How to handle AWS S3 bucket not found file error? - Express

Issue

I've an images/:key route with this controller:

public getImage(request: Request, response: Response): Response {
    try {
        const key = request.params.key;
        const read = getFileStream(key);

        return read.pipe(response);
    } catch (error) {
        return response.status(404).json({
            message: 'Image not found.'
        });
    }
}

And the following function:

// aws.ts

export function getFileStream(fileKey: any) {
    const downloadParams = {
        Key: fileKey,
        Bucket: bucketName
    };

    return s3.getObject(downloadParams).createReadStream();
}

So, the problem is when I get an unexpected key that doesn't exist in the S3 bucket because the try/catch doesn't work and then my app crash with an error code that say 'Access denied', How can i fix that?. A lot of thanks 😁

Solution

I had to validate first of the key refers to a valid object, so i get the object data before get the object and if it doesn't exist it throws an error who i'm able to catch, like this:

// aws.ts

export async function getFileStream(key: string) {
    const downloadParams = {
        Key: key,
        Bucket: bucketName
    };

    try {
        // Verify if exists
        const head = await s3.headObject(downloadParams).promise();

        // Return object
        return s3.getObject(downloadParams).createReadStream();
    } catch (headErr: any) {
        // If get an error returns null
        return null;
    }
}

And then in the controller:

public async getFile(request: Request, response: Response) {
    const key = request.params.key;

    const read = await getFileStream(key);

    if (read != null) return read.pipe(response);
    else return response.sendStatus(404);
}

Yo have to put in the s3 policy the list bucket option, it's required for be able to use headObject(), this is an example of the policy required:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "s3:PutObject",
                "s3:DeleteObject",
                // The following actions are required
                "s3:GetObject",
                "s3:ListBucket",
            ],
            "Resource": [
                "arn:aws:s3:::YOUR-BUCKET-NAME-HERE",
                "arn:aws:s3:::YOUR-BUCKET-NAME-HERE/*"
            ]
        }
    ]
}

Answered By - JuanDa237