From 162cd72b0c4c1da7fe6b10297c79cf3b49dca6b9 Mon Sep 17 00:00:00 2001
From: Didactic Drunk <1479616+didactic-drunk@users.noreply.github.com>
Date: Sat, 29 Jun 2019 17:21:00 -0700
Subject: [PATCH] Add seed support to CryptoBox and Sign.

Wiping now supports multiple variables by Annotation.
---
 README.md                                     |  2 +-
 spec/sodium/crypto_box/secret_key_spec.cr     |  7 +++
 spec/sodium/{ => digest}/blake2b_spec.cr      |  2 +-
 .../{secret_key.cr => secret_key_spec.cr}     | 11 +++--
 src/sodium.cr                                 |  4 --
 src/sodium/crypto_box/box.cr                  |  1 +
 src/sodium/crypto_box/public_key.cr           |  6 +++
 src/sodium/crypto_box/secret_key.cr           | 43 +++++++++++--------
 src/sodium/digest/blake2b.cr                  | 19 ++++----
 src/sodium/kdf.cr                             | 13 +++---
 src/sodium/key.cr                             |  4 ++
 src/sodium/lib_sodium.cr                      | 40 +++++++++++++----
 src/sodium/pwhash.cr                          |  4 +-
 src/sodium/secret_box.cr                      |  1 +
 src/sodium/sign/public_key.cr                 |  6 +++
 src/sodium/sign/secret_key.cr                 | 33 ++++++++------
 src/sodium/wipe.cr                            | 19 +++++++-
 17 files changed, 149 insertions(+), 66 deletions(-)
 rename spec/sodium/{ => digest}/blake2b_spec.cr (98%)
 rename spec/sodium/sign/{secret_key.cr => secret_key_spec.cr} (79%)

diff --git a/README.md b/README.md
index 251c76e..0c2a2a2 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,8 @@ Crystal bindings for the [libsodium API](https://libsodium.gitbook.io/doc/)
 
 ## Goals
 
-* Provide an easy to use API based on reviewing most other [libsodium bindings](https://libsodium.gitbook.io/doc/bindings_for_other_languages).
 * Provide the most commonly used libsodium API's.
+* Provide an easy to use API based on reviewing most other [libsodium bindings](https://libsodium.gitbook.io/doc/bindings_for_other_languages).
 * Test for compatibility against other libsodium bindings to ensure interoperability.
 * Always provide a stream interface to handle arbitrarily sized data when one is available.
 * Drop in replacement classes compatible with OpenSSL::{Digest,Cipher} when possible.
diff --git a/spec/sodium/crypto_box/secret_key_spec.cr b/spec/sodium/crypto_box/secret_key_spec.cr
index 82a22e7..f577d2a 100644
--- a/spec/sodium/crypto_box/secret_key_spec.cr
+++ b/spec/sodium/crypto_box/secret_key_spec.cr
@@ -12,6 +12,13 @@ describe Sodium::CryptoBox::SecretKey do
     key1.public_key.bytes.should eq key2.public_key.bytes
   end
 
+  it "recomputes the public_key" do
+    key1 = Sodium::CryptoBox::SecretKey.new
+    key2 = Sodium::CryptoBox::SecretKey.new key1.bytes
+    key1.bytes.should eq key2.bytes
+    key1.public_key.bytes.should eq key2.public_key.bytes
+  end
+
   it "seed keys" do
     seed = Bytes.new Sodium::CryptoBox::SecretKey::SEED_SIZE
     key1 = Sodium::CryptoBox::SecretKey.new seed: seed
diff --git a/spec/sodium/blake2b_spec.cr b/spec/sodium/digest/blake2b_spec.cr
similarity index 98%
rename from spec/sodium/blake2b_spec.cr
rename to spec/sodium/digest/blake2b_spec.cr
index 9d22e0e..70238c7 100644
--- a/spec/sodium/blake2b_spec.cr
+++ b/spec/sodium/digest/blake2b_spec.cr
@@ -1,4 +1,4 @@
-require "../spec_helper"
+require "../../spec_helper"
 
 libsodium_comparisons = [
   {
diff --git a/spec/sodium/sign/secret_key.cr b/spec/sodium/sign/secret_key_spec.cr
similarity index 79%
rename from spec/sodium/sign/secret_key.cr
rename to spec/sodium/sign/secret_key_spec.cr
index 1aa3f1f..4a36983 100644
--- a/spec/sodium/sign/secret_key.cr
+++ b/spec/sodium/sign/secret_key_spec.cr
@@ -1,7 +1,7 @@
 require "../../spec_helper"
 require "../../../src/sodium/sign/secret_key"
 
-private def new_key_bytes
+private def new_sign_key_bytes
   Sodium::Sign::SecretKey.new.bytes
 end
 
@@ -11,8 +11,13 @@ describe Sodium::Sign::SecretKey do
     key2 = Sodium::Sign::SecretKey.new key1.bytes, key1.public_key.bytes
     key1.bytes.should eq key2.bytes
     key1.public_key.bytes.should eq key2.public_key.bytes
+  end
 
-    # TODO: test loading when missing public_key
+  it "recomputes the public key" do
+    key1 = Sodium::Sign::SecretKey.new
+    key2 = Sodium::Sign::SecretKey.new key1.bytes
+    key1.bytes.should eq key2.bytes
+    key1.public_key.bytes.should eq key2.public_key.bytes
   end
 
   it "seed keys" do
@@ -42,6 +47,6 @@ describe Sodium::Sign::SecretKey do
   end
 
   it "checks wiped" do
-    check_wiped new_key_bytes
+    check_wiped new_sign_key_bytes
   end
 end
diff --git a/src/sodium.cr b/src/sodium.cr
index 3ab1381..3d3646c 100644
--- a/src/sodium.cr
+++ b/src/sodium.cr
@@ -15,7 +15,3 @@ module Sodium
 end
 
 require "./sodium/**"
-
-if Sodium::LibSodium.sodium_init == -1
-  abort "Failed to init libsodium"
-end
diff --git a/src/sodium/crypto_box/box.cr b/src/sodium/crypto_box/box.cr
index 7d12faf..19e8dd5 100644
--- a/src/sodium/crypto_box/box.cr
+++ b/src/sodium/crypto_box/box.cr
@@ -5,6 +5,7 @@ module Sodium::CryptoBox
     include Wipe
 
     # BUG: precompute size
+    @[Wipe::Var]
     @bytes = Bytes.new(1)
 
     def initialize(@secret_key : SecretKey, @public_key : PublicKey)
diff --git a/src/sodium/crypto_box/public_key.cr b/src/sodium/crypto_box/public_key.cr
index ea02d54..9670038 100644
--- a/src/sodium/crypto_box/public_key.cr
+++ b/src/sodium/crypto_box/public_key.cr
@@ -7,6 +7,12 @@ module Sodium::CryptoBox
 
     getter bytes : Bytes
 
+    # :nodoc:
+    # Only used by SecretKey
+    def initialize
+      @bytes = Bytes.new KEY_SIZE
+    end
+
     def initialize(@bytes : Bytes)
       if bytes.bytesize != KEY_SIZE
         raise ArgumentError.new("Public key must be #{KEY_SIZE} bytes, got #{bytes.bytesize}")
diff --git a/src/sodium/crypto_box/secret_key.cr b/src/sodium/crypto_box/secret_key.cr
index 1e49c78..85c2355 100644
--- a/src/sodium/crypto_box/secret_key.cr
+++ b/src/sodium/crypto_box/secret_key.cr
@@ -1,34 +1,42 @@
 require "../lib_sodium"
 
 module Sodium::CryptoBox
+  # WARNING: This class takes ownership of any key material passed to it.
+  # If you don't want this behavior pass a duplicate of the key/seed to initialize().
   class SecretKey < Key
     include Wipe
     KEY_SIZE  = LibSodium.crypto_box_secretkeybytes
     SEED_SIZE = LibSodium.crypto_box_seedbytes
     MAC_SIZE  = LibSodium::MAC_SIZE
 
-    getter public_key
+    getter public_key : PublicKey
+
+    @[Wipe::Var]
     getter bytes : Bytes
+    @[Wipe::Var]
     @seed : Bytes?
 
     # Generate a new random secret/public key pair.
     def initialize
-      pkey = Bytes.new(PublicKey::KEY_SIZE)
       @bytes = Bytes.new(KEY_SIZE)
-      @public_key = PublicKey.new pkey
-      v = LibSodium.crypto_box_keypair(pkey, @bytes)
-      if v != 0
-        raise Sodium::Error.new("crypto_box_keypair #{v}")
+      @public_key = PublicKey.new
+      if LibSodium.crypto_box_keypair(@public_key.bytes, @bytes) != 0
+        raise Sodium::Error.new("crypto_box_keypair")
       end
     end
 
-    # Use existing Secret and Public keys.
-    def initialize(@bytes : Bytes, pkey : Bytes)
-      # TODO: finish regenerating public_key
-      if bytes.bytesize != KEY_SIZE
-        raise ArgumentError.new("Secret key must be #{KEY_SIZE} bytes, got #{bytes.bytesize}")
+    # Use existing secret and public keys.
+    # Recomputes the public key from a secret key if missing.
+    def initialize(@bytes : Bytes, pkey : Bytes? = nil)
+      raise ArgumentError.new("Secret key must be #{KEY_SIZE} bytes, got #{bytes.bytesize}") if bytes.bytesize != KEY_SIZE
+      if pk = pkey
+        @public_key = PublicKey.new pk
+      else
+        @public_key = PublicKey.new
+        if LibSodium.crypto_scalarmult_base(@public_key.bytes, @bytes) != 0
+          raise Sodium::Error.new("crypto_scalarmult_base")
+        end
       end
-      @public_key = PublicKey.new pkey
     end
 
     # Derive a new secret/public key pair based on a consistent seed.
@@ -36,10 +44,9 @@ module Sodium::CryptoBox
       raise ArgumentError.new("Secret sign seed must be #{SEED_SIZE}, got #{seed.bytesize}") unless seed.bytesize == SEED_SIZE
       @seed = seed
 
-      pkey = Bytes.new(PublicKey::KEY_SIZE)
       @bytes = Bytes.new(KEY_SIZE)
-      @public_key = PublicKey.new pkey
-      if LibSodium.crypto_box_seed_keypair(pkey, @bytes, seed) != 0
+      @public_key = PublicKey.new
+      if LibSodium.crypto_box_seed_keypair(@public_key.bytes, @bytes, seed) != 0
         raise Sodium::Error.new("crypto_box_seed_keypair")
       end
     end
@@ -51,11 +58,11 @@ module Sodium::CryptoBox
 
     # Create a new box and automatically close when the block exits.
     def box(public_key)
-      pa = box public_key
+      b = box public_key
       begin
-        yield pa
+        yield b
       ensure
-        pa.close
+        b.close
       end
     end
   end
diff --git a/src/sodium/digest/blake2b.cr b/src/sodium/digest/blake2b.cr
index ef70e61..7a378f7 100644
--- a/src/sodium/digest/blake2b.cr
+++ b/src/sodium/digest/blake2b.cr
@@ -4,6 +4,7 @@ module Sodium::Digest
   class Blake2b
     # provides copying digest/hexdigest methods
     include OpenSSL::DigestBase
+    include Wipe
 
     KEY_SIZE     = LibSodium.crypto_generichash_blake2b_keybytes
     KEY_SIZE_MIN = LibSodium.crypto_generichash_blake2b_keybytes_min
@@ -19,42 +20,40 @@ module Sodium::Digest
 
     getter digest_size
 
+    @[Wipe::Var]
     @state = StaticArray(UInt8, 384).new 0
     @key_size = 0
-    @have_salt = false
-    @have_personal = false
 
     # implemented as static array's so clone works without jumping through hoops.
+    @[Wipe::Var]
     @key = StaticArray(UInt8, 64).new 0
     @salt = StaticArray(UInt8, 16).new 0
     @personal = StaticArray(UInt8, 16).new 0
 
     def initialize(@digest_size : Int32 = OUT_SIZE, key : Bytes? = nil, salt : Bytes? = nil, personal : Bytes? = nil)
       if k = key
-        raise ArgumentError.new("key larger than KEY_SIZE_MAX, got #{k.bytesize}") if k.bytesize > KEY_SIZE_MAX
+        raise ArgumentError.new("key larger than KEY_SIZE_MAX(#{KEY_SIZE_MAX}), got #{k.bytesize}") if k.bytesize > KEY_SIZE_MAX
         @key_size = k.bytesize
         k.copy_to @key.to_slice
       end
 
       if sa = salt
-        raise ArgumentError.new("salt must be SALT_SIZE bytes, got #{sa.bytesize}") if sa.bytesize != SALT_SIZE
+        raise ArgumentError.new("salt must be SALT_SIZE(#{SALT_SIZE}) bytes, got #{sa.bytesize}") if sa.bytesize != SALT_SIZE
         sa.copy_to @salt.to_slice
-        @have_salt = true
       end
 
       if pe = personal
-        raise ArgumentError.new("personal must be PERSONAL_SIZE bytes, got #{pe.bytesize}") if pe.bytesize != PERSONAL_SIZE
+        raise ArgumentError.new("personal must be PERSONAL_SIZE(#{PERSONAL_SIZE}) bytes, got #{pe.bytesize}") if pe.bytesize != PERSONAL_SIZE
         pe.copy_to @personal.to_slice
-        @have_personal = true
       end
 
       reset
     end
 
     def reset
-      key = @key_size > 0 ? @key.to_unsafe : nil
-      salt = @have_salt ? @salt.to_unsafe : nil
-      personal = @have_personal ? @personal.to_unsafe : nil
+      key = @key.to_unsafe
+      salt = @salt.to_unsafe
+      personal = @personal.to_unsafe
 
       if LibSodium.crypto_generichash_blake2b_init_salt_personal(@state, key, @key_size, @digest_size, salt, personal) != 0
         raise Sodium::Error.new("blake2b_init_key_salt_personal")
diff --git a/src/sodium/kdf.cr b/src/sodium/kdf.cr
index fac7b78..7a82e4c 100644
--- a/src/sodium/kdf.cr
+++ b/src/sodium/kdf.cr
@@ -1,26 +1,29 @@
 module Sodium
   class Kdf
+    KDF_KEY_SIZE     = LibSodium.crypto_kdf_keybytes
+    KDF_CONTEXT_SIZE = LibSodium.crypto_kdf_contextbytes
+
     property bytes : Bytes
 
     delegate to_slice, to: @bytes
 
     def initialize(bytes : Bytes)
-      if bytes.bytesize != LibSodium::KDF_KEY_SIZE
-        raise ArgumentError.new("bytes must be #{LibSodium::KDF_KEY_SIZE}, got #{bytes.bytesize}")
+      if bytes.bytesize != KDF_KEY_SIZE
+        raise ArgumentError.new("bytes must be #{KDF_KEY_SIZE}, got #{bytes.bytesize}")
       end
 
       @bytes = bytes
     end
 
     def initialize
-      @bytes = Random::Secure.random_bytes(LibSodium::KDF_KEY_SIZE)
+      @bytes = Random::Secure.random_bytes(KDF_KEY_SIZE)
     end
 
     # context must be 8 bytes
     # subkey_size must be 16..64 bytes as of libsodium 1.0.17
     def derive(context, subkey_id, subkey_size)
-      if context.bytesize != LibSodium::KDF_CONTEXT_SIZE
-        raise ArgumentError.new("context must be #{LibSodium::KDF_CONTEXT_SIZE}, got #{context.bytesize}")
+      if context.bytesize != KDF_CONTEXT_SIZE
+        raise ArgumentError.new("context must be #{KDF_CONTEXT_SIZE}, got #{context.bytesize}")
       end
 
       subkey = Bytes.new subkey_size
diff --git a/src/sodium/key.cr b/src/sodium/key.cr
index 4a6298a..d1e4a82 100644
--- a/src/sodium/key.cr
+++ b/src/sodium/key.cr
@@ -1,5 +1,9 @@
+require "./wipe"
+
 module Sodium
   abstract class Key
+    include Sodium::Wipe
+
     abstract def bytes
 
     delegate to_slice, to: @bytes
diff --git a/src/sodium/lib_sodium.cr b/src/sodium/lib_sodium.cr
index d041cc7..8797456 100644
--- a/src/sodium/lib_sodium.cr
+++ b/src/sodium/lib_sodium.cr
@@ -42,14 +42,9 @@ module Sodium
     fun crypto_generichash_blake2b_personalbytes : LibC::SizeT
     fun sodium_memzero(Pointer(LibC::UChar), LibC::SizeT) : Nil
 
-    PUBLIC_KEY_SIZE  = crypto_box_publickeybytes()
-    SECRET_KEY_SIZE  = crypto_box_secretkeybytes()
-    NONCE_SIZE       = crypto_box_noncebytes()
-    MAC_SIZE         = crypto_box_macbytes()
-    SIGNATURE_SIZE   = crypto_sign_bytes()
-    KDF_KEY_SIZE     = crypto_kdf_keybytes()
-    KDF_CONTEXT_SIZE = crypto_kdf_contextbytes()
-    PWHASH_STR_SIZE  = crypto_pwhash_strbytes()
+    NONCE_SIZE     = crypto_box_noncebytes()
+    MAC_SIZE       = crypto_box_macbytes()
+    SIGNATURE_SIZE = crypto_sign_bytes()
 
     fun crypto_secretbox_easy(
       output : Pointer(LibC::UChar),
@@ -93,6 +88,11 @@ module Sodium
       seed : Pointer(LibC::UChar)
     ) : LibC::Int
 
+    fun crypto_scalarmult_base(
+      public_key_output : Pointer(LibC::UChar),
+      secret_key_output : Pointer(LibC::UChar)
+    ) : LibC::Int
+
     fun crypto_box_easy(
       output : Pointer(LibC::UChar),
       data : Pointer(LibC::UChar),
@@ -111,6 +111,21 @@ module Sodium
       recipient_secret_key : Pointer(LibC::UChar)
     ) : LibC::Int
 
+    fun crypto_box_seal(
+      output : Pointer(LibC::UChar),
+      data : Pointer(LibC::UChar),
+      data_size : LibC::ULongLong,
+      recipient_public_key : Pointer(LibC::UChar)
+    ) : LibC::Int
+
+    fun crypto_box_seal_open(
+      output : Pointer(LibC::UChar),
+      data : Pointer(LibC::UChar),
+      data_size : LibC::ULongLong,
+      recipient_public_key : Pointer(LibC::UChar),
+      recipient_secret_key : Pointer(LibC::UChar)
+    ) : LibC::Int
+
     fun crypto_sign_keypair(
       public_key_output : Pointer(LibC::UChar),
       secret_key_output : Pointer(LibC::UChar)
@@ -122,6 +137,11 @@ module Sodium
       seed : Pointer(LibC::UChar)
     ) : LibC::Int
 
+    fun crypto_sign_ed25519_sk_to_pk(
+      public_key_output : Pointer(LibC::UChar),
+      secret_key_output : Pointer(LibC::UChar)
+    ) : LibC::Int
+
     fun crypto_sign_detached(
       signature_output : Pointer(LibC::UChar),
       signature_output_size : Pointer(LibC::ULongLong),
@@ -198,6 +218,10 @@ module Sodium
     ) : LibC::Int
   end
 
+  if LibSodium.sodium_init != 0
+    abort "Failed to init libsodium"
+  end
+
   if LibSodium.crypto_secretbox_noncebytes != LibSodium.crypto_box_noncebytes
     raise "Assumptions in this library regarding nonce sizes may not be valid"
   end
diff --git a/src/sodium/pwhash.cr b/src/sodium/pwhash.cr
index 5b5fbdf..4cf1e02 100644
--- a/src/sodium/pwhash.cr
+++ b/src/sodium/pwhash.cr
@@ -18,6 +18,8 @@ module Sodium
     MEMLIMIT_MAX         = LibSodium.crypto_pwhash_memlimit_max
     MEMLIMIT_INTERACTIVE = LibSodium.crypto_pwhash_memlimit_interactive
 
+    PWHASH_STR_SIZE = LibSodium.crypto_pwhash_strbytes
+
     # Use the most recent algorithm Argon2id13 for new applications.
     enum Algorithm
       Argon2i13  = 1
@@ -37,7 +39,7 @@ module Sodium
     # * the automatically generated salt used for the previous computation
     # * the other parameters required to verify the password, including the algorithm identifier, its version, opslimit and memlimit.
     def store(pass)
-      outstr = Bytes.new LibSodium::PWHASH_STR_SIZE
+      outstr = Bytes.new PWHASH_STR_SIZE
       if LibSodium.crypto_pwhash_str(outstr, pass, pass.bytesize, @opslimit, @memlimit) != 0
         raise Sodium::Error.new("crypto_pwhash_str")
       end
diff --git a/src/sodium/secret_box.cr b/src/sodium/secret_box.cr
index 3327594..f8935fd 100644
--- a/src/sodium/secret_box.cr
+++ b/src/sodium/secret_box.cr
@@ -17,6 +17,7 @@ module Sodium
     NONCE_SIZE = LibSodium.crypto_secretbox_noncebytes
     MAC_SIZE   = LibSodium::MAC_SIZE
 
+    @[Wipe::Var]
     property bytes : Bytes
 
     # Generate a new random key.
diff --git a/src/sodium/sign/public_key.cr b/src/sodium/sign/public_key.cr
index 83529cc..b311bf2 100644
--- a/src/sodium/sign/public_key.cr
+++ b/src/sodium/sign/public_key.cr
@@ -7,6 +7,12 @@ module Sodium
 
     getter bytes : Bytes
 
+    # :nodoc:
+    # Only used by SecretKey
+    def initialize
+      @bytes = Bytes.new(KEY_SIZE)
+    end
+
     def initialize(@bytes : Bytes)
       if bytes.bytesize != KEY_SIZE
         raise ArgumentError.new("Public key must be #{KEY_SIZE} bytes, got #{bytes.bytesize}")
diff --git a/src/sodium/sign/secret_key.cr b/src/sodium/sign/secret_key.cr
index 30cf907..005dff2 100644
--- a/src/sodium/sign/secret_key.cr
+++ b/src/sodium/sign/secret_key.cr
@@ -8,32 +8,38 @@ module Sodium
   # key.public_key.verify_detached data
   # ```
   class Sign::SecretKey < Sodium::Key
-    include Wipe
     KEY_SIZE  = LibSodium.crypto_sign_secretkeybytes
     SEED_SIZE = LibSodium.crypto_sign_seedbytes
 
+    getter public_key : PublicKey
+
+    @[Wipe::Var]
     getter bytes : Bytes
-    getter public_key
+    @[Wipe::Var]
     @seed : Bytes?
 
     # Generates a new random secret/public key pair.
     def initialize
-      pkey = Bytes.new(Sign::PublicKey::KEY_SIZE)
       @bytes = Bytes.new(KEY_SIZE)
-      @public_key = PublicKey.new pkey
-      if LibSodium.crypto_sign_keypair(pkey, @bytes) != 0
+      @public_key = PublicKey.new
+      if LibSodium.crypto_sign_keypair(@public_key.bytes, @bytes) != 0
         raise Sodium::Error.new("crypto_sign_keypair")
       end
     end
 
-    # Use existing Secret and Public keys.
+    # Use existing secret and public keys.
+    # Recomputes the public key from a secret key if missing.
     def initialize(@bytes : Bytes, pkey : Bytes? = nil)
-      pkey ||= Bytes.new(Sign::PublicKey::KEY_SIZE).tap do |pk|
-        # BUG: Finish regenerating public_key
-        raise "Needs crypto_sign_ed25519_sk_to_pk"
-      end
       raise ArgumentError.new("Secret sign key must be #{KEY_SIZE}, got #{@bytes.bytesize}") unless @bytes.bytesize == KEY_SIZE
-      @public_key = PublicKey.new pkey
+
+      if pk = pkey
+        @public_key = PublicKey.new pkey
+      else
+        @public_key = PublicKey.new
+        if LibSodium.crypto_sign_ed25519_sk_to_pk(@public_key.bytes, @bytes) != 0
+          raise Sodium::Error.new("crypto_sign_ed25519_sk_to_pk")
+        end
+      end
     end
 
     # Derive a new secret/public key pair based on a consistent seed.
@@ -41,10 +47,9 @@ module Sodium
       raise ArgumentError.new("Secret sign seed must be #{SEED_SIZE}, got #{seed.bytesize}") unless seed.bytesize == SEED_SIZE
       @seed = seed
 
-      pkey = Bytes.new(Sign::PublicKey::KEY_SIZE)
       @bytes = Bytes.new(KEY_SIZE)
-      @public_key = PublicKey.new pkey
-      if LibSodium.crypto_sign_seed_keypair(pkey, @bytes, seed) != 0
+      @public_key = PublicKey.new
+      if LibSodium.crypto_sign_seed_keypair(@public_key.bytes, @bytes, seed) != 0
         raise Sodium::Error.new("crypto_sign_seed_keypair")
       end
     end
diff --git a/src/sodium/wipe.cr b/src/sodium/wipe.cr
index 1735411..199c20b 100644
--- a/src/sodium/wipe.cr
+++ b/src/sodium/wipe.cr
@@ -1,4 +1,7 @@
 module Sodium::Wipe
+  annotation Var
+  end
+
   @closed = false
 
   def close
@@ -9,7 +12,21 @@ module Sodium::Wipe
 
   protected def wipe
     return if @closed
-    Sodium.memzero @bytes
+
+    {% for ivar in @type.instance_vars %}
+      {% if ann = ivar.annotation(Wipe::Var) %}
+        {% if ivar.type.id == StaticArray.id %}
+#puts "wiping static {{ivar}}"
+#            Sodium.memzero @{{ ivar.id }}.to_slice
+        {% else %}
+          if var = @{{ ivar.id }}
+#puts "wiping {{ivar}}"
+#            Sodium.memzero var
+            Sodium.memzero var.to_slice
+          end
+        {% end %}
+      {% end %}
+    {% end %}
   end
 
   def finalize