Fixing security issue with lookup returns not tainting the jinja2 environment

CVE-2017-7481

Lookup returns wrap the result in unsafe, however when used through the
standard templar engine, this does not result in the jinja2 environment being
marked as unsafe as a whole. This means the lookup result looses the unsafe
protection and may become simple unicode strings, which can result in bad
things being re-templated.

This also adds a global lookup param and cfg options for lookups to allow
unsafe returns, so users can force the previous (insecure) behavior.

(cherry picked from commit 72dfb1570d22ac519350a8c09e76c458789120ed)

docs/docsite/rst/intro_configuration.rst

@@ -86,6 +86,20 @@ different locations::
 Most users will not need to use this feature.  See :doc:`dev_guide/developing_plugins` for more details.
 
 
+.. _allow_unsafe_lookups:
+
+allow_unsafe_lookups
+====================
+
+.. versionadded:: 2.2.3, 2.3.1
+
+When enabled, this option allows lookup plugins (whether used in variables as `{{lookup('foo')}}` or as a loop as `with_foo`) to return data that is **not** marked "unsafe". By default, such data is marked as unsafe to prevent the templating engine from evaluating any jinja2 templating language, as this could represent a security risk.
+
+This option is provided to allow for backwards-compatibility, however users should first consider adding `allow_unsafe=True` to any lookups which may be expected to contain data which may be run through the templating engine later. For example::
+
+    {{lookup('pipe', '/path/to/some/command', allow_unsafe=True)}}
+
+
 .. _allow_world_readable_tmpfiles:
 
 allow_world_readable_tmpfiles

examples/ansible.cfg

@@ -281,7 +281,7 @@
 # Controls showing custom stats at the end, off by default
 #show_custom_stats = True
 
-# Controlls which files to ignore when using a directory as inventory with
+# Controls which files to ignore when using a directory as inventory with
 # possibly multiple sources (both static and dynamic)
 #inventory_ignore_extensions = ~, .orig, .bak, .ini, .cfg, .retry, .pyc, .pyo
 
@@ -289,6 +289,12 @@
 # only update this setting if you know how this works, otherwise it can break module execution
 #network_group_modules=['eos', 'nxos', 'ios', 'iosxr', 'junos', 'vyos']
 
+# When enabled, this option allows lookups (via variables like {{lookup('foo')}} or when used as
+# a loop with `with_foo`) to return data that is not marked "unsafe". This means the data may contain
+# jinja2 templating language which will be run through the templating engine.
+# ENABLING THIS COULD BE A SECURITY RISK
+#allow_unsafe_lookups = False
+
 [privilege_escalation]
 #become=True
 #become_method=sudo

lib/ansible/constants.py

@@ -234,6 +234,7 @@ DEFAULT_FORCE_HANDLERS    = get_config(p, DEFAULTS, 'force_handlers', 'ANSIBLE_F
 DEFAULT_INVENTORY_IGNORE  = get_config(p, DEFAULTS, 'inventory_ignore_extensions', 'ANSIBLE_INVENTORY_IGNORE', ["~", ".orig", ".bak", ".ini", ".cfg", ".retry", ".pyc", ".pyo"], value_type='list')
 DEFAULT_VAR_COMPRESSION_LEVEL = get_config(p, DEFAULTS, 'var_compression_level', 'ANSIBLE_VAR_COMPRESSION_LEVEL', 0, value_type='integer')
 DEFAULT_INTERNAL_POLL_INTERVAL = get_config(p, DEFAULTS, 'internal_poll_interval', None, 0.001, value_type='float')
+DEFAULT_ALLOW_UNSAFE_LOOKUPS = get_config(p, DEFAULTS, 'allow_unsafe_lookups', None, False, value_type='boolean')
 ERROR_ON_MISSING_HANDLER  = get_config(p, DEFAULTS, 'error_on_missing_handler', 'ANSIBLE_ERROR_ON_MISSING_HANDLER', True, value_type='boolean')
 SHOW_CUSTOM_STATS = get_config(p, DEFAULTS, 'show_custom_stats', 'ANSIBLE_SHOW_CUSTOM_STATS', False, value_type='boolean')
 

lib/ansible/template/__init__.py

@@ -251,6 +251,9 @@ class Templar:
             loader=FileSystemLoader(self._basedir),
         )
 
+        # the current rendering context under which the templar class is working
+        self.cur_context = None
+
         self.SINGLE_VAR = re.compile(r"^%s\s*(\w*)\s*%s$" % (self.environment.variable_start_string, self.environment.variable_end_string))
 
         self.block_start    = self.environment.block_start_string
@@ -564,6 +567,7 @@ class Templar:
 
         if instance is not None:
             wantlist = kwargs.pop('wantlist', False)
+            allow_unsafe = kwargs.pop('allow_unsafe', C.DEFAULT_ALLOW_UNSAFE_LOOKUPS)
 
             from ansible.utils.listify import listify_lookup_plugin_terms
             loop_terms = listify_lookup_plugin_terms(terms=args, templar=self, loader=self._loader, fail_on_undefined=True, convert_bare=False)
@@ -577,7 +581,8 @@ class Templar:
                     raise AnsibleError("An unhandled exception occurred while running the lookup plugin '%s'. Error was a %s, original message: %s" % (name, type(e), e))
                 ran = None
 
-            if ran:
+            if ran and not allow_unsafe:
+                from ansible.vars.unsafe_proxy import UnsafeProxy, wrap_var
                 if wantlist:
                     ran = wrap_var(ran)
                 else:
@@ -589,6 +594,8 @@ class Templar:
                         else:
                             ran = wrap_var(ran)
 
+                if self.cur_context:
+                    self.cur_context.unsafe = True
             return ran
         else:
             raise AnsibleError("lookup plugin (%s) not found" % name)
@@ -645,7 +652,7 @@ class Templar:
 
             jvars = AnsibleJ2Vars(self, t.globals)
 
-            new_context = t.new_context(jvars, shared=True)
+            self.cur_context = new_context = t.new_context(jvars, shared=True)
             rf = t.root_render_func(new_context)
 
             try: