vim-patch:8.1.0881: can execute shell commands in rvim through interfaces

Problem:    Can execute shell commands in rvim through interfaces.
Solution:   Disable using interfaces in restricted mode. Allow for writing
            file with writefile(), histadd() and a few others.
https://github.com/vim/vim/commit/8c62a08faf89663e5633dc5036cd8695c80f1075

5 files changed, 134 insertions, 19 deletions

diff --git a/runtime/doc/starting.txt b/runtime/doc/starting.txt
index e3f0d593a7..af7d233619 100644
--- a/runtime/doc/starting.txt
+++ b/runtime/doc/starting.txt
@@ -184,12 +184,17 @@ argument.
 		the 'modifiable' and 'write' options can be set to enable
 		changes and writing.
 
-						*-Z* *restricted-mode* *E145*
+					*-Z* *restricted-mode* *E145* *E981*
 -Z		Restricted mode.  All commands that make use of an external
 		shell are disabled.  This includes suspending with CTRL-Z,
-		":sh", filtering, the system() function, backtick expansion,
-		delete(), rename(), mkdir(), writefile(), libcall(),
-		jobstart(), etc.
+		":sh", filtering, the system() function, backtick expansion
+		and libcall().
+		Also disallowed are delete(), rename(), mkdir(), jobstart(),
+		etc.
+		Interfaces, such as Python, Ruby and Lua, are also disabled,
+		since they could be used to execute shell commands.
+		Note that the user may still find a loophole to execute a
+		shell command, it has only been made difficult.
 
 -e							*-e* *-E*
 -E		Start Nvim in Ex mode |gQ|.
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 25e57d54f0..6d67279e64 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -4317,7 +4317,7 @@ static void f_histadd(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   HistoryType histype;
 
   rettv->vval.v_number = false;
-  if (check_restricted() || check_secure()) {
+  if (check_secure()) {
     return;
   }
   const char *str = tv_get_string_chk(&argvars[0]);  // NULL on type error
@@ -7779,8 +7779,7 @@ static void f_setbufline(typval_T *argvars, typval_T *rettv, FunPtr fptr)
  */
 static void f_setbufvar(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
-  if (check_restricted()
-      || check_secure()
+  if (check_secure()
       || !tv_check_str_or_nr(&argvars[0])) {
     return;
   }
@@ -8284,7 +8283,7 @@ static void f_settabvar(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
   rettv->vval.v_number = 0;
 
-  if (check_restricted() || check_secure()) {
+  if (check_secure()) {
     return;
   }
 
@@ -11005,7 +11004,7 @@ static void f_writefile(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
   rettv->vval.v_number = -1;
 
-  if (check_restricted() || check_secure()) {
+  if (check_secure()) {
     return;
   }
 
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index bc6821f60f..ba66b666e0 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -3008,18 +3008,18 @@ void ex_z(exarg_T *eap)
   ex_no_reprint = true;
 }
 
-/*
- * Check if the restricted flag is set.
- * If so, give an error message and return TRUE.
- * Otherwise, return FALSE.
- */
-int check_restricted(void)
+// Check if the restricted flag is set.
+// If so, give an error message and return true.
+// Otherwise, return false.
+bool check_restricted(void)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
   if (restricted) {
-    EMSG(_("E145: Shell commands not allowed in restricted mode"));
-    return TRUE;
+    EMSG(_("E145: Shell commands and some functionality not allowed"
+           " in restricted mode"));
+    return true;
   }
-  return FALSE;
+  return false;
 }
 
 /*
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index 28ecaf684a..abe394dc3a 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -1783,10 +1783,14 @@ static char_u * do_one_cmd(char_u **cmdlinep,
 
   if (!ea.skip) {
     if (sandbox != 0 && !(ea.argt & SBOXOK)) {
-      /* Command not allowed in sandbox. */
+      // Command not allowed in sandbox.
       errormsg = (char_u *)_(e_sandbox);
       goto doend;
     }
+    if (restricted != 0 && (ea.argt & RESTRICT)) {
+      errormsg = (char_u *)_("E981: Command not allowed in restricted mode");
+      goto doend;
+    }
     if (!MODIFIABLE(curbuf) && (ea.argt & MODIFY)
         // allow :put in terminals
         && (!curbuf->terminal || ea.cmdidx != CMD_put)) {
diff --git a/src/nvim/testdir/test_restricted.vim b/src/nvim/testdir/test_restricted.vim
new file mode 100644
index 0000000000..9dd937cf3e
--- /dev/null
+++ b/src/nvim/testdir/test_restricted.vim
@@ -0,0 +1,107 @@
+" Test for "rvim" or "vim -Z"
+
+source shared.vim
+
+func Test_restricted()
+  let cmd = GetVimCommand('Xrestricted')
+  if cmd == ''
+    return
+  endif
+
+  call writefile([
+	\ "silent !ls",
+	\ "call writefile([v:errmsg], 'Xrestrout')",
+	\ "qa!",
+	\ ], 'Xrestricted')
+  call system(cmd . ' -Z')
+  call assert_match('E145:', join(readfile('Xrestrout')))
+
+  call delete('Xrestricted')
+  call delete('Xrestrout')
+endfunc
+
+func Run_restricted_test(ex_cmd, error)
+  let cmd = GetVimCommand('Xrestricted')
+  if cmd == ''
+    return
+  endif
+
+  call writefile([
+	\ a:ex_cmd,
+	\ "call writefile([v:errmsg], 'Xrestrout')",
+	\ "qa!",
+	\ ], 'Xrestricted')
+  call system(cmd . ' -Z')
+  call assert_match(a:error, join(readfile('Xrestrout')))
+
+  call delete('Xrestricted')
+  call delete('Xrestrout')
+endfunc
+
+func Test_restricted_lua()
+  if !has('lua')
+    throw 'Skipped: Lua is not supported'
+  endif
+  call Run_restricted_test('lua print("Hello, Vim!")', 'E981:')
+  call Run_restricted_test('luado return "hello"', 'E981:')
+  call Run_restricted_test('luafile somefile', 'E981:')
+  call Run_restricted_test('call luaeval("expression")', 'E145:')
+endfunc
+
+func Test_restricted_mzscheme()
+  if !has('mzscheme')
+    throw 'Skipped: MzScheme is not supported'
+  endif
+  call Run_restricted_test('mzscheme statement', 'E981:')
+  call Run_restricted_test('mzfile somefile', 'E981:')
+  call Run_restricted_test('call mzeval("expression")', 'E145:')
+endfunc
+
+func Test_restricted_perl()
+  if !has('perl')
+    throw 'Skipped: Perl is not supported'
+  endif
+  " TODO: how to make Safe mode fail?
+  " call Run_restricted_test('perl system("ls")', 'E981:')
+  " call Run_restricted_test('perldo system("hello")', 'E981:')
+  " call Run_restricted_test('perlfile somefile', 'E981:')
+  " call Run_restricted_test('call perleval("system(\"ls\")")', 'E145:')
+endfunc
+
+func Test_restricted_python()
+  if !has('python')
+    throw 'Skipped: Python is not supported'
+  endif
+  call Run_restricted_test('python print "hello"', 'E981:')
+  call Run_restricted_test('pydo return "hello"', 'E981:')
+  call Run_restricted_test('pyfile somefile', 'E981:')
+  call Run_restricted_test('call pyeval("expression")', 'E145:')
+endfunc
+
+func Test_restricted_python3()
+  if !has('python3')
+    throw 'Skipped: Python3 is not supported'
+  endif
+  call Run_restricted_test('py3 print "hello"', 'E981:')
+  call Run_restricted_test('py3do return "hello"', 'E981:')
+  call Run_restricted_test('py3file somefile', 'E981:')
+  call Run_restricted_test('call py3eval("expression")', 'E145:')
+endfunc
+
+func Test_restricted_ruby()
+  if !has('ruby')
+    throw 'Skipped: Ruby is not supported'
+  endif
+  call Run_restricted_test('ruby print "Hello"', 'E981:')
+  call Run_restricted_test('rubydo print "Hello"', 'E981:')
+  call Run_restricted_test('rubyfile somefile', 'E981:')
+endfunc
+
+func Test_restricted_tcl()
+  if !has('tcl')
+    throw 'Skipped: Tcl is not supported'
+  endif
+  call Run_restricted_test('tcl puts "Hello"', 'E981:')
+  call Run_restricted_test('tcldo puts "Hello"', 'E981:')
+  call Run_restricted_test('tclfile somefile', 'E981:')
+endfunc