From df977f18e831f4a9bd23e59880fb27a25144a24c Mon Sep 17 00:00:00 2001
From: Didactic Drunk <1479616+didactic-drunk@users.noreply.github.com>
Date: Mon, 14 Jun 2021 12:07:31 -0700
Subject: [PATCH] Add Crypto::Secret::Stateless

---
 src/crypto-secret/not.cr       |  4 ++-
 src/crypto-secret/secret.cr    | 55 +++++++++++++---------------------
 src/crypto-secret/stateless.cr | 54 +++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 35 deletions(-)
 create mode 100644 src/crypto-secret/stateless.cr

diff --git a/src/crypto-secret/not.cr b/src/crypto-secret/not.cr
index 3e7be60..185f278 100644
--- a/src/crypto-secret/not.cr
+++ b/src/crypto-secret/not.cr
@@ -1,10 +1,12 @@
+require "./stateless"
+
 # A not very secret secret
 #
 # Not locked in memory
 # Not access protected
 # No guard pages
 struct Crypto::Secret::Not
-  include Crypto::Secret
+  include Crypto::Secret::Stateless
 
   def self.new(size)
     new Bytes.new(size)
diff --git a/src/crypto-secret/secret.cr b/src/crypto-secret/secret.cr
index 00e4f61..dfc7371 100644
--- a/src/crypto-secret/secret.cr
+++ b/src/crypto-secret/secret.cr
@@ -1,13 +1,12 @@
 require "crypto/subtle"
 
 lib LibC
-  fun explicit_bzero(Void*, LibC::SizeT) : Int
+  fun explicit_bzero(Void*, LibC::SizeT) : Void
 end
 
 struct Slice(T)
   def wipe
-    r = LibC.explicit_bzero slice.to_unsafe, slice.bytesize
-    raise RunTimeError.from_errno("explicit_bzero") if r != 0
+    LibC.explicit_bzero to_unsafe, bytesize
   end
 end
 
@@ -21,41 +20,21 @@ module Crypto::Secret
   class Error < Exception
     class KeyWiped < Error
     end
-  end
 
-  def readwrite
-  end
+    class InvalidStateTransition < Error
+    end
 
-  # Yields a Slice that is readable and writable
-  #
-  # `slice` is only available within the block
-  #
-  # Not thread safe
-  def readwrite
-    to_slice do |slice|
-      yield slice
+    # Check RLIMIT_MEMLOCK if you receive this
+    class OutOfMemory < Error
     end
   end
 
-  def readonly
-  end
-
-  # Yields a Slice that is readable possibly writable depending on the prior protection level and underlying implementation
-  # Don't write to it
-  #
-  # Not thread safe
-  def readonly
-    to_slice do |slice|
-      yield slice
-    end
-  end
-
-  def noaccess
-  end
-
-  # Not thread safe
-  def noaccess
-    yield
+  enum State
+    Cloning
+    Wiped
+    Noaccess
+    Readonly
+    Readwrite
   end
 
   # For debugging.
@@ -66,7 +45,7 @@ module Crypto::Secret
 
   def wipe
     readwrite do |slice|
-      slice.wipe
+      wipe_impl slice
     end
   end
 
@@ -105,6 +84,10 @@ module Crypto::Secret
     io << self.class.to_s << "(***SECRET***)"
   end
 
+  abstract def readwrite
+  abstract def readonly
+  abstract def noaccess
+
   abstract def to_slice(& : Bytes -> Nil)
   abstract def bytesize : Int32
 
@@ -119,4 +102,8 @@ module Crypto::Secret
       {{object.id}}.bytesize
     end
   end
+
+  def wipe_impl(slice : Bytes) : Nil
+    slice.wipe
+  end
 end
diff --git a/src/crypto-secret/stateless.cr b/src/crypto-secret/stateless.cr
new file mode 100644
index 0000000..9061830
--- /dev/null
+++ b/src/crypto-secret/stateless.cr
@@ -0,0 +1,54 @@
+require "./secret"
+
+# Provides a 0 overhead implementation of [#readwrite, #readonly, #noaccess, #reset] with no protection
+#
+# Data is still erased when out of scope
+module Crypto::Secret::Stateless
+  include Crypto::Secret
+
+  # Not thread safe
+  def readwrite
+  end
+
+  # Yields a Slice that is readable and writable
+  #
+  # `slice` is only available within the block
+  #
+  # Not thread safe
+  def readwrite
+    to_slice do |slice|
+      yield slice
+    end
+  end
+
+  # Not thread safe
+  def readonly
+  end
+
+  # Yields a Slice that is readable possibly writable depending on the prior protection level and underlying implementation
+  # Don't write to it
+  #
+  # Not thread safe
+  def readonly
+    to_slice do |slice|
+      yield slice
+    end
+  end
+
+  # Not thread safe
+  def noaccess
+  end
+
+  # Not thread safe
+  def noaccess
+    yield
+  end
+
+  # Not thread safe
+  def reset
+  end
+
+  def finalize
+    wipe
+  end
+end