Vault Hashicorp: Passing aws dynamic secret to a script - amazon-s3

Question

1/ Everyday at 3am, we are runnning a script alfa.sh on server A in order to send some backups to AWS (s3 bucket).
As a requirement we had to configure AWS (aws configure) on the server which means the Secret Key and Access Key are stored on this server. We now would like to use short TTL credential valid only from 3am to 3:15am . Vault Hashicorp does that very well
2/ On server B we have a Vault Hashicorp installed and we managed to generate short ttl dynamic secrets for our s3 bucket (access key / secret key).
3/We now would like to pass the the daily generated dynamic secrets to our alpha.sh. Any idea how to achieve this?
4/Since we are generating a new Secret Key and Access Key, I understand that a new AWS configuration "aws configure" will have to be performed on server A in order to be able to perform the backup. Any experience with this?

Answer 1

DISCLAIMER: I have no experience with aws configure so someone else may have to answer this part of the question. But I believe it's not super relevant to the problem here, so I'll give my partial answer.
First things first - solve your "secret zero" problem. If you are using the AWS secrets engine, it seems unlikely that your server is running on AWS, as you could skip the middle man and just give your server an IAM policy that allowed direct access to the S3 resource. So find the best Vault auth method for your use case. If your server is in a cloud like AWS, Azure, GCP, etc or container like K8S, CF provider, or has a JWT token delivered along with a JWKS endpoint Vault can trust, target one of those, and if all else fails, use AppRole authentication delivering a wrapped token via a trusted CI solution.
Then, log into Vault in your shell script using those credentials. The login will look different depending on the auth method chosen. You can also leverage Vault Agent to automatically handle the login for you, and cache secrets locally.
#!/usr/bin/env bash
## Dynamic Login
vault login -method="${DYNAMIC_AUTH_METHOD}" role=my-role
## OR AppRole Login
resp=$(vault write -format=json auth/approle/login role-id="${ROLE_ID}" secret-id="${SECRET_ID}")
VAULT_TOKEN=$(echo "${resp}" | jq -r .auth.client_token)
export VAULT_TOKEN
Then, pull down the AWS dynamic secret. Each time you read a creds endpoint you will get a new credential pair, so it is important not to make multiple API calls here, and instead cache the entire API response, then parse the response for each necessary field.
#!/usr/bin/env bash
resp=$(vault read -format=json aws/creds/my-role)
AWS_ACCESS_KEY_ID=$(echo "${resp}" | jq -r .data.access_key)
export AWS_ACCESS_KEY_ID
AWS_SECRET_KEY_ID=$(echo "${resp}" | jq -r .data.secret_key)
export AWS_SECRET_KEY_ID
This is a very general answer establishing a pattern. Your environment particulars will determine manner of execution. You can improve this pattern by leveraging features like CIDR binds, number of uses of auth credentials, token wrapping, and delivery via CI solution.