add change_password! method (#21)

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- Support for changing or removing the password from the private key
+
 ## [0.1.0] - 2024-02-09
 
 ### Added

README.md

@@ -6,6 +6,7 @@ A rubygem for creating and verifying [Minisign](http://jedisct1.github.io/minisi
   - [Read a public key](#read-a-public-key)
   - [Verify a signature](#verify-a-signature)
   - [Read a private key](#read-a-private-key)
+  - [Change the private key's password](#change-the-private-keys-password)
   - [Create a signature](#create-a-signature)
   - [Generate a key pair](#generate-a-key-pair)
 - [Local Development](#local-development)
@@ -41,6 +42,15 @@ password = "password" # optional, if the key is not encrypted
 private_key = Minisign::PrivateKey.new(File.read("minisign.key"), password)
 ```
 
+### Change the private key's password
+
+```rb
+password = "new password"
+private_key.change_password! password
+# or remove the password
+private_key.change_password! nil
+```
+
 ### Create a signature
 
 ```rb

lib/minisign/private_key.rb

@@ -61,6 +61,14 @@ def to_s
       "untrusted comment: #{@untrusted_comment}\n#{Base64.strict_encode64(data)}\n"
     end
 
+    # Change or remove a password
+    #
+    # @param new_password [String]
+    def change_password!(new_password)
+      @password = new_password
+      @bytes[2..3] = [0, 0] if new_password.nil? # kdf_algorithm
+    end
+
     private
 
     def signature_algorithm

spec/minisign/private_key_spec.rb

@@ -107,4 +107,45 @@
              )).to be(true)
     end
   end
+
+  describe '#change_password!' do
+    before do
+      @private_key = Minisign::PrivateKey.new(File.read('test/minisign.key'), 'password')
+    end
+    it 'changes the password' do
+      random_trusted_comment = SecureRandom.uuid
+      new_password = SecureRandom.uuid
+      original_public_key = @private_key.public_key
+      original_signature = @private_key.sign('example.txt', 'example', random_trusted_comment)
+      original_private_key = @private_key.to_s
+      @private_key.change_password! new_password
+      new_signature = @private_key.sign('example.txt', 'example', random_trusted_comment)
+      expect(original_signature.to_s).to eq(new_signature.to_s)
+      expect(original_public_key.to_s).to eq(@private_key.public_key.to_s)
+      expect(original_private_key.to_s).not_to eq(@private_key.to_s)
+      expect do
+        Minisign::PrivateKey.new(@private_key.to_s, new_password)
+      end.not_to raise_error
+      expect do
+        Minisign::PrivateKey.new(@private_key.to_s)
+      end.to raise_error('Missing password for encrypted key')
+
+      File.write('test/generated/new-password.key', @private_key)
+      path = 'test/generated'
+      command = "echo #{new_password} | #{path}/minisign -Sm #{path}/.keep -s #{path}/new-password.key"
+      expect(system(command)).to be(true)
+    end
+
+    it 'removes the password if nil' do
+      @private_key.change_password! nil
+      expect do
+        Minisign::PrivateKey.new(@private_key.to_s)
+      end.not_to raise_error
+      File.write('test/generated/removed-password.key', @private_key)
+      path = 'test/generated'
+      # does not prompt for password
+      command = "#{path}/minisign -Sm #{path}/.keep -s #{path}/removed-password.key"
+      expect(system(command)).to be(true)
+    end
+  end
 end