Error authorizing security group ingress rules: InvalidPermission.Duplicate: the specified rule peer sg-xxxxxxx
This lovely gem popped up out of no where while applying a terraform config. I mitigated it by changing the security group ID to the full ARN of the security group:
arn:aws:ec2:region
:account-id
:security-group/security-group-id
and then switching it back. I think there may have been a state mismatch due to someone manually editing the security group ingress rules.