split PS wrapper and payload (CVE-2018-16859) (#49143)
* prevent scriptblock logging from logging payload contents * added tests to verify no payload contents in PS Operational event log * fix script action to send split-aware wrapper * fix CLIXML error parser (return to -EncodedCommand exposed problems with it)
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9 changed files with 66 additions and 24 deletions
2
changelogs/fragments/ps_sb_logging.yaml
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2
changelogs/fragments/ps_sb_logging.yaml
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@ -0,0 +1,2 @@
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bugfixes:
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- Windows - prevent sensitive content from appearing in scriptblock logging (CVE 2018-16859)
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@ -912,7 +912,8 @@ def _find_module_utils(module_name, b_module_data, module_path, module_args, tas
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# FUTURE: smuggle this back as a dict instead of serializing here; the connection plugin may need to modify it
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module_json = json.dumps(exec_manifest)
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b_module_data = exec_wrapper.replace(b"$json_raw = ''", b"$json_raw = @'\r\n%s\r\n'@" % to_bytes(module_json))
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# delimit the payload JSON from the wrapper to keep sensitive contents out of scriptblocks (which can be logged)
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b_module_data = to_bytes(exec_wrapper) + b'\0\0\0\0' + to_bytes(module_json)
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elif module_substyle == 'jsonargs':
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module_args_json = to_bytes(json.dumps(module_args))
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0
lib/ansible/executor/powershell/__init__.py
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0
lib/ansible/executor/powershell/__init__.py
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7
lib/ansible/executor/powershell/bootstrap_wrapper.ps1
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7
lib/ansible/executor/powershell/bootstrap_wrapper.ps1
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@ -0,0 +1,7 @@
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&chcp.com 65001 > $null
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$exec_wrapper_str = $input | Out-String
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$split_parts = $exec_wrapper_str.Split(@("`0`0`0`0"), 2, [StringSplitOptions]::RemoveEmptyEntries)
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If (-not $split_parts.Length -eq 2) { throw "invalid payload" }
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Set-Variable -Name json_raw -Value $split_parts[1]
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$exec_wrapper = [ScriptBlock]::Create($split_parts[0])
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&$exec_wrapper
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@ -126,12 +126,13 @@ class ActionModule(ActionBase):
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exec_data = None
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# WinRM requires a special wrapper to work with environment variables
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if self._connection.transport == "winrm":
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pay = self._connection._create_raw_wrapper_payload(script_cmd,
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env_dict)
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exec_data = exec_wrapper.replace(b"$json_raw = ''",
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b"$json_raw = @'\r\n%s\r\n'@"
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% to_bytes(pay))
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script_cmd = "-"
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pay = self._connection._create_raw_wrapper_payload(script_cmd, env_dict)
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exec_data = to_bytes(exec_wrapper) + b"\0\0\0\0" + to_bytes(pay)
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# build the necessary exec wrapper command
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# FUTURE: this still doesn't let script work on Windows with non-pipelined connections or
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# full manual exec of KEEP_REMOTE_FILES
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script_cmd = self._connection._shell.build_module_command(env_string='', shebang='#!powershell', cmd='')
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result.update(self._low_level_execute_command(cmd=script_cmd, in_data=exec_data, sudoable=True, chdir=chdir))
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@ -278,6 +278,7 @@ class Connection(ConnectionBase):
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# starting a new interpreter to save on time
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b_command = base64.b64decode(cmd.split(" ")[-1])
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script = to_text(b_command, 'utf-16-le')
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in_data = to_text(in_data, errors="surrogate_or_strict", nonstring="passthru")
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display.vvv("PSRP: EXEC %s" % script, host=self._psrp_host)
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else:
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# in other cases we want to execute the cmd as the script
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@ -103,6 +103,7 @@ import traceback
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import json
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import tempfile
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import subprocess
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import xml.etree.ElementTree as ET
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HAVE_KERBEROS = False
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try:
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@ -550,14 +551,17 @@ class Connection(ConnectionBase):
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return (result.status_code, result.std_out, result.std_err)
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def is_clixml(self, value):
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return value.startswith(b"#< CLIXML")
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return value.startswith(b"#< CLIXML\r\n")
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# hacky way to get just stdout- not always sure of doc framing here, so use with care
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def parse_clixml_stream(self, clixml_doc, stream_name='Error'):
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clear_xml = clixml_doc.replace(b'#< CLIXML\r\n', b'')
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doc = xmltodict.parse(clear_xml)
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lines = [l.get('#text', '').replace('_x000D__x000A_', '') for l in doc.get('Objs', {}).get('S', {}) if l.get('@S') == stream_name]
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return '\r\n'.join(lines)
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clixml = ET.fromstring(clixml_doc.split(b"\r\n", 1)[-1])
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namespace_match = re.match(r'{(.*)}', clixml.tag)
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namespace = "{%s}" % namespace_match.group(1) if namespace_match else ""
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strings = clixml.findall("./%sS" % namespace)
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lines = [e.text.replace('_x000D__x000A_', '') for e in strings if e.attrib.get('S') == stream_name]
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return to_bytes('\r\n'.join(lines))
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# FUTURE: determine buffer size at runtime via remote winrm config?
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def _put_file_stdin_iterator(self, in_path, out_path, buffer_size=250000):
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@ -44,6 +44,7 @@ import base64
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import os
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import re
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import shlex
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import pkgutil
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from ansible.errors import AnsibleError
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from ansible.module_utils._text import to_text
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@ -78,9 +79,11 @@ begin {
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# stream JSON including become_pw, ps_module_payload, bin_module_payload, become_payload, write_payload_path, preserve directives
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# exec runspace, capture output, cleanup, return module output
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# NB: do not adjust the following line- it is replaced when doing non-streamed module output
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# only init and stream in $json_raw if it wasn't set by the enclosing scope
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if (-not $(Get-Variable "json_raw" -ErrorAction SilentlyContinue)) {
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$json_raw = ''
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}
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}
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process {
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$input_as_string = [string]$input
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@ -929,9 +932,11 @@ namespace AnsibleBecome
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$become_exec_wrapper = {
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chcp.com 65001 > $null
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$ProgressPreference = "SilentlyContinue"
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$exec_wrapper_str = [System.Console]::In.ReadToEnd()
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$exec_wrapper = [ScriptBlock]::Create($exec_wrapper_str)
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&$exec_wrapper
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$raw = [System.Console]::In.ReadToEnd()
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$split_parts = $raw.Split(@("`0`0`0`0"), 0)
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If (-not $split_parts.Length -eq 2) { throw "invalid payload" }
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$json_raw = $split_parts[1]
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&([ScriptBlock]::Create($split_parts[0]))
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}
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$exec_wrapper = {
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@ -955,10 +960,9 @@ $exec_wrapper = {
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# stream JSON including become_pw, ps_module_payload, bin_module_payload, become_payload, write_payload_path, preserve directives
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# exec runspace, capture output, cleanup, return module output. Do not change this as it is set become before being passed to the
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# become process.
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$json_raw = ""
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If (-not $json_raw) {
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Write-Error "no input given" -Category InvalidArgument
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if (-not $(Get-Variable "json_raw" -ErrorAction SilentlyContinue)) {
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Write-Error "no payload supplied" -Category InvalidArgument
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}
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$payload = ConvertTo-HashtableFromPsCustomObject -myPsObject (ConvertFrom-Json $json_raw)
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@ -1095,7 +1099,7 @@ Function Run($payload) {
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# wrapper which calls our read wrapper passed through stdin. Cannot use 'powershell -' as
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# the $ErrorActionPreference is always set to Stop and cannot be changed
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$payload_string = $payload | ConvertTo-Json -Depth 99 -Compress
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$exec_wrapper = $exec_wrapper.ToString().Replace('$json_raw = ""', "`$json_raw = '$payload_string'")
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$exec_wrapper = $exec_wrapper.ToString() + "`0`0`0`0" + $payload_string
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$rc = 0
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$exec_command = [Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes($become_exec_wrapper.ToString()))
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@ -1584,9 +1588,11 @@ class ShellModule(ShellBase):
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return self._encode_script(script)
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def build_module_command(self, env_string, shebang, cmd, arg_path=None):
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bootstrap_wrapper = pkgutil.get_data("ansible.executor.powershell", "bootstrap_wrapper.ps1")
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# pipelining bypass
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if cmd == '':
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return '-'
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return self._encode_script(script=bootstrap_wrapper, strict_mode=False, preserve_rc=False)
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# non-pipelining
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@ -1594,8 +1600,11 @@ class ShellModule(ShellBase):
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cmd_parts = list(map(to_text, cmd_parts))
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if shebang and shebang.lower() == '#!powershell':
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if not self._unquote(cmd_parts[0]).lower().endswith('.ps1'):
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# we're running a module via the bootstrap wrapper
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cmd_parts[0] = '"%s.ps1"' % self._unquote(cmd_parts[0])
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cmd_parts.insert(0, '&')
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wrapper_cmd = "type " + cmd_parts[0] + " | " + self._encode_script(script=bootstrap_wrapper,
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strict_mode=False, preserve_rc=False)
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return wrapper_cmd
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elif shebang and shebang.startswith('#!'):
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cmd_parts.insert(0, shebang[2:])
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elif not shebang:
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@ -1,7 +1,7 @@
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- set_fact:
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become_test_username: ansible_become_test
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become_test_admin_username: ansible_become_admin
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gen_pw: password123! + {{ lookup('password', '/dev/null chars=ascii_letters,digits length=8') }}
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gen_pw: "{{ 'password123!' + lookup('password', '/dev/null chars=ascii_letters,digits length=8') }}"
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- name: create unprivileged user
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win_user:
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@ -29,6 +29,10 @@
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- SeInteractiveLogonRight
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- SeBatchLogonRight
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- name: fetch current target date/time for log filtering
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raw: '[datetime]::now | Out-String'
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register: test_starttime
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- name: execute tests and ensure that test user is deleted regardless of success/failure
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block:
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- name: ensure current user is not the become user
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assert:
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that:
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- whoami_out is successful
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- become_test_username in whoami_out.stdout
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- name: test failure with string become invalid key
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vars: *become_vars
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- nonascii_output.stdout_lines[0] == 'über den Fußgängerübergang gehen'
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- nonascii_output.stderr == ''
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- name: get PS events containing password or module args created since test start
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raw: |
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$dt=[datetime]"{{ test_starttime.stdout|trim }}"
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(Get-WinEvent -LogName Microsoft-Windows-Powershell/Operational |
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? { $_.TimeCreated -ge $dt -and $_.Message -match "{{ gen_pw }}|whoami" }).Count
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register: ps_log_count
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- name: assert no PS events contain password or module args
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assert:
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that:
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- ps_log_count.stdout | int == 0
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# FUTURE: test raw + script become behavior once they're running under the exec wrapper again
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# FUTURE: add standalone playbook tests to include password prompting and play become keywords
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