A storage account that is created as part of an Azure Function App out of the box has some configuration tradeoffs that can be considered vulnerabilities. Let’s look at what can be changed to improve the security of the storage account without affecting the functionality of the Azure Function App.
Public (anonymous) Access
Storage account blob anonymous (public ) access should be disallowed. Though having this Enabled does not allow anonymous access to blobs automatically, it is recommended to disable public access unless the scenario requires it. Storage account that support Azure Function App is not supposed to be shared anonymously.
Navigate to your Storage Account at Azure portal, Settings/Configuration, then for “Allow Blob anonymous access” select “Disabled”:
MS: “When allow blob anonymous access is enabled, one is permitted to configure container ACLs to allow anonymous access to blobs within the storage account. When disabled, no anonymous access to blobs within the storage account is permitted, regardless of underlying ACL configurations. Learn more about allowing blob anonymous access“.
Storage account key access
This is also considered as vulnerability and it is recommended to disable Storage account key access.
NB: (Jan 2025) It is not possible to Set “Allow storage account key access” to Disabled if you are using Consumption or Elastic Premium plans on both Windows and Linux without breaking the function app. For other plans – it’s possible but requires some work.
Set “Allow storage account key access” to Disabled:
MS: “When Allow storage account key access is disabled, any requests to the account that are authorized with Shared Key, including shared access signatures (SAS), will be denied. Client applications that currently access the storage account using Shared Key will no longer work. Learn more about Allow storage account key access“
The problem is it seems like the function app ootb is configured to use key access, so just disabling storage account key access breaks the function app.
For the function app to adopt this new setting, you’d need:
provide access for the function app to the storage account
reconfigure the function app for authorization via Microsoft Entra credentials
Azure key vault is something where you can store keys, secrets, certificates that you’d need to access services (e.g. call Graph API).
What if somebody malicious get access to key vault (that is not what we want but we should consider this as possible risk)? Surely leaked secrets is a serious issue (separate topic), but imagine if that somebody also deletes key vault content – if so, we will simply lose this data, which will break the functionality of the solution and our existing systems will stop working.
So enabling purge protection on key vaults is a critical security measure to prevent permanent data loss. This feature enforces a mandatory retention period for soft-deleted key vault contents (e.g. secrets), making them immune to purging during the retention period.
In a nutshell, you’d just select “Enable purge protection” under the key vault Settings/Properties (notice, that once enabled, this option cannot be disabled):
For details, please refer to the following articles:
Note: When you follow instructions provided by Microsoft, beware that “Connect-AzureAD” works only in Windows .net framework – i.e. PowerShell 5.1. if you try to run it in PowerShell 7 – you can get “Connect-AzureAD: One or more errors occurred. (Could not load type ‘System.Security.Cryptography.SHA256Cng’ from assembly ‘System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089’.)” Error. (check Connect-AzureAD Could not load type ‘System.Security.Cryptography.SHA256Cng’ from assembly)
Configuring Sensitivity Labels
Sensitivity labels are configured under Microsoft Purview (Compliance Center), Solutions, Information Protection. You’d need a global admin or “Compliance Administrator” or “Azure Information Protection Administrator” (?) role:
Since we are talking sensitivity labels for SharePoint Sites (not documents), we define label scope as “Groups and Sites”: “Configure privacy, access control, and other settings to protect labeled Teams, Microsoft 365 Groups, and SharePoint sites.”
Then we define which protection settings for groups and sites we should configure on the next steps: – Privacy and external user access settings – Control the level of access that internal and external users will have to labeled teams and Microsoft 365 Groups. – External sharing and conditional access settings – Control external sharing and configure Conditional Access settings to protect labeled SharePoint sites.
If we selected previously “Privacy and external user access settings” – now we need to select group/team privacy (These options apply to all Microsoft 365 Groups and teams, but not standalone sites). When applied, these settings will replace any existing privacy settings for the team or group. If the label is removed, users can change privacy settings again. You can also allow external user access – if group owner will be able to add guests:
Next step – define external sharing and conditional access settings. Specifically, if the content of the SharePoint site can be shared with Anyone (anonymously) or with authenticated users (new or existing) or no external sharing is allowed:
And you can either control the level of access users have from unmanaged devices or select an existing authentication context to enforce restrictions:
Configuring sensitivity labels policies
Sensitivity label policy is basically which label should be available to apply for what users and some other settings like – do users need to provide justification before removing a label or replacing it with one that has a lower-order number or – will users be required to apply labels and optionall the default label
View existing sensitivity labels
“Global reader” role allows view existing sensitivity labels configuration:
Wording would be a little different, but all aspects of the label configuration will be mentioned. E.g. when editing GUI says label scope is “Groups & sites”, read-only label summary defines Scope as “Site, UnifiedGroup”.
Gotchas
Site sensitivity label is applied to site collection only and cannot be applied to subsite (web object).
Applying sensitivity labels programmatically
To apply a label to a m365 group or Teams site with a group behind: MS Graph API support only Delegated permissions.
“Set-PnPSiteSensitivityLabel” works in the current site context. Description says “If the site does not have a Microsoft 365 Group behind it, it will set the label on the SharePoint Online site and will not require Microsoft Graph permissions and will work with both delegate as well as app only logins.” In fact (7/22/2022) app permissions are not working. This cmdlet can assign label to a standalone or a group-based site only with delegated permissions.
“Set-PnPTenantSite” allows you to remove or apply site sensitivity label to both standalone and group-based sites with app permissions. Furthermore, group and team settings respect this. I.e. if you apply label to a group-based site – group will pick this up.
Channel sites should inherit sensitivity label from root site. I’m not sure if it’s a bug but – when you create a team and select sensitivity label as part of team creation process – all the channel sites you create after (Private or Shared) will inherit sensitivity label immediately – when you apply sensitivity label to an existing team – with existing channel sites – in this case Private channel sites inherit team sensitivity label immediately, but with Shared channel sites it’s strange: GUI shows sensitivity label assigned, but site object model does not.
The error “The term ‘Search-UnifiedAuditLog’ is not recognized”:
Search-UnifiedAuditLog: C:\scripts\PowerShell.auth\Search-AuditLog-w-App.ps1:16:12 Line | 16 | $results = Search-UnifiedAuditLog -StartDate $start -EndDate $end -Re … | ~~~~~~ | The term 'Search-UnifiedAuditLog' is not recognized as a name of a cmdlet, function, script file, or executable | program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
means a proper administrative role (e.g. “Exchange administrator”) is not assigned.
Update (May 2023): You can use Get-PnPAzureACSPrincipal to returns the lists of all Azure ACS principals installed in your Tenant including subsites.
Update: Sites.Selected API MS Graph permissions was introduced by Microsoft in 2021. It was a good move towards site-level development, but still developers were limited with only what MS Graph API provides for SharePoint dev. So devs had to use AppInv.aspx at site level to provide ACS permissions to their apps to be able to use SharePoint CSOM and REST APIs. Recently Microsoft introduced Sites.Selected SharePoint API permissions for registered Azure Apps! So now devs should be fully happy without ACS-based permissions.
Update: I’m not sure when Microsoft implemented that, but I recently found another Record Type – “SharePointAppPermissionOperation”. There is an Activity type – AppPermissionGrant… To be explored…
After all the updates the original article below is probably obsolete…
Scenario
Developers in the organization can use both – Azure Apps and SharePoint Apps to work with SharePoint sites in their “daemon” applications.
It is recommended to use Azure apps so, you want to know – what are SharePoint Apps registered and their owners, who registered SharePoint Apps. Eventually you would disable SharePoint Apps-only principal but before that you’d move Devs from SP-App-only to Azure App (see Disable Custom App Authentication).
(SharePoint App-only service principals aka SP-App-Only are SPN or App registered from within SharePoint using AppRegNew.aspx system page).
One of the approaches is to track Apps/Owners (or who register an app) with Unified Audit Log
returns events with operation = ‘Add service principal.’ Nice, but… if an app was registered in Azure – event contains an UPN under UserIds property:
Unfortunately, in case with registering app in SharePoint, an audit log event will be like:
i.e. UserId registered is “spo_service@support.onmicrosoft.com”, so we do not know who registered a SharePoint-only app
In theory – we could use events recorded immediately before and after “Add service principal” event to track a user and site who has registered a SharePoint-only app… But for me it seems like too complicated for automation.
Instead we can do simple search through audit log for events “AppRegNew.aspx page visited”. This gives us a good approximation of who registered SP-App-only principal. Worst scenario – we reach more people than we really need (including those who started registering sp-app-only but did not complete) but all of them would be definitely our target auditory.
There is a known problem in SharePoint (and Teams*) – complicated permissions system. Site owners/administrators provide access, site contributors upload documents and at any moment nobody knows – who has access to which files. As a result – sometimes sensitive documents become overshared (over-exposed). The biggest concern is when sites content is shared with “Everyone”. How do we know which content is shared with “Everyone”? Is there a report?
Obviously, only data owner knows who should have access to site documents, so we (SharePoint admins) do not fix permissions automatically (until there is a policy), but at least we can help site owners with reports and maybe initiate permissions review for “nasty” sites?
Below I’m sharing 4 possible solutions:
Solution #0 – Out-of-the-box EEEU report, but it comes with Premium license only
Solution #1 – also OotB report that comes with some 3-rd party tools
Solution #2 – PowerShell “Brute force” – free but require advanced skills and efforts
Solution #3 – Search-based – also free, and require less skills and efforts
(*) Microsoft with the introduction of Teams had to simplify permissions in SharePoint – since there should only be 3 types of access levels – owner, member and visitor. It was… in some ways, but in other ways it made things worse.
You are lucky if you can use 3-rd party tools (e.g. ShareGate, SysKit Point, AvePoint, Metalogix etc.), with the ability to get full permissions report. Though – if your m365 environment is not small – there might be a problem to get full permissions report for all tenant sites. Some tools allow you to get tenant-wide permissions report for specific Ids – this option should work better for large environments.
Still there might be another problem. Consider the following. When I say “shared with Everyone” – I actually mean at least 3 possible “everyone” system logins:
Everyone
Everyone except external users
All users
– those are system id’s, but what if there are other ids – e.g. migrated from on-prem or cloud-born custom security groups in tenant that also includes everyone or many users (e.g. dynamic security group that includes all org accounts)?
What if your Identity management operates security groups “All employee” or “Contractors” or “All licensed users”? Do you think these groups can be identified as “Everyone” groups? Do you think it’d be a good idea to check if content is shared with other large groups (not only system Everyone…)? Would you like to run permissions report separately for all groups that include “all” or “almost all” users?
Also, knowing that full reports heavily load the system, 3-rd party tools might by default limit “how deep report is” to the root site and lists/libraries, not including e.g. folders and items. So you might need go to settings and turn on “full deep” option Keep it in mind.
Obviously this option #1 is not free, as it requires licenses to be obtained. And still it worth to consider option 3.
Solution #2 (PowerShell “Brute force”)
You can get full permissions report per site or for entire tenant with PowerShell, which if free… The only you need is to write a script yourself or find existing one. Sounds easy?
Well, first problem is it takes a decent amount of time and competences to write such script. If if you find one – it would require some skills to adopt and run it. Frankly say, I have not seen so far scripts that were out-of-the-box ready to do that job. And it is not a good idea to run scripts you got from internet against your production environment until you understand it tested it and fully confident with.
Another possible problem – size of environment. The script I designed and use to get comprehensive permissions report might run hours against a good site – if I need full details on site/subsites, lists/libraries, folders and list items levels. So if you have less than 1000 sites – probably this approach can fly. But if your environment is 10K+ sites – it will take forever. So the approach might not work for large enterprise environments.
One might say – we can limit report with only root web permissions to get it faster. But this would be not accurate. And what is not accurate in the IT security – leads to even bigger risks. So, we need check permissions up to every item level deep, as even one file with sensitive info shared inappropriately can cause security issue. (Btw, 3-rd party tools usually by default limit reports to libraries level, so check reporting options…)
The other issue with this approach… Let say you got full permissions report… It would look like “resource -> group -> permissions”… How do you know for each group – what is the group in terms of membership?
Ok, if this solution is not easy to get working – what are other options?
Solution #3 (Search-based)
This solution is based on simple but clever idea: why do we need to iterate through all the tenant documents/items if all the content is already crawled by search? Search is also respect permissions. Can we just use search to get files shared with Everyone? Let us see.
What if we use some dummy user account with no specific permissions provided and no group memberships and try to search content on behalf of that account. The idea is if this user can see some data – then these data is open to everyone.
With this option we would use search query “*” and all 5 possible SharePoint entities – driveItem’,’listItem’,’list’,’drive’,’site’ to find everything that is shared with everyone. We’d pull results with paging (we’d use “from” option in a loop to pull all results). After we get all results – we’d select only unique site collections. But! We might have some problems here.
Problem #1. Again, for small environments or if there are not much “Open” sites – it would work. But for large enterprise environments the problem is the same as in “brute force”. Search would returns too many results – and it might take weeks (exact time is unpredictable) to get all of them. (Surely there are sites “legally” shared with everyone, public Office 365 group based sites, communication sites… So your search will be flooded with content from sites you already know are shared with all).
Problem #2. We are getting results with paging. But recently Microsoft started limiting number of returning results. E.g. your search request result might say like “there are 3659735 total hits” but after result number 1000 it just stops returning anything, even with paging.
Solution#3 Option #2 – loop sites
The idea is: why do we need to get all search results if even one result from a site would be enough to put the site to the list of “open” sites. In other words, we do not need all results from the site, we only need to know if there are any results from the site, at least one – so we know if the site is open for everyone or not.
So, consider the following approach:
You get list of all sites in tenant.
You run search request against each site in the loop (e.g. consider KQL option “Site: https://yourTenant.SharePoint.com/sites/YourSite”. If at least something found in the site – add the site to the “Open Sites” list. With this approach you will get list of sites shared with “Everyone…” in a predictable time.
Solution#3 Option #3 – exclude known “open” sites
There are sites “legally” shared with everyone – e.g. corporate portal, department communication sites, public teams, public Viva Engage communities etc. If it is know that these sites are public – you can exclude them from all sites list – so in the “Solution#3 Option #2 – loop sites” – you’d loop only through sites that are not supposed to be public. I know – percentage of “legally public” sites in tenant to all sites is a relatively small number, so should not significantly decrease elapsed time… but still.
Pros and cons of the Solution # 3
Pro 1: the only fast enough (at least predictable time to complete) and accurate enough to rely on solution.
Pro 2: There might be custom security groups intended to hold all or part of the enterprise (e.g. “All employee” or “all contractors”). If the enterprise comprises from several businesses or regions – it might be “All Business 1” or “All EMEA”… you got the idea. So you can tweak this search-based solution by adding your dummy account you are running search on behalf of to some of theses groups to find out if there are resources shared maybe not with everyone but with all “North America based” users or with “all employees”, which might make sense also.
Con 1 : crawling and indexing takes time, so search-based reports can miss recent changes in data and permissions
Con 2: this approach cannot be automated (since we need an interactive authentication). I.e. we need to run it manually every time.
Con 3: After we get all sites shared with everyone – we do not know – at what level permissions are broken and provided to everyone. It might be entire site or one file. It does not really help if you try to get all search results from the site. If you want to know what exactly is shared with everyone – on the site – run permissions report against this site (shortlist of sites).
Notes
Note 1: consider there are resources like “Styles Library” shared with everyone by default, especially on migrated sites
Note 2: this is a separate topic, but consider implementing/using sensitivity labels. At least you can start with high-sensitive sites. With sensitivity labels – site owners/member would know – what kind of site they are working on.
What’s next
Ok, we know list of SharePoint resources shared with everyone, but what would be the next step? Should we communicate to site owners – if so how to let site owners know that there are resources shared with Everyone… on their sites. To be continued…
