Fix reading config files starting with http: (#9275)

config/config.go

@@ -50,6 +50,10 @@ var (
 		`\`, `\\`,
 	)
 	httpLoadConfigRetryInterval = 10 * time.Second
+
+	// fetchURLRe is a regex to determine whether the requested file should
+	// be fetched from a remote or read from the filesystem.
+	fetchURLRe = regexp.MustCompile(`^\w+://`)
 )
 
 // Config specifies the URL/user/password for the database that telegraf
@@ -902,17 +906,21 @@ func escapeEnv(value string) string {
 }
 
 func loadConfig(config string) ([]byte, error) {
-	u, err := url.Parse(config)
-	if err != nil {
-		return nil, err
+	if fetchURLRe.MatchString(config) {
+		u, err := url.Parse(config)
+		if err != nil {
+			return nil, err
+		}
+
+		switch u.Scheme {
+		case "https", "http":
+			return fetchConfig(u)
+		default:
+			return nil, fmt.Errorf("scheme %q not supported", u.Scheme)
+		}
 	}
 
-	switch u.Scheme {
-	case "https", "http":
-		return fetchConfig(u)
-	default:
-		// If it isn't a https scheme, try it as a file.
-	}
+	// If it isn't a https scheme, try it as a file
 	return ioutil.ReadFile(config)
 }
 

config/config_test.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -323,6 +324,19 @@ func TestConfig_URLRetries3FailsThenPasses(t *testing.T) {
 	require.Equal(t, 4, responseCounter)
 }
 
+func TestConfig_URLLikeFileName(t *testing.T) {
+	c := NewConfig()
+	err := c.LoadConfig("http:##www.example.com.conf")
+	require.Error(t, err)
+
+	if runtime.GOOS == "windows" {
+		// The error file not found error message is different on windows
+		require.Equal(t, "Error loading config file http:##www.example.com.conf: open http:##www.example.com.conf: The system cannot find the file specified.", err.Error())
+	} else {
+		require.Equal(t, "Error loading config file http:##www.example.com.conf: open http:##www.example.com.conf: no such file or directory", err.Error())
+	}
+}
+
 /*** Mockup INPUT plugin for testing to avoid cyclic dependencies ***/
 type MockupInputPlugin struct {
 	Servers      []string `toml:"servers"`