feat: add vim.secure.read()

This function accepts a path to a file and prompts the user if the file
is trusted. If the user confirms that the file is trusted, the contents
of the file are returned. The user's decision is stored in a trust
database at $XDG_STATE_HOME/nvim/trust. When this function is invoked
with a path that is already marked as trusted in the trust database, the
user is not prompted for a response.

6 files changed, 300 insertions, 0 deletions

diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index cab2f49d94..c5ede97725 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -2354,4 +2354,20 @@ parents({start})                                            *vim.fs.parents()*
     Return: ~
         (function) Iterator
 
+
+==============================================================================
+Lua module: secure                                                *lua-secure*
+
+read({path})                                               *vim.secure.read()*
+    Attempt to read the file at {path} prompting the user if the file should
+    be trusted. The user's choice is persisted in a trust database at
+    $XDG_STATE_HOME/nvim/trust.
+
+    Parameters: ~
+      • {path}  (string) Path to a file to read.
+
+    Return: ~
+        (string|nil) The contents of the given file if it exists and is
+        trusted, or nil otherwise.
+
  vim:tw=78:ts=8:sw=4:sts=4:et:ft=help:norl:
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index d339df8479..2aa4bea73b 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -39,6 +39,9 @@ NEW FEATURES                                                    *news-features*
 
 The following new APIs or features were added.
 
+• |vim.secure.read()| reads a file and prompts the user if it should be
+  trusted and, if so, returns the file's contents.
+
 • When using Nvim inside tmux 3.2 or later, the default clipboard provider
   will now copy to the system clipboard. |provider-clipboard|
 
diff --git a/runtime/lua/vim/_editor.lua b/runtime/lua/vim/_editor.lua
index 0013f38d89..ad4dc20efb 100644
--- a/runtime/lua/vim/_editor.lua
+++ b/runtime/lua/vim/_editor.lua
@@ -36,6 +36,7 @@ for k, v in pairs({
   ui = true,
   health = true,
   fs = true,
+  secure = true,
 }) do
   vim._submodules[k] = v
 end
diff --git a/runtime/lua/vim/secure.lua b/runtime/lua/vim/secure.lua
new file mode 100644
index 0000000000..341ff8df05
--- /dev/null
+++ b/runtime/lua/vim/secure.lua
@@ -0,0 +1,106 @@
+local M = {}
+
+--- Attempt to read the file at {path} prompting the user if the file should be
+--- trusted. The user's choice is persisted in a trust database at
+--- $XDG_STATE_HOME/nvim/trust.
+---
+---@param path (string) Path to a file to read.
+---
+---@return (string|nil) The contents of the given file if it exists and is
+---        trusted, or nil otherwise.
+function M.read(path)
+  vim.validate({ path = { path, 's' } })
+  local fullpath = vim.loop.fs_realpath(vim.fs.normalize(path))
+  if not fullpath then
+    return nil
+  end
+
+  local trust = {}
+  do
+    local f = io.open(vim.fn.stdpath('state') .. '/trust', 'r')
+    if f then
+      local contents = f:read('*a')
+      if contents then
+        for line in vim.gsplit(contents, '\n') do
+          local hash, file = string.match(line, '^(%S+) (.+)$')
+          if hash and file then
+            trust[file] = hash
+          end
+        end
+      end
+      f:close()
+    end
+  end
+
+  if trust[fullpath] == '!' then
+    -- File is denied
+    return nil
+  end
+
+  local contents
+  do
+    local f = io.open(fullpath, 'r')
+    if not f then
+      return nil
+    end
+    contents = f:read('*a')
+    f:close()
+  end
+
+  local hash = vim.fn.sha256(contents)
+  if trust[fullpath] == hash then
+    -- File already exists in trust database
+    return contents
+  end
+
+  -- File either does not exist in trust database or the hash does not match
+  local choice = vim.fn.confirm(
+    string.format('%s is not trusted.', fullpath),
+    '&ignore\n&view\n&deny\n&allow',
+    1
+  )
+
+  if choice == 0 or choice == 1 then
+    -- Cancelled or ignored
+    return nil
+  elseif choice == 2 then
+    -- View
+    vim.cmd('new')
+    local buf = vim.api.nvim_get_current_buf()
+    local lines = vim.split(string.gsub(contents, '\n$', ''), '\n')
+    vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+    vim.bo[buf].bufhidden = 'hide'
+    vim.bo[buf].buftype = 'nofile'
+    vim.bo[buf].swapfile = false
+    vim.bo[buf].modeline = false
+    vim.bo[buf].buflisted = false
+    vim.bo[buf].readonly = true
+    vim.bo[buf].modifiable = false
+    return nil
+  elseif choice == 3 then
+    -- Deny
+    trust[fullpath] = '!'
+    contents = nil
+  elseif choice == 4 then
+    -- Allow
+    trust[fullpath] = hash
+  end
+
+  do
+    local f, err = io.open(vim.fn.stdpath('state') .. '/trust', 'w')
+    if not f then
+      error(err)
+    end
+
+    local t = {}
+    for p, h in pairs(trust) do
+      t[#t + 1] = string.format('%s %s\n', h, p)
+    end
+    f:write(table.concat(t))
+    f:close()
+  end
+
+  return contents
+end
+
+return M
diff --git a/scripts/gen_vimdoc.py b/scripts/gen_vimdoc.py
index e77d3ea286..a720f055ed 100755
--- a/scripts/gen_vimdoc.py
+++ b/scripts/gen_vimdoc.py
@@ -131,6 +131,7 @@ CONFIG = {
             'filetype.lua',
             'keymap.lua',
             'fs.lua',
+            'secure.lua',
         ],
         'files': [
             'runtime/lua/vim/_editor.lua',
@@ -140,6 +141,7 @@ CONFIG = {
             'runtime/lua/vim/filetype.lua',
             'runtime/lua/vim/keymap.lua',
             'runtime/lua/vim/fs.lua',
+            'runtime/lua/vim/secure.lua',
         ],
         'file_patterns': '*.lua',
         'fn_name_prefix': '',
@@ -166,6 +168,7 @@ CONFIG = {
             'filetype': 'vim.filetype',
             'keymap': 'vim.keymap',
             'fs': 'vim.fs',
+            'secure': 'vim.secure',
         },
         'append_only': [
             'shared.lua',
diff --git a/test/functional/lua/secure_spec.lua b/test/functional/lua/secure_spec.lua
new file mode 100644
index 0000000000..c348526d65
--- /dev/null
+++ b/test/functional/lua/secure_spec.lua
@@ -0,0 +1,171 @@
+local helpers = require('test.functional.helpers')(after_each)
+local Screen = require('test.functional.ui.screen')
+
+local eq = helpers.eq
+local clear = helpers.clear
+local command = helpers.command
+local pathsep = helpers.get_pathsep()
+local iswin = helpers.iswin()
+local curbufmeths = helpers.curbufmeths
+local exec_lua = helpers.exec_lua
+local feed_command = helpers.feed_command
+local feed = helpers.feed
+local funcs = helpers.funcs
+local pcall_err = helpers.pcall_err
+
+describe('vim.secure', function()
+  describe('read()', function()
+    local xstate = 'Xstate'
+
+    setup(function()
+      helpers.mkdir_p(xstate .. pathsep .. (iswin and 'nvim-data' or 'nvim'))
+    end)
+
+    teardown(function()
+      helpers.rmdir(xstate)
+    end)
+
+    before_each(function()
+      helpers.write_file('Xfile', [[
+        let g:foobar = 42
+      ]])
+      clear{env={XDG_STATE_HOME=xstate}}
+    end)
+
+    after_each(function()
+      os.remove('Xfile')
+      helpers.rmdir(xstate)
+    end)
+
+    it('works', function()
+      local screen = Screen.new(80, 8)
+      screen:attach()
+      screen:set_default_attr_ids({
+        [1] = {bold = true, foreground = Screen.colors.Blue1},
+        [2] = {bold = true, reverse = true},
+        [3] = {bold = true, foreground = Screen.colors.SeaGreen},
+        [4] = {reverse = true},
+      })
+
+      local cwd = funcs.getcwd()
+
+      -- Need to use feed_command instead of exec_lua because of the confirmation prompt
+      feed_command([[lua vim.secure.read('Xfile')]])
+      screen:expect{grid=[[
+                                                                                        |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {2:                                                                                }|
+        :lua vim.secure.read('Xfile')                                                   |
+        {3:]] .. cwd .. pathsep .. [[Xfile is untrusted}{MATCH:%s+}|
+        {3:[i]gnore, (v)iew, (d)eny, (a)llow: }^                                             |
+      ]]}
+      feed('d')
+      screen:expect{grid=[[
+        ^                                                                                |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+                                                                                        |
+      ]]}
+
+      local trust = helpers.read_file(funcs.stdpath('state') .. pathsep .. 'trust')
+      eq(string.format('! %s', cwd .. pathsep .. 'Xfile'), vim.trim(trust))
+      eq(helpers.NIL, exec_lua([[return vim.secure.read('Xfile')]]))
+
+      os.remove(funcs.stdpath('state') .. pathsep .. 'trust')
+
+      feed_command([[lua vim.secure.read('Xfile')]])
+      screen:expect{grid=[[
+                                                                                        |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {2:                                                                                }|
+        :lua vim.secure.read('Xfile')                                                   |
+        {3:]] .. cwd .. pathsep .. [[Xfile is untrusted}{MATCH:%s+}|
+        {3:[i]gnore, (v)iew, (d)eny, (a)llow: }^                                             |
+      ]]}
+      feed('a')
+      screen:expect{grid=[[
+        ^                                                                                |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+                                                                                        |
+      ]]}
+
+      local hash = funcs.sha256(helpers.read_file('Xfile'))
+      trust = helpers.read_file(funcs.stdpath('state') .. pathsep .. 'trust')
+      eq(string.format('%s %s', hash, cwd .. pathsep .. 'Xfile'), vim.trim(trust))
+      eq(helpers.NIL, exec_lua([[vim.secure.read('Xfile')]]))
+
+      os.remove(funcs.stdpath('state') .. pathsep .. 'trust')
+
+      feed_command([[lua vim.secure.read('Xfile')]])
+      screen:expect{grid=[[
+                                                                                        |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {2:                                                                                }|
+        :lua vim.secure.read('Xfile')                                                   |
+        {3:]] .. cwd .. pathsep .. [[Xfile is untrusted}{MATCH:%s+}|
+        {3:[i]gnore, (v)iew, (d)eny, (a)llow: }^                                             |
+      ]]}
+      feed('i')
+      screen:expect{grid=[[
+        ^                                                                                |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+                                                                                        |
+      ]]}
+
+      -- Trust database is not updated
+      trust = helpers.read_file(funcs.stdpath('state') .. pathsep .. 'trust')
+      eq(nil, trust)
+
+      feed_command([[lua vim.secure.read('Xfile')]])
+      screen:expect{grid=[[
+                                                                                        |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {2:                                                                                }|
+        :lua vim.secure.read('Xfile')                                                   |
+        {3:]] .. cwd .. pathsep .. [[Xfile is untrusted}{MATCH:%s+}|
+        {3:[i]gnore, (v)iew, (d)eny, (a)llow: }^                                             |
+      ]]}
+      feed('v')
+      screen:expect{grid=[[
+        ^  let g:foobar = 42                                                             |
+        {1:~                                                                               }|
+        {1:~                                                                               }|
+        {2:]] .. cwd .. pathsep .. [[Xfile [RO]{MATCH:%s+}|
+                                                                                        |
+        {1:~                                                                               }|
+        {4:[No Name]                                                                       }|
+                                                                                        |
+      ]]}
+
+      -- Trust database is not updated
+      trust = helpers.read_file(funcs.stdpath('state') .. pathsep .. 'trust')
+      eq(nil, trust)
+
+      -- Cannot write file
+      pcall_err(command, 'write')
+      eq(false, curbufmeths.get_option('modifiable'))
+    end)
+  end)
+end)