From ce23cc12edce9d717a7f28a2fe6fd301a4f45378 Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Thu, 29 Dec 2016 18:36:31 +0100 Subject: 33c3: add generated html --- 2016/cellular_modems_33c3/33c3-modems.html | 5514 ++++++++++++++++++++++++++++ 1 file changed, 5514 insertions(+) create mode 100644 2016/cellular_modems_33c3/33c3-modems.html (limited to '2016') diff --git a/2016/cellular_modems_33c3/33c3-modems.html b/2016/cellular_modems_33c3/33c3-modems.html new file mode 100644 index 0000000..e735f9b --- /dev/null +++ b/2016/cellular_modems_33c3/33c3-modems.html @@ -0,0 +1,5514 @@ + + + + +Dissecting modern (3G/4G) cellular modems + + + + + + + + +
+

This talk

+
+
    +
  • + +Our motivation + +
    • +
  • + +A bit of History + +
    • +
  • + +Selecting a device + +
    • +
  • + +An unexpected surprise + +
    • +
  • + +Firmware upgrade + +
    • +
  • + +Outlook/Recommendations/Wishes + +
    • +
+
+
+
+

Motivation

+
+
    +
  • + +Implementing GSM specifications for the last decade (OpenMoko, Osmocom) + +
    • +
  • + +8 years since Anatomy of Smartphone Hardware at 25C3 + +
    • +
  • + +7 years since OsmocomBB for GSM + +
    • +
  • + +Used and built M2M devices using 2G modems at work + +
    • +
  • + +so we’re looking for a modem that can be used for + +
      +
    • + +our next-generation M2M/embedded devices + +
      • +
    • + +testing/logging/tracing Osmocom 3G/4G network-side software + +
      • +
    • + +building more tools to help understanding cellular technology + +
      • +
    +
    • +
+
+
+
+

Cellular Modems in M2M

+
+

+images/sl6087_hw.png +

+
    +
  • + +Assume you want to build a M2M device + +
    • +
  • + +Classic approach to M2M/Embedded cellular: + +
      +
    • + +Cellular modem with AT commands over Serial/USB + +
      • +
    • + +Main Processor runs M2M application + +
      • +
    +
    • +
  • + +if you run Application in Modem, you can save PCB space, power and BOM cost + +
      +
    • + +OpenAT by Sierra Wireless + +
        +
      • + +Write C code using OpenAT APIs + +
        • +
      • + +Dynamically loaded into the RTOS + +
        • +
      • + +Runs without privilege separation, MMU + +
        • +
      • + +Protocol to multiplex AT, log, debug + +
        • +
      • + +Discontinued HW platform ⇒ Locked in + +
        • +
      • + +Various other limitations + +
        • +
      +
      • +
    +
    • +
+
+
+
+

Device requirements

+
+

Our requirements for a good modem

+
    +
  • + +Ability to run application code inside modem + +
    • +
  • + +Avoid modem supplier vendor lock-in (EOL, …) + +
    • +
  • + +Get textual logging when handling messages + +
    • +
  • + +Get a copy of the radio network messages and export to GSMTAP + +
      +
    • + +Like Tobias Engels x-goldmon + +
      • +
    • + +But for all GPRS, EGPRS, UMTS and LTE messages + +
      • +
    +
    • +
+
+
+
+

Qualcomm DIAG protocol

+
+
    +
  • + +Qualcomm DIAG in many products (DVB-H, GSM, …) + +
    • +
  • + +Presented by Guillaume Delugre at 28C3 + +
    • +
  • + +Simple HDLC frame (0x7e), cmd, data, CRC16 + +
    • +
  • + +Events, Logging, Command/Response + +
    • +
  • + +Thousands of different message structures + +
    • +
  • + +ModemManager, gsm-parser consume only a small fraction + +
    • +
+

+images/diag_frame.svg +

+
+
+
+

Selecting a device

+
+

+images/28c3_option_stick.png +

+
    +
  • + +Old Option Icon 225 stick exposes DIAG out of the box + +
    • +
  • + +Quectel UC20 (2G+3G) expose DIAG by default + +
      +
    • + +but no LTE support + +
      • +
    +
    • +
  • + +Quectel EC20 (2G+3G+4G) expose DIAG by default + +
      +
    • + +2G, 3G and 4G sounds quite nice + +
      • +
    • + +EC20 not only a LGA solder module but also as mini-PCIe + +
        +
      • + +convenient for early testing / prototyping without custom board + +
        • +
      +
      • +
    +
    • +
+

+images/ec20.png +

+
    +
  • + +EC20 using a Qualcomm MDM9615 chipset + +
      +
    • + +Also used in the iPhone5 + +
      • +
    • + +Almost no documentation on MDM9615 available + +
      • +
    • + +Still, a good candidate for starting our research… + +
      • +
    +
    • +
+
+
+
+

An unexpected surprise

+
+
+
+
+

Firmware update, hints of Linux

+
+
    +
  • + +Got a firmware upgrade to fix stability / bugs + +
    • +
  • + +Looks like it contains traces of Linux? + +
    • +
  • + +Looks like it uses fastboot for the update + +
    • +
  • + +Other people have already found Linux in MDM9615 based products (e.g Mickey Shkatov at DEFCON 23) + +
    • +
  • + +But why would there be Linux inside a Modem? + +
      +
    • + +Qualcomm is known for their REX/AMSS on Hexagon baseband ?!? + +
      • +
    +
    • +
  • + +And if it contains Linux, GPL requires them to mention that, include + License text and provide source code ?!? + +
    • +
+
+
+
+

GPL compliance

+
+
    +
  • + +No written offer, let’s see if it runs Linux + +
    • +
  • + +Armijn Hemels gpltool.git has unyaffs to unpack yaffs + +
    • +
  • + +strings, etc. clearly reveal Linux, glibc, busybox + +
      +
    • + +other interesting strings like AT+QLINUXCMD=? show up + +
      • +
    +
    • +
  • + +The fun and exploration begins… + +
      +
    • + +technical analysis (serial console, firmware reversing, …) + +
      • +
    • + +legal enforcement to get source code of GPL/LGPL components (Harald is founder of gpl-violations.org) + +
      • +
    +
    • +
+
+
+
+

Hardware based analysis

+
+
    +
  • + +mPCIe modules often expose additional signals like PCM audio on + non-standard pins + +
    • +
  • + +existing PC/embedded mainboards don’t use those signals + +
    • +
  • + +create Osmocom mPCIe-breakout board to access those signals + +
    • +
  • + +https://osmocom.org/projects/mpcie-breakout/wiki + +
    • +
+

+images/mpcie_breakout.jpg +

+
+
+
+

Serial Console

+
+
    +
  • + +EC20 solder module documents DBG_UART pinout, but not all modules + have it enabled? + +
    • +
  • + +serial console is at 1.8V, but the 1.8V supply is not accessible (so + not easy to add external level shifter / Vref) + +
    • +
  • + +create Osmocom multi-voltage USB-UART with selectable 1.8, + 2.3, 2.5, 2.8, 3.0 and 3.3V logic level + +
    • +
+

+images/mv_uart.jpg +

+ +
+
+
+

Retro-fitting Serial Console to mPCIe module

+
+
    +
  • + +unfortunately the DBG_UART on the LGA module solder pads is not + exposed to mPCIE + +
    • +
  • + +some soldering required to retro-fit a 2.54mm header: + +
    • +
+

+images/ec20_uart.jpg +

+
+
+
+

GPL compliance

+
+ +
+
I tried instruction above to build yaffs2 for MDM9615, so I downloaded source M9615AAAARNLZA1611161.xml but during compilation I faced some libs that are missing such as libQMI and acdb-loader..
+
+— Tonino Perazzi +
+

+images/qualcom_many_releases.png +

+
+
+
+

GPL compliance

+
+
    +
  1. +

    +Asking for the complete and corresponding source +

    +
      +
    • + +The source code of Qflash tool in Linux is attached, […] + +
      • +
    +
    2. +
  2. +

    +Asking again for the complete and corresponding source +

    +
    3. +
+
+
We never been in legal dispute and we always make sure to understand IPR ahead of using technology belonging to third party.
+
+— Quectel +
+

+images/quectel_ipr.jpg +

+
+
+
+

GPL compliance

+
+
    +
  1. +

    +Asking for the complete and corresponding source +

    +
    +
    We appreciate the efforts that your client had put into the open source +project netfilter/iptable. However, […] your client does not have the right to +empower the copyright. We think software netfilter/iptable is built on +the code operating system GUN/Linux, thus subject to GPL terms, where FSF +requires that each author of code incorporated in FSF projects either +provide copyright assignment to FSF or disclaim copyright. Therefore, +It seems that your client does not have the copyright on netfilter/iptable.
    +
    +As one of the leading providers of wireless solution, Quectel is always +respectful IPR. We would like to compliant with GPL and do some necessary +statements，including a disclaimer or appropriate notices. Under the terms +of GPL, we would like to dedicate Kernel code of EC25x to free software +community.
    +
    +— Quectel +
    +
    2. +
+
+
+
+

GPL compliance

+
+
    +
  1. +

    +Asking for the complete and corresponding source +

    +
    +
    Many thanks for your detailed explanations GPL/LGPL license terms and the practical methods. I will carefully study your suggestions again and find a proper way to open GLP/LGPL licensed software. Basically, we will simply provide a tarball of open source for download at this time. And release the git repositories in next step.
    +
    +— Quectel +
    +
    2. +
  2. +

    +Asking for the complete and corresponding source +

    +
    +
    We are always willing to achieve GPL compliance.
    +
    +— Quectel +
    +
    3. +
  3. +

    +Asking for the complete and corresponding source +

    +
    +
    So we need some time to know of all things and construct the Open Source projects. Within a short time, we cannot construct a perfect web site to present Open Source things now. However, we will continue to do like that.
    +
    +— Quectel +
    +
    4. +
+
+
+
+

GPL compliance

+
+
    +
  1. +

    +Your tarball is missing some files +

    +
    2. +
+
+
We have issued all GPL licensed source code. +We have no the xt_dscp file in the project, and nor Qulacomm. It must be +caused by your compilation environment. +If you have more question or problem during the development with Quectel +module, please add my Skype ID (XXXXX), I will continue to support you +on Skype.
+The email will not discuss the compiling issue any more.
+
+— Quectel +
+
+
+
+

GPL compliance

+
+
    +
  • + +… many months later + +
      +
    • + +we have received various source tarballs + +
      • +
    • + +they contain not only GPL/LGPL code but other FOSS code (thanks!) + +
      • +
    • + +full license compliance still not achieved, but improving… + +
      • +
    +
    • +
  • + +Sierra Wireless Legato is a positive example of a competitor + +
      +
    • + +they not only provide the OE/Linux source but extensive +documentation! + +
      • +
    • + +but they try to lure customers into a proprietary Legato framework, +and thus again vendor-lock-in :( + +
      • +
    +
    • +
+

+images/legato_flash.png +

+
+
+
+

MDM 9615 HW and SW

+
+
+
+
+

Qualcomm Hardware

+
+
    +
  • + +Qualcomm MDM9615 chipset + +
    • +
  • + +Used in the iPhone 5 and automotive + +
    • +
  • + +Modems like Quectel EC20, Sierra Wireless MC7355 + +
    • +
  • + +No public HW documentation?! + +
    • +
  • + +Either not many people study it or are not allowed to share? + +
    • +
+
+
+
+

MDM 9615 HW Overview

+
+
    +
  • + +???? + + + + +
    • +
+
+
+
+

How to access the system?

+
+
    +
  • + +serial console requires soldering re-work and is slow + +
    • +
  • + +easy mechanism to get shell and transfer files from/to target + +
    • +
  • + +Android adbd present on the modem but not exposed via USB + +
    • +
  • + +it’s possible to re-configure the Linux kernel Android USB Gadget: + +
      +
    • + +AT+QLINUXCMD="/usr/bin/usb_uartdiag" + +
      • +
    • + +device re-enumerates with different composite USB interfaces + +
      • +
    +
    • +
  • + +Linux kernel driver on host needs patching (static interface + mapping assumption) + +
      +
    • + +patches available in quectel-experiments.git, documented in wiki + +
      • +
    +
    • +
+
+
+
+

MDM 9615 AP SW Overview

+
+

+images/gandroid_logo.png +

+

The software stack seems to be called Qualcomm LE

+
    +
  • + +Android Bootloader + +
    • +
  • + +Android Linux kernel + +
    • +
  • + +Android Debug Bridge (adb) + +
    • +
  • + +but: GNU libc, busybox userland + +
    • +
  • + +Using OpenEmbedded to build images + +
    • +
  • + +Developed and maintained by Qualcomm + +
    • +
+
+
+
+

Qualcomm Linux kernel overview

+
+
    +
  • + +Qualcomm Android Linux kernel + +
    • +
  • + +Huge changes compared to mainline git diff -w | wc -l + +
      +
    • + +v3.0.21 in EC20: 1.5 million lines + +
      • +
    • + +v3.18.20 in EC25: 1.9 million lines + +
      • +
    +
    • +
  • + +Expected: CPU + peripheral drivers + +
    • +
  • + +Less expected: + +
      +
    • + +smem_log (shared memory logging) + +
      • +
    • + +ipc_log (inter-processOR communication) + +
      • +
    • + +remote spinlocks + +
      • +
    +
    • +
+
+
+
+

Qualcomm Linux kernel subsystems

+
+

Some of the Qualcomm-specific kernel sub-systems

+
+ +++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

SMD

Shared Memory Device

IPC

Inter Processor Communications

RMNET

Remote Network

BAM

Bus Access Manager

IPA

Internet Packet Accelerator

DIAGFWD

DIAG Forwarding

AF_MSM_IPC

Socket family for Qualcomm IPC

+
+
+
+
+

Qualcomm LE System Architecture

+
+

+images/qualcomm_le.svg +

+
    +
  • + +simplified block diagram + +
    • +
  • + +USB interface fully controlled by Linux AP + +
      +
    • + +very complex Qualcomm Android USB Gadget + +
      • +
    • + +some endpoints mapped to SMD queues + +
      • +
    • + +other endpoints handled by regular Linux + +
      • +
    • + +GPS NMEA takes completely different path than AT commands, despite +both being serial ports? + +
      • +
    • + +DIAG and QMI handled in more complex ways + +
      • +
    +
    • +
+
+
+
+

DIAG in Qualcomm LE

+
+
    +
  • + +DIAG interface of Modem exposed on SMD + +
    • +
  • + +diagfwd distributes messages between USB, SMD and /dev/diagchar + +
    • +
  • + +Linux userspace processes don’t use syslog, but diag msg for logging via libdiag.so + +
    • +
+

+images/diag.svg +

+
+
+
+

QMI in Qualcomm LE

+
+

every rmnet data device has associated QMI control

+
    +
  • + +on your Linux PC: qmi_wwan and /dev/cdc-wdm + +
    • +
  • + +on Qualcomm LE modem: /dev/smdcntlN, multiplexed by qmuxd + +
    • +
+

+images/qmi_smd_qmuxd.svg +

+
+
+
+

Tools for analysis

+
+

We created some tools to help our analysis

+
    +
  • + +used OE to build matching opkg and OE packages for socat, lsof, strace + +
    • +
  • + +FOSS programs for the Linux AP linked against proprietary libqmi-framework.so + +
      +
    • + +qmi_test: Simple program to read IMEI via QMI + +
      • +
    • + +atcop_test: Test program to implement AT commands in Linux userspace + +
      • +
    +
    • +
  • + +100% FOSS programs + +
      +
    • + +qmuxd_wrapper: LD_PRELOAD wrapper for tracing between qmuxd and QMI clients + +
      • +
    • + +libqmi-glib transport support for qmuxd (work in progress) + +
      • +
    • + +osmo-qcdiag: Host tool for obtaining DIAG based logs from Linux programs + QMI traces, decoded via libmi-glib + +
      • +
    +
    • +
+
+
+
+

Userspace programs

+
+

We found a bunch of proprietary Linux userspace programs

+
+ +++ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

adbd

Implements Android Debug Bridge

atfwd_daemon

Implement Quectel-Specific AT Commands

quectel_daemon

?; various ASoC related bits

qti

?

mbim

Mobile Broadband IF Model (translates MBIM to QMI)

QCMAP_ConnectionManager

runs linux-base WiFi AP/router with LTE backhaul

quec_bridge

reads GPS NMEA from /dev/nmea and writes it to /dev/ttyGS0

+
+
+
+
+

Funny bits + pieces

+
+
+
+
+

Funny AT commands

+
+
    +
  • + +AT+QLINUXCMD, e.g. switch usb config to get adb + +
      +
    • + +arbitrary shell commands executed as root on r/w rootfs! + +
      • +
    +
    • +
  • + +AT+QFASTBOOT, switch to the bootloader + +
    • +
  • + +AT+QPRINT, print dmesg + +
    • +
  • + +AT for system("echo mem > /sys/power/state") + +
    • +
+
+
+
+

How many processes does it take to reboot a system?

+
+
    +
  • + +rebootdiagapp registers DIAG command (cmd code 0x29) + +
      +
    • + +spawns thread that runs system("qmi_simple_ril_test input=/tmp/reset") + +
      • +
    • + +system("echo 'modem reset' > /tmp/reset") + +
        +
      • + +makes qmi_simple_ril_test send a QMI message to modem + +
        • +
      +
      • +
    • + +system("rm /tmp/reset") + +
      • +
    • + +writes "REBOOT" to /dev/rebooterdev this time using fwrite()! + +
      • +
    +
    • +
  • + +reboot_daemon reads /dev/rebooterdev + +
    • +
+
+
+
read_count = read(pipe_fd,buf,MAX_BUF-1);
+/* if read REBOOT_STR, then call reboot */
+if(strncmp(buf,REBOOT_STR,strlen(REBOOT_STR)) == 0) {
+    debug_printf("going for reboot\n");
+    printf("reboot-daemon: initiating reboot\n");
+    system("reboot");
+}
+
+
+
+
+

C programs that look like shell scripts

+
+
    +
  • + +strings /usr/bin/quectel_daemon + +
    • +
+
+
+
echo "nau8814-aif1" > /sys/devices/platform/soc-audio.0/tx_dai_name
+cp -f /cache/usb/qcfg_usbcfg /etc/; cp -f /cache/usb/usb /etc/init.d/
+echo 90 >/sys/kernel/debug/pm8xxx-pwm-dbg/0/duty-cycle
+pkill -f "/bin/sh /usr/bin/nmea_demon.sh"
+ps ef | grep "quec_bridge /dev/nmea /dev/ttyGS0" | grep -v grep
+cd /cache/ufs;ls
+
+
+
+
+

Firmware upgrade

+
+
+
+
+

recovery and applypatch

+
+
    +
  • + +Qualcomm uses recovery.git from Android ~4.0 + +
    • +
  • + +Updates are zip files with deltas, SHA1+RSA + +
    • +
  • + +recovery started on boot, drives applypatch + +
    • +
+
+
+
// Look for an RSA signature embedded in the .ZIP file comment given
+// the path to the zip.  Verify it matches one of the given public
+// keys.
+
+
+
+
+

Qualcomm EC20 firmware upgrade

+
+

+images/redbend.png +

+
    +
  • + +Based on the recovery.git code + +
    • +
  • + +But for some reason using RedBend for the update (legacy?) + +
    • +
  • + +RSA still linked into the binary but not used + +
    • +
  • + +RedBend used by many more companies and systems (e.g. Quectel UC20, automotive) + +
    • +
+
+
+
+

RedBend (delta update) software

+
+
    +
  • + +Used in OMA DeviceManagement as well? (e.g. Mathew Solnik) + +
    • +
  • + +Lots of starring at hexdumps, lots of help from Dieter Spaar + +
    • +
  • + +Created tools to partially extract and create .diff files + +
    • +
  • + +Heavy in pointers/offsets, not robust + +
    • +
  • + +Crashes on crafted files + +
    • +
  • + +Not cryptographically signed! + +
    • +
+

+images/delta_header.png +

+
+
+
+

Firmware upgrade overview

+
+

+images/upgrade_process.svg +

+
+
+
$ strings atfwd_daemon | egrep  "wget|QCMAP|fota|update.z"
+
+... QCMAP_ConnectionManager /etc/mobileap_cfg.xml n n fotanet
+/usr/bin/wget -T 20 -t 3 %s -O %s
+mv %s %s && mkdir -p /cache/fota && echo %s > %s
+/cache/fota/ipth_config_dfs.txt
+rm -rf /cache/fota /cache/recovery /cache/update.zip
+Start download fota for update.zip
+
+
    +
  • + +atfwd_daemon can be asked to start upgrade + +
    • +
  • + +Configure APN, specify URL, store result to update.zip + +
    • +
  • + +Add status and reboot to recovery + +
    • +
  • + +Apply update.zip and reboot + +
    • +
+
+
+
+

Recommendation to modem vendors

+
+
    +
  • + +It is great to have an open and accessible Qualcomm based modem for + further research and developing custom applications/extensions + +
    • +
  • + +Security issues (particularly unverified FOTA) must be fixed + +
    • +
  • + +We need security from attackers without locking out the user/owner + +
      +
    • + +If vendors introduce verified boot and/or FOTA, allow owner specified keys! + +
      • +
    +
    • +
  • + +Please keep it open, good for learning and many applications + +
    • +
  • + +Allow owners to modify the software of their device + +
    • +
  • + +Secure the FOTA upgrading with owner specified keys + +
    • +
+
+
+
+

Status and Outlook

+
+
    +
  • + +Status today + +
      +
    • + +Osmocom wiki with all our findings public now! + +
      • +
    • + +debug tools (osmo-qcdiag, LD_PRELOAD wrapper, qmi_test, etc.) released + +
      • +
    • + +mpcie-breakout + mv-uart released + available + +
      • +
    • + +libqmi-glib integration WIP + +
      • +
    +
    • +
  • + +Outlook + +
      +
    • + +we hope to grow documentation in wiki + +
      • +
    • + +please help us out: read code, play with devices + update wiki + +
      • +
    • + +OE/opkg package feed planned + +
      • +
    • + +aim is to have 100% FOSS userland on Cortex-A5 + +
      • +
    +
    • +
+
+
+
+

Unrelated Announcement

+
+
    +
  • + +Osmocom project has gained support for 3G/3.5G during 2016 + +
    • +
  • + +Osmocom suffers from lack of contributions :( + +
    • +
  • + +We want to motivate more contributions + +
      +
    • + +Accelerate 3.5G programme provides 50 free 3.5 femtocells to contributors + +
      • +
    • + +tell us how you would use your free femtocell to improve Osmocom + +
      • +
    • + +Call for Proposals runs until January 31st, 2017. + +
      • +
    • + +see http://sysmocom.de/downloads/accelerate_3g5_cfp.pdf + +
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    • +
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+

Questions

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    +
  • + +Questions? + +
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Links

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+ + -- cgit v1.2.3