feat(exchange): add new check exchange_transport_config_smtp_auth_disabled (#7640)

Co-authored-by: Andoni A. <14891798+andoniaf@users.noreply.github.com>

prowler/CHANGELOG.md

@@ -38,6 +38,7 @@ All notable changes to the **Prowler SDK** are documented in this file.
 - Add Prowler Threat Score Compliance Framework [(#7603)](https://github.com/prowler-cloud/prowler/pull/7603)
 - Add new check `sharepoint_onedrive_sync_restricted_unmanaged_devices` [(#7589)](https://github.com/prowler-cloud/prowler/pull/7589)
 - Add new check for Additional Storage restricted for Exchange in M365 [(#7638)](https://github.com/prowler-cloud/prowler/pull/7638)
+- Add new check for SMTP Auth disabled for Exchange in M365 [(#7640)](https://github.com/prowler-cloud/prowler/pull/7640)
 - Add new check for MailTips full enabled for Exchange in M365 [(#7637)](https://github.com/prowler-cloud/prowler/pull/7637)
 
 ### Fixed

prowler/providers/m365/lib/powershell/m365_powershell.py

@@ -487,6 +487,23 @@ class M365PowerShell(PowerShellSession):
             "Get-HostedContentFilterPolicy | ConvertTo-Json", json_parse=True
         )
 
+    def get_transport_config(self) -> dict:
+        """
+        Get Exchange Online Transport Configuration.
+
+        Retrieves the current transport configuration settings for Exchange Online.
+
+        Returns:
+            dict: Transport configuration settings in JSON format.
+
+        Example:
+            >>> get_transport_config()
+            {
+                "SmtpClientAuthenticationDisabled": True,
+            }
+        """
+        return self.execute("Get-TransportConfig | ConvertTo-Json", json_parse=True)
+
 
 # This function is used to install the required M365 PowerShell modules in Docker containers
 def initialize_m365_powershell_modules():

prowler/providers/m365/services/exchange/exchange_service.py

@@ -14,6 +14,7 @@ class Exchange(M365Service):
         self.mailboxes_config = []
         self.external_mail_config = []
         self.transport_rules = []
+        self.transport_config = None
         self.mailbox_policy = None
 
         if self.powershell:
@@ -22,6 +23,7 @@ class Exchange(M365Service):
             self.mailboxes_config = self._get_mailbox_audit_config()
             self.external_mail_config = self._get_external_mail_config()
             self.transport_rules = self._get_transport_rules()
+            self.transport_config = self._get_transport_config()
             self.mailbox_policy = self._get_mailbox_policy()
             self.powershell.close()
 
@@ -126,6 +128,23 @@ class Exchange(M365Service):
             )
         return transport_rules
 
+    def _get_transport_config(self):
+        logger.info("Microsoft365 - Getting transport configuration...")
+        transport_config = []
+        try:
+            transport_configuration = self.powershell.get_transport_config()
+            if transport_configuration:
+                transport_config = TransportConfig(
+                    smtp_auth_disabled=transport_configuration.get(
+                        "SmtpClientAuthenticationDisabled", False
+                    ),
+                )
+        except Exception as error:
+            logger.error(
+                f"{error.__class__.__name__}[{error.__traceback__.tb_lineno}]: {error}"
+            )
+        return transport_config
+
     def _get_mailbox_policy(self):
         logger.info("Microsoft365 - Getting mailbox policy configuration...")
         mailboxes_policy = None
@@ -172,6 +191,10 @@ class TransportRule(BaseModel):
     sender_domain_is: list[str]
 
 
+class TransportConfig(BaseModel):
+    smtp_auth_disabled: bool
+
+
 class MailboxPolicy(BaseModel):
     id: str
     additional_storage_enabled: bool

prowler/providers/m365/services/exchange/exchange_transport_config_smtp_auth_disabled/exchange_transport_config_smtp_auth_disabled.metadata.json

@@ -0,0 +1,30 @@
+{
+  "Provider": "m365",
+  "CheckID": "exchange_transport_config_smtp_auth_disabled",
+  "CheckTitle": "Ensure SMTP AUTH is disabled.",
+  "CheckType": [],
+  "ServiceName": "exchange",
+  "SubServiceName": "",
+  "ResourceIdTemplate": "",
+  "Severity": "high",
+  "ResourceType": "Exchange Transport Config",
+  "Description": "Ensure that SMTP AUTH is disabled at the organization level in Exchange Online to reduce exposure to legacy protocols that can be exploited for malicious use.",
+  "Risk": "Leaving SMTP AUTH enabled allows legacy clients to authenticate using outdated methods, increasing the risk of credential compromise and unauthorized email sending.",
+  "RelatedUrl": "https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission",
+  "Remediation": {
+    "Code": {
+      "CLI": "Set-TransportConfig -SmtpClientAuthenticationDisabled $true",
+      "NativeIaC": "",
+      "Other": "1. Navigate to Exchange admin center https://admin.exchange.microsoft.com. 2. Select Settings > Mail flow. 3. Ensure 'Turn off SMTP AUTH protocol for your organization' is checked.",
+      "Terraform": ""
+    },
+    "Recommendation": {
+      "Text": "Disable SMTP AUTH at the organization level to support secure, modern authentication practices and block legacy protocol usage.",
+      "Url": "https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission"
+    }
+  },
+  "Categories": [],
+  "DependsOn": [],
+  "RelatedTo": [],
+  "Notes": ""
+}

prowler/providers/m365/services/exchange/exchange_transport_config_smtp_auth_disabled/exchange_transport_config_smtp_auth_disabled.py

@@ -0,0 +1,44 @@
+from typing import List
+
+from prowler.lib.check.models import Check, CheckReportM365
+from prowler.providers.m365.services.exchange.exchange_client import exchange_client
+
+
+class exchange_transport_config_smtp_auth_disabled(Check):
+    """Check if SMTP AUTH is disabled in Exchange Online Transport Config.
+
+    Attributes:
+        metadata: Metadata associated with the check (inherited from Check).
+    """
+
+    def execute(self) -> List[CheckReportM365]:
+        """Execute the check for SMTP AUTH setting in Transport Config.
+
+        This method checks if SMTP AUTH is disabled at the organization level in Exchange Online.
+
+        Returns:
+            List[CheckReportM365]: A list of reports containing the result of the check.
+        """
+        findings = []
+        transport_config = exchange_client.transport_config
+        if transport_config:
+            report = CheckReportM365(
+                metadata=self.metadata(),
+                resource=transport_config,
+                resource_name="Transport Configuration",
+                resource_id="transport_config",
+            )
+            report.status = "FAIL"
+            report.status_extended = (
+                "SMTP AUTH is enabled in the Exchange Online Transport Config."
+            )
+
+            if transport_config.smtp_auth_disabled:
+                report.status = "PASS"
+                report.status_extended = (
+                    "SMTP AUTH is disabled in the Exchange Online Transport Config."
+                )
+
+            findings.append(report)
+
+        return findings

tests/providers/m365/services/exchange/exchange_service_test.py

@@ -8,6 +8,7 @@ from prowler.providers.m365.services.exchange.exchange_service import (
     MailboxAuditConfig,
     MailboxPolicy,
     Organization,
+    TransportConfig,
     TransportRule,
 )
 from tests.providers.m365.m365_fixtures import DOMAIN, set_mocked_m365_provider
@@ -60,6 +61,12 @@ def mock_exchange_get_transport_rules(_):
     ]
 
 
+def mock_exchange_get_transport_config(_):
+    return TransportConfig(
+        smtp_auth_disabled=True,
+    )
+
+
 def mock_exchange_get_mailbox_policy(_):
     return MailboxPolicy(
         id="test",
@@ -203,3 +210,23 @@ class Test_Exchange_Service:
             assert mailbox_policy.id == "test"
             assert mailbox_policy.additional_storage_enabled is True
             exchange_client.powershell.close()
+
+    @patch(
+        "prowler.providers.m365.services.exchange.exchange_service.Exchange._get_transport_config",
+        new=mock_exchange_get_transport_config,
+    )
+    def test_get_transport_config(self):
+        with (
+            mock.patch(
+                "prowler.providers.m365.lib.powershell.m365_powershell.M365PowerShell.connect_exchange_online"
+            ),
+        ):
+            exchange_client = Exchange(
+                set_mocked_m365_provider(
+                    identity=M365IdentityInfo(tenant_domain=DOMAIN)
+                )
+            )
+            transport_config = exchange_client.transport_config
+            assert transport_config.smtp_auth_disabled is True
+
+            exchange_client.powershell.close()

tests/providers/m365/services/exchange/exchange_transport_config_smtp_auth_disabled/exchange_transport_config_smtp_auth_disabled_test.py

@@ -0,0 +1,112 @@
+from unittest import mock
+
+from tests.providers.m365.m365_fixtures import DOMAIN, set_mocked_m365_provider
+
+
+class Test_exchange_transport_config_smtp_auth_disabled:
+    def test_no_transport_config(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+        exchange_client.transport_config = None
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.lib.powershell.m365_powershell.M365PowerShell.connect_exchange_online"
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_transport_config_smtp_auth_disabled.exchange_transport_config_smtp_auth_disabled.exchange_client",
+                new=exchange_client,
+            ),
+        ):
+            from prowler.providers.m365.services.exchange.exchange_transport_config_smtp_auth_disabled.exchange_transport_config_smtp_auth_disabled import (
+                exchange_transport_config_smtp_auth_disabled,
+            )
+
+            check = exchange_transport_config_smtp_auth_disabled()
+            result = check.execute()
+            assert len(result) == 0
+
+    def test_smtp_auth_enabled(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.lib.powershell.m365_powershell.M365PowerShell.connect_exchange_online"
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_transport_config_smtp_auth_disabled.exchange_transport_config_smtp_auth_disabled.exchange_client",
+                new=exchange_client,
+            ),
+        ):
+            from prowler.providers.m365.services.exchange.exchange_service import (
+                TransportConfig,
+            )
+            from prowler.providers.m365.services.exchange.exchange_transport_config_smtp_auth_disabled.exchange_transport_config_smtp_auth_disabled import (
+                exchange_transport_config_smtp_auth_disabled,
+            )
+
+            exchange_client.transport_config = TransportConfig(smtp_auth_disabled=False)
+
+            check = exchange_transport_config_smtp_auth_disabled()
+            result = check.execute()
+            assert len(result) == 1
+            assert result[0].status == "FAIL"
+            assert (
+                result[0].status_extended
+                == "SMTP AUTH is enabled in the Exchange Online Transport Config."
+            )
+            assert result[0].resource == exchange_client.transport_config.dict()
+            assert result[0].resource_name == "Transport Configuration"
+            assert result[0].resource_id == "transport_config"
+            assert result[0].location == "global"
+
+    def test_smtp_auth_disabled(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.lib.powershell.m365_powershell.M365PowerShell.connect_exchange_online"
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_transport_config_smtp_auth_disabled.exchange_transport_config_smtp_auth_disabled.exchange_client",
+                new=exchange_client,
+            ),
+        ):
+            from prowler.providers.m365.services.exchange.exchange_service import (
+                TransportConfig,
+            )
+            from prowler.providers.m365.services.exchange.exchange_transport_config_smtp_auth_disabled.exchange_transport_config_smtp_auth_disabled import (
+                exchange_transport_config_smtp_auth_disabled,
+            )
+
+            exchange_client.transport_config = TransportConfig(smtp_auth_disabled=True)
+
+            check = exchange_transport_config_smtp_auth_disabled()
+            result = check.execute()
+            assert len(result) == 1
+            assert result[0].status == "PASS"
+            assert (
+                result[0].status_extended
+                == "SMTP AUTH is disabled in the Exchange Online Transport Config."
+            )
+            assert result[0].resource == exchange_client.transport_config.dict()
+            assert result[0].resource_name == "Transport Configuration"
+            assert result[0].resource_id == "transport_config"
+            assert result[0].location == "global"