Using class properties as keys poses a security risk due to their vulnerability, making the operation unsafe

Utilizing a custom FileArgument class to store file upload information:

export class FileArgument {
  name: string;
  path: string;
  file: File;
}

The upload procedure is successful, and the server responds with the uploaded file's path. The goal is to save this path in a dictionary using fileArgument.name as the key. Here is an overview of the component, focusing on the onSubmit() method:

export class InputModuleComponent {
    private vsmodule: InputModule;
    private moduleArguments = {};
    private fileArgument: FileArgument = new FileArgument();

    @Input()
    module: InputModule;

    constructor(private inputModuleService: InputModuleService) {}

    onSubmit(): void {
        this.inputModuleService.postFile(this.fileArgument.file).subscribe(
            response => {
                this.moduleArguments[this.fileArgument.name] = response.filename;
                console.log(this.moduleArguments);
            },
            error => {}
        );
    }

    onFileChange(event): void {
        this.fileArgument.file = event.originalTarget.files[0];
        this.fileArgument.name = event.originalTarget.id;
    }
}

The line 14 (

this.moduleArguments[this.fileArgument.name] = response.filename;
) triggers an error in Firefox:

EXCEPTION: Uncaught (in promise): SecurityError: The operation is insecure.

and Chrome displays:

core.umd.js:5995 EXCEPTION: Uncaught (in promise): InvalidStateError: Failed to set the 'value' property on 'HTMLInputElement': This input element accepts a filename, which may only be programmatically set to the empty string.

No errors occur when replacing that line with something like:

this.moduleArguments['hello'] = response.filename;

The use of fileArgument.name as a dictionary key seems to be causing the issue, although the reason is unclear.

EDIT: Below is the postFile() method from the service:

postFile (file: File): Observable<any> {
    console.log('input-module.service - postFile()');
    var url = this.uploadURL;

    return Observable.create(observer => {
        var formData: FormData = new FormData()
        var xhr: XMLHttpRequest = new XMLHttpRequest();

        formData.append("upload", file, file.name);

        xhr.onreadystatechange = () => {
            if (xhr.readyState === 4) {
                if (xhr.status === 200) {
                    observer.next(JSON.parse(xhr.response));
                    observer.complete();
                } else {
                observer.error(xhr.response);
                }
            }
        };

        xhr.open('POST', url, true);
        xhr.send(formData);
    });
}

The HTML code for the component:

<a (click)="modal.open()">
    {{vsmodule.displayName}}
</a>

<modal #modal>
    <form (ngSubmit)="onSubmit()">
        <modal-header [show-close]="true">
            <h4 class="modal-title">Input Module - {{vsmodule.displayName}}</h4>
        </modal-header>

        <modal-body>
            <p>{{vsmodule.description}}</p>
            <hr>
                <ul>
                    <li *ngFor="let arg of vsmodule.args; let i = index">
                        <fieldset *ngIf="arg.type == 'file'">
                            <label>{{ arg.displayName }}</label>
                            <input 
                                name="{{arg.name}}" 
                                id="{{ arg.name }}"
                                type="file"

                                [(ngModel)]="moduleArguments[arg.name]"
                                (change)="onFileChange($event)" 
                            >
                            <p>{{ arg.description }}<p>
                        </fieldset>
                    </li>
                </ul>
        </modal-body>

        <modal-footer>
            <button type="button" class="btn btn-default" data-dismiss="modal" (click)="modal.dismiss()">Dismiss</button>
            <button type="submit" class="btn btn-primary">Run</button>
        </modal-footer>
    </form>
</modal>

Answer №1

When the onChange function is triggered, the value of fileArgument.name is set to match the id of a specific HTML element on the page called event.originalTarget.id.

However, a Chrome error message displays:

The 'value' property on 'HTMLInputElement' could not be set.

After reviewing the added HTML, it appears that you've linked the 'moduleArguments' property to the ngModel of the file input element. This connection prompts Angular to attempt modifying the value property of the file input, which is prohibited.

What is the purpose behind updating this value? Is it solely for user feedback?

If you remove the ngModel binding from the input element, the functionality should improve since the onFileChange event already captures the new filename (even though in the controller it's named onChange?).

Answer №2

Short Answer: It is not possible to alter the value of

this.moduleArguments[this.fileArgument.name]
for security reasons.

Explanation: Modifying the actual value of this.fileArgument.name could pose a security risk by allowing unauthorized individuals to manipulate files. This type of vulnerability can be exploited to redirect file usage to malicious sources, hence why programming languages like Java refrain from enabling such changes programmatically.

By implementing a workaround that does not involve setting a File data member, JavaScript mitigates potential security threats.

Keep in mind that any action involving website or server code can potentially be abused by malicious users, underscoring the importance of preventing alterations to specific standard objects like File. Hopefully, this explanation sheds light on the topic!

Answer №3

Have you given this a shot?

let fileName = this.fileArguments.title;
this.moduleArguments[fileName] = response.filename;

In addition, if you happen to be modifying the 'value' of your tag in JS, you may encounter that issue. Check out:

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