content: # Copyright (c) 2018 VMware, Inc.
  #
  # SPDX-License-Identifier: Apache-2.0
  r"""
  ==========================================
  B507: Test for missing host key validation
  ==========================================
  
  Encryption in general is typically critical to the security of many
  applications.  Using SSH can greatly increase security by guaranteeing the
  identity of the party you are communicating with.  This is accomplished by one
  or both parties presenting trusted host keys during the connection
  initialization phase of SSH.
  
  When paramiko methods are used, host keys are verified by default. If host key
  verification is disabled, Bandit will return a HIGH severity error.
  
  :Example:
  
  .. code-block:: none
  
      >> Issue: [B507:ssh_no_host_key_verification] Paramiko call with policy set
      to automatically trust the unknown host key.
      Severity: High   Confidence: Medium
      CWE: CWE-295 (https://cwe.mitre.org/data/definitions/295.html)
      Location: examples/no_host_key_verification.py:4
      3   ssh_client = client.SSHClient()
      4   ssh_client.set_missing_host_key_policy(client.AutoAddPolicy)
      5   ssh_client.set_missing_host_key_policy(client.WarningPolicy)
  
  
  .. versionadded:: 1.5.1
  
  .. versionchanged:: 1.7.3
      CWE information added
  
  """
  import ast
  
  import bandit
  from bandit.core import issue
  from bandit.core import test_properties as test
  
  
  @test.checks("Call")
  @test.test_id("B507")
  def ssh_no_host_key_verification(context):
      if (
          context.is_module_imported_like("paramiko")
          and context.call_function_name == "set_missing_host_key_policy"
          and context.node.args
      ):
          policy_argument = context.node.args[0]
  
          policy_argument_value = None
          if isinstance(policy_argument, ast.Attribute):
              policy_argument_value = policy_argument.attr
          elif isinstance(policy_argument, ast.Name):
              policy_argument_value = policy_argument.id
          elif isinstance(policy_argument, ast.Call):
              if isinstance(policy_argument.func, ast.Attribute):
                  policy_argument_value = policy_argument.func.attr
              elif isinstance(policy_argument.func, ast.Name):
                  policy_argument_value = policy_argument.func.id
  
          if policy_argument_value in ["AutoAddPolicy", "WarningPolicy"]:
              return bandit.Issue(
                  severity=bandit.HIGH,
                  confidence=bandit.MEDIUM,
                  cwe=issue.Cwe.IMPROPER_CERT_VALIDATION,
                  text="Paramiko call with policy set to automatically trust "
                  "the unknown host key.",
                  lineno=context.get_lineno_for_call_arg(
                      "set_missing_host_key_policy"
                  ),
              )
  