feat: add create and overwrite file operations

This adds `create` and `overwrite` file operations so that we can have
better sanity checks around extra files.

Signed-off-by: Andrew Rynhard <andrew@andrewrynhard.com>

docs/website/content/v0.3/en/configuration/v1alpha1.md

@@ -242,6 +242,10 @@ install:
 #### files
 
 Allows the addition of user specified files.
+The value of `op` can be `create`, `overwrite`, or `append`.
+In the case of `create`, `path` must not exist.
+In the case of `overwrite`, and `append`, `path` must be a valid file.
+If an `op` value of `append` is used, the existing file will be appended.
 Note that the file contents are not required to be base64 encoded.
 
 Type: `array`
@@ -249,11 +253,12 @@ Type: `array`
 Examples:
 
 ```yaml
-kubelet:
-  contents: |
-    ...
-  permissions: 0666
-  path: /tmp/file.txt
+files:
+  - content: |
+      ...
+    permissions: 0666
+    path: /tmp/file.txt
+    op: append
 
 ```
 

docs/website/content/v0.3/en/customization/proxy.md

@@ -10,7 +10,7 @@ Put into each machine the PEM encoded certificate:
 machine:
   ...
   files:
-    - contents: |
+    - content: |
         -----BEGIN CERTIFICATE-----
         ...
         -----END CERTIFICATE-----

internal/app/machined/internal/phase/config/extra_files.go

@@ -31,12 +31,30 @@ func (task *ExtraFiles) TaskFunc(mode runtime.Mode) phase.TaskFunc {
 	return task.runtime
 }
 
+// nolint: gocyclo
 func (task *ExtraFiles) runtime(r runtime.Runtime) (err error) {
 	var result *multierror.Error
 
 	for _, f := range r.Config().Machine().Files() {
-		// Slurp existing file if append is our op and add contents to it
-		if f.Op == "append" {
+		content := f.Content
+
+		switch f.Op {
+		case "create":
+			if err = doesNotExists(f.Path); err != nil {
+				result = multierror.Append(result, fmt.Errorf("file must not exist: %q", f.Path))
+				continue
+			}
+		case "overwrite":
+			if err = existsAndIsFile(f.Path); err != nil {
+				result = multierror.Append(result, err)
+				continue
+			}
+		case "append":
+			if err = existsAndIsFile(f.Path); err != nil {
+				result = multierror.Append(result, err)
+				continue
+			}
+
 			var existingFileContents []byte
 
 			existingFileContents, err = ioutil.ReadFile(f.Path)
@@ -45,7 +63,10 @@ func (task *ExtraFiles) runtime(r runtime.Runtime) (err error) {
 				continue
 			}
 
-			f.Contents = string(existingFileContents) + "\n" + f.Contents
+			content = string(existingFileContents) + "\n" + f.Content
+		default:
+			result = multierror.Append(result, fmt.Errorf("unknown operation for file %q: %q", f.Path, f.Op))
+			continue
 		}
 
 		// Determine if supplied path is in /var or not.
@@ -62,12 +83,18 @@ func (task *ExtraFiles) runtime(r runtime.Runtime) (err error) {
 			inVar = false
 		}
 
+		// We do not want to support creating new files anywhere outside of
+		// /var. If a valid use case comes up, we can reconsider then.
+		if !inVar && f.Op == "create" {
+			return fmt.Errorf("create operation not allowed outside of /var: %q", f.Path)
+		}
+
 		if err = os.MkdirAll(filepath.Dir(p), os.ModeDir); err != nil {
 			result = multierror.Append(result, err)
 			continue
 		}
 
-		if err = ioutil.WriteFile(p, []byte(f.Contents), f.Permissions); err != nil {
+		if err = ioutil.WriteFile(p, []byte(content), f.Permissions); err != nil {
 			result = multierror.Append(result, err)
 			continue
 		}
@@ -82,3 +109,35 @@ func (task *ExtraFiles) runtime(r runtime.Runtime) (err error) {
 
 	return result.ErrorOrNil()
 }
+
+func doesNotExists(p string) (err error) {
+	_, err = os.Stat(p)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+
+		return err
+	}
+
+	return fmt.Errorf("file exists")
+}
+
+func existsAndIsFile(p string) (err error) {
+	var info os.FileInfo
+
+	info, err = os.Stat(p)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			return err
+		}
+
+		return fmt.Errorf("file must exist: %q", p)
+	}
+
+	if !info.Mode().IsRegular() {
+		return fmt.Errorf("invalid mode: %q", info.Mode().String())
+	}
+
+	return nil
+}

pkg/config/machine/machine.go

@@ -44,7 +44,7 @@ type Env = map[string]string
 
 // File represents a file to write to disk.
 type File struct {
-	Contents    string      `yaml:"contents"`
+	Content     string      `yaml:"content"`
 	Permissions os.FileMode `yaml:"permissions"`
 	Path        string      `yaml:"path"`
 	Op          string      `yaml:"op"`

pkg/config/types/v1alpha1/v1alpha1_types.go

@@ -125,14 +125,19 @@ type MachineConfig struct {
 	MachineInstall *InstallConfig `yaml:"install,omitempty"`
 	//   description: |
 	//     Allows the addition of user specified files.
+	//     The value of `op` can be `create`, `overwrite`, or `append`.
+	//     In the case of `create`, `path` must not exist.
+	//     In the case of `overwrite`, and `append`, `path` must be a valid file.
+	//     If an `op` value of `append` is used, the existing file will be appended.
 	//     Note that the file contents are not required to be base64 encoded.
 	//   examples:
 	//     - |
-	//       kubelet:
-	//         contents: |
-	//           ...
-	//         permissions: 0666
-	//         path: /tmp/file.txt
+	//       files:
+	//         - content: |
+	//             ...
+	//           permissions: 0666
+	//           path: /tmp/file.txt
+	//           op: append
 	MachineFiles []machine.File `yaml:"files,omitempty"` // Note: The specified `path` is relative to `/var`.
 	//   description: |
 	//     The `env` field allows for the addition of environment variables to a machine.