refactor: use atomic renames for uploaded files (#372)

Co-authored-by: Kyle Mendell <kmendell@ofkm.us>
Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/model/app_config.go

@@ -1,5 +1,9 @@
 package model
 
+import (
+	"strconv"
+)
+
 type AppConfigVariable struct {
 	Key          string `gorm:"primaryKey;not null"`
 	Type         string
@@ -9,6 +13,11 @@ type AppConfigVariable struct {
 	DefaultValue string
 }
 
+func (a *AppConfigVariable) IsTrue() bool {
+	ok, _ := strconv.ParseBool(a.Value)
+	return ok
+}
+
 type AppConfig struct {
 	// General
 	AppName             AppConfigVariable

backend/internal/service/user_service.go

@@ -59,7 +59,7 @@ func (s *UserService) GetProfilePicture(userID string) (io.Reader, int64, error)
 		return nil, 0, &common.InvalidUUIDError{}
 	}
 
-	profilePicturePath := fmt.Sprintf("%s/profile-pictures/%s.png", common.EnvConfig.UploadPath, userID)
+	profilePicturePath := common.EnvConfig.UploadPath + "/profile-pictures/" + userID + ".png"
 	file, err := os.Open(profilePicturePath)
 	if err == nil {
 		// Get the file size
@@ -94,7 +94,8 @@ func (s *UserService) GetUserGroups(userID string) ([]model.UserGroup, error) {
 
 func (s *UserService) UpdateProfilePicture(userID string, file io.Reader) error {
 	// Validate the user ID to prevent directory traversal
-	if err := uuid.Validate(userID); err != nil {
+	err := uuid.Validate(userID)
+	if err != nil {
 		return &common.InvalidUUIDError{}
 	}
 
@@ -105,20 +106,14 @@ func (s *UserService) UpdateProfilePicture(userID string, file io.Reader) error
 	}
 
 	// Ensure the directory exists
-	profilePictureDir := fmt.Sprintf("%s/profile-pictures", common.EnvConfig.UploadPath)
-	if err := os.MkdirAll(profilePictureDir, os.ModePerm); err != nil {
+	profilePictureDir := common.EnvConfig.UploadPath + "/profile-pictures"
+	err = os.MkdirAll(profilePictureDir, os.ModePerm)
+	if err != nil {
 		return err
 	}
 
 	// Create the profile picture file
-	createdProfilePicture, err := os.Create(fmt.Sprintf("%s/%s.png", profilePictureDir, userID))
-	if err != nil {
-		return err
-	}
-	defer createdProfilePicture.Close()
-
-	// Copy the image to the file
-	_, err = io.Copy(createdProfilePicture, profilePicture)
+	err = utils.SaveFileStream(profilePicture, profilePictureDir+"/"+userID+".png")
 	if err != nil {
 		return err
 	}
@@ -133,12 +128,12 @@ func (s *UserService) DeleteUser(userID string) error {
 	}
 
 	// Disallow deleting the user if it is an LDAP user and LDAP is enabled
-	if user.LdapID != nil && s.appConfigService.DbConfig.LdapEnabled.Value == "true" {
+	if user.LdapID != nil && s.appConfigService.DbConfig.LdapEnabled.IsTrue() {
 		return &common.LdapUserUpdateError{}
 	}
 
 	// Delete the profile picture
-	profilePicturePath := fmt.Sprintf("%s/profile-pictures/%s.png", common.EnvConfig.UploadPath, userID)
+	profilePicturePath := common.EnvConfig.UploadPath + "/profile-pictures/" + userID + ".png"
 	if err := os.Remove(profilePicturePath); err != nil && !os.IsNotExist(err) {
 		return err
 	}
@@ -175,7 +170,7 @@ func (s *UserService) UpdateUser(userID string, updatedUser dto.UserCreateDto, u
 	}
 
 	// Disallow updating the user if it is an LDAP group and LDAP is enabled
-	if !allowLdapUpdate && user.LdapID != nil && s.appConfigService.DbConfig.LdapEnabled.Value == "true" {
+	if !allowLdapUpdate && user.LdapID != nil && s.appConfigService.DbConfig.LdapEnabled.IsTrue() {
 		return model.User{}, &common.LdapUserUpdateError{}
 	}
 
@@ -199,7 +194,7 @@ func (s *UserService) UpdateUser(userID string, updatedUser dto.UserCreateDto, u
 }
 
 func (s *UserService) RequestOneTimeAccessEmail(emailAddress, redirectPath string) error {
-	isDisabled := s.appConfigService.DbConfig.EmailOneTimeAccessEnabled.Value != "true"
+	isDisabled := !s.appConfigService.DbConfig.EmailOneTimeAccessEnabled.IsTrue()
 	if isDisabled {
 		return &common.OneTimeAccessDisabledError{}
 	}
@@ -376,7 +371,7 @@ func (s *UserService) ResetProfilePicture(userID string) error {
 	}
 
 	// Build path to profile picture
-	profilePicturePath := fmt.Sprintf("%s/profile-pictures/%s.png", common.EnvConfig.UploadPath, userID)
+	profilePicturePath := common.EnvConfig.UploadPath + "/profile-pictures/" + userID + ".png"
 
 	// Check if file exists and delete it
 	if _, err := os.Stat(profilePicturePath); err == nil {

backend/internal/utils/file_util.go

@@ -1,10 +1,15 @@
 package utils
 
 import (
+	"errors"
+	"fmt"
+	"hash/crc64"
 	"io"
 	"mime/multipart"
 	"os"
 	"path/filepath"
+	"strconv"
+	"time"
 
 	"github.com/pocket-id/pocket-id/backend/resources"
 )
@@ -69,14 +74,70 @@ func SaveFile(file *multipart.FileHeader, dst string) error {
 		return err
 	}
 
-	out, err := os.Create(dst)
-	if err != nil {
-		return err
+	return SaveFileStream(src, dst)
 }
-	defer out.Close()
 
-	_, err = io.Copy(out, src)
-	return err
+// SaveFileStream saves a stream to a file.
+func SaveFileStream(r io.Reader, dstFileName string) error {
+	// Our strategy is to save to a separate file and then rename it to override the original file
+	// First, get a temp file name that doesn't exist already
+	var tmpFileName string
+	var i int64
+	for {
+		seed := strconv.FormatInt(time.Now().UnixNano()+i, 10)
+		suffix := crc64.Checksum([]byte(dstFileName+seed), crc64.MakeTable(crc64.ISO))
+		tmpFileName = dstFileName + "." + strconv.FormatUint(suffix, 10)
+		exists, err := FileExists(tmpFileName)
+		if err != nil {
+			return fmt.Errorf("failed to check if file '%s' exists: %w", tmpFileName, err)
+		}
+		if !exists {
+			break
+		}
+		i++
+	}
+
+	// Write to the temporary file
+	tmpFile, err := os.Create(tmpFileName)
+	if err != nil {
+		return fmt.Errorf("failed to open file '%s' for writing: %w", tmpFileName, err)
+	}
+
+	n, err := io.Copy(tmpFile, r)
+	if err != nil {
+		// Delete the temporary file; we ignore errors here
+		_ = tmpFile.Close()
+		_ = os.Remove(tmpFileName)
+
+		return fmt.Errorf("failed to write to file '%s': %w", tmpFileName, err)
+	}
+
+	err = tmpFile.Close()
+	if err != nil {
+		// Delete the temporary file; we ignore errors here
+		_ = os.Remove(tmpFileName)
+
+		return fmt.Errorf("failed to close stream to file '%s': %w", tmpFileName, err)
+	}
+
+	if n == 0 {
+		// Delete the temporary file; we ignore errors here
+		_ = os.Remove(tmpFileName)
+
+		return errors.New("no data written")
+	}
+
+	// Rename to the final file, which overrides existing files
+	// This is an atomic operation
+	err = os.Rename(tmpFileName, dstFileName)
+	if err != nil {
+		// Delete the temporary file; we ignore errors here
+		_ = os.Remove(tmpFileName)
+
+		return fmt.Errorf("failed to rename file '%s': %w", dstFileName, err)
+	}
+
+	return nil
 }
 
 // FileExists returns true if a file exists on disk and is a regular file

backend/internal/utils/image/profile_picture.go

@@ -3,22 +3,24 @@ package profilepicture
 import (
 	"bytes"
 	"fmt"
-	"github.com/disintegration/imageorient"
-	"github.com/disintegration/imaging"
-	"github.com/pocket-id/pocket-id/backend/resources"
-	"golang.org/x/image/font"
-	"golang.org/x/image/font/opentype"
-	"golang.org/x/image/math/fixed"
 	"image"
 	"image/color"
 	"io"
 	"strings"
+
+	"github.com/disintegration/imageorient"
+	"github.com/disintegration/imaging"
+	"golang.org/x/image/font"
+	"golang.org/x/image/font/opentype"
+	"golang.org/x/image/math/fixed"
+
+	"github.com/pocket-id/pocket-id/backend/resources"
 )
 
 const profilePictureSize = 300
 
 // CreateProfilePicture resizes the profile picture to a square
-func CreateProfilePicture(file io.Reader) (*bytes.Buffer, error) {
+func CreateProfilePicture(file io.Reader) (io.Reader, error) {
 	img, _, err := imageorient.Decode(file)
 	if err != nil {
 		return nil, fmt.Errorf("failed to decode image: %w", err)
@@ -26,13 +28,17 @@ func CreateProfilePicture(file io.Reader) (*bytes.Buffer, error) {
 
 	img = imaging.Fill(img, profilePictureSize, profilePictureSize, imaging.Center, imaging.Lanczos)
 
-	var buf bytes.Buffer
-	err = imaging.Encode(&buf, img, imaging.PNG)
+	pr, pw := io.Pipe()
+	go func() {
+		err = imaging.Encode(pw, img, imaging.PNG)
 		if err != nil {
-		return nil, fmt.Errorf("failed to encode image: %v", err)
+			_ = pw.CloseWithError(fmt.Errorf("failed to encode image: %v", err))
+			return
 		}
+		pw.Close()
+	}()
 
-	return &buf, nil
+	return pr, nil
 }
 
 // CreateDefaultProfilePicture creates a profile picture with the initials