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# [iOS 18.6.2] System-Wide Trust Collapse via Anchor Corruption and ATS Reset
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**Status:** Confirmed (based on real device logs from 2025‑08‑20)
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**Severity:** Critical
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**Impact:** TLS/ATS, WebKit, iCloud/CloudKit, Accessories (CHIP/Matter), Proximity/Find My, Baseband, Privacy (TCC)
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---
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## Summary
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I identified a critical system-wide trust failure in iOS 18.6.2 triggered by an entitlement validation failure that caused corrupted trust anchor reloading. This state caused trust evaluations to return "OK" despite pending status, effectively disabling certificate validation across multiple security-sensitive subsystems.
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Key observations:
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* `trustd` failed to parse trust anchors: `"Malformed anchor records, not an array"`
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* `securityd` reinitialized client connections, which disabled ATS in `nsurlsessiond`
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* TLS handshakes advanced with "evaluation pending" status, but were still marked "OK"
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* Trust failure affected: WebKit, CloudKit, CHIP/Matter accessories, CommCenter, and `tccd`
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---
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## Root Cause
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At `18:08:00.106`, the following entitlement validation failure occurred for the `financed` process:
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```log
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SecTaskLoadEntitlements: failed to get cs_flags, error=3, pid=294
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```
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Immediately following this, `tccd` incorrectly granted entitlements:
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```log
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tccd: Granting TCCDProcess: identifier=com.apple.financed ... via entitlement 'com.apple.private.tcc.allow'
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```
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This TCC inconsistency triggered a trust subsystem reload, which surfaced malformed trust anchor records:
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```log
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trustd: Malformed anchor records, not an array
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```
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**Conclusion:** The entitlement inconsistency caused `trustd` to reload trust anchors. Because the anchor store was malformed, a system-wide trust failure followed, affecting all trust-dependent services.
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---
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## Timeline of Failure (EDT – 2025‑08‑20)
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| Time | Event |
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| ------------ | ------------------------------------------------------------------------------------------ |
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| 18:08:00.106 | `SecTaskLoadEntitlements` fails with `error=3` for `financed` |
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| 18:08:00.156 | `tccd` grants entitlement anyway |
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| 18:09:03.758 | `trustd` reports: `"Malformed anchor records, not an array"` |
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| 18:09:04.514 | `securityd` spawns new client threads |
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| 18:09:06.654 | `nsurlsessiond`: BoringSSL context rebuilt, ATS disabled |
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| | → `set_ats_enforced = false`, `min_rsa/ecdsa/sigalg = 0` |
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| 18:09:06.565 | TLS: `evaluate_trust_async` returns certificate evaluation result pending |
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| 18:09:03–06 | Subsystems affected: Accessory trust, WebKit churn, CloudKit sync, CommCenter init, `tccd` |
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| 18:09:06.748 | `tccd`: `AUTHREQ_RESULT authValue=2` |
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---
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## Confirmed Affected Components
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* **Trust services:** `trustd`, `securityd`, `secd`, `ctkd`
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* **ATS/TLS clients:** `nsurlsessiond`, `cloudd`, `appstored`, third-party apps
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* **WebKit:** `WebKit.Networking`, `WebKit.GPU` (affecting Safari, Mail, and other WebKit apps)
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* **Accessories and Proximity:** `accessoryupdaterd`, `accessoryd`, `searchpartyd`
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* **Cloud services:** `akd`, `syncdefaultsd`, `ProtectedCloudKeySyncing`
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* **Baseband and radio:** `CommCenter`, QMI lanes
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* **Privacy subsystem:** `tccd`
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---
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## Technical Analysis
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* `trustd` failed to parse the anchor store due to a malformed structure (`not an array`)
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* `securityd` reinitialized and spawned new client threads
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* `nsurlsessiond` rebuilt its SSL context with:
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```
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ATS enforcement = false
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min_rsa_key_size = 0
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min_ecdsa_key_size = 0
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min_signature_algorithm = 0
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```
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* TLS handshakes continued with pending trust evaluation, but were still marked "OK"
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* The broken trust state propagated to multiple subsystems: WebKit, CloudKit, CommCenter, accessories
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---
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## Indicators (Log-Based)
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| Predicate | Description |
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| --------------------------------------------------------------------------------------- | ------------------ |
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| `process == "trustd"` AND eventMessage CONTAINS "Malformed anchor records" | Anchor failure |
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| `process == "nsurlsessiond"` AND eventMessage CONTAINS "set\_ats\_enforced" | ATS reset detected |
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| `eventMessage CONTAINS "certificate evaluation result pending"` | Trust TOCTOU |
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| `process == "accessoryupdaterd"` AND eventMessage CONTAINS\[c] "Certificate is trusted" | Accessory trust |
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| `process == "securityd"` AND eventMessage CONTAINS "SecSecurityClientGet new thread" | Keychain reset |
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---
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## Validation (Logs Only)
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| Validation Check | Confirmed | Evidence |
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| -------------------------------------------------- | --------- | ---------------------------------------------------------- |
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| V‑1: Trigger occurred within 60 seconds of failure | Yes | `SecTaskLoadEntitlements` at 18:08:00.106 |
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| V‑2: Malformed anchor appears <3s before ATS reset | Yes | `trustd` at 18:09:03 → `nsurlsessiond` reset at 18:09:06 |
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| V‑3: Accessory trust occurred during collapse | Yes | `accessoryupdaterd` trusted record at 18:09:03 |
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| V‑4: WebKit activity in failure window | Yes | `WebKit.Networking` and `GPU` churn from 18:08:58–18:09:06 |
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| V‑5: Concurrent activity in Cloud, radio, TCC | Yes | `cloudd`, `CommCenter`, and `tccd` all active at 18:09:06 |
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---
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## Risk Profile
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| Category | Exposure Description |
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| ------------------- | ------------------------------------------------------------------------- |
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| **Confidentiality** | TLS interception (Safari, Mail, WebKit apps), iCloud impersonation |
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| **Integrity** | Accessory provisioning tampering, CloudKit sync spoofing, Find My attacks |
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| **Availability** | Crashes and trust errors in WebKit, accessory setup failures |
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| **Scope** | Affects all layers: trust stack, network, identity, privacy, baseband |
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---
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## Mitigation Guidance
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### For Impacted Devices:
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* **Reboot** the device to restore ATS and trust system state
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* Avoid the following actions during the affected window:
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* Pairing accessories
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* Performing firmware updates
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* Connecting to untrusted or new networks
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### Monitoring Recommendations:
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Set alerts for:
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* `"Malformed anchor records"` in `trustd`
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* `set_ats_enforced = false` in `nsurlsessiond`
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* Trusted accessory certificates issued within ±2 seconds of either event
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---
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## Engineering Recommendations
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* **Fail-closed trust evaluation:** Immediately block certificate validation when anchors cannot be parsed
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* **Lock ATS enforcement parameters post-boot:** Prevent runtime lowering of key size or algorithm floors
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* **Fix TLS trust evaluation TOCTOU flaw:** Prevent handshakes from proceeding with pending evaluations
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* **Harden anchor deserialization:** Add schema validation and crash on unexpected structure
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* **Audit ECDSA encoding fallbacks:** Guard against incorrect fallback between X9.62 and RFC4754
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---
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## Final Confidence Assessment
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| Criterion | Status |
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| ----------------------- | ------ |
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| Confirmed trigger | Yes |
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| Root cause identified | Yes |
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| Cross-subsystem effects | Yes |
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| Reproducible from logs | Yes |
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| Confidence level | High |
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---
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