feat(m365): add exchange application access policy check (#11247)

Co-authored-by: Hugo P.Brito <hugopbrit@gmail.com>

prowler/CHANGELOG.md

@@ -6,6 +6,7 @@ All notable changes to the **Prowler SDK** are documented in this file.
 
 ### 🚀 Added
 
+- `exchange_application_access_policy_restricts_mailbox_apps` check for M365 provider, verifying every service principal with Microsoft Graph application-level Exchange mailbox permissions is restricted by an Exchange Online Application Access Policy, preventing tenant-wide mailbox access by unscoped applications [(#11247)](https://github.com/prowler-cloud/prowler/pull/11247)
 - Per-requirement configuration validation for compliance frameworks via `ConfigRequirements`, so a requirement is reported as FAIL when its configurable checks ran with a configuration too loose to satisfy it (applied across all compliance outputs: CSV, OCSF, and console tables) [(#11669)](https://github.com/prowler-cloud/prowler/pull/11669)
 - `entra_conditional_access_policy_explicitly_targets_azure_devops` check for M365 provider, verifying at least one enabled Conditional Access policy explicitly includes the Azure DevOps cloud application instead of relying on a broad "All cloud apps" policy [(#11182)](https://github.com/prowler-cloud/prowler/pull/11182)
 - `entra_conditional_access_policy_no_exclusion_gaps` check for M365 provider, verifying every user, group, role, or application excluded from an enabled Conditional Access policy stays in scope of another enabled policy [(#11577)](https://github.com/prowler-cloud/prowler/pull/11577)

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

@@ -1002,6 +1002,31 @@ class M365PowerShell(PowerShellSession):
             json_parse=True,
         )
 
+    def get_application_access_policies(self) -> dict:
+        """
+        Get Exchange Online Application Access Policies.
+
+        Retrieves all Exchange Online Application Access Policies.
+
+        Returns:
+            dict: Application access policies in JSON format.
+
+        Example:
+            >>> get_application_access_policies()
+            [
+                {
+                    "Identity": "Policy1",
+                    "AppId": "12345678-1234-1234-1234-123456789012",
+                    "AccessRight": "RestrictAccess",
+                    "Description": "Restrict mailbox access"
+                }
+            ]
+        """
+        return self.execute(
+            "Get-ApplicationAccessPolicy | ConvertTo-Json -Depth 10",
+            json_parse=True,
+        )
+
     def get_user_account_status(self) -> dict:
         """
         Get User Account Status.

prowler/providers/m365/services/entra/entra_service.py

@@ -1,4 +1,5 @@
 import asyncio
+import importlib
 import json
 from asyncio import gather
 from datetime import datetime, timezone
@@ -9,9 +10,6 @@ from uuid import UUID
 from kiota_abstractions.base_request_configuration import RequestConfiguration
 from msgraph.generated.groups.groups_request_builder import GroupsRequestBuilder
 from msgraph.generated.models.o_data_errors.o_data_error import ODataError
-from msgraph.generated.security.microsoft_graph_security_run_hunting_query.run_hunting_query_post_request_body import (
-    RunHuntingQueryPostRequestBody,
-)
 from msgraph.generated.users.users_request_builder import UsersRequestBuilder
 from pydantic.v1 import BaseModel, validator
 
@@ -19,6 +17,10 @@ from prowler.lib.logger import logger
 from prowler.providers.m365.lib.service.service import M365Service
 from prowler.providers.m365.m365_provider import M365Provider
 
+run_hunting_query_body = importlib.import_module(
+    "msgraph.generated.security.microsoft_graph_security_run_hunting_query."
+    "run_hunting_query_post_request_body"
+)
 # Sentinel identifiers used in Conditional Access ``conditions.users``
 # collections that do not correspond to real directory objects and must not be
 # resolved against Graph. Shared by the resolver below and the check that reads
@@ -84,6 +86,7 @@ class Entra(M365Service):
         self.tenant_domain = provider.identity.tenant_domain
         self.tenant_id = getattr(provider.identity, "tenant_id", None)
         self.user_registration_details_error: Optional[str] = None
+        self.exchange_mailbox_permission_service_principals_error: Optional[str] = None
         attributes = loop.run_until_complete(
             gather(
                 self._get_authorization_policy(),
@@ -98,6 +101,7 @@ class Entra(M365Service):
                 self._get_authentication_method_configurations(),
                 self._get_service_principals(),
                 self._get_app_registrations(),
+                self._get_exchange_mailbox_permission_service_principals(),
             )
         )
 
@@ -115,6 +119,9 @@ class Entra(M365Service):
         ] = attributes[9]
         self.service_principals: Dict[str, "ServicePrincipal"] = attributes[10]
         self.app_registrations: Dict[str, "AppRegistration"] = attributes[11]
+        self.exchange_mailbox_permission_service_principals: Dict[
+            str, "ServicePrincipal"
+        ] = attributes[12]
         self.user_accounts_status = {}
 
         # Resolve directory-object identifiers referenced by Conditional Access
@@ -1054,7 +1061,9 @@ OAuthAppInfo
 | project OAuthAppId, AppName, AppStatus, PrivilegeLevel, Permissions,
           ServicePrincipalId, IsAdminConsented, LastUsedTime, AppOrigin
 """
-            request_body = RunHuntingQueryPostRequestBody(query=query)
+            request_body = run_hunting_query_body.RunHuntingQueryPostRequestBody(
+                query=query
+            )
 
             result = await self.client.security.microsoft_graph_security_run_hunting_query.post(
                 request_body
@@ -1382,6 +1391,112 @@ OAuthAppInfo
             )
         return service_principals
 
+    async def _get_exchange_mailbox_permission_service_principals(self):
+        """Retrieve service principals with Exchange mailbox Graph app roles."""
+        logger.info(
+            "Entra - Getting service principals with Exchange mailbox permissions..."
+        )
+        self.exchange_mailbox_permission_service_principals_error = None
+        service_principals = {}
+        graph_service_principal = None
+        candidate_service_principals = []
+
+        try:
+            sp_response = await self.client.service_principals.get()
+            while sp_response:
+                for sp in getattr(sp_response, "value", []) or []:
+                    app_id = getattr(sp, "app_id", None)
+                    if app_id == MICROSOFT_GRAPH_APP_ID:
+                        graph_service_principal = sp
+                        continue
+
+                    if not getattr(sp, "account_enabled", True):
+                        continue
+
+                    raw_owner = getattr(sp, "app_owner_organization_id", None)
+                    app_owner_org_id = str(raw_owner).lower() if raw_owner else None
+                    if app_owner_org_id in MICROSOFT_FIRST_PARTY_TENANT_IDS:
+                        continue
+
+                    candidate_service_principals.append(sp)
+
+                next_link = getattr(sp_response, "odata_next_link", None)
+                if not next_link:
+                    break
+                sp_response = await self.client.service_principals.with_url(
+                    next_link
+                ).get()
+
+            if graph_service_principal is None:
+                return service_principals
+
+            graph_service_principal_id = getattr(graph_service_principal, "id", None)
+            exchange_app_roles = {}
+            for role in getattr(graph_service_principal, "app_roles", []) or []:
+                role_value = getattr(role, "value", "") or ""
+                allowed_member_types = getattr(role, "allowed_member_types", []) or []
+                if (
+                    role_value in EXCHANGE_MAILBOX_GRAPH_PERMISSIONS
+                    and "Application" in allowed_member_types
+                ):
+                    exchange_app_roles[str(getattr(role, "id", ""))] = role_value
+
+            if not graph_service_principal_id or not exchange_app_roles:
+                return service_principals
+
+            for sp in candidate_service_principals:
+                assignments_response = (
+                    await self.client.service_principals.by_service_principal_id(
+                        sp.id
+                    ).app_role_assignments.get()
+                )
+                exchange_permissions = set()
+
+                while assignments_response:
+                    for assignment in getattr(assignments_response, "value", []) or []:
+                        resource_id = str(getattr(assignment, "resource_id", ""))
+                        app_role_id = str(getattr(assignment, "app_role_id", ""))
+                        if resource_id == graph_service_principal_id:
+                            permission = exchange_app_roles.get(app_role_id)
+                            if permission:
+                                exchange_permissions.add(permission)
+
+                    next_link = getattr(assignments_response, "odata_next_link", None)
+                    if not next_link:
+                        break
+                    assignments_response = (
+                        await self.client.service_principals.by_service_principal_id(
+                            sp.id
+                        )
+                        .app_role_assignments.with_url(next_link)
+                        .get()
+                    )
+
+                if exchange_permissions:
+                    raw_owner = getattr(sp, "app_owner_organization_id", None)
+                    service_principals[sp.id] = ServicePrincipal(
+                        id=sp.id,
+                        name=getattr(sp, "display_name", "") or "",
+                        app_id=getattr(sp, "app_id", "") or "",
+                        app_owner_organization_id=(
+                            str(raw_owner).lower() if raw_owner else None
+                        ),
+                        account_enabled=getattr(sp, "account_enabled", True),
+                        service_principal_type=getattr(
+                            sp, "service_principal_type", "Application"
+                        ),
+                        exchange_mailbox_permissions=sorted(exchange_permissions),
+                    )
+        except Exception as error:
+            self.exchange_mailbox_permission_service_principals_error = (
+                f"{error.__class__.__name__}: {error}"
+            )
+            logger.error(
+                f"{error.__class__.__name__}[{error.__traceback__.tb_lineno}]: {error}"
+            )
+
+        return service_principals
+
     async def _get_app_registrations(self) -> Dict[str, "AppRegistration"]:
         """Retrieve application registrations from Microsoft Entra.
 
@@ -2064,6 +2179,27 @@ TIER_0_ROLE_TEMPLATE_IDS = {
     "e00e864a-17c5-4a4b-9c06-f5b95a8d5bd8",  # Partner Tier2 Support
 }
 
+MICROSOFT_GRAPH_APP_ID = "00000003-0000-0000-c000-000000000000"
+
+MICROSOFT_FIRST_PARTY_TENANT_IDS = {
+    "72f988bf-86f1-41af-91ab-2d7cd011db47",
+    "f8cdef31-a31e-4b4a-93e4-5f571e91255a",
+}
+
+EXCHANGE_MAILBOX_GRAPH_PERMISSIONS = {
+    "Calendars.Read",
+    "Calendars.ReadWrite",
+    "Contacts.Read",
+    "Contacts.ReadWrite",
+    "Mail.Read",
+    "Mail.ReadBasic",
+    "Mail.ReadBasic.All",
+    "Mail.ReadWrite",
+    "Mail.Send",
+    "MailboxSettings.Read",
+    "MailboxSettings.ReadWrite",
+}
+
 
 class ServicePrincipal(BaseModel):
     """Model representing a Microsoft Entra ID service principal.
@@ -2096,6 +2232,9 @@ class ServicePrincipal(BaseModel):
     password_credentials: List[PasswordCredential] = []
     key_credentials: List[KeyCredential] = []
     directory_role_template_ids: List[str] = []
+    account_enabled: bool = True
+    service_principal_type: str = "Application"
+    exchange_mailbox_permissions: List[str] = []
     sp_owner_ids: List[str] = []
     app_owner_ids: List[str] = []
 

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

@@ -0,0 +1,41 @@
+{
+  "Provider": "m365",
+  "CheckID": "exchange_application_access_policy_restricts_mailbox_apps",
+  "CheckTitle": "Apps with Exchange mailbox permissions must be scoped via Application Access Policy",
+  "CheckType": [],
+  "ServiceName": "exchange",
+  "SubServiceName": "",
+  "ResourceIdTemplate": "",
+  "Severity": "medium",
+  "ResourceType": "NotDefined",
+  "ResourceGroup": "collaboration",
+  "Description": "**Microsoft 365 Exchange Online** applications with mailbox access permissions should be restricted using **Application Access Policies**.\n\nThis check evaluates whether applications granted Exchange-related Microsoft Graph application permissions are scoped using Exchange Online `ApplicationAccessPolicy` objects.",
+  "Risk": "Applications with unrestricted Exchange mailbox permissions may gain tenant-wide mailbox access. Without **Application Access Policies**, compromised or over-privileged applications can read or manipulate mail across all mailboxes, leading to unauthorized access, data exfiltration, phishing, and loss of confidentiality and integrity.",
+  "RelatedUrl": "",
+  "AdditionalURLs": [
+    "https://learn.microsoft.com/en-us/graph/auth-limit-mailbox-access",
+    "https://learn.microsoft.com/en-us/powershell/module/exchange/new-applicationaccesspolicy",
+    "https://learn.microsoft.com/en-us/powershell/module/exchange/get-applicationaccesspolicy",
+    "https://learn.microsoft.com/en-us/graph/api/resources/serviceprincipal?view=graph-rest-1.0",
+    "https://learn.microsoft.com/en-us/graph/api/serviceprincipal-list-approleassignments?view=graph-rest-1.0"
+  ],
+  "Remediation": {
+    "Code": {
+      "CLI": "New-ApplicationAccessPolicy -AppId <AppId> -PolicyScopeGroupId <Group> -AccessRight RestrictAccess -Description \"Restrict mailbox access\"",
+      "NativeIaC": "",
+      "Other": "1. Connect to Exchange Online PowerShell\n2. Run Get-ApplicationAccessPolicy to review existing policies\n3. Identify applications with Exchange-related Graph application permissions\n4. Create an Application Access Policy for each required application\n5. Scope mailbox access using a dedicated mail-enabled security group",
+      "Terraform": ""
+    },
+    "Recommendation": {
+      "Text": "Restrict applications with Exchange mailbox permissions using **Application Access Policies**. Apply least privilege by limiting mailbox scope to only required users or groups. Regularly review app permissions and remove unused or excessive mailbox access.",
+      "Url": "https://hub.prowler.com/check/exchange_application_access_policy_restricts_mailbox_apps"
+    }
+  },
+  "Categories": [
+    "identity-access",
+    "email-security"
+  ],
+  "DependsOn": [],
+  "RelatedTo": [],
+  "Notes": ""
+}

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

@@ -0,0 +1,99 @@
+import importlib
+from typing import List
+
+from prowler.lib.check.models import Check, CheckReportM365
+from prowler.providers.m365.services.entra.entra_client import entra_client
+
+exchange_client = importlib.import_module(
+    "prowler.providers.m365.services.exchange.exchange_client"
+).exchange_client
+
+
+class exchange_application_access_policy_restricts_mailbox_apps(Check):
+    """
+    Check if applications with Exchange mailbox permissions
+    are restricted using Exchange Application Access Policies.
+    """
+
+    def execute(self) -> List[CheckReportM365]:
+        findings = []
+
+        application_access_policies = exchange_client.application_access_policies
+        if application_access_policies is None:
+            report = CheckReportM365(
+                metadata=self.metadata(),
+                resource=exchange_client.organization_config,
+                resource_name="Exchange Online",
+                resource_id="ExchangeOnlineTenant",
+            )
+            report.status = "MANUAL"
+            report.status_extended = (
+                "Exchange Online PowerShell is unavailable. "
+                "Enable Exchange Online PowerShell credentials to evaluate "
+                "Application Access Policies."
+            )
+            findings.append(report)
+            return findings
+
+        mailbox_permission_collection_error = getattr(
+            entra_client,
+            "exchange_mailbox_permission_service_principals_error",
+            None,
+        )
+        if isinstance(mailbox_permission_collection_error, str):
+            report = CheckReportM365(
+                metadata=self.metadata(),
+                resource=exchange_client.organization_config,
+                resource_name="Exchange Online",
+                resource_id="ExchangeOnlineTenant",
+            )
+            report.status = "MANUAL"
+            report.status_extended = (
+                "Microsoft Graph mailbox permission collection failed. "
+                "Manually verify whether applications with Exchange mailbox "
+                "permissions are restricted using Application Access Policies."
+            )
+            findings.append(report)
+            return findings
+
+        policy_app_ids = {
+            policy.app_id.lower()
+            for policy in application_access_policies
+            if getattr(policy, "app_id", None)
+            and getattr(policy, "access_right", None) == "RestrictAccess"
+        }
+
+        service_principals = (
+            entra_client.exchange_mailbox_permission_service_principals.values()
+        )
+        for service_principal in service_principals:
+            report = CheckReportM365(
+                metadata=self.metadata(),
+                resource=service_principal,
+                resource_name=service_principal.name,
+                resource_id=service_principal.id,
+            )
+            permissions = ", ".join(service_principal.exchange_mailbox_permissions)
+
+            if service_principal.app_id.lower() in policy_app_ids:
+                report.status = "PASS"
+                report.status_extended = (
+                    f"Service principal '{service_principal.name}' "
+                    f"({service_principal.app_id}) "
+                    "has Exchange mailbox permissions "
+                    f"({permissions}) and is restricted using an Application "
+                    "Access Policy."
+                )
+            else:
+                report.status = "FAIL"
+                report.status_extended = (
+                    f"Service principal '{service_principal.name}' "
+                    f"({service_principal.app_id}) "
+                    "has Exchange mailbox permissions "
+                    f"({permissions}) but is not restricted using an Application "
+                    "Access Policy."
+                )
+
+            findings.append(report)
+
+        return findings

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

@@ -43,6 +43,7 @@ class Exchange(M365Service):
         self.role_assignment_policies = []
         self.mailbox_audit_properties = []
         self.shared_mailboxes = []
+        self.application_access_policies = None
         self.mailboxes = None
 
         if self.powershell:
@@ -56,6 +57,9 @@ class Exchange(M365Service):
                 self.role_assignment_policies = self._get_role_assignment_policies()
                 self.mailbox_audit_properties = self._get_mailbox_audit_properties()
                 self.shared_mailboxes = self._get_shared_mailboxes()
+                self.application_access_policies = (
+                    self._get_application_access_policies()
+                )
                 self.mailboxes = self._get_mailboxes()
             self.powershell.close()
 
@@ -366,6 +370,53 @@ class Exchange(M365Service):
             )
         return shared_mailboxes
 
+    def _get_application_access_policies(self):
+        """
+        Get Exchange Online Application Access Policies.
+
+        Returns:
+            Optional[list[ApplicationAccessPolicy]]: List of application access
+            policies, or None if the PowerShell command failed.
+        """
+        logger.info("Microsoft365 - Getting application access policies...")
+
+        application_access_policies = []
+
+        try:
+            policies_data = self.powershell.get_application_access_policies()
+
+            if not policies_data:
+                return application_access_policies
+
+            if isinstance(policies_data, dict):
+                policies_data = [policies_data]
+
+            for policy in policies_data:
+                if policy:
+                    application_access_policies.append(
+                        ApplicationAccessPolicy(
+                            identity=policy.get("Identity", ""),
+                            app_id=policy.get("AppId", ""),
+                            access_right=policy.get(
+                                "AccessRight",
+                                "",
+                            ),
+                            description=policy.get(
+                                "Description",
+                                "",
+                            ),
+                        )
+                    )
+
+        except Exception as error:
+            logger.error(
+                f"{error.__class__.__name__}"
+                f"[{error.__traceback__.tb_lineno}]: {error}"
+            )
+            return None
+
+        return application_access_policies
+
     def _get_mailboxes(self) -> Optional[list["Mailbox"]]:
         """
         Get all recipient-facing mailboxes from Exchange Online.
@@ -554,6 +605,17 @@ class SharedMailbox(BaseModel):
     identity: str
 
 
+class ApplicationAccessPolicy(BaseModel):
+    """
+    Model for Exchange Online Application Access Policy.
+    """
+
+    identity: str
+    app_id: str
+    access_right: str
+    description: str
+
+
 class Mailbox(BaseModel):
     """
     Model for an Exchange Online recipient-facing mailbox.

tests/providers/m365/services/entra/microsoft365_entra_service_test.py

@@ -1,40 +1,41 @@
 import asyncio
+import importlib
 from datetime import datetime, timezone
 from types import SimpleNamespace
 from unittest.mock import AsyncMock, MagicMock, patch
 
 from prowler.providers.m365.models import M365IdentityInfo
-from prowler.providers.m365.services.entra.entra_service import (
-    AdminConsentPolicy,
-    AdminRoles,
-    ApplicationEnforcedRestrictions,
-    ApplicationsConditions,
-    AppManagementRestrictions,
-    AuthorizationPolicy,
-    AuthPolicyRoles,
-    ConditionalAccessGrantControl,
-    ConditionalAccessPolicy,
-    ConditionalAccessPolicyState,
-    Conditions,
-    CredentialRestriction,
-    DefaultAppManagementPolicy,
-    DefaultUserRolePermissions,
-    Entra,
-    GrantControlOperator,
-    GrantControls,
-    InvitationsFrom,
-    Organization,
-    PersistentBrowser,
-    SessionControls,
-    SignInFrequency,
-    SignInFrequencyInterval,
-    SignInFrequencyType,
-    User,
-    UserAction,
-    UsersConditions,
-)
+from prowler.providers.m365.services.entra import entra_service
 from tests.providers.m365.m365_fixtures import DOMAIN, set_mocked_m365_provider
 
+AdminConsentPolicy = entra_service.AdminConsentPolicy
+AdminRoles = entra_service.AdminRoles
+ApplicationEnforcedRestrictions = entra_service.ApplicationEnforcedRestrictions
+ApplicationsConditions = entra_service.ApplicationsConditions
+AppManagementRestrictions = entra_service.AppManagementRestrictions
+AuthorizationPolicy = entra_service.AuthorizationPolicy
+AuthPolicyRoles = entra_service.AuthPolicyRoles
+ConditionalAccessGrantControl = entra_service.ConditionalAccessGrantControl
+ConditionalAccessPolicy = entra_service.ConditionalAccessPolicy
+ConditionalAccessPolicyState = entra_service.ConditionalAccessPolicyState
+Conditions = entra_service.Conditions
+CredentialRestriction = entra_service.CredentialRestriction
+DefaultAppManagementPolicy = entra_service.DefaultAppManagementPolicy
+DefaultUserRolePermissions = entra_service.DefaultUserRolePermissions
+Entra = entra_service.Entra
+GrantControlOperator = entra_service.GrantControlOperator
+GrantControls = entra_service.GrantControls
+InvitationsFrom = entra_service.InvitationsFrom
+Organization = entra_service.Organization
+PersistentBrowser = entra_service.PersistentBrowser
+SessionControls = entra_service.SessionControls
+SignInFrequency = entra_service.SignInFrequency
+SignInFrequencyInterval = entra_service.SignInFrequencyInterval
+SignInFrequencyType = entra_service.SignInFrequencyType
+User = entra_service.User
+UserAction = entra_service.UserAction
+UsersConditions = entra_service.UsersConditions
+
 
 async def mock_entra_get_authorization_policy(_):
     return AuthorizationPolicy(
@@ -697,9 +698,12 @@ class Test_Entra_Service:
         a descriptive error message naming the missing AuditLog.Read.All permission.
         """
         from msgraph.generated.models.o_data_errors.main_error import MainError
-        from msgraph.generated.models.o_data_errors.o_data_error import ODataError
 
-        odata_error = ODataError()
+        o_data_error = importlib.import_module(
+            "msgraph.generated.models.o_data_errors.o_data_error"
+        )
+
+        odata_error = o_data_error.ODataError()
         odata_error.error = MainError()
         odata_error.error.code = "Authorization_RequestDenied"
 
@@ -879,6 +883,134 @@ class Test_Entra_Service:
         assert merged.password_credentials[0].display_name == "app-level-secret"
         assert merged.password_credentials[0].is_active()
 
+    def test__get_exchange_mailbox_permission_service_principals(self):
+        """Service principals with Exchange Graph application roles are returned."""
+        graph_sp_id = "graph-sp-id"
+        mail_read_role_id = "11111111-1111-1111-1111-111111111111"
+        user_read_role_id = "22222222-2222-2222-2222-222222222222"
+
+        graph_sp = SimpleNamespace(
+            id=graph_sp_id,
+            display_name="Microsoft Graph",
+            app_id="00000003-0000-0000-c000-000000000000",
+            app_owner_organization_id="f8cdef31-a31e-4b4a-93e4-5f571e91255a",
+            app_roles=[
+                SimpleNamespace(
+                    id=mail_read_role_id,
+                    value="Mail.Read",
+                    allowed_member_types=["Application"],
+                ),
+                SimpleNamespace(
+                    id=user_read_role_id,
+                    value="User.Read.All",
+                    allowed_member_types=["Application"],
+                ),
+            ],
+            account_enabled=True,
+            service_principal_type="Application",
+        )
+        mailbox_app = SimpleNamespace(
+            id="sp-mailbox",
+            display_name="Mailbox App",
+            app_id="app-mailbox",
+            app_owner_organization_id="33333333-3333-3333-3333-333333333333",
+            app_roles=[],
+            account_enabled=True,
+            service_principal_type="Application",
+        )
+        disabled_app = SimpleNamespace(
+            id="sp-disabled",
+            display_name="Disabled App",
+            app_id="app-disabled",
+            app_owner_organization_id="33333333-3333-3333-3333-333333333333",
+            app_roles=[],
+            account_enabled=False,
+            service_principal_type="Application",
+        )
+        first_party_app = SimpleNamespace(
+            id="sp-first-party",
+            display_name="Microsoft App",
+            app_id="app-first-party",
+            app_owner_organization_id="f8cdef31-a31e-4b4a-93e4-5f571e91255a",
+            app_roles=[],
+            account_enabled=True,
+            service_principal_type="Application",
+        )
+
+        app_role_assignments = {
+            "sp-mailbox": SimpleNamespace(
+                value=[
+                    SimpleNamespace(
+                        resource_id=graph_sp_id,
+                        app_role_id=mail_read_role_id,
+                    ),
+                    SimpleNamespace(
+                        resource_id=graph_sp_id,
+                        app_role_id=user_read_role_id,
+                    ),
+                ],
+                odata_next_link=None,
+            )
+        }
+
+        def by_service_principal_id(service_principal_id):
+            return SimpleNamespace(
+                app_role_assignments=SimpleNamespace(
+                    get=AsyncMock(
+                        return_value=app_role_assignments.get(
+                            service_principal_id,
+                            SimpleNamespace(value=[], odata_next_link=None),
+                        )
+                    ),
+                    with_url=MagicMock(),
+                )
+            )
+
+        entra_service = Entra.__new__(Entra)
+        entra_service.client = SimpleNamespace(
+            service_principals=SimpleNamespace(
+                get=AsyncMock(
+                    return_value=SimpleNamespace(
+                        value=[graph_sp, mailbox_app, disabled_app, first_party_app],
+                        odata_next_link=None,
+                    )
+                ),
+                with_url=MagicMock(),
+                by_service_principal_id=MagicMock(side_effect=by_service_principal_id),
+            )
+        )
+
+        result = asyncio.run(
+            entra_service._get_exchange_mailbox_permission_service_principals()
+        )
+
+        assert set(result.keys()) == {"sp-mailbox"}
+        assert result["sp-mailbox"].app_id == "app-mailbox"
+        assert result["sp-mailbox"].exchange_mailbox_permissions == ["Mail.Read"]
+
+    def test__get_exchange_mailbox_permission_service_principals_records_error(self):
+        """
+        Graph collection failures preserve unavailable state separately from empty results.
+        """
+        entra_service = Entra.__new__(Entra)
+        entra_service.client = SimpleNamespace(
+            service_principals=SimpleNamespace(
+                get=AsyncMock(side_effect=RuntimeError("Graph unavailable"))
+            )
+        )
+
+        result = asyncio.run(
+            entra_service._get_exchange_mailbox_permission_service_principals()
+        )
+
+        assert result == {}
+        assert "RuntimeError" in (
+            entra_service.exchange_mailbox_permission_service_principals_error
+        )
+        assert "Graph unavailable" in (
+            entra_service.exchange_mailbox_permission_service_principals_error
+        )
+
     def test__resolve_identifiers_for_type_flags_only_404(self):
         """Only HTTP 404 / Request_ResourceNotFound mark an id as deleted.
 

tests/providers/m365/services/exchange/exchange_application_access_policy_restricts_mailbox_apps/exchange_application_access_policy_restricts_mailbox_apps_test.py

@@ -0,0 +1,271 @@
+import importlib
+from unittest import mock
+
+from prowler.providers.m365.services.entra import entra_service
+from prowler.providers.m365.services.exchange import exchange_service
+from tests.providers.m365.m365_fixtures import DOMAIN, set_mocked_m365_provider
+
+CHECK_MODULE = (
+    "prowler.providers.m365.services.exchange."
+    "exchange_application_access_policy_restricts_mailbox_apps."
+    "exchange_application_access_policy_restricts_mailbox_apps"
+)
+
+
+class Test_exchange_application_access_policy_restricts_mailbox_apps:
+    def test_powershell_unavailable_returns_manual(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+        exchange_client.organization_config = None
+        exchange_client.application_access_policies = None
+
+        entra_client = mock.MagicMock()
+        entra_client.exchange_mailbox_permission_service_principals = {}
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.exchange_client",
+                new=exchange_client,
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.entra_client",
+                new=entra_client,
+            ),
+        ):
+            check_module = importlib.import_module(CHECK_MODULE)
+
+            result = (
+                check_module.exchange_application_access_policy_restricts_mailbox_apps().execute()
+            )
+
+        assert len(result) == 1
+        assert result[0].status == "MANUAL"
+        assert result[0].resource_id == "ExchangeOnlineTenant"
+        assert "Exchange Online PowerShell is unavailable" in result[0].status_extended
+
+    def test_no_resources(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+        exchange_client.organization_config = None
+        exchange_client.application_access_policies = []
+
+        entra_client = mock.MagicMock()
+        entra_client.exchange_mailbox_permission_service_principals = {}
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.exchange_client",
+                new=exchange_client,
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.entra_client",
+                new=entra_client,
+            ),
+        ):
+            check_module = importlib.import_module(CHECK_MODULE)
+
+            result = (
+                check_module.exchange_application_access_policy_restricts_mailbox_apps().execute()
+            )
+
+        assert len(result) == 0
+
+    def test_graph_collection_unavailable_returns_manual(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+        exchange_client.organization_config = None
+        exchange_client.application_access_policies = []
+
+        entra_client = mock.MagicMock()
+        entra_client.exchange_mailbox_permission_service_principals = {}
+        entra_client.exchange_mailbox_permission_service_principals_error = (
+            "RuntimeError: Graph unavailable"
+        )
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.exchange_client",
+                new=exchange_client,
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.entra_client",
+                new=entra_client,
+            ),
+        ):
+            check_module = importlib.import_module(CHECK_MODULE)
+
+            result = (
+                check_module.exchange_application_access_policy_restricts_mailbox_apps().execute()
+            )
+
+        assert len(result) == 1
+        assert result[0].status == "MANUAL"
+        assert result[0].resource_id == "ExchangeOnlineTenant"
+        assert (
+            "Microsoft Graph mailbox permission collection failed"
+            in result[0].status_extended
+        )
+
+    def test_service_principal_without_policy_fails(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+        exchange_client.organization_config = None
+        exchange_client.application_access_policies = []
+
+        entra_client = mock.MagicMock()
+        entra_client.exchange_mailbox_permission_service_principals = {
+            "sp-id": entra_service.ServicePrincipal(
+                id="sp-id",
+                name="Mailbox App",
+                app_id="app-id",
+                exchange_mailbox_permissions=["Mail.Read", "Mail.Send"],
+            )
+        }
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.exchange_client",
+                new=exchange_client,
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.entra_client",
+                new=entra_client,
+            ),
+        ):
+            check_module = importlib.import_module(CHECK_MODULE)
+
+            result = (
+                check_module.exchange_application_access_policy_restricts_mailbox_apps().execute()
+            )
+
+        assert len(result) == 1
+        assert result[0].status == "FAIL"
+        assert result[0].resource_id == "sp-id"
+        assert result[0].resource_name == "Mailbox App"
+        assert "app-id" in result[0].status_extended
+        assert "Mail.Read, Mail.Send" in result[0].status_extended
+
+    def test_service_principal_with_policy_passes(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+        exchange_client.organization_config = None
+        exchange_client.application_access_policies = [
+            exchange_service.ApplicationAccessPolicy(
+                identity="policy-id",
+                app_id="app-id",
+                access_right="RestrictAccess",
+                description="Restrict mailbox access",
+            )
+        ]
+
+        entra_client = mock.MagicMock()
+        entra_client.exchange_mailbox_permission_service_principals = {
+            "sp-id": entra_service.ServicePrincipal(
+                id="sp-id",
+                name="Mailbox App",
+                app_id="app-id",
+                exchange_mailbox_permissions=["Mail.Read"],
+            )
+        }
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.exchange_client",
+                new=exchange_client,
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.entra_client",
+                new=entra_client,
+            ),
+        ):
+            check_module = importlib.import_module(CHECK_MODULE)
+
+            result = (
+                check_module.exchange_application_access_policy_restricts_mailbox_apps().execute()
+            )
+
+        assert len(result) == 1
+        assert result[0].status == "PASS"
+        assert result[0].resource_id == "sp-id"
+        assert (
+            "is restricted using an Application Access Policy"
+            in result[0].status_extended
+        )
+
+    def test_service_principal_with_deny_access_policy_fails(self):
+        exchange_client = mock.MagicMock()
+        exchange_client.audited_tenant = "audited_tenant"
+        exchange_client.audited_domain = DOMAIN
+        exchange_client.organization_config = None
+        exchange_client.application_access_policies = [
+            exchange_service.ApplicationAccessPolicy(
+                identity="policy-id",
+                app_id="app-id",
+                access_right="DenyAccess",
+                description="Deny mailbox access",
+            )
+        ]
+
+        entra_client = mock.MagicMock()
+        entra_client.exchange_mailbox_permission_service_principals = {
+            "sp-id": entra_service.ServicePrincipal(
+                id="sp-id",
+                name="Mailbox App",
+                app_id="app-id",
+                exchange_mailbox_permissions=["Mail.Read"],
+            )
+        }
+
+        with (
+            mock.patch(
+                "prowler.providers.common.provider.Provider.get_global_provider",
+                return_value=set_mocked_m365_provider(),
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.exchange_client",
+                new=exchange_client,
+            ),
+            mock.patch(
+                "prowler.providers.m365.services.exchange.exchange_application_access_policy_restricts_mailbox_apps.exchange_application_access_policy_restricts_mailbox_apps.entra_client",
+                new=entra_client,
+            ),
+        ):
+            check_module = importlib.import_module(CHECK_MODULE)
+
+            result = (
+                check_module.exchange_application_access_policy_restricts_mailbox_apps().execute()
+            )
+
+        assert len(result) == 1
+        assert result[0].status == "FAIL"
+        assert result[0].resource_id == "sp-id"
+        assert result[0].resource_name == "Mailbox App"
+        assert (
+            "is not restricted using an Application Access Policy"
+            in result[0].status_extended
+        )