Add .netrc support

main.go

@@ -53,6 +53,21 @@ func main() {
 			Usage:  "whether or not to suppress terraform commands to stdout",
 			EnvVar: "PLUGIN_SENSITIVE",
 		},
+		cli.StringFlag{
+			Name:   "netrc.machine",
+			Usage:  "netrc machine",
+			EnvVar: "DRONE_NETRC_MACHINE",
+		},
+		cli.StringFlag{
+			Name:   "netrc.username",
+			Usage:  "netrc username",
+			EnvVar: "DRONE_NETRC_USERNAME",
+		},
+		cli.StringFlag{
+			Name:   "netrc.password",
+			Usage:  "netrc password",
+			EnvVar: "DRONE_NETRC_PASSWORD",
+		},
 		cli.StringFlag{
 			Name:   "role_arn_to_assume",
 			Usage:  "A role to assume before running the terraform commands",
@@ -142,6 +157,11 @@ func run(c *cli.Context) error {
 			VarFiles:    c.StringSlice("var_files"),
 			Destroy:     c.Bool("destroy"),
 		},
+		Netrc: Netrc{
+			Login:    c.String("netrc.username"),
+			Machine:  c.String("netrc.machine"),
+			Password: c.String("netrc.password"),
+		},
 		Terraform: Terraform{
 			Version: c.String("tf.version"),
 		},

plugin.go

@@ -5,6 +5,8 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"os/user"
+	"path/filepath"
 	"regexp"
 	"strings"
 	"time"
@@ -33,6 +35,12 @@ type (
 		Destroy     bool
 	}
 
+	Netrc struct {
+		Machine  string
+		Login    string
+		Password string
+	}
+
 	// InitOptions include options for the Terraform's init command
 	InitOptions struct {
 		BackendConfig []string `json:"backend-config"`
@@ -43,6 +51,7 @@ type (
 	// Plugin represents the plugin instance to be executed
 	Plugin struct {
 		Config    Config
+		Netrc     Netrc
 		Terraform Terraform
 	}
 )
@@ -62,6 +71,12 @@ func (p Plugin) Exec() error {
 		assumeRole(p.Config.RoleARN)
 	}
 
+	// writing the .netrc file with Github credentials in it.
+	err := writeNetrc(p.Netrc.Machine, p.Netrc.Login, p.Netrc.Password)
+	if err != nil {
+		return err
+	}
+
 	var commands []*exec.Cmd
 
 	commands = append(commands, exec.Command("terraform", "version"))
@@ -303,3 +318,32 @@ func assumeRole(roleArn string) {
 func trace(cmd *exec.Cmd) {
 	fmt.Println("$", strings.Join(cmd.Args, " "))
 }
+
+// helper function to write a netrc file.
+// The following code comes from the official Git plugin for Drone:
+// https://github.com/drone-plugins/drone-git/blob/8386effd2fe8c8695cf979427f8e1762bd805192/utils.go#L43-L68
+func writeNetrc(machine, login, password string) error {
+	if machine == "" {
+		return nil
+	}
+	out := fmt.Sprintf(
+		netrcFile,
+		machine,
+		login,
+		password,
+	)
+
+	home := "/root"
+	u, err := user.Current()
+	if err == nil {
+		home = u.HomeDir
+	}
+	path := filepath.Join(home, ".netrc")
+	return ioutil.WriteFile(path, []byte(out), 0600)
+}
+
+const netrcFile = `
+machine %s
+login %s
+password %s
+`