Add user authentication helpers

auth/pass.go

@@ -0,0 +1,21 @@
+package auth
+
+import "golang.org/x/crypto/bcrypt"
+
+func clear(b []byte) {
+	for i := 0; i < len(b); i++ {
+		b[i] = 0
+	}
+}
+
+func HashPass(password []byte) ([]byte, error) {
+	// Clear memory where plaintext password was stored.
+	// http://stackoverflow.com/questions/18545676/golang-app-engine-securely-hashing-a-users-password#comment36585613_19828153
+	defer clear(password)
+	// Return hash
+	return bcrypt.GenerateFromPassword(password, 12)
+}
+
+func Authenticated(hash, pass []byte) bool {
+	return bcrypt.CompareHashAndPassword(hash, pass) == nil
+}