Don't allow null chars in various strings

Various places that now reject null chars inside strings
- Primitive file operations reject it in filenames.
- Primitive environment variable operations reject it in
  names and values.
- os:cmd() reject it in its input.

Also '=' characters are rejected by primitive environment
variable operations in environment variable names.

Documentation has been updated to document null characters
in these types of data as invalid. Currently these operations
accept null chars at the end of strings, but that will change
in the future.

2 files changed, 44 insertions, 21 deletions

diff --git a/lib/kernel/src/kernel.app.src b/lib/kernel/src/kernel.app.src
index 2a88cc7e26..080b11fc4d 100644
--- a/lib/kernel/src/kernel.app.src
+++ b/lib/kernel/src/kernel.app.src
@@ -120,6 +120,6 @@
   {applications, []},
   {env, [{error_logger, tty}]},
   {mod, {kernel, []}},
-  {runtime_dependencies, ["erts-9.1", "stdlib-3.4", "sasl-3.0"]}
+  {runtime_dependencies, ["erts-10.0", "stdlib-3.5", "sasl-3.0"]}
  ]
 }.
diff --git a/lib/kernel/src/os.erl b/lib/kernel/src/os.erl
index 0250783632..3675e923a3 100644
--- a/lib/kernel/src/os.erl
+++ b/lib/kernel/src/os.erl
@@ -25,6 +25,8 @@
 
 -include("file.hrl").
 
+-export_type([env_var_name/0, env_var_value/0, env_var_name_value/0, command_input/0]).
+
 %%% BIFs
 
 -export([getenv/0, getenv/1, getenv/2, getpid/0,
@@ -32,21 +34,29 @@
          putenv/2, set_signal/2, system_time/0, system_time/1,
 	 timestamp/0, unsetenv/1]).
 
--spec getenv() -> [string()].
+-type env_var_name() :: nonempty_string().
+
+-type env_var_value() :: string().
+
+-type env_var_name_value() :: nonempty_string().
+
+-type command_input() :: atom() | io_lib:chars().
+
+-spec getenv() -> [env_var_name_value()].
 
 getenv() -> erlang:nif_error(undef).
 
 -spec getenv(VarName) -> Value | false when
-      VarName :: string(),
-      Value :: string().
+      VarName :: env_var_name(),
+      Value :: env_var_value().
 
 getenv(_) ->
     erlang:nif_error(undef).
 
 -spec getenv(VarName, DefaultValue) -> Value when
-      VarName :: string(),
-      DefaultValue :: string(),
-      Value :: string().
+      VarName :: env_var_name(),
+      DefaultValue :: env_var_value(),
+      Value :: env_var_value().
 
 getenv(VarName, DefaultValue) ->
     case os:getenv(VarName) of
@@ -75,8 +85,8 @@ perf_counter(Unit) ->
       erlang:convert_time_unit(os:perf_counter(), perf_counter, Unit).
 
 -spec putenv(VarName, Value) -> true when
-      VarName :: string(),
-      Value :: string().
+      VarName :: env_var_name(),
+      Value :: env_var_value().
 
 putenv(_, _) ->
     erlang:nif_error(undef).
@@ -99,7 +109,7 @@ timestamp() ->
     erlang:nif_error(undef).
 
 -spec unsetenv(VarName) -> true when
-      VarName :: string().
+      VarName :: env_var_name().
 
 unsetenv(_) ->
     erlang:nif_error(undef).
@@ -232,10 +242,9 @@ extensions() ->
 
 %% Executes the given command in the default shell for the operating system.
 -spec cmd(Command) -> string() when
-      Command :: atom() | io_lib:chars().
+      Command :: os:command_input().
 cmd(Cmd) ->
-    validate(Cmd),
-    {SpawnCmd, SpawnOpts, SpawnInput, Eot} = mk_cmd(os:type(), Cmd),
+    {SpawnCmd, SpawnOpts, SpawnInput, Eot} = mk_cmd(os:type(), validate(Cmd)),
     Port = open_port({spawn, SpawnCmd}, [binary, stderr_to_stdout,
                                          stream, in, hide | SpawnOpts]),
     MonRef = erlang:monitor(port, Port),
@@ -255,8 +264,6 @@ mk_cmd({win32,Wtype}, Cmd) ->
                   {Cspec,_} -> lists:concat([Cspec," /c",Cmd])
               end,
     {Command, [], [], <<>>};
-mk_cmd(OsType,Cmd) when is_atom(Cmd) ->
-    mk_cmd(OsType, atom_to_list(Cmd));
 mk_cmd(_,Cmd) ->
     %% Have to send command in like this in order to make sh commands like
     %% cd and ulimit available
@@ -279,17 +286,33 @@ mk_cmd(_,Cmd) ->
      <<$\^D>>}.
 
 validate(Atom) when is_atom(Atom) ->
-    ok;
+    validate(atom_to_list(Atom));
 validate(List) when is_list(List) ->
-    validate1(List).
+    case validate1(List) of
+        false ->
+            List;
+        true -> 
+            %% Had zeros at end; remove them...
+            string:trim(List, trailing, [0])
+    end.
 
-validate1([C|Rest]) when is_integer(C) ->
+validate1([0|Rest]) ->
+    validate2(Rest);
+validate1([C|Rest]) when is_integer(C), C > 0 ->
     validate1(Rest);
 validate1([List|Rest]) when is_list(List) ->
-    validate1(List),
-    validate1(Rest);
+    validate1(List) or validate1(Rest);
 validate1([]) ->
-    ok.
+    false.
+
+%% Ensure that the rest is zero only...
+validate2([]) ->
+    true;
+validate2([0|Rest]) ->
+    validate2(Rest);
+validate2([List|Rest]) when is_list(List) ->
+    validate2(List),
+    validate2(Rest).
 
 get_data(Port, MonRef, Eot, Sofar) ->
     receive