installer/pkg: Replace writeFile with ioutil.WriteFile

The writeFile helpers are from 2b82fbe (installer: Integrate
multistep cli with configuration, 2018-02-16,
coreos/tectonic-installer#2960) and 461ff5f (cli: add support for
user ignition files, 2018-03-23, coreos/tectonic-installer#3120).  But
ioutil's function has almost the same signature.  Remove our local
versions and use the stdlib's instead.

The \n addition is because ioutil.WriteFile does not append newlines
(which workflow.writeFile did via Fprintln).

I've used os.Create's 0666 [1] in most cases; callers can set a umask
if they want to restrict that.  The exception is in
generatePrivateKey, where I've set 0600 to avoid leaking a private key
even in the presence of a weak umask.

[1]: https://golang.org/pkg/os/#Create

installer/pkg/config-generator/ignition.go

@@ -158,5 +158,5 @@ func ignCfgToFile(ignCfg ignconfigtypes.Config, filePath string) error {
 		return err
 	}
 
-	return writeFile(filePath, string(data))
+	return ioutil.WriteFile(filePath, data, 0666)
 }

installer/pkg/config-generator/tls.go

@@ -136,7 +136,7 @@ func generatePrivateKey(clusterDir string, path string) (*rsa.PrivateKey, error)
 	if err != nil {
 		return nil, fmt.Errorf("error writing private key: %v", err)
 	}
-	if err := writeFile(fileTargetPath, tls.PrivateKeyToPem(key)); err != nil {
+	if err := ioutil.WriteFile(fileTargetPath, []byte(tls.PrivateKeyToPem(key)), 0600); err != nil {
 		return nil, err
 	}
 	return key, nil
@@ -240,7 +240,7 @@ func generateRootCA(path string, key *rsa.PrivateKey) (*x509.Certificate, error)
 	if err != nil {
 		return nil, fmt.Errorf("error generating self signed certificate: %v", err)
 	}
-	if err := writeFile(fileTargetPath, tls.CertToPem(cert)); err != nil {
+	if err := ioutil.WriteFile(fileTargetPath, []byte(tls.CertToPem(cert)), 0666); err != nil {
 		return nil, err
 	}
 	return cert, nil
@@ -258,7 +258,7 @@ func generateSignedCert(cfg *tls.CertCfg,
 		return nil, fmt.Errorf("error signing certificate: %v", err)
 	}
 	fileTargetPath := filepath.Join(clusterDir, path)
-	if err := writeFile(fileTargetPath, tls.CertToPem(cert)); err != nil {
+	if err := ioutil.WriteFile(fileTargetPath, []byte(tls.CertToPem(cert)), 0666); err != nil {
 		return nil, err
 	}
 	return cert, nil

installer/pkg/config-generator/utils.go

@@ -1,26 +1,10 @@
 package configgenerator
 
 import (
-	"bufio"
 	"io"
 	"os"
 )
 
-func writeFile(path, content string) error {
-	f, err := os.Create(path)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-	w := bufio.NewWriter(f)
-	if _, err := f.WriteString(content); err != nil {
-		return err
-	}
-	w.Flush()
-
-	return nil
-}
-
 func copyFile(fromFilePath, toFilePath string) error {
 	from, err := os.Open(fromFilePath)
 	if err != nil {

installer/pkg/workflow/init.go

@@ -3,6 +3,7 @@ package workflow
 import (
 	"errors"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 
@@ -57,7 +58,7 @@ func buildInternalConfig(clusterDir string) error {
 	if err != nil {
 		return err
 	}
-	return writeFile(filepath.Join(clusterDir, internalFileName), string(internalFileContent))
+	return ioutil.WriteFile(filepath.Join(clusterDir, internalFileName), internalFileContent, 0666)
 }
 
 func generateTerraformVariablesStep(m *metadata) error {
@@ -67,7 +68,7 @@ func generateTerraformVariablesStep(m *metadata) error {
 	}
 
 	terraformVariablesFilePath := filepath.Join(m.clusterDir, terraformVariablesFileName)
-	return writeFile(terraformVariablesFilePath, vars)
+	return ioutil.WriteFile(terraformVariablesFilePath, []byte(vars), 0666)
 }
 
 func prepareWorspaceStep(m *metadata) error {

installer/pkg/workflow/init_test.go

@@ -125,7 +125,7 @@ func TestGenerateTerraformVariablesStep(t *testing.T) {
 	}
 	expected := string(expectedData)
 
-	if got != expected {
+	if got + "\n" != expected {
 		t.Errorf("expected: %s, got: %s", expected, got)
 	}
 }

installer/pkg/workflow/utils.go

@@ -1,10 +1,10 @@
 package workflow
 
 import (
-	"bufio"
 	"errors"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"path"
 	"path/filepath"
@@ -98,7 +98,7 @@ func generateClusterConfigMaps(m *metadata) error {
 	}
 
 	kcoConfigFilePath := filepath.Join(clusterGeneratedPath, kcoConfigFileName)
-	if err := writeFile(kcoConfigFilePath, kcoConfig); err != nil {
+	if err := ioutil.WriteFile(kcoConfigFilePath, []byte(kcoConfig), 0666); err != nil {
 		return err
 	}
 
@@ -108,7 +108,7 @@ func generateClusterConfigMaps(m *metadata) error {
 	}
 
 	tncoConfigFilePath := filepath.Join(clusterGeneratedPath, tncoConfigFileName)
-	if err := writeFile(tncoConfigFilePath, tncoConfig); err != nil {
+	if err := ioutil.WriteFile(tncoConfigFilePath, []byte(tncoConfig), 0666); err != nil {
 		return err
 	}
 
@@ -123,7 +123,7 @@ func generateClusterConfigMaps(m *metadata) error {
 	}
 
 	kubeSystemConfigFilePath := filepath.Join(kubePath, kubeSystemFileName)
-	if err := writeFile(kubeSystemConfigFilePath, kubeSystem); err != nil {
+	if err := ioutil.WriteFile(kubeSystemConfigFilePath, []byte(kubeSystem), 0666); err != nil {
 		return err
 	}
 
@@ -138,7 +138,7 @@ func generateClusterConfigMaps(m *metadata) error {
 	}
 
 	tectonicSystemConfigFilePath := filepath.Join(tectonicPath, tectonicSystemFileName)
-	return writeFile(tectonicSystemConfigFilePath, tectonicSystem)
+	return ioutil.WriteFile(tectonicSystemConfigFilePath, []byte(tectonicSystem), 0666)
 }
 
 func readClusterConfig(configFilePath string, internalFilePath string) (*config.Cluster, error) {
@@ -179,22 +179,6 @@ func readClusterConfigStep(m *metadata) error {
 	return nil
 }
 
-func writeFile(path, content string) error {
-	f, err := os.Create(path)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
-	w := bufio.NewWriter(f)
-	if _, err := fmt.Fprintln(w, content); err != nil {
-		return err
-	}
-	w.Flush()
-
-	return nil
-}
-
 func baseLocation() (string, error) {
 	ex, err := os.Executable()
 	if err != nil {