Add support for env variables to shim config (#7603)

plugins/inputs/execd/shim/goshim.go

@@ -9,6 +9,7 @@ import (
 	"io/ioutil"
 	"os"
 	"os/signal"
+	"strings"
 	"sync"
 	"syscall"
 	"time"
@@ -23,9 +24,13 @@ import (
 type empty struct{}
 
 var (
-	stdout  io.Writer = os.Stdout
-	stdin   io.Reader = os.Stdin
-	forever           = 100 * 365 * 24 * time.Hour
+	stdout        io.Writer = os.Stdout
+	stdin         io.Reader = os.Stdin
+	forever                 = 100 * 365 * 24 * time.Hour
+	envVarEscaper           = strings.NewReplacer(
+		`"`, `\"`,
+		`\`, `\\`,
+	)
 )
 
 const (
@@ -257,11 +262,13 @@ func LoadConfig(filePath *string) ([]telegraf.Input, error) {
 		return nil, err
 	}
 
+	s := expandEnvVars(b)
+
 	conf := struct {
 		Inputs map[string][]toml.Primitive
 	}{}
 
-	md, err := toml.Decode(string(b), &conf)
+	md, err := toml.Decode(s, &conf)
 	if err != nil {
 		return nil, err
 	}
@@ -274,6 +281,16 @@ func LoadConfig(filePath *string) ([]telegraf.Input, error) {
 	return loadedInputs, err
 }
 
+func expandEnvVars(contents []byte) string {
+	return os.Expand(string(contents), getEnv)
+}
+
+func getEnv(key string) string {
+	v := os.Getenv(key)
+
+	return envVarEscaper.Replace(v)
+}
+
 func loadConfigIntoInputs(md toml.MetaData, inputConfigs map[string][]toml.Primitive) ([]telegraf.Input, error) {
 	renderedInputs := []telegraf.Input{}
 

plugins/inputs/execd/shim/shim_test.go

@@ -4,13 +4,15 @@ import (
 	"bufio"
 	"bytes"
 	"io"
+	"os"
 	"strings"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
 )
 
 func TestShimWorks(t *testing.T) {
@@ -118,3 +120,55 @@ func (i *testInput) Start(acc telegraf.Accumulator) error {
 
 func (i *testInput) Stop() {
 }
+
+func TestLoadConfig(t *testing.T) {
+	os.Setenv("SECRET_TOKEN", "xxxxxxxxxx")
+	os.Setenv("SECRET_VALUE", `test"\test`)
+
+	inputs.Add("test", func() telegraf.Input {
+		return &serviceInput{}
+	})
+
+	c := "./testdata/plugin.conf"
+	inputs, err := LoadConfig(&c)
+	require.NoError(t, err)
+
+	inp := inputs[0].(*serviceInput)
+
+	require.Equal(t, "awesome name", inp.ServiceName)
+	require.Equal(t, "xxxxxxxxxx", inp.SecretToken)
+	require.Equal(t, `test"\test`, inp.SecretValue)
+}
+
+type serviceInput struct {
+	ServiceName string `toml:"service_name"`
+	SecretToken string `toml:"secret_token"`
+	SecretValue string `toml:"secret_value"`
+}
+
+func (i *serviceInput) SampleConfig() string {
+	return ""
+}
+
+func (i *serviceInput) Description() string {
+	return ""
+}
+
+func (i *serviceInput) Gather(acc telegraf.Accumulator) error {
+	acc.AddFields("measurement",
+		map[string]interface{}{
+			"field": 1,
+		},
+		map[string]string{
+			"tag": "tag",
+		}, time.Unix(1234, 5678))
+
+	return nil
+}
+
+func (i *serviceInput) Start(acc telegraf.Accumulator) error {
+	return nil
+}
+
+func (i *serviceInput) Stop() {
+}

plugins/inputs/execd/shim/testdata/plugin.conf

@@ -0,0 +1,4 @@
+[[inputs.test]]
+	service_name = "awesome name"
+	secret_token = "${SECRET_TOKEN}"
+	secret_value = "$SECRET_VALUE"