I’m starting to learn how to authenticate to vault with an IAM instance profile, but stopped by an error:
* error validating X-Vault-AWS-IAM-Server-ID header: missing header "X-Vault-AWS-IAM-Server-ID"
I followed these steps in the documentation:
On the vault server, I skipped the part running
vault write auth/aws/config/client secret_key=vCtSM8ZUEQ3mOFVlYPBQkf2sO6F/W7a5TVzrl3Oj access_key=VKIAJBRHKH6EVTTNXDHA```
Since it says it would use the IAM profile if the secret key is not defined. just writing no args won’t work.
vault write auth/aws/config/client Must supply data or use -force
so I presume no entry is required then, since it says it would use the IAM profile if the secret key is not defined. The instance profile of the vault server mathces the profile provided by the instructions, it includes ec2:DescribeInstances and iam:GetInstanceProfile, so we should be ok to skip this.
I followed all the other steps, and I can get the client instance to login with a root token no problem, (just to verify that a connection is infact possible) using the FQDN address resolved by consul in a private subnet.
…this will allow me to login via other methods.
There is however a problem with iam_server_id_header_value. I can update the value:
[ec2-user@ip-10-4-101-166 ~]$ vault write auth/aws/config/client iam_server_id_header_value=vault.service.consul Success! Data written to: auth/aws/config/client
I hope the private FQDN here is acceptable, AWS wont be aware of it.
Doing this though, I cannot login with the IAM instance profile…
[ec2-user@ip-10-4-101-166 ~]$ vault login -method=aws region=ap-southeast-2 role=dev-role-iam Error authenticating: Error making API request. URL: PUT https://vault.service.consul:8200/v1/auth/aws/login Code: 400. Errors: * error validating X-Vault-AWS-IAM-Server-ID header: missing header "X-Vault-AWS-IAM-Server-ID"
So the only difference between the steps documented and what I did specifically were:
- entering the specific role ARN for the instance profile.
- using vault.service.consul for the private name.
- skipping vault write auth/aws/config/client since it should be aquired by the vault server instance profile.
Based on the error what else can I check to determine what I might have configured incorrectly?