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Ansible Modules with Go

2019-06-30


Since Ansible 2.2 you can use binary applications as modules for Ansible. This means you can write modules in languages other than Python. The downside is that the modules aren’t integrated as well as if they were written in Python with Ansiballz. The binary modules only takes the filename as an argument which is a temporary file containing the JSON data of the modules parameters.

I took the boilerplate code that Ansible had here and created a small module to generate a random password. The only parameters for the module are the password length and the type of password (alpha, numeric, alphanumeric, full). If you don’t pass any parameters, it defaults to full (numbers, letters, and symbols) and 20 characters. The way it is written right now, it won’t show a change when it generates a password. To show a change just set Response.ChangedResponse.Changed to true in your logic.

package main
import (
        "encoding/json"
        "fmt"
        "io/ioutil"
        "math/rand"
        "os"
        "time"
)
const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const numbers = "0123456789"
const symbols = `!@#$%^&*()\/><}{[]`
type ModuleArgs struct {
        Length int
        Type   string
}
type Response struct {
        Password string `json:"password"`
        Changed  bool   `json:"changed"`
        Failed   bool   `json:"failed"`
}
func ExitJson(responseBody Response) {
        returnResponse(responseBody)
}
func FailJson(responseBody Response) {
        responseBody.Failed = true
        returnResponse(responseBody)
}
func returnResponse(responseBody Response) {
        var response []byte
        var err error
        response, err = json.Marshal(responseBody)
        if err != nil {
                response, _ = json.Marshal(Response{Password: "Invalid response object"})
        }
        fmt.Println(string(response))
        if responseBody.Failed {
                os.Exit(1)
        } else {
                os.Exit(0)
        }
}
func GeneratePassword(l int, s string) string {
        data := make([]byte, l)
        var characters string
        switch s {
        case "full":
                characters = letters + numbers + symbols
        case "alpha":
                characters = letters
        case "numeric":
                characters = numbers
        case "alphanumeric":
                characters = letters + numbers
        }
        n := len(characters)
        for i := range data {
                data[i] = characters[rand.Intn(n)]
        }
        return string(data)
}
func main() {
        var response Response
        rand.Seed(time.Now().UTC().UnixNano())
        if len(os.Args) != 2 {
                response.Password = "No argument file provided"
                FailJson(response)
        }
        argsFile := os.Args[1]
        text, err := ioutil.ReadFile(argsFile)
        if err != nil {
                response.Password = "Could not read configuration file: " + argsFile
                FailJson(response)
        }
        var moduleArgs ModuleArgs
        err = json.Unmarshal(text, &moduleArgs)
        if err != nil {
                response.Password = "Configuration file not valid JSON: " + argsFile
                FailJson(response)
        }
        var length = 20
        if moduleArgs.Length != 0 {
                length = moduleArgs.Length
        }
        var style = "full"
        if moduleArgs.Type != "" {
                style = moduleArgs.Type
        }
        password := GeneratePassword(length, style)
        response.Password = password
        ExitJson(response)
}
package main
import (
        "encoding/json"
        "fmt"
        "io/ioutil"
        "math/rand"
        "os"
        "time"
)
const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const numbers = "0123456789"
const symbols = `!@#$%^&*()\/><}{[]`
type ModuleArgs struct {
        Length int
        Type   string
}
type Response struct {
        Password string `json:"password"`
        Changed  bool   `json:"changed"`
        Failed   bool   `json:"failed"`
}
func ExitJson(responseBody Response) {
        returnResponse(responseBody)
}
func FailJson(responseBody Response) {
        responseBody.Failed = true
        returnResponse(responseBody)
}
func returnResponse(responseBody Response) {
        var response []byte
        var err error
        response, err = json.Marshal(responseBody)
        if err != nil {
                response, _ = json.Marshal(Response{Password: "Invalid response object"})
        }
        fmt.Println(string(response))
        if responseBody.Failed {
                os.Exit(1)
        } else {
                os.Exit(0)
        }
}
func GeneratePassword(l int, s string) string {
        data := make([]byte, l)
        var characters string
        switch s {
        case "full":
                characters = letters + numbers + symbols
        case "alpha":
                characters = letters
        case "numeric":
                characters = numbers
        case "alphanumeric":
                characters = letters + numbers
        }
        n := len(characters)
        for i := range data {
                data[i] = characters[rand.Intn(n)]
        }
        return string(data)
}
func main() {
        var response Response
        rand.Seed(time.Now().UTC().UnixNano())
        if len(os.Args) != 2 {
                response.Password = "No argument file provided"
                FailJson(response)
        }
        argsFile := os.Args[1]
        text, err := ioutil.ReadFile(argsFile)
        if err != nil {
                response.Password = "Could not read configuration file: " + argsFile
                FailJson(response)
        }
        var moduleArgs ModuleArgs
        err = json.Unmarshal(text, &moduleArgs)
        if err != nil {
                response.Password = "Configuration file not valid JSON: " + argsFile
                FailJson(response)
        }
        var length = 20
        if moduleArgs.Length != 0 {
                length = moduleArgs.Length
        }
        var style = "full"
        if moduleArgs.Type != "" {
                style = moduleArgs.Type
        }
        password := GeneratePassword(length, style)
        response.Password = password
        ExitJson(response)
}

From here you can just go build random.gogo build random.go and put the executable in the libraries directory that you’ve defined. Then you just call the module like normal:


playbook

- name: Generate Password
  hosts: localhost
  tasks:
    - name: Generate random pass
      random:
        length: 125
        type: full
      register: password
    - name: Print password
      debug:
        var: password.password
- name: Generate Password
  hosts: localhost
  tasks:
    - name: Generate random pass
      random:
        length: 125
        type: full
      register: password
    - name: Print password
      debug:
        var: password.password


output

PLAY [localhost] *****************************************************************************************************************************************************************************************************************************
TASK [Generate random pass] ******************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [Print password] *********************************************************************************************************************************************************************************************************************************
ok: [localhost] => {
    "password.password": "ylXFw0gtZ[ch/gc>rO7fd/A}gC5{Oe\\o<6MAf5ByHyM7vPIr<)u44!<2eGR)%T&*h8DAYIm[>$^%YSI#$9ES$ma#lLqXm]StW!WA4/xmz3juDjm@JkYDn@dBK/0<a"
}
PLAY RECAP ***********************************************************************************************************************************************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
PLAY [localhost] *****************************************************************************************************************************************************************************************************************************
TASK [Generate random pass] ******************************************************************************************************************************************************************************************************************
ok: [localhost]
TASK [Print password] *********************************************************************************************************************************************************************************************************************************
ok: [localhost] => {
    "password.password": "ylXFw0gtZ[ch/gc>rO7fd/A}gC5{Oe\\o<6MAf5ByHyM7vPIr<)u44!<2eGR)%T&*h8DAYIm[>$^%YSI#$9ES$ma#lLqXm]StW!WA4/xmz3juDjm@JkYDn@dBK/0<a"
}
PLAY RECAP ***********************************************************************************************************************************************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0