Merge pull request #37 from ripienaar/36

(#36) only write certs when they change when always overwrite is set

filesec/file_security.go

@@ -338,12 +338,25 @@ func (s *FileSecurity) CachePublicData(data []byte, identity string) error {
 		return err
 	}
 
-	if !s.conf.AlwaysOverwriteCache {
-		_, err = os.Stat(certfile)
-		if err == nil {
+	_, err = os.Stat(certfile)
+	if err == nil {
+		if !s.conf.AlwaysOverwriteCache {
 			s.log.Debugf("Already have a certificate in %s, refusing to overwrite with a new one", certfile)
 			return nil
 		}
+
+		// it exists, lets check if its required to update it, quicker to just update it but that
+		// risks failing when disks are full etc this attempts that risky step only when needed
+		rsum := sha256.Sum256([]byte(data))
+		fsum, err := fsha256(certfile)
+		if err != nil {
+			return fmt.Errorf("could not determine sha256 of current certificate in %s: %s", certfile, err)
+		}
+
+		if fmt.Sprintf("%x", fsum) == fmt.Sprintf("%x", rsum) {
+			s.log.Debugf("Received certificate is the same as cached certificate %s, not updating cache", certfile)
+			return nil
+		}
 	}
 
 	err = ioutil.WriteFile(certfile, []byte(data), os.FileMode(int(0644)))

filesec/file_security_test.go

@@ -529,7 +529,7 @@ var _ = Describe("FileSSL", func() {
 			Expect(err).ToNot(HaveOccurred())
 			defer os.Remove(cpath)
 
-			// deliberatly change the file so that we can figure out if its being changed
+			// deliberately change the file so that we can figure out if its being changed
 			// I'd check time stamps but they are per second so not much use
 			err = ioutil.WriteFile(cpath, []byte("too many secrets"), os.FileMode(int(0644)))
 			Expect(err).ToNot(HaveOccurred())

filesec/util.go

@@ -1,6 +1,8 @@
 package filesec
 
 import (
+	"crypto/sha256"
+	"io"
 	"os"
 	"regexp"
 	"runtime"
@@ -38,3 +40,19 @@ func runtimeOs() string {
 
 	return runtime.GOOS
 }
+
+func fsha256(file string) ([]byte, error) {
+	f, err := os.Open(file)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	h := sha256.New()
+	_, err = io.Copy(h, f)
+	if err != nil {
+		return nil, err
+	}
+
+	return h.Sum(nil), nil
+}