Fixed problem escaping string in JSON

lib/chef-vault/exceptions.rb

@@ -51,5 +51,8 @@ class IdMismatch < Exceptions
 
     class V1Format < Exceptions
     end
+
+    class InvalidValue < Exceptions
+    end
   end
 end

lib/chef/knife/mixin/helper.rb

@@ -39,10 +39,38 @@ def values_from_file(file)
       end
 
       def values_from_json(json)
+        validate_json(json)
         JSON.parse(json)
       rescue JSON::ParserError
         raise JSON::ParserError, "#{json} is not valid JSON!"
       end
+
+      # I/P: json string
+      # Raises `InvalidValue` if any of the json's values contain non-printable characters.
+      def validate_json(json)
+        begin
+          evaled_json = eval(json)
+        rescue SyntaxError => e
+          raise ChefVault::Exceptions::InvalidValue, "#{json} is not valid JSON!"
+        end
+
+        if evaled_json.is_a?(Hash)
+          evaled_json.each do |key, value|
+            next unless printable?(value.to_s)
+
+            msg = "Value '#{value}' of key '#{key}' contains non-printable characters. Check that backslashes are escaped with another backslash (e.g. C:\\\\Windows) in double-quoted strings."
+            raise ChefVault::Exceptions::InvalidValue, msg
+          end
+        end
+      end
+
+      # I/P: String
+      # O/P: true/false
+      # returns true if string is free of non-printable characters (escape sequences)
+      # this returns false for whitespace escape sequences as well, e.g. \n\t
+      def printable?(string)
+        /[^[:print:]]/.match(string)
+      end
     end
   end
 end

spec/chef/helper_spec.rb

@@ -0,0 +1,24 @@
+require "spec_helper"
+require "chef/knife/mixin/helper"
+
+RSpec.describe ChefVault::Mixin::Helper do
+  include ChefVault::Mixin::Helper
+
+  let(:json_data) { '{"username": "root", "password": "abcabc"}' }
+  let(:json_data_control_char) { '{"username": "root", "password": "abc\abc"}' }
+  let(:buggy_json_data) { '{"username": "root", "password": "abc\abc"' }
+
+  describe "#validate_json" do
+    it "Raises InvalidValue Exception when invalid data provided" do
+      expect { validate_json(buggy_json_data) }.to raise_error(ChefVault::Exceptions::InvalidValue)
+    end
+
+    it "Raises InvalidValue Exception when value consist of control characters" do
+      expect { validate_json(json_data_control_char) }.to raise_error(ChefVault::Exceptions::InvalidValue)
+    end
+
+    it "Not to raise error if valid data provided" do
+      expect { validate_json(json_data) }.to_not raise_error
+    end
+  end
+end