finto

finto (-a) /'finto (-a)/ agg 1 posticcio; artificiàle

Overview

finto is a web server that emulates EC2 instance profile roles on a workstation through STS's assume role function. It was born as an experiment to ease local interaction with AWS services in a deeply-federated, role-based environment. finto ships with a basic API for moving between roles, and handles credentials caching and expiration.

Installation

At its simplest:

go get github.com/threadwaste/finto/cmd/finto

Usage

Usage of finto:
  -addr="169.254.169.254": bind to addr
  -config="/home/demo/.fintorc": location of config file
  -log="": log http to file
  -port=16925: listen on port

While running, finto provides credentials to EC2 instance profile providers. This provider is last in the default provider chain of each SDK. For more information, refer to the official documentation on EC2 instance profile roles and the standardized credentials interface.

Below is sample output of finto serving credentials to the AWS CLI:

$ aws s3 ls --debug
<truncated>
2016-01-03 11:52:01,895 - MainThread - botocore.credentials - DEBUG - Looking for credentials via: env
2016-01-03 11:52:01,895 - MainThread - botocore.credentials - DEBUG - Looking for credentials via: assume-role
2016-01-03 11:52:01,895 - MainThread - botocore.credentials - DEBUG - Looking for credentials via: shared-credentials-file
2016-01-03 11:52:01,896 - MainThread - botocore.credentials - DEBUG - Looking for credentials via: config-file
2016-01-03 11:52:01,896 - MainThread - botocore.credentials - DEBUG - Looking for credentials via: ec2-credentials-file
2016-01-03 11:52:01,896 - MainThread - botocore.credentials - DEBUG - Looking for credentials via: boto-config
2016-01-03 11:52:01,897 - MainThread - botocore.credentials - DEBUG - Looking for credentials via: iam-role
2016-01-03 11:52:01,902 - MainThread - botocore.vendored.requests.packages.urllib3.connectionpool - INFO - Starting new HTTP connection (1): 169.254.169.254
2016-01-03 11:52:01,904 - MainThread - botocore.vendored.requests.packages.urllib3.connectionpool - DEBUG - "GET /latest/meta-data/iam/security-credentials/ HTTP/1.1" 200 5
2016-01-03 11:52:02,259 - MainThread - botocore.vendored.requests.packages.urllib3.connectionpool - DEBUG - "GET /latest/meta-data/iam/security-credentials/example HTTP/1.1" 200 635
2016-01-03 11:52:02,261 - MainThread - botocore.credentials - INFO - Found credentials from IAM Role: example
<truncated>
2016-01-03 11:52:03,282 - MainThread - botocore.hooks - DEBUG - Event after-call.s3.ListBuckets: calling handler <awscli.errorhandler.ErrorHandler object at 0x10483fc90>
2016-01-03 11:52:03,282 - MainThread - awscli.errorhandler - DEBUG - HTTP Response Code: 200

finto also includes an API for bouncing between available roles. Helper functions for bash and fish shells are available.

$ curl 169.254.169.254/roles
{"roles":["example","example2"]}
$ curl 169.254.169.254/roles/example
{"arn":"arn:aws:iam::123456789012:role/example","session_name":"finto-example"}
$ curl 169.254.169.254/roles/example/credentials
{
  "AccessKeyId": "<redacted>",
  "Code": "Success",
  "Expiration": "2016-01-03T19:40:30Z",
  "LastUpdated": "2015-07-07T23:06:33Z",
  "SecretAccessKey": "<redacted>",
  "Token": "<redacted>",
  "Type": "AWS-HMAC"
}
$ curl 169.254.169.254/latest/meta-data/iam/security-credentials/
example
$ curl -XPUT -d'{"alias":"example2"}' 169.254.169.254/roles
{"active_role":"example2"}
$ curl 169.254.169.254/latest/meta-data/iam/security-credentials/
example2

Configuration

finto uses a JSON configuration file to setup its credentials and the roles it will serve. It currently uses a shared credentials provider only. Exluding the credentials file or profile will use the defaults "~/.aws/credentials" and "default," respectively.

{
  "credentials": {
    "file": "/home/demo/.finto/credentials",
    "profile": "identity"
  },
  "roles": {
    "example": "arn:aws:iam::123456789012:role/example",
    "example2": "arn:aws:iam::123456789012:role/example2"
  }
  "default_role": "example",
}

Running

There are essentially two basic requirements for running finto:

Routing the EC2 meta-data endpoint
Using (or chaining to) the EC2 instance profile provider

The first can be achieved in several ways: interface aliasing, network redirection, virtual machines, and so on. The wiki contains a couple of basic examples.

The second is client-dependent. In the case of clients like the AWS CLI, the user must clear a path to the EC2 instance profile provider. Multiple shared credentials profiles can still be configured, and accessed with e.g. the --profile option or AWS_DEFAULT_PROFILE environment variable.

Development

After cloning the repository, running make will fetch and build dependencies; run tests; and install the binary. During development, make testall requires the following environment variables for its integration tests:

AWS_ACCESS_KEY_ID
AWS_SECRET_ACCESS_KEY
FINTO_VALID_ARN - an IAM role ARN that can be assumed
FINTO_INVALID_ARN - a false IAM role ARN that will fail

The target test can be used to skip the integration tests, and avoid this setup.