… because sometimes you just need to reliably identify your machines.

Main Features

• Cross-Platform (tested on Win7+, Debian 8+, Ubuntu 14.04+, OS X 10.6+, FreeBSD 11+)
• No admin privileges required
• Hardware independent (no usage of MAC, BIOS or CPU — those are too unreliable, especially in a VM environment)
• IDs are unique¹ to the installed OS

Installation

Get the library with

go get github.com/denisbrodbeck/machineid

You can also add the cli app directly to your $GOPATH/bin with

go get github.com/denisbrodbeck/machineid/cmd/machineid

Usage

package main

import (
  "fmt"
  "log"
  "github.com/denisbrodbeck/machineid"
)

func main() {
  id, err := machineid.ID()
  if err != nil {
    log.Fatal(err)
  }
  fmt.Println(id)
}

Or even better, use securely hashed machine IDs:

package main

import (
  "fmt"
  "log"
  "github.com/denisbrodbeck/machineid"
)

func main() {
  id, err := machineid.ProtectedID("myAppName")
  if err != nil {
    log.Fatal(err)
  }
  fmt.Println(id)
}

Function: ID() (string, error)

Returns original machine id as a string.

Function: ProtectedID(appID string) (string, error)

Returns hashed version of the machine ID as a string. The hash is generated in a cryptographically secure way, using a fixed, application-specific key (calculates HMAC-SHA256 of the app ID, keyed by the machine ID).

What you get

This package returns the OS native machine UUID/GUID, which the OS uses for internal needs.

All machine IDs are usually generated during system installation and stay constant for all subsequent boots.

The following sources are used:

• AIX uses the OS (or WPAR if applicable) UUID from the os_uuid attribute
• BSD uses /etc/hostid and smbios.system.uuid as a fallback
• Linux uses /var/lib/dbus/machine-id (man)
• OS X uses IOPlatformUUID
• Windows uses the MachineGuid from HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography

Unique Key Reliability

Do note, that machine-id and MachineGuid can be changed by root/admin, although that may not come without cost (broken system services and more). Most IDs won't be regenerated by the OS, when you clone/image/restore a particular OS installation. This is a well known issue with cloned windows installs (not using the official sysprep tools).

Linux users can generate a new id with dbus-uuidgen and put the id into /var/lib/dbus/machine-id and /etc/machine-id. Windows users can use the sysprep toolchain to create images, which produce valid images ready for distribution. Such images produce a new unique machine ID on each deployment.

Security Considerations

A machine ID uniquely identifies the host. Therefore it should be considered "confidential", and must not be exposed in untrusted environments. If you need a stable unique identifier for your app, do not use the machine ID directly.

A reliable solution is to hash the machine ID in a cryptographically secure way, using a fixed, application-specific key.

That way the ID will be properly unique, and derived in a constant way from the machine ID but there will be no way to retrieve the original machine ID from the application-specific one.

Do something along these lines:

package main

import (
  "crypto/hmac"
  "crypto/sha256"
  "fmt"
  "github.com/denisbrodbeck/machineid"
)

const appKey = "WowSuchNiceApp"

func main() {
  id, _ := machineid.ID()
  fmt.Println(protect(appKey, id))
  // Output: dbabdb7baa54845f9bec96e2e8a87be2d01794c66fdebac3df7edd857f3d9f97
}

func protect(appID, id string) string {
  mac := hmac.New(sha256.New, []byte(id))
  mac.Write([]byte(appID))
  return fmt.Sprintf("%x", mac.Sum(nil))
}

Or simply use the convenience API call:

hashedID, err := machineid.ProtectedID("myAppName")

Snippets

Don't want to download code, and just need a way to get the data by yourself?

AIX:

lsattr -l sys0 -a os_uuid -E | cut -f 2 -d ' '

BSD:

cat /etc/hostid
# or (might be empty)
kenv -q smbios.system.uuid

Linux:

cat /var/lib/dbus/machine-id
# or when not found (e.g. Fedora 20)
cat /etc/machine-id

OS X:

ioreg -rd1 -c IOPlatformExpertDevice | grep IOPlatformUUID

Windows:

reg query HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography /v MachineGuid

or

• Open Windows Registry via regedit
• Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography
• Take value of key MachineGuid

Credits

The Go gopher was created by Denis Brodbeck with gopherize.me, based on original artwork from Renee French.

License

The MIT License (MIT) — Denis Brodbeck. Please have a look at the LICENSE.md for more details.