From f036295aa3a518c88b13bf17608282c6319a7de6 Mon Sep 17 00:00:00 2001
From: Didactic Drunk <1479616+didactic-drunk@users.noreply.github.com>
Date: Thu, 28 Apr 2022 12:14:35 -0700
Subject: [PATCH] Sign:   Add `.copy_from` `.move_from` instead of *erase*  
 Prefer `.random`   Deprecate old `.initialize`

---
 README.md                           |  2 +-
 spec/sodium/sign/secret_key_spec.cr | 23 +++-------
 src/sodium/sign/secret_key.cr       | 68 ++++++++++++++++++++---------
 3 files changed, 55 insertions(+), 38 deletions(-)

diff --git a/README.md b/README.md
index 8fce8f1..8374b96 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ Crystal bindings for the [libsodium API](https://libsodium.gitbook.io/doc/)
 - [Public-Key Cryptography](https://libsodium.gitbook.io/doc/public-key_cryptography)
   - [x] ☑ [Crypto Box Easy](https://libsodium.gitbook.io/doc/public-key_cryptography/authenticated_encryption)
   - [x] [Sealed Box](https://libsodium.gitbook.io/doc/public-key_cryptography/sealed_boxes)
-  - [ ] [Combined Signatures](https://libsodium.gitbook.io/doc/public-key_cryptography/public-key_signatures)
+  - [x] [Combined Signatures](https://libsodium.gitbook.io/doc/public-key_cryptography/public-key_signatures)
   - [x] ☑ [Detached Signatures](https://libsodium.gitbook.io/doc/public-key_cryptography/public-key_signatures)
   - [ ] [Pre-hashed Signatures](https://libsodium.gitbook.io/doc/public-key_cryptography/public-key_signatures)
 - [Secret-Key Cryptography](https://libsodium.gitbook.io/doc/secret-key_cryptography)
diff --git a/spec/sodium/sign/secret_key_spec.cr b/spec/sodium/sign/secret_key_spec.cr
index 1952bee..7150930 100644
--- a/spec/sodium/sign/secret_key_spec.cr
+++ b/spec/sodium/sign/secret_key_spec.cr
@@ -31,18 +31,9 @@ end
 
 describe Sodium::Sign::SecretKey do
   it "loads keys" do
-    key1 = Sodium::Sign::SecretKey.new
+    key1 = Sodium::Sign::SecretKey.random
     key2 = key1.key.readonly do |kslice|
-      Sodium::Sign::SecretKey.new kslice, key1.public_key.to_slice
-    end
-    key1.key.should eq key2.key
-    key1.public_key.to_slice.should eq key2.public_key.to_slice
-  end
-
-  it "recomputes the public key" do
-    key1 = Sodium::Sign::SecretKey.new
-    key2 = key1.key.readonly do |kslice|
-      Sodium::Sign::SecretKey.new kslice
+      Sodium::Sign::SecretKey.copy_from kslice
     end
     key1.key.should eq key2.key
     key1.public_key.to_slice.should eq key2.public_key.to_slice
@@ -52,7 +43,7 @@ describe Sodium::Sign::SecretKey do
     seed = Bytes.new Sodium::Sign::SecretKey::SEED_SIZE
     key1 = Sodium::Sign::SecretKey.new seed: seed
     key2 = key1.key.readonly do |kslice|
-      Sodium::Sign::SecretKey.new kslice
+      Sodium::Sign::SecretKey.copy_from kslice
     end
     key3 = Sodium::Sign::SecretKey.new seed: key2.seed
     key1.key.should eq key2.key
@@ -66,7 +57,7 @@ describe Sodium::Sign::SecretKey do
 
   it "signs and verifies combined" do
     message = "foo"
-    skey = Sodium::Sign::SecretKey.new
+    skey = Sodium::Sign::SecretKey.random
     sig = skey.sign message
 
     message2 = skey.public_key.verify_string sig
@@ -75,7 +66,7 @@ describe Sodium::Sign::SecretKey do
 
   it "signs and verifies detached" do
     message = "foo"
-    skey = Sodium::Sign::SecretKey.new
+    skey = Sodium::Sign::SecretKey.random
     sig = skey.sign_detached message
 
     skey.public_key.verify_detached message, sig
@@ -83,7 +74,7 @@ describe Sodium::Sign::SecretKey do
 
   it "signs and fails" do
     message = "foo"
-    skey = Sodium::Sign::SecretKey.new
+    skey = Sodium::Sign::SecretKey.random
     sig = skey.sign_detached message
 
     expect_raises Sodium::Error::VerificationFailed do
@@ -93,7 +84,7 @@ describe Sodium::Sign::SecretKey do
 
   it "to_curve25519" do
     message = "foo"
-    sskey = Sodium::Sign::SecretKey.new
+    sskey = Sodium::Sign::SecretKey.random
     cskey = sskey.to_curve25519
 
     spkey = sskey.public_key
diff --git a/src/sodium/sign/secret_key.cr b/src/sodium/sign/secret_key.cr
index 523039d..c3ae296 100644
--- a/src/sodium/sign/secret_key.cr
+++ b/src/sodium/sign/secret_key.cr
@@ -18,12 +18,12 @@ module Sodium
     SIG_SIZE  = LibSodium.crypto_sign_bytes.to_i
     SEED_SIZE = LibSodium.crypto_sign_seedbytes.to_i
 
-    getter public_key : PublicKey
-
     @[Deprecated("Switching to Crypto::Secret.  Use `key.readonly` or `key.readwrite`")]
     delegate_to_slice to: @key
 
     getter key : Crypto::Secret
+    getter public_key = PublicKey.new
+
     @seed : Crypto::Secret?
 
     # Generates a new random secret/public key pair.
@@ -37,40 +37,54 @@ module Sodium
       end
     end
 
-    # Use existing secret and public keys.
-    # Copies secret key to a SecureBuffer.
-    # Recomputes the public key from a secret key if missing.
-    def initialize(bytes : Bytes, pkey : Bytes? = nil, *, erase = false)
-      raise ArgumentError.new("Secret sign key must be #{KEY_SIZE}, got #{bytes.bytesize}") unless bytes.bytesize == KEY_SIZE
 
-      @key = SecureBuffer.new bytes, erase: erase
-      if pk = pkey
-        @public_key = PublicKey.new pk
+    # Copies secret *key* to a `SecureBuffer`
+    def self.copy_from(key : Bytes)
+      new SecureBuffer.copy_from(key)
+    end
+
+    # Copies secret *key* to a `SecureBuffer`
+    # Erases *key*
+    def self.move_from(key : Bytes)
+      new SecureBuffer.move_from(key)
+    end
+
+    # Copies secret *key* to a `SecureBuffer`
+    @[Deprecated("Use .copy_from or .move_from")]
+    def self.new(key : Bytes, erase = false)
+      raise ArgumentError.new("Secret sign key must be #{KEY_SIZE}, got #{key.bytesize}") unless key.bytesize == KEY_SIZE
+
+      if erase
+        move_from key
       else
-        @public_key = PublicKey.new
-        @key.readwrite do |kslice|
-          if LibSodium.crypto_sign_ed25519_sk_to_pk(@public_key.to_slice, kslice) != 0
-            raise Sodium::Error.new("crypto_sign_ed25519_sk_to_pk")
-          end
+        copy_from key
+      end
+    end
+
+    # References existing Crypto::Secret
+    def initialize(@key : Crypto::Secret)
+      # Set @public_key
+      @key.readwrite do |kslice|
+        if LibSodium.crypto_sign_ed25519_sk_to_pk(@public_key.to_slice, kslice) != 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.
-    # Copies seed to a SecureBuffer.
-    def initialize(*, seed : Bytes, erase = false)
+    # Copies seed to a `SecureBuffer`
+    def self.new(*, seed : Bytes, erase = false)
       raise ArgumentError.new("Secret sign seed must be #{SEED_SIZE}, got #{seed.bytesize}") unless seed.bytesize == SEED_SIZE
-      initialize(seed: SecureBuffer.new(seed, erase: erase))
+      new(seed: SecureBuffer.new(seed, erase: erase))
     end
 
     # Derive a new secret/public key pair based on a consistent seed.
-    # References passed SecureBuffer
-    def initialize(*, seed : SecureBuffer)
+    # References passed `SecureBuffer`
+    def initialize(*, seed : Crypto::Secret)
       raise ArgumentError.new("Secret sign seed must be #{SEED_SIZE}, got #{seed.bytesize}") unless seed.bytesize == SEED_SIZE
       @seed = seed
 
       @key = SecureBuffer.new KEY_SIZE
-      @public_key = PublicKey.new
       seed.readonly do |seed_slice|
         @key.readwrite do |kslice|
           if LibSodium.crypto_sign_seed_keypair(@public_key.to_slice, kslice, seed_slice) != 0
@@ -80,6 +94,18 @@ module Sodium
       end
     end
 
+    # :nodoc:
+    def initialize(random : Bool)
+      @key = SecureBuffer.new KEY_SIZE
+      @key.readwrite do |kslice|
+        if LibSodium.crypto_sign_keypair(@public_key.to_slice, kslice) != 0
+          raise Sodium::Error.new("crypto_sign_keypair")
+        end
+      end
+    end
+
+
+
     getter seed : Crypto::Secret do
       SecureBuffer.new(SEED_SIZE).tap do |seed_buf|
         @key.readonly do |kslice|