无法访问tmp目录中的文件

Question

I am trying to access the .json file that I have downloaded to the /tmp/ directory using the ebconfig to store private keys on S3 .

files:
  "/tmp/firebaseadminsdk.json" :
    mode: "000400"
    owner: root 
    group: root
    authentication: "S3Auth"
    source: 'source url'

But its giving me the following error

Error: EACCES: permission denied, open '/tmp/firebaseadminsdk.json'

There a paragraph in the documentation which says

The second entry uses the S3Auth authentication method to download the private key from the specified URL and save it to /etc/pki/tls/certs/server.key. The proxy server can then read the private key from this location to terminate HTTPS connections at the instance.

Unfortunately I am not using any proxy as it is recommended not to use one and if I was to change it to , it causes the health of the instance to turn to severe.

I have double confirm that the IAM account has read and write access to the bucket containing the file. I have also added a bucket policy to give the IAM account full access to interact with the bucket as seen below

{
    "Version": "2012-10-17",
    "Id": "Policy1546355608026",
    "Statement": [
        {
            "Sid": "Stmt_____",
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::______:role/aws-elasticbeanstalk-ec2-role"
            },
            "Action": "s3:*",
            "Resource": "arn:aws:s3:::_____/firebaseadminsdk.json"
        }
    ]
}

I also went to ec2 into my instance and added the S3fullaccess policy to the IAM role being used by the instance but after doing all of that the error still remains.

I am also using a load balancer which might cause some issues?

Error Message

Error: EACCES: permission denied, open '/tmp/firebaseadminsdk.json'
    at Object.openSync (fs.js:436:3)
    at Object.readFileSync (fs.js:341:35)
    at Object.Module._extensions..json (internal/modules/cjs/loader.js:705:20)
    at Module.load (internal/modules/cjs/loader.js:598:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:537:12)
    at Function.Module._load (internal/modules/cjs/loader.js:529:3)
    at Module.require (internal/modules/cjs/loader.js:636:17)
    at require (internal/modules/cjs/helpers.js:20:18)
    at Object.<anonymous> (/var/app/current/index.js:9:22)
    at Module._compile (internal/modules/cjs/loader.js:688:30)
fs.js:115
    throw err;

Answer 1

In your code for file copying change permissions from owner read 400 to read for everyone 444 .

files:
  "/tmp/firebaseadminsdk.json" :
    mode: "000444"
    owner: root 
    group: root
    authentication: "S3Auth"
    source: 'source url'

Permission read for everyone on private keys may be unsecure.

But I am using it for alpha version of app and later will implement AWS KMS (key management service) also because of key rotation.