Question

在Angular应用程序中，我有一个带有文件上传输入的联系表。如果合并的文件大于20 MB，则在前端输入的文件上传不允许发送联系表。 有什么方法可以在Cloud Storage for Firebase中实现相同的逻辑吗？目前我只能限制20 MB，但是对于每个文件，即如果某人将上传10个文件，每19 MB /人将无法发送表单，但是文件将发送到我不需要的无服务器后端。

contact.component.html

<mat-form-field>
  <!--
    Accept only files in the following format: .doc, .docx, .jpg, .jpeg, .pdf, .png, .xls, .xlsx. However, this is easy to bypass, Cloud Storage rules has been set up on the back-end side.
  -->
  <ngx-mat-file-input
    [accept]="[
      '.doc',
      '.docx',
      '.jpg',
      '.jpeg',
      '.pdf',
      '.png',
      '.xls',
      '.xlsx'
    ]"
    (change)="uploadFile($event)"
    formControlName="fileUploader"
    multiple
    aria-label="Here you can add additional files about your project, which can be helpeful for us."
    placeholder="Additional files"
    title="Additional files"
    type="file"
  >
  </ngx-mat-file-input>
  <mat-icon matSuffix>folder</mat-icon>
  <mat-hint
    >Accepted formats: DOC, DOCX, JPG, JPEG, PDF, PNG, XLS and XLSX,
    maximum files upload size: 20 MB.
  </mat-hint>
  <!--
    Non-null assertion operators are required to let know the compiler that this value is not empty and exists.
  -->
  <mat-error
    *ngIf="contactForm.get('fileUploader')!.hasError('maxContentSize')"
  >
    This size is too large,
    <strong
      >maximum acceptable upload size is
      {{
        contactForm.get('fileUploader')?.getError('maxContentSize')
          .maxSize | byteFormat
      }}</strong
    >
    (uploaded size:
    {{
      contactForm.get('fileUploader')?.getError('maxContentSize')
        .actualSize | byteFormat
    }}).
  </mat-error>
</mat-form-field>

contact.component.ts （大小验证器）

public maxFileSize = 20971520;
public contactForm: FormGroup = this.formBuilder.group({
    fileUploader: [
      '',
      Validators.compose([
        FileValidator.maxContentSize(this.maxFileSize),
        Validators.maxLength(512),
        Validators.minLength(2)
      ])
    ].toString()
})

contact.component.ts （文件上传器）

/**
   * @description Upload additional files to Cloud Firestore and get URL to the files.
   * @param {event} - object of sent files.
   * @returns {void}
   */
  public uploadFile(event: any): void {
    // Iterate through all uploaded files.
    for (let i = 0; i < event.target.files.length; i++) {
      const randomId = Math.random()
        .toString(36)
        .substring(2); // Create random ID, so the same file names can be uploaded to Cloud Firestore.

      const file = event.target.files[i]; // Get each uploaded file.

      // Get file reference.
      const fileRef: AngularFireStorageReference = this.angularFireStorage.ref(
        randomId
      );

      // Create upload task.
      const task: AngularFireUploadTask = this.angularFireStorage.upload(
        randomId,
        file
      );

      // Upload file to Cloud Firestore.
      task
        .snapshotChanges()
        .pipe(
          finalize(() => {
            fileRef.getDownloadURL().subscribe((downloadURL: string) => {
              this.angularFirestore
                .collection(process.env.FIRESTORE_COLLECTION_FILES!) // Non-null assertion operator is required to let know the compiler that this value is not empty and exists.
                .add({ downloadURL: downloadURL });
              this.downloadURL.push(downloadURL);
            });
          }),
          catchError((error: any) => {
            return throwError(error);
          })
        )
        .subscribe();
    }
  }

storage.rules

rules_version = '2';
service firebase.storage {
  match /b/{bucket}/o {
    match /{allPaths=**} {
        allow read; // Required in order to send this as attachment.
      // Allow write files Firebase Storage, only if:
      // 1) File is no more than 20MB
      // 2) Content type is in one of the following formats: .doc, .docx, .jpg, .jpeg, .pdf, .png, .xls, .xlsx.
      allow write: if request.resource.size <= 20 * 1024 * 1024
        && (request.resource.contentType.matches('application/msword')
        || request.resource.contentType.matches('application/vnd.openxmlformats-officedocument.wordprocessingml.document')
        || request.resource.contentType.matches('image/jpg')
        || request.resource.contentType.matches('image/jpeg')
        || request.resource.contentType.matches('application/pdf')
                || request.resource.contentType.matches('image/png')
        || request.resource.contentType.matches('application/vnd.ms-excel')
        || request.resource.contentType.matches('application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'))
    }
  }
}

Answer 1

Cloud Storage for Firebase中的限制安全规则分别适用于每个文件/对象，不适用于整个操作。在Cloud Storage规则的上下文中，这种限制类型也没有多大意义，因为用户可以启动另一个操作来上传其他文件。

要考虑的一些选项：

如果您对用户上传的文件名进行硬编码（这也意味着您将限制他们可以上传的文件数），并为每个特定用户创建文件文件夹，则可以确定用户文件夹中所有文件的总和，从而以这种方式限制总和。
或者，您可以在客户端上将所有文件压缩在一起，然后上传生成的存档。在这种情况下，安全规则可以强制执行该文件的最大大小。
当然，在这两种情况下，您都可以包含客户端JavaScript代码来检查组合文件的最大大小。恶意用户可以轻松绕过此JavaScript，但是大多数用户不是恶意用户，并且感谢您通过阻止无论如何都会被拒绝的上传来节省带宽。
您还可以使用HTTPS Cloud Function作为上传目标，然后仅在满足要求时将文件传递到Cloud Storage。
或者，您可以使用云功能，该云功能在从用户上传时触发，并在更改后为该用户验证文件。此时，您可以纠正这种情况。

许多这些情况要求（或更好地工作）您具有一个结构，从路径可以看到哪个用户上载了每个文件。有关此结构的更多信息，请参见user-private files上的文档。

Firebase的Cloud Storage限制（合并）多个文件上传的大小

1 个答案: