponseWriter, r *http.Request) {
	if !utils.Cfg.FileSettings.EnablePublicLink {
		c.Err = model.NewLocAppError("getPublicLink", "api.file.get_public_link.disabled.app_error", nil, "")
		c.Err.StatusCode = http.StatusNotImplemented
		return
	}

	info, err := getFileInfoForRequest(c, r, true)
	if err != nil {
		c.Err = err
		return
	}

	if len(info.PostId) == 0 {
		c.Err = model.NewLocAppError("getPublicLink", "api.file.get_public_link.no_post.app_error", nil, "file_id="+info.Id)
		c.Err.StatusCode = http.StatusBadRequest
		return
	}

	w.Write([]byte(model.StringToJson(generatePublicLink(c.GetSiteURL(), info))))
}

func generatePublicLink(siteURL string, info *model.FileInfo) string {
	hash := generatePublicLinkHash(info.Id, *utils.Cfg.FileSettings.PublicLinkSalt)
	return fmt.Sprintf("%s%s/public/files/%v/get?h=%s", siteURL, model.API_URL_SUFFIX, info.Id, hash)
}

func generatePublicLinkHash(fileId, salt string) string {
	hash := sha256.New()
	hash.Write([]byte(salt))
	hash.Write([]byte(fileId))

	return base64.RawURLEncoding.EncodeToString(hash.Sum(nil))
}

// Creates and stores FileInfos for a post created before the FileInfos table existed.
func migrateFilenamesToFileInfos(post *model.Post) []*model.FileInfo {
	if len(post.Filenames) == 0 {
		l4g.Warn(utils.T("api.file.migrate_filenames_to_file_infos.no_filenames.warn"), post.Id)
		return []*model.FileInfo{}
	}

	cchan := Srv.Store.Channel().Get(post.ChannelId)

	// There's a weird bug that rarely happens where a post ends up with duplicate Filenames so remove those
	filenames := utils.RemoveDuplicatesFromStringArray(post.Filenames)

	var channel *model.Channel
	if result := <-cchan; result.Err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.channel.app_error"), post.Id, post.ChannelId, result.Err)
		return []*model.FileInfo{}
	} else {
		channel = result.Data.(*model.Channel)
	}

	// Find the team that was used to make this post since its part of the file path that isn't saved in the Filename
	var teamId string
	if channel.TeamId == "" {
		// This post was made in a cross-team DM channel so we need to find where its files were saved
		teamId = findTeamIdForFilename(post, filenames[0])
	} else {
		teamId = channel.TeamId
	}

	// Create FileInfo objects for this post
	infos := make([]*model.FileInfo, 0, len(filenames))
	fileIds := make([]string, 0, len(filenames))
	if teamId == "" {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.team_id.error"), post.Id, filenames)
	} else {
		for _, filename := range filenames {
			info := getInfoForFilename(post, teamId, filename)
			if info == nil {
				continue
			}

			if result := <-Srv.Store.FileInfo().Save(info); result.Err != nil {
				l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.save_file_info.app_error"), post.Id, info.Id, filename, result.Err)
				continue
			}

			fileIds = append(fileIds, info.Id)
			infos = append(infos, info)
		}
	}

	// Copy and save the updated post
	newPost := &model.Post{}
	*newPost = *post

	newPost.Filenames = []string{}
	newPost.FileIds = fileIds

	// Update Posts to clear Filenames and set FileIds
	if result := <-Srv.Store.Post().Update(newPost, post); result.Err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.save_post.app_error"), post.Id, newPost.FileIds, post.Filenames, result.Err)
		return []*model.FileInfo{}
	} else {
		return infos
	}
}

func findTeamIdForFilename(post *model.Post, filename string) string {
	split := strings.SplitN(filename, "/", 5)
	id := split[3]
	name, _ := url.QueryUnescape(split[4])

	// This post is in a direct channel so we need to figure out what team the files are stored under.
	if result := <-Srv.Store.Team().GetTeamsByUserId(post.UserId); result.Err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.teams.app_error"), post.Id, result.Err)
	} else if teams := result.Data.([]*model.Team); len(teams) == 1 {
		// The user has only one team so the post must've been sent from it
		return teams[0].Id
	} else {
		for _, team := range teams {
			path := fmt.Sprintf("teams/%s/channels/%s/users/%s/%s/%s", team.Id, post.ChannelId, post.UserId, id, name)
			if _, err := ReadFile(path); err == nil {
				// Found the team that this file was posted from
				return team.Id
			}
		}
	}

	return ""
}

func getInfoForFilename(post *model.Post, teamId string, filename string) *model.FileInfo {
	// Find the path from the Filename of the form /{channelId}/{userId}/{uid}/{nameWithExtension}
	split := strings.SplitN(filename, "/", 5)
	if len(split) < 5 {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.unexpected_filename.error"), post.Id, filename)
		return nil
	}

	channelId := split[1]
	userId := split[2]
	oldId := split[3]
	name, _ := url.QueryUnescape(split[4])

	if split[0] != "" || split[1] != post.ChannelId || split[2] != post.UserId || strings.Contains(split[4], "/") {
		l4g.Warn(utils.T("api.file.migrate_filenames_to_file_infos.mismatched_filename.warn"), post.Id, post.ChannelId, post.UserId, filename)
	}

	pathPrefix := fmt.Sprintf("teams/%s/channels/%s/users/%s/%s/", teamId, channelId, userId, oldId)
	path := pathPrefix + name

	// Open the file and populate the fields of the FileInfo
	var info *model.FileInfo
	if data, err := ReadFile(path); err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.file_not_found.error"), post.Id, filename, path, err)
		return nil
	} else {
		var err *model.AppError
		info, err = model.GetInfoForBytes(name, data)
		if err != nil {
			l4g.Warn(utils.T("api.file.migrate_filenames_to_file_infos.info.app_error"), post.Id, filename, err)
		}
	}

	// Generate a new ID because with the old system, you could very rarely get multiple posts referencing the same file
	info.Id = model.NewId()
	info.CreatorId = post.UserId
	info.PostId = post.Id
	info.CreateAt = post.CreateAt
	info.UpdateAt = post.UpdateAt
	info.Path = path

	if info.IsImage() {
		nameWithoutExtension := name[:strings.LastIndex(name, ".")]
		info.PreviewPath = pathPrefix + nameWithoutExtension + "_preview.jpg"
		info.ThumbnailPath = pathPrefix + nameWithoutExtension + "_thumb.jpg"
	}

	return info
}

func WriteFile(f []byte, path string) *model.AppError {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		var auth aws.Auth
		auth.AccessKey = utils.Cfg.FileSettings.AmazonS3AccessKeyId
		auth.SecretKey = utils.Cfg.FileSettings.AmazonS3SecretAccessKey

		s := s3.New(auth, awsRegion())
		bucket := s.Bucket(utils.Cfg.FileSettings.AmazonS3Bucket)

		ext := filepath.Ext(path)

		var err error
		if model.IsFileExtImage(ext) {
			options := s3.Options{}
			err = bucket.Put(path, f, model.GetImageMimeType(ext), s3.Private, options)

		} else {
			options := s3.Options{}
			err = bucket.Put(path, f, "binary/octet-stream", s3.Private, options)
		}

		if err != nil {
			return model.NewLocAppError("WriteFile", "api.file.write_file.s3.app_error", nil, err.Error())
		}
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
		if err := writeFileLocally(f, utils.Cfg.FileSettings.Directory+path); err != nil {
			return err
		}
	} else {
		return model.NewLocAppError("WriteFile", "api.file.write_file.configured.app_error", nil, "")
	}

	return nil
}

func MoveFile(oldPath, newPath string) *model.AppError {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		fileBytes, _ := ReadFile(oldPath)

		if fileBytes == nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.get_from_s3.app_error", nil, "")
		}

		var auth aws.Auth
		auth.AccessKey = utils.Cfg.FileSettings.AmazonS3AccessKeyId
		auth.SecretKey = utils.Cfg.FileSettings.AmazonS3SecretAccessKey

		s := s3.New(auth, awsRegion())
		bucket := s.Bucket(utils.Cfg.FileSettings.AmazonS3Bucket)

		if err := bucket.Del(oldPath); err != nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.delete_from_s3.app_error", nil, err.Error())
		}

		if err := WriteFile(fileBytes, newPath); err != nil {
			return err
		}
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {

		if err := os.MkdirAll(filepath.Dir(utils.Cfg.FileSettings.Directory+newPath), 0774); err != nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.rename.app_error", nil, err.Error())
		}

		if err := os.Rename(utils.Cfg.FileSettings.Directory+oldPath, utils.Cfg.FileSettings.Directory+newPath); err != nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.rename.app_error", nil, err.Error())
		}
	} else {
		return model.NewLocAppError("moveFile", "api.file.move_file.configured.app_error", nil, "")
	}

	return nil
}

func writeFileLocally(f []byte, path string) *model.AppError {
	if err := os.MkdirAll(filepath.Dir(path), 0774); err != nil {
		directory, _ := filepath.Abs(filepath.Dir(path))
		return model.NewLocAppError("WriteFile", "api.file.write_file_locally.create_dir.app_error", nil, "directory="+directory+", err="+err.Error())
	}

	if err := ioutil.WriteFile(path, f, 0644); err != nil {
		return model.NewLocAppError("WriteFile", "api.file.write_file_locally.writing.app_error", nil, err.Error())
	}

	return nil
}

func ReadFile(path string) ([]byte, *model.AppError) {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		var auth aws.Auth
		auth.AccessKey = utils.Cfg.FileSettings.AmazonS3AccessKeyId
		auth.SecretKey = utils.Cfg.FileSettings.AmazonS3SecretAccessKey

		s := s3.New(auth, awsRegion())
		bucket := s.Bucket(utils.Cfg.FileSettings.AmazonS3Bucket)

		// try to get the file from S3 with some basic retry logic
		tries := 0
		for {
			tries++

			f, err := bucket.Get(path)

			if f != nil {
				return f, nil
			} else if tries >= 3 {
				return nil, model.NewLocAppError("ReadFile", "api.file.read_file.get.app_error", nil, "path="+path+", err="+err.Error())
			}
			time.Sleep(3000 * time.Millisecond)
		}
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
		if f, err := ioutil.ReadFile(utils.Cfg.FileSettings.Directory + path); err != nil {
			return nil, model.NewLocAppError("ReadFile", "api.file.read_file.reading_local.app_error", nil, err.Error())
		} else {
			return f, nil
		}
	} else {
		return nil, model.NewLocAppError("ReadFile", "api.file.read_file.configured.app_error", nil, "")
	}
}

func openFileWriteStream(path string) (io.Writer, *model.AppError) {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.s3.app_error", nil, "")
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
		if err := os.MkdirAll(filepath.Dir(utils.Cfg.FileSettings.Directory+path), 0774); err != nil {
			return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.creating_dir.app_error", nil, err.Error())
		}

		if fileHandle, err := os.Create(utils.Cfg.FileSettings.Directory + path); err != nil {
			return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.local_server.app_error", nil, err.Error())
		} else {
			fileHandle.Chmod(0644)
			return fileHandle, nil
		}
	}

	return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.configured.app_error", nil, "")
}

func closeFileWriteStream(file io.Writer) {
	file.(*os.File).Close()
}

func awsRegion() aws.Region {
	if region, ok := aws.Regions[utils.Cfg.FileSettings.AmazonS3Region]; ok {
		return region
	}

	return aws.Region{
		Name:                 utils.Cfg.FileSettings.AmazonS3Region,
		S3Endpoint:           utils.Cfg.FileSettings.AmazonS3Endpoint,
		S3BucketEndpoint:     utils.Cfg.FileSettings.AmazonS3BucketEndpoint,
		S3LocationConstraint: *utils.Cfg.FileSettings.AmazonS3LocationConstraint,
		S3LowercaseBucket:    *utils.Cfg.FileSettings.AmazonS3LowercaseBucket,
	}
}