Unencrypted keys (#6)

CHANGELOG.md

@@ -6,6 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- Support signing with unencrypted keys
+
 ## [0.0.8] - 2024-02-03
 
 ### Added

lib/minisign/private_key.rb

@@ -9,6 +9,7 @@ class PrivateKey
 
     # rubocop:disable Metrics/AbcSize
     # rubocop:disable Layout/LineLength
+    # rubocop:disable Metrics/MethodLength
 
     # Parse signing information from the minisign private key
     #
@@ -20,14 +21,31 @@ def initialize(str, password = nil)
       bytes = Base64.decode64(contents.last).bytes
       @signature_algorithm, @kdf_algorithm, @cksum_algorithm =
         [bytes[0..1], bytes[2..3], bytes[4..5]].map { |a| a.pack('U*') }
+      raise 'Missing password for encrypted key' if @kdf_algorithm.bytes.sum != 0 && password.nil?
+
       @kdf_salt = bytes[6..37]
       @kdf_opslimit = bytes[38..45].pack('V*').unpack('N*').sum
       @kdf_memlimit = bytes[46..53].pack('V*').unpack('N*').sum
-      kdf_output = derive_key(password, @kdf_salt, @kdf_opslimit, @kdf_memlimit)
-      @key_id, @secret_key, @public_key, @checksum = xor(kdf_output, bytes[54..157])
+      key_data_bytes = if password
+                         kdf_output = derive_key(password, @kdf_salt, @kdf_opslimit, @kdf_memlimit)
+                         xor(kdf_output, bytes[54..157])
+                       else
+                         bytes[54..157]
+                       end
+      @key_id, @secret_key, @public_key, @checksum = key_data(key_data_bytes)
+      assert_keypair_match!
     end
     # rubocop:enable Layout/LineLength
     # rubocop:enable Metrics/AbcSize
+    # rubocop:enable Metrics/MethodLength
+
+    def assert_keypair_match!
+      raise 'Wrong password for that key' if @public_key != ed25519_signing_key.verify_key.to_bytes.bytes
+    end
+
+    def key_data(bytes)
+      [bytes[0..7], bytes[8..39], bytes[40..71], bytes[72..103]]
+    end
 
     # @return [String] the <kdf_output> used to xor the ed25519 keys
     def derive_key(password, kdf_salt, kdf_opslimit, kdf_memlimit)
@@ -45,10 +63,9 @@ def derive_key(password, kdf_salt, kdf_opslimit, kdf_memlimit)
     # @return [Array<32 bit unsigned ints>] the byte array containing the key id, the secret and public ed25519 keys, and the checksum
     def xor(kdf_output, contents)
       # rubocop:enable Layout/LineLength
-      xored = kdf_output.each_with_index.map do |b, i|
+      kdf_output.each_with_index.map do |b, i|
         contents[i] ^ b
       end
-      [xored[0..7], xored[8..39], xored[40..71], xored[72..103]]
     end
 
     # @return [Ed25519::SigningKey] the ed25519 signing key

spec/minisign/private_key_spec.rb

@@ -14,6 +14,18 @@
       expect(@private_key.kdf_algorithm).to eq('Sc')
     end
 
+    it 'raises if the private key requires a password but is not supplied' do
+      expect do
+        Minisign::PrivateKey.new(File.read('test/minisign.key'))
+      end.to raise_error('Missing password for encrypted key')
+    end
+
+    it 'raises if the password is incorrect for the private key' do
+      expect do
+        Minisign::PrivateKey.new(File.read('test/minisign.key'), 'not the right password')
+      end.to raise_error('Wrong password for that key')
+    end
+
     it 'parses the cksum_algorithm' do
       expect(@private_key.cksum_algorithm).to eq('B2')
     end
@@ -53,15 +65,25 @@
 
   describe 'sign' do
     it 'signs a file' do
-      Dir.glob('test/generated/*').each { |file| File.delete(file) }
-      filename = "#{SecureRandom.uuid}.txt"
-      message = SecureRandom.uuid
-      File.write("test/generated/#{filename}", message)
-      signature = @private_key.sign(filename, message)
-      File.write("test/generated/#{filename}.minisig", signature)
+      @filename = 'encrypted-key.txt'
+      @message = SecureRandom.uuid
+      File.write("test/generated/#{@filename}", @message)
+      signature = @private_key.sign(@filename, @message)
+      File.write("test/generated/#{@filename}.minisig", signature)
       @signature = Minisign::Signature.new(signature)
       @public_key = Minisign::PublicKey.new('RWSmKaOrT6m3TGwjwBovgOmlhSbyBUw3hyhnSOYruHXbJa36xHr8rq2M')
-      expect(@public_key.verify(@signature, message)).to match('Signature and comment signature verified')
+      expect(@public_key.verify(@signature, @message)).to match('Signature and comment signature verified')
+    end
+    it 'signs a file with an unencrypted key' do
+      @filename = 'unencrypted-key.txt'
+      @message = SecureRandom.uuid
+      File.write("test/generated/#{@filename}", @message)
+      @unencrypted_private_key = Minisign::PrivateKey.new(File.read('test/unencrypted.key'))
+      signature = @unencrypted_private_key.sign(@filename, @message)
+      File.write("test/generated/#{@filename}.minisig", signature)
+      @signature = Minisign::Signature.new(signature)
+      @public_key = Minisign::PublicKey.new('RWT/N/MXaBIWRAPzfdEKqVRq9txskjf5qh7EbqMLVHjkNTGFazO3zMw2')
+      expect(@public_key.verify(@signature, @message)).to match('Signature and comment signature verified')
     end
   end
 end

spec/verify.sh

@@ -4,10 +4,12 @@ if [[ "$OSTYPE" == "darwin"* ]]; then
     url="https://github.com/jedisct1/minisign/releases/download/0.11/minisign-0.11-macos.zip"
     curl -sL $url -o test/generated/minisign.zip
     unzip -o test/generated/minisign.zip -d test/generated
-    test/generated/minisign -Vm test/generated/*.txt -p test/minisign.pub
 else
     url="https://github.com/jedisct1/minisign/releases/download/0.11/minisign-0.11-linux.tar.gz"
     curl -sL $url -o test/generated/minisign.tar.gz
     tar -xvzf test/generated/minisign.tar.gz -C test/generated
-    test/generated/minisign-linux/x86_64/minisign -Vm test/generated/*.txt -p test/minisign.pub
+    mv test/generated/minisign-linux/x86_64/minisign test/generated/minisign
 fi
+
+test/generated/minisign -Vm test/generated/encrypted-key.txt -p test/minisign.pub || exit 1
+test/generated/minisign -Vm test/generated/unencrypted-key.txt -p test/unencrypted.pub || exit 1

test/unencrypted.key

@@ -0,0 +1,2 @@
+untrusted comment: minisign encrypted secret key
+RWQAAEIyAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/zfzF2gSFkTKpvJz4Zf4HGG/b6OCfwWzUBt6qubTzn3j1XSgZwRHwQPzfdEKqVRq9txskjf5qh7EbqMLVHjkNTGFazO3zMw2AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=

test/unencrypted.pub

@@ -0,0 +1,2 @@
+untrusted comment: minisign public key 4416126817F337FF
+RWT/N/MXaBIWRAPzfdEKqVRq9txskjf5qh7EbqMLVHjkNTGFazO3zMw2