Fix unsafe shell invocation in amber exec

spec/amber/cli/commands/exec_spec.cr

@@ -44,10 +44,30 @@ module Amber::CLI
         File.read(logs.last?.to_s).should eq "[:a, :b]\n"
       end
 
-      it "opens editor and executes .cr file on close" do
-        MainCommand.run(["exec", "-e", "echo 'puts 1000' > "])
-        logs = `ls tmp/*_console_result.log`.strip.split(/\s/).sort
-        File.read(logs.last?.to_s).should eq "1000\n"
+      it "does not execute shell metacharacters in the editor option" do
+        marker = "amber_exec_editor_pwned"
+        File.delete(marker) if File.exists?(marker)
+
+        expect_raises(Exception) do
+          MainCommand.run(["exec", "-e", "sh -c 'touch #{marker}' #"])
+        end
+
+        File.exists?(marker).should be_false
+      end
+
+      it "does not execute shell metacharacters in copied filenames" do
+        filename = "amber_exec_spec_test; touch amber_exec_copy_pwned #.cr"
+        marker = "amber_exec_copy_pwned"
+        File.delete(marker) if File.exists?(marker)
+        File.write filename, "puts([:safe])"
+
+        begin
+          MainCommand.run(["exec", filename, "-e", "tail"])
+        ensure
+          File.delete(filename) if File.exists?(filename)
+        end
+
+        File.exists?(marker).should be_false
       end
 
       it "copies previous run into new file for editing and runs it returning results" do

src/amber/cli/commands/exec.cr

@@ -35,7 +35,7 @@ module Amber::CLI
                       Dir.glob("./tmp/*_console.cr").sort.reverse![options.back.to_i(strict: false) - 1]?
                     end
 
-        system("cp #{_filename} #{@filename}") if _filename
+        Process.run("cp", [_filename, @filename]) if _filename
       end
 
       private def show
@@ -72,7 +72,7 @@ module Amber::CLI
 
         if args.code.blank? || File.exists?(args.code)
           prepare_file
-          system("#{options.editor} #{@filename}")
+          Process.run(options.editor, [@filename], output: Process::Redirect::Inherit, error: Process::Redirect::Inherit)
         else
           File.write(@filename, wrap(args.code))
         end