Limes

Limes provides an easy work flow with MFA protected access keys, temporary credentials and access to multiple roles/accounts.

Limes is the Local Instance MEtadata Service and emulates parts of the AWS Instance Metadata Service running on Amazon Linux. The AWS SDK and AWS CLI can therefor utilize this service to authenticate.

Attribution

This project is a continuation of otm/limes - a fantastic tool that has served me well for many years. Due to no additional maintenance of this tool - this fork has been created.

Warning

The AWS SDK refreshes credentials automatically when using limes. So all services will change profile if the profile is changed in limes.

Installation

1. Download binary for your architecture from https://github.com/alexejk/limes/releases/latest
2. Copy the file to /usr/local/bin or appropriate location in PATH
3. Make it executable: chmod +x /usr/local/bin/limes
4. Linux: Allow limes to bind to privileged ports setcap 'cap_net_bind_service=+ep' /usr/local/bin/limes

Note: On Mac OS limes server is needed to run as root for the time being.

Configuring the Loop Back Device

The configuration below adds the necessary IP configuration on the loop back device. Without this configuration the service can not start.

Note: This configuration is not persistent between reboots.

Linux

sudo ip addr add 169.254.169.254/24 broadcast 169.254.169.255 dev lo:metadata
sudo ip link set dev lo:metadata up

Mac

sudo /sbin/ifconfig lo0 alias 169.254.169.254

Configuring IMS (Instance Meta-data Service)

There is an example configuration file. The configuration file is documented. Make a copy of the file and place it in ~/.limes/config.

mkdir -p ~/.limes
wget -O ~/.limes/config https://raw.githubusercontent.com/otm/limes/master/config.example

Use your favorite text editor to update ~/.limes/config

Usage

Running limes in your terminal prints usage information.

Starting the Service

The service is started with limes start.

Assuming Profiles

A profile is assumed with limes assume <profile-name>, where profile-name is a configured profile. Please note that this does not refer to AWS profiles but profiles configured in limes.

Running Applications with Alternate Profile

If you have assumed a role on limes you might want to run an application once with an alternate profile. This is possible without assuming the profile with the run subcommand.

limes --profile <name> run <application> [args...]

Tip With limes --profile <name> run bash it is possible to quickly start a shell with exported environment variables that is valid for an hour.

Protected Profiles

By adding protected: true to your profile it will not be possible to assume that role. It will only be possible to utilize the subcommands run and env.

Service Status

By running limes status it is possible to see the current status, and also it can detect common problems and misconfiguration.

Known Problems

If AWS environment variables, .aws/credentials or .aws/config are present there is a chance that the limes does not work. This can be checked with limes status.

Security

The service should be configured on the loop back device, and only accessible from the host it is running on.

Note: It is important not to run any service that could forwards request on the host running Limes as this would be a security risk. However, this is no difference from the setup on an Amazon Linux instance in AWS. If an attacker could forward requests to 169.254.169.254/24 your credentials could be compromised. Please note that an attacker could utilize a DNS to resolve to this address, so always be aware where you forward requests to.

Build

To build you need a Go compiler and environment setup. See https://golang.org/ for more information regarding setting up and configuring Go. You may also fully rely on Docker instead. Additional dependencies include make.

Building with make:

go get github.com/alexejk/limes
make all

Building with docker:

make build-in-docker