Merge pull request rapid7#20906 from rudraditya21/fix/ssh-cmd-exec-trailing-newlines

Fix SSH command shells dying on cmd_exec with trailing newline

Author: cgranleese-r7

lib/msf/core/session/provider/single_command_shell.rb

@@ -145,7 +145,7 @@ def shell_command_token_base(cmd, timeout=10, command_separator="\n")
 
     # Send the command to the session's stdin.
     delimiter = "echo #{token}"
-    if cmd.strip.end_with?(command_separator)
+    if cmd.match?(/\r?\n\z/) || cmd.strip.end_with?(command_separator)
       # This command already ends with a delimiter - don't need to add another one
       shell_data = cmd + "#{delimiter}#{command_termination}"
     else

spec/lib/msf/core/session/provider/single_command_shell_spec.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Msf::Session::Provider::SingleCommandShell do
+  class DummySingleCommandShell
+    include Msf::Session::Provider::SingleCommandShell
+
+    attr_reader :writes
+
+    def initialize
+      @writes = []
+    end
+
+    def platform
+      'linux'
+    end
+
+    def shell_init
+      true
+    end
+
+    def shell_read(*)
+      nil
+    end
+
+    def shell_write(buf)
+      @writes << buf
+    end
+
+    def shell_close
+      true
+    end
+
+    def shell_read_until_token(_token, _wanted_idx = 0, _timeout = 10)
+      ''
+    end
+  end
+
+  describe '#shell_command_token_base' do
+    it 'does not inject a separator after a trailing newline' do
+      shell = DummySingleCommandShell.new
+
+      shell.shell_command_token_base("id\n", 1, ';')
+
+      expect(shell.writes.last).not_to match(/\n;/)
+    end
+  end
+end