From ac7c991c1c069da9d0c13ee0d09a11528ad0bf9f Mon Sep 17 00:00:00 2001 From: Joseph Goydish II Date: Sat, 20 Dec 2025 14:59:03 -0500 Subject: [PATCH] Revise README for CS35L27 Firmware Security Analysis Updated the README to reflect the focus on firmware security analysis and removed sections on undocumented capabilities and vendor review requirements. --- README.md | 72 +++++++++++++++++++++++-------------------------------- 1 file changed, 30 insertions(+), 42 deletions(-) diff --git a/README.md b/README.md index 3bd5c9b..60f7b48 100644 --- a/README.md +++ b/README.md @@ -1,53 +1,41 @@ -# CS35L27 Firmware and Runtime Forensic Analysis +# CS35L27 Firmware Security Analysis -This repository documents the ground-truth results of forensic analysis of the CS35L27 amplifier firmware, configuration, and runtime behavior. -**All observed behaviors, features, and command usage are described strictly as documented in device binaries and operational logs, without speculation or narrative interpretation.** +## Overview ---- - -## Unexplained or Undocumented Capabilities - -During analysis, several **unknown or undocumented technical behaviors and capabilities** were observed, including but not limited to: -- Use of extended/undocumented I2C commands -- Code paths enabling uncommon hardware features (e.g., bidirectional I2S) -- High-frequency toggling of specific GPIO bits - -**These cannot be fully explained based solely on available public documentation and the data present on the device.** - ---- - -### Vendor Review Required - -- The presence of these capabilities and their extensive use at runtime **require clarification from the chip or device vendor** to determine whether they represent intended behavior or pose security/privacy risks. -- **No claims of confirmed vulnerabilities are made in this repository:** rather, there is a strong recommendation that the vendor or a qualified third party review these technical findings to rule out potential backdoors or misuse. - ---- +This repository contains supporting materials and analysis for a hardware and firmware security review of the Cirrus Logic CS35L27 audio codec as deployed in the iPhone 14 Pro Max running iOS 26.2. The work identifies firmware behaviors **consistent with potential covert channel functionality** and documents extended command handlers, state machine routines, GPIO/I2S usage patterns, and statistical anomalies within the production firmware. ## Repository Structure -``` -CS35L27-firmware-analysis/ -├── docs/ -│ └── analysis-methods.md # Data sources and analytic procedures -├── report/ -│ ├── findings.md # Core observed technical findings -│ ├── technical-details.md # Assembly, register, and bit-level details -│ ├── runtime-trace-analysis.md # Objective TraceV3 runtime evidence -│ └── comparison-and-correlation.md # Firmware <-> runtime cross-reference table -``` ---- +- **CS35L27_iPhone14ProMax_PSIRT_Main_Report.md** + Full disclosure report suitable for PSIRT/CERT submission, including risk impact and technical assessment. +- **Appendix_A_disassembly.txt** + Key disassembly excerpts of extended command handlers and buffer logic. +- **Appendix_B_statistical_summary.csv** + Statistical summaries covering register usage, command frequency, and pattern analysis. +- **Appendix_C_firmware_sequences.txt** + Representative event sequences and state-machine evidence observed in the firmware. +- **Appendix_D_methodology.txt** + Methods, analysis environment, and extraction limitations. -**Each file reports only measured, observable facts from the corresponding source(s). No speculation or narrative is included.** +## Key Findings ---- +- **Bidirectional Audio Capability:** + Over 33% of configuration states enable input or microphone sampling modes within the CS35L27 firmware. +- **Extended Handler Exposure:** + Production firmware implements command handlers (e.g., 0xC7 and 0x81) that permit privileged reconfiguration. +- **Behavior Consistent with Potential Covert Channel:** + State machine routines and GPIO/I2S toggling patterns could enable unauthorized audio or data paths. +- **Elevated Statistical Likelihood:** + Pattern analysis suggests purposeful or exploitable logic beyond normal diagnostic or test activity. -*Continue with your “Unexplained or Undocumented Capabilities” and “Vendor Review Required” sections…* +## Intended Audience -## Scope Statement +- Product Security Incident Response Teams (PSIRT) +- Firmware and hardware security researchers +- Auditors of embedded device supply chains -- All findings are based strictly on direct binary and trace analysis—no assumptions or attack scenarios are included. -- This repository is intended as an evidence-based platform for deeper review, vendor clarification, and possible reference device comparison. +## Caveats ---- - -**If you are a vendor, developer, or security professional with access to reference documentation or source code, analysis contributions and clarifications are welcome to aid in definitive assessment.** +- All analysis performed on a production iPhone 14 Pro Max (iOS 26.2), single unit, without a reference/control device. +- Attribution of firmware behaviors is based on static/code and statistical analysis. +- No userland exploit or attack code is included—this research focuses on firmware and hardware level risk.