Option "login" now simulates login in unix

Added:
* Secondary groups from etc files
* Set environment variables like `su` would
* Set primary group to user's primary group if no other group specified

All only if `login` is set

2 files changed, 64 insertions, 4 deletions

diff --git a/lib/mixlib/shellout.rb b/lib/mixlib/shellout.rb
index e0fb3cc..3b7bf24 100644
--- a/lib/mixlib/shellout.rb
+++ b/lib/mixlib/shellout.rb
@@ -42,6 +42,10 @@ module Mixlib
     attr_accessor :password
     attr_accessor :with_logon
 
+    # Whether to simulate logon as the user. Normally set via options passed to new
+    # Always enabled on windows
+    attr_accessor :login
+
     # Group the command will run as. Normally set via options passed to new
     attr_accessor :group
 
@@ -141,6 +145,8 @@ module Mixlib
     #   child process. Generally this is used to copy data from the child to
     #   the parent's stdout so that users may observe the progress of
     #   long-running commands.
+    # * +login+: Whether to simulate a login (set secondary groups, primary group, environment
+    #   variables etc) as done by the OS in an actual login
     # === Examples:
     # Invoke find(1) to search for .rb files:
     #   find = Mixlib::ShellOut.new("find . -name '*.rb'")
@@ -200,8 +206,9 @@ module Mixlib
     # The gid that the subprocess will switch to. If the group attribute is
     # given as a group name, it is converted to a gid by Etc.getgrnam
     def gid
-      return nil unless group
-      group.kind_of?(Integer) ? group : Etc.getgrnam(group.to_s).gid
+      return group.kind_of?(Integer) ? group : Etc.getgrnam(group.to_s).gid if group
+      return Etc.getpwuid(uid).gid if using_login?
+      return nil
     end
 
     def timeout
@@ -322,7 +329,8 @@ module Mixlib
           self.log_tag = setting
         when 'environment', 'env'
           self.environment = setting || {}
-
+        when 'login'
+          self.login = setting
         else
           raise InvalidCommandOption, "option '#{option.inspect}' is not a valid option for #{self.class.name}"
         end
@@ -332,6 +340,9 @@ module Mixlib
     end
 
     def validate_options(opts)
+      if login && !user
+        raise InvalidCommandOption, "cannot set login without specifying a user"
+      end
       super
     end
   end
diff --git a/lib/mixlib/shellout/unix.rb b/lib/mixlib/shellout/unix.rb
index 40d7efa..d8063df 100644
--- a/lib/mixlib/shellout/unix.rb
+++ b/lib/mixlib/shellout/unix.rb
@@ -30,6 +30,47 @@ module Mixlib
         # No options to validate, raise exceptions here if needed
       end
 
+      # Whether we're simulating a login shell
+      def using_login?
+        return login && user
+      end
+
+      # Helper method for sgids
+      def all_seconderies
+        ret = []
+        Etc.endgrent
+        while ( g = Etc.getgrent ) do
+          ret << g
+        end
+        Etc.endgrent
+        return ret
+      end
+
+      # The secondary groups that the subprocess will switch to.
+      # Currently valid only if login is used, and is set
+      # to the user's secondary groups
+      def sgids
+        return nil unless using_login?
+        user_name = Etc.getpwuid(uid).name
+        all_seconderies.select{|g| g.mem.include?(user_name)}.map{|g|g.gid}
+      end
+
+      # The environment variables that are deduced from simulating logon
+      # Only valid if login is used
+      def logon_environment
+        return {} unless using_login?
+        entry = Etc.getpwuid(uid)
+        # According to `man su`, the set fields are:
+        #  $HOME, $SHELL, $USER, $LOGNAME, $PATH, and $IFS 
+        # Values are copied from "shadow" package in Ubuntu 14.10
+        {'HOME'=>entry.dir, 'SHELL'=>entry.shell, 'USER'=>entry.name, 'LOGNAME'=>entry.name, 'PATH'=>'/sbin:/bin:/usr/sbin:/usr/bin', 'IFS'=>"\t\n"}
+      end
+
+      # Merges the two environments for the process
+      def process_environment
+        logon_environment.merge(self.environment)
+      end
+
       # Run the command, writing the command's standard out and standard error
       # to +stdout+ and +stderr+, and saving its exit status object to +status+
       # === Returns
@@ -133,8 +174,15 @@ module Mixlib
         end
       end
 
+      def set_secondarygroups
+        if sgids
+          Process.groups = sgids
+        end
+      end
+
       def set_environment
-        environment.each do |env_var,value|
+        # user-set variables should override the login ones
+        process_environment.each do |env_var,value|
           ENV[env_var] = value
         end
       end
@@ -295,6 +343,7 @@ module Mixlib
 
           configure_subprocess_file_descriptors
 
+          set_secondarygroups
           set_group
           set_user
           set_environment