Make creds file executable (#1119)

* Make creds file executable
* Implementing code review
* Abstract reading creds file into function
* Implement code review

providers/config/providerConfig.go

@@ -8,24 +8,36 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"strings"
 
 	"github.com/DisposaBoy/JsonConfigReader"
 	"github.com/TomOnTime/utfutil"
 )
 
-// LoadProviderConfigs will open the specified file name, and parse its contents. It will replace environment variables it finds if any value matches $[A-Za-z_-0-9]+
+// LoadProviderConfigs will open or execute the specified file name, and parse its contents. It will replace environment variables it finds if any value matches $[A-Za-z_-0-9]+
 func LoadProviderConfigs(fname string) (map[string]map[string]string, error) {
 	var results = map[string]map[string]string{}
-	dat, err := utfutil.ReadFile(fname, utfutil.POSIX)
-	if err != nil {
-		// no creds file is ok. Bind requires nothing for example. Individual providers will error if things not found.
-		if os.IsNotExist(err) {
-			fmt.Printf("INFO: Config file %q does not exist. Skipping.\n", fname)
-			return results, nil
+
+	var dat []byte
+	var err error
+
+	if strings.HasPrefix(fname, "!") {
+		dat, err = executeCredsFile(strings.TrimPrefix(fname, "!"))
+		if err != nil {
+			return nil, err
 		}
-		return nil, fmt.Errorf("failed reading provider credentials file %v: %v", fname, err)
+	} else if isExecutable(fname) {
+		dat, err = executeCredsFile(fname)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		// no executable bit found nor marked as executable so read it in
+		dat, err = readCredsFile(fname)
 	}
+
 	s := string(dat)
 	r := JsonConfigReader.New(strings.NewReader(s))
 	err = json.NewDecoder(r).Decode(&results)
@@ -38,6 +50,38 @@ func LoadProviderConfigs(fname string) (map[string]map[string]string, error) {
 	return results, nil
 }
 
+func isExecutable(filename string) bool {
+	if stat, statErr := os.Stat(filename); statErr == nil {
+		if mode := stat.Mode(); mode&0111 == 0111 {
+			return true
+		}
+	}
+	return false
+}
+
+func readCredsFile(filename string) ([]byte, error) {
+	dat, err := utfutil.ReadFile(filename, utfutil.POSIX)
+	if err != nil {
+		// no creds file is ok. Bind requires nothing for example. Individual providers will error if things not found.
+		if os.IsNotExist(err) {
+			fmt.Printf("INFO: Config file %q does not exist. Skipping.\n", filename)
+			return []byte{}, nil
+		}
+		return nil, fmt.Errorf("failed reading provider credentials file %v: %v", filename, err)
+	}
+	return dat, nil
+}
+
+func executeCredsFile(filename string) ([]byte, error) {
+	cmd := filename
+	if !strings.HasPrefix(filename, "/") {
+		// if the path doesn't start with `/` make sure we aren't relying on $PATH.
+		cmd = strings.Join([]string{".", filename}, string(filepath.Separator))
+	}
+	out, err := exec.Command(cmd).Output()
+	return out, err
+}
+
 func replaceEnvVars(m map[string]map[string]string) error {
 	for _, keys := range m {
 		for k, v := range keys {