BIND: Automatically create the subdirectories leading up to zonefiles (#2397)

documentation/providers/bind.md

@@ -96,7 +96,6 @@ The filenameformat is a string with a few printf-like `%` verbs:
   * `%%`  `%`
   * ordinary characters (not `%`) are copied unchanged to the output stream
   * FYI: format strings must not end with an incomplete `%` or `%?`
-  * FYI: `/` or other filesystem separators result in undefined behavior
 
 Typical values:
 
@@ -116,6 +115,12 @@ a different `directory` setting. Otherwise `dnscontrol` will write
 both domains to the same file, flapping between the two back and
 forth.
 
+(new in v4.2.0) `dnscontrol push` will create subdirectories along the path to
+the filename. This includes both the portion of the path created by the
+`directory` setting and the `filenameformat` setting. The automatic creation of
+subdirectories is disabled if `dnscontrol` is running as root for security
+reasons.
+
 # FYI: get-zones
 
 The DNSControl `get-zones all` subcommand scans the directory for

providers/bind/bindProvider.go

@@ -156,7 +156,7 @@ func (c *bindProvider) ListZones() ([]string, error) {
 func (c *bindProvider) GetZoneRecords(domain string, meta map[string]string) (models.Records, error) {
 
 	if _, err := os.Stat(c.directory); os.IsNotExist(err) {
-		printer.Printf("\nWARNING: BIND directory %q does not exist!\n", c.directory)
+		printer.Printf("\nWARNING: BIND directory %q does not exist! (will create)\n", c.directory)
 	}
 
 	if c.zonefile == "" {
@@ -312,7 +312,11 @@ func (c *bindProvider) GetZoneRecordsCorrections(dc *models.DomainConfig, foundR
 				Msg: msg,
 				F: func() error {
 					printer.Printf("WRITING ZONEFILE: %v\n", c.zonefile)
-					zf, err := os.Create(c.zonefile)
+					fname, err := preprocessFilename(c.zonefile)
+					if err != nil {
+						return fmt.Errorf("could not create zonefile: %w", err)
+					}
+					zf, err := os.Create(fname)
 					if err != nil {
 						return fmt.Errorf("could not create zonefile: %w", err)
 					}
@@ -335,3 +339,21 @@ func (c *bindProvider) GetZoneRecordsCorrections(dc *models.DomainConfig, foundR
 
 	return corrections, nil
 }
+
+// preprocessFilename pre-processes a filename we're about to os.Create()
+// * On Windows systems, it translates the seperator.
+// * It attempts to mkdir the directories leading up to the filename.
+// * If running on Linux as root, it does not attempt to create directories.
+func preprocessFilename(name string) (string, error) {
+	universalName := filepath.FromSlash(name)
+	// Running as root? Don't create the parent directories. It is unsafe.
+	if os.Getuid() != 0 {
+		// Create the parent directories
+		dir := filepath.Dir(name)
+		universalDir := filepath.FromSlash(dir)
+		if err := os.MkdirAll(universalDir, 0750); err != nil {
+			return "", err
+		}
+	}
+	return universalName, nil
+}