Dealing with an AWS S3 bucket file not found error: A comprehensive guide

Question

Dealing with an AWS S3 bucket file not found error: A comprehensive guide

My image route uses a controller like this:

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.'
        });
    }
}

Additionally, I have the following function:

// aws.ts

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

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

However, I encounter an issue when I provide a key that doesn't exist in the S3 bucket. The try/catch block does not handle this scenario, causing my app to crash with an 'Access denied' error code. How can I resolve this situation? Thank you! 😁

typescript express amazon-s3

Answer 1

Answer №1

In order to ensure that the key refers to a valid object, I first validate it by retrieving the object data before attempting to access the object itself. If the object does not exist, an error is thrown which can be caught, as shown below:

// aws.ts

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

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

        // Return the object
        return s3.getObject(downloadParams).createReadStream();
    } catch (headErr: any) {
        // Return null if an error occurs
        return null;
    }
}

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);
}

Make sure to include the list bucket option in your S3 policy, as it is required to use the headObject() method. Below is an example of the policy needed:

{
    "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/*"
            ]
        }
    ]
}

Answer 2

In order to ensure that the key refers to a valid object, I first validate it by retrieving the object data before attempting to access the object itself. If the object does not exist, an error is thrown which can be caught, as shown below:

// aws.ts

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

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

        // Return the object
        return s3.getObject(downloadParams).createReadStream();
    } catch (headErr: any) {
        // Return null if an error occurs
        return null;
    }
}

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);
}

Make sure to include the list bucket option in your S3 policy, as it is required to use the headObject() method. Below is an example of the policy needed:

{
    "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/*"
            ]
        }
    ]
}

Dealing with an AWS S3 bucket file not found error: A comprehensive guide

Answer №1

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