middleware/root: add it (#330)

This PR adds the *root* middleware that specifies a path where
all zone file (the *file* middleware is the only consumer now) can
be found. It works the same as in Caddy.

Documentation can be found in the README.md of the middleware.

Fixes #307

10 files changed, 184 insertions, 3 deletions

diff --git a/core/coredns.go b/core/coredns.go
index 8b53c0dda..558b03efc 100644
--- a/core/coredns.go
+++ b/core/coredns.go
@@ -21,6 +21,7 @@ import (
 	_ "github.com/miekg/coredns/middleware/pprof"
 	_ "github.com/miekg/coredns/middleware/proxy"
 	_ "github.com/miekg/coredns/middleware/rewrite"
+	_ "github.com/miekg/coredns/middleware/root"
 	_ "github.com/miekg/coredns/middleware/secondary"
 	_ "github.com/miekg/coredns/middleware/whoami"
 )
diff --git a/core/dnsserver/config.go b/core/dnsserver/config.go
index cbe2fd5da..20ff8389a 100644
--- a/core/dnsserver/config.go
+++ b/core/dnsserver/config.go
@@ -17,6 +17,10 @@ type Config struct {
 	// The port to listen on.
 	Port string
 
+	// Root points to a base directory we we find user defined "things".
+	// First consumer is the file middleware to looks for zone files in this place.
+	Root string
+
 	// Middleware stack.
 	Middleware []middleware.Middleware
 
diff --git a/core/dnsserver/directives.go b/core/dnsserver/directives.go
index e2883a1c2..5898f8365 100644
--- a/core/dnsserver/directives.go
+++ b/core/dnsserver/directives.go
@@ -73,6 +73,7 @@ func RegisterDevDirective(name, before string) {
 // (after) them during a request, but they must not
 // care what middleware above them are doing.
 var directives = []string{
+	"root",
 	"bind",
 	"health",
 	"pprof",
diff --git a/middleware/file/README.md b/middleware/file/README.md
index eee2517b4..4cc27e2de 100644
--- a/middleware/file/README.md
+++ b/middleware/file/README.md
@@ -13,7 +13,8 @@ zonefile.
 file DBFILE [ZONES...]
 ~~~
 
-* **DBFILE** the database file to read and parse.
+* **DBFILE** the database file to read and parse. If the path is relative the path from the *root*
+  directive will be prepended to it.
 * **ZONES** zones it should be authoritative for. If empty, the zones from the configuration block
     are used.
 
diff --git a/middleware/file/setup.go b/middleware/file/setup.go
index dd1f17d9a..95e3209f4 100644
--- a/middleware/file/setup.go
+++ b/middleware/file/setup.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net"
 	"os"
+	"path"
 
 	"github.com/miekg/coredns/core/dnsserver"
 	"github.com/miekg/coredns/middleware"
@@ -49,6 +50,8 @@ func fileParse(c *caddy.Controller) (Zones, error) {
 	names := []string{}
 	origins := []string{}
 
+	config := dnsserver.GetConfig(c)
+
 	for c.Next() {
 		if c.Val() == "file" {
 			// file db.file [zones...]
@@ -64,6 +67,10 @@ func fileParse(c *caddy.Controller) (Zones, error) {
 				origins = args
 			}
 
+			if !path.IsAbs(fileName) && config.Root != "" {
+				fileName = path.Join(config.Root, fileName)
+			}
+
 			reader, err := os.Open(fileName)
 			if err != nil {
 				// bail out
diff --git a/middleware/file/setup_test.go b/middleware/file/setup_test.go
index 9f37fd688..9fd9e3587 100644
--- a/middleware/file/setup_test.go
+++ b/middleware/file/setup_test.go
@@ -51,7 +51,7 @@ func TestFileParse(t *testing.T) {
 	}
 
 	for i, test := range tests {
-		c := caddy.NewTestController("file", test.inputFileRules)
+		c := caddy.NewTestController("dns", test.inputFileRules)
 		actualZones, err := fileParse(c)
 
 		if err == nil && test.shouldErr {
diff --git a/middleware/root/README.md b/middleware/root/README.md
new file mode 100644
index 000000000..5d09a31f3
--- /dev/null
+++ b/middleware/root/README.md
@@ -0,0 +1,21 @@
+# root
+
+*root* simply specifies the root of where CoreDNS finds (e.g.) zone files.
+The default root is the current working directory of CoreDNS.
+A relative root path is relative to the current working directory.
+
+## Syntax
+
+~~~ txt
+root PATH
+~~~
+
+**PATH** is the directory to set as CoreDNS' root.
+
+## Examples
+
+Serve zone data (when the *file* middleware is used) from `/etc/coredns/zones`:
+
+~~~ txt
+root /etc/coredns/zones
+~~~
diff --git a/middleware/root/root.go b/middleware/root/root.go
new file mode 100644
index 000000000..6a7f9fe9f
--- /dev/null
+++ b/middleware/root/root.go
@@ -0,0 +1,42 @@
+package root
+
+import (
+	"log"
+	"os"
+
+	"github.com/miekg/coredns/core/dnsserver"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("root", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	config := dnsserver.GetConfig(c)
+
+	for c.Next() {
+		if !c.NextArg() {
+			return c.ArgErr()
+		}
+		config.Root = c.Val()
+	}
+
+	// Check if root path exists
+	_, err := os.Stat(config.Root)
+	if err != nil {
+		if os.IsNotExist(err) {
+			// Allow this, because the folder might appear later.
+			// But make sure the user knows!
+			log.Printf("[WARNING] Root path does not exist: %s", config.Root)
+		} else {
+			return c.Errf("Unable to access root path '%s': %v", config.Root, err)
+		}
+	}
+
+	return nil
+}
diff --git a/middleware/root/root_test.go b/middleware/root/root_test.go
new file mode 100644
index 000000000..06c81a05e
--- /dev/null
+++ b/middleware/root/root_test.go
@@ -0,0 +1,104 @@
+package root
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/miekg/coredns/core/dnsserver"
+
+	"github.com/mholt/caddy"
+)
+
+func TestRoot(t *testing.T) {
+	// Predefined error substrings
+	parseErrContent := "Parse error:"
+	unableToAccessErrContent := "Unable to access root path"
+
+	existingDirPath, err := getTempDirPath()
+	if err != nil {
+		t.Fatalf("BeforeTest: Failed to find an existing directory for testing! Error was: %v", err)
+	}
+
+	nonExistingDir := filepath.Join(existingDirPath, "highly_unlikely_to_exist_dir")
+
+	existingFile, err := ioutil.TempFile("", "root_test")
+	if err != nil {
+		t.Fatalf("BeforeTest: Failed to create temp file for testing! Error was: %v", err)
+	}
+	defer func() {
+		existingFile.Close()
+		os.Remove(existingFile.Name())
+	}()
+
+	inaccessiblePath := getInaccessiblePath(existingFile.Name())
+
+	tests := []struct {
+		input              string
+		shouldErr          bool
+		expectedRoot       string // expected root, set to the controller. Empty for negative cases.
+		expectedErrContent string // substring from the expected error. Empty for positive cases.
+	}{
+		// positive
+		{
+			fmt.Sprintf(`root %s`, nonExistingDir), false, nonExistingDir, "",
+		},
+		{
+			fmt.Sprintf(`root %s`, existingDirPath), false, existingDirPath, "",
+		},
+		// negative
+		{
+			`root `, true, "", parseErrContent,
+		},
+		{
+			fmt.Sprintf(`root %s`, inaccessiblePath), true, "", unableToAccessErrContent,
+		},
+		{
+			fmt.Sprintf(`root {
+				%s
+			}`, existingDirPath), true, "", parseErrContent,
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		err := setup(c)
+		cfg := dnsserver.GetConfig(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+		}
+
+		// check root only if we are in a positive test.
+		if !test.shouldErr && test.expectedRoot != cfg.Root {
+			t.Errorf("Root not correctly set for input %s. Expected: %s, actual: %s", test.input, test.expectedRoot, cfg.Root)
+		}
+	}
+}
+
+// getTempDirPath returnes the path to the system temp directory. If it does not exists - an error is returned.
+func getTempDirPath() (string, error) {
+	tempDir := os.TempDir()
+	_, err := os.Stat(tempDir)
+	if err != nil {
+		return "", err
+	}
+	return tempDir, nil
+}
+
+func getInaccessiblePath(file string) string {
+	return filepath.Join("C:", "file\x00name") // null byte in filename is not allowed on Windows AND unix
+}
diff --git a/middleware/secondary/setup_test.go b/middleware/secondary/setup_test.go
index 8eea1460f..c58483f6b 100644
--- a/middleware/secondary/setup_test.go
+++ b/middleware/secondary/setup_test.go
@@ -29,7 +29,7 @@ func TestSecondaryParse(t *testing.T) {
 	}
 
 	for i, test := range tests {
-		c := caddy.NewTestController("secondary", test.inputFileRules)
+		c := caddy.NewTestController("dns", test.inputFileRules)
 		_, err := secondaryParse(c)
 
 		if err == nil && test.shouldErr {