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Addresses SpecterOps#4 Microsoft's AD DS tier model lists AD FS by name under Tier 0, the identity control plane, the same list that already justifies the existing Entra Connect entry. Admin on the AD FS server lets an attacker decrypt the token-signing key (from process memory, or via the AD FS service account's access to the Distributed Key Manager key in AD plus the encrypted key in the configuration database) and mint Golden SAML tokens for any user against any relying party AD FS trusts, including Entra ID Global Administrator when federated. The backing configuration database is scoped IT DEPENDS rather than YES by default: most farms run on WID, local to the AD FS server and readable only by its service account, so the database server asset doesn't exist in most deployments. It only appears once a farm is large enough to need a full SQL Server backend, and even then DB access alone can't forge tokens without the DKM key from AD, but it exposes the encrypted key blob to a separate, often broader admin population.
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Included review availability: Your plan provides up to 2 included reviews per hour; 0 remain after this review. WalkthroughThe Tier Zero table now classifies AD FS servers based on federation, relying-party trusts, and service-account membership. It adds a Tier Zero classification for dedicated SQL configuration database servers when a farm uses SQL instead of WID. It also adjusts the indentation of an existing vCenter entry. ChangesAD FS Tier Zero classification
Priority: ⬆️ High Estimated code review effort: 2 (Simple) | ~10 minutes Change: Feature Merge Risk: ⚪ Minimal · up to The new entries are conditional, and no concrete issue is established that would hold up merging after normal checks. Security Architecture ReviewSecurity architecture risk: 🔵 Low · up to The new entries affect security inventory decisions, but do not change access controls or deployment behavior. One classification needs a clearer basis: the SQL server is labeled Tier Zero whenever present even though the entry says database access alone cannot forge tokens. Retained concerns
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Inline comments:
In `@TierZeroTable.json`:
- Line 903: Update the Description entry for AD FS configuration storage to
describe SQL Server as an optional backend available to farms of any size, while
noting that larger farms require it instead of WID. Preserve the existing
details about the configuration database and encrypted token-signing key.
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CodeRabbit correctly flagged that SQL Server isn't only used once a farm exceeds WID's limits. Microsoft's docs also list it as an available choice for smaller farms wanting high availability, SAML artifact resolution, or token replay detection, none of which WID supports. Reworded so the entry doesn't imply small SQL-backed farms should be excluded from inventory.
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Inline comments:
In `@TierZeroTable.json`:
- Line 935: Update the two AD FS description entries to qualify WID/DKM
decryption and storage claims as applying only to automatically generated, AD
FS-managed token-signing certificates. Clarify that externally enrolled
certificates use their configured cryptographic provider and that HSM-backed
keys do not follow the process-memory or WID/DKM recovery path, while preserving
the Tier Zero classification and existing farm/database details.
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CodeRabbit correctly flagged that the WID/DKM decryption path only applies to AD FS's default, automatically generated token-signing certificate. A custom certificate keeps its private key in the local certificate store or an HSM instead, which doesn't follow that path. Qualified both entries accordingly.
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ADFS should be Tier Zero by default, but I think that it might be technically possible for ADFS to not be Tier Zero. For instance, I assume it's possible to have a configuration where no downstream Tier Zero accounts are managed via ADFS. What are your thoughts @chryzsh? |
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However, if the service account is member of Key Admins, then it should be Tier Zero regardless |
JonasBK pointed out AD FS's Tier Zero reach depends on what trusts it, unlike a domain controller or Entra Connect, so a config with no Entra federation and no privileged relying party wouldn't reach Tier Zero. Changed to IT DEPENDS with three conditions: Entra ID federated through it, a relying party trust granting Tier Zero-equivalent access, or the AD FS service account being a member of Key Admins/Enterprise Key Admins, which on-premises WHFB Key Trust deployments require and which gives a Shadow Credentials path independent of federation scope.
Say plainly what depends on what: relying parties and Entra federation for AD FS, versus a domain controller holding every credential in the domain regardless of configuration.
State the condition directly instead of the formal legalistic phrasing.
Drop the "but its reach depends on" staging and state the three Tier Zero conditions and the domain controller comparison as plain facts, split into short paragraphs by topic (classification, Golden SAML mechanism, Key Admins path).
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That's a fair point, it's only Tier Zero if Entra ID is federated through it, or a relying party trust grants access equivalent to a Tier Zero principal. Reworded it to IT DEPENDS on those two conditions, plus a third: if the AD FS service account is in Key Admins, which on-prem WHFB Key Trust deployments require. |
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Inline comments:
In `@TierZeroTable.json`:
- Line 939: Update the rationale text to qualify the msDS-KeyCredentialLink
Shadow Credentials path as applying to inheriting, unprotected user objects, and
note that protected accounts require effective write permission through
AdminSDHolder. Keep Key Admins or Enterprise Key Admins membership as an
independent Tier Zero condition for the AD FS service account.
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CodeRabbit correctly noted the Shadow Credentials write only reaches unprotected users, since AdminSDHolder-protected accounts have inheritance disabled and their ACLs reset hourly by SDProp. Key Admins and Enterprise Key Admins are themselves on Microsoft's protected accounts and groups list, the same list every other AdminSDHolder- protected group in this table is on, so that's the actual basis for treating AD FS service account membership in them as Tier Zero, not what the group's ACE can reach. Swapped the shadow-credentials reference for Microsoft's protected accounts and groups appendix.
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Side note while working through this: Key Admins and Enterprise Key Admins are on Microsoft's own protected accounts and groups list, same as Domain Admins, Account Operators, etc., but neither has its own entry in this table yet. Might be worth a separate PR to add them ... I guess. |
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Addresses #4
Microsoft's AD DS tier model lists AD FS by name under Tier 0, the identity control plane, the same list that already justifies the existing Entra Connect entry. Admin on the AD FS server lets an attacker decrypt the token-signing key (from process memory, or via the AD FS service account's access to the Distributed Key Manager key in AD plus the encrypted key in the configuration database) and mint Golden SAML tokens for any user against any relying party AD FS trusts, including Entra ID Global Administrator when federated.
I defined the backing configuration database as IT DEPENDS rather than YES. Because most ADFS farms run on WID (Windows Internal Database), local to the AD FS server and readable only by its service account, so the database server asset doesn't exist in most deployments. It is only relevant once a farm is large enough to need a full SQL Server backend, and even then DB access alone can't forge tokens without the DKM key from AD. However, the database does expose the encrypted signing key blob to the SQL admins, who may be different to whoever has local admin on the AD FS server itself.
Summary by CodeRabbit
sysadminordb_owneraccess can expose the encrypted signing-key blob; the AD Distributed Key Manager key is also required.