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authorHarald Welte <laforge@osmocom.org>2019-12-27 15:25:41 +0100
committerHarald Welte <laforge@osmocom.org>2019-12-27 15:25:41 +0100
commitbd4b6a16a75405d5c74609790f2205d319b9242c (patch)
treeceeef312edfbb14766d09e833dfc7def50d0d343
parent0b42584c6d27149af06552d3b3717bf7542d5524 (diff)
WIP: SIM card talk 36C3HEADmaster
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+\documentclass[aspectratio=169,11pt]{beamer}
+\usetheme{default}
+%\setbeamertemplate{frametitle}{}
+\newenvironment{myline}
+ %{\usebeamerfont{frametitle}\usebeamercolor[fg]{frametitle}\vfill\centering}
+ {\usebeamerfont{frametitle}\vfill\centering}
+ {\par\vfill}
+
+\usetheme{Warsaw}
+\usecolortheme{whale}
+
+\title{SIM card technology from A to Z}
+%\subtitle{Subtitle}
+\author{Harald~Welte}
+\date[Dec 2019, 36C3]{Chaos Communication Congress 2019}
+\institute{osmocom.org}
+
+
+\begin{document}
+
+\begin{frame}
+\titlepage
+\end{frame}
+
+
+\begin{frame}{Outline}
+ \tableofcontents[hideallsubsections]
+\end{frame}
+
+
+\begin{frame}{About the speaker}
+\begin{itemize}
+ \item Free Software + OSHW developer for more than 20 years
+ \item Used to work on the Linux kernel from 1999-2009
+ \item working with contact chip cards since ~1999, contactless since ~2006
+ \item developing FOSS in cellular communications (Osmocom) since ~2008
+ \begin{itemize}
+ \item developed various SIM card related tools in software an hardware
+ \end{itemize}
+ \item Living and working in Berlin, Germany.
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Relation of SIM card specifications}
+\includegraphics[width=150mm]{sim_card_specs.png}
+\end{frame}
+
+% from APDU to Z... ?
+
+\begin{frame}{The SIM: Subscriber Identity Module}
+\begin{itemize}
+ \item probably anyone in the audience has at least one, likely more
+ \item ubiquitous; every device withe cellular connectivity has at least one
+ \item not many people outside the telecom industry ever look at them in much detail
+ \item SIM card hacking (in the security sense) has a tradition at CCC since at least 1998
+ \begin{itemize}
+ \item Vodafone Germany SIM card cloning: https://ftp.ccc.de/software/gsm/gsm\_hack.tar.gz
+ \item SIM card simulator in Turbo C (1998): https://ftp.ccc.de/software/gsm/SIM\_sim.zip
+ \end{itemize}
+ \item meanwhile: SIM technology stack is getting more complex and deep
+ \item let's recap what SIM cards actually are, and what they do
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}{Classic SIM in early GSM}
+\begin{itemize}
+ \item Idea of storing subscriber identity predates GSM (e.g. C-Netz since 1988)
+ % c-netz-karte.jpg
+ \item GSM from the very beginning introduces concept of SIM card
+ \item store subscriber identity outside of the phone
+ \item store some network related parameters
+ \begin{itemize}
+ \item static (like access control class)
+ \item dynamic (like TMSI, Kc, ...)
+ \end{itemize}
+ \item full credit card size so it can be used in radios installed in (rented, shared company) cars.
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}{ISO 7816}
+\begin{itemize}
+ \item the {\em mother of all smart card} spec
+ \item "Integrated circuit(s) cards with contacts"
+ \item 15 parts, most relevant are below:
+ \begin{itemize}
+ \item Part 1: Physical characteristics
+ \item Part 2: Dimensions and location of the contacts
+ \item Part 3: Electronic signals and transmission protocols
+ \item Part 4: Interindustry commands for interchange
+ \begin{itemize}
+ \item Why not international inter-industry commands for interworking information interchange? Anyone?
+ \end{itemize}
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{GSM TS 11.11}
+\begin{itemize}
+ \item {\em Specification of the Subscriber Identity Module - Mobile Equipment (SIM-ME) Interface}
+ \item repeats (and some times amends) large portions of 7816-1/2/3/4
+ \begin{itemize}
+ \item Section 4: physical characteristics
+ \item Section 5: electronic signals, transmission protocol
+ \end{itemize}
+ \item but also specifies what makes the SIM a SIM: Information model, file system, commands
+ \item lats, but not least how to execute authentication: RUN GSM ALGORITHM
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Physical Smart Card Interface}
+\begin{itemize}
+ \item Relevant pins:
+ \begin{itemize}
+ \item VCC: Provides supply voltage (5V, 3V or 1.8V)
+ \item CLK: Provides a clock signal ()
+ \item RST: To reset the card
+ \item IO: bidirectional serial communications
+ \end{itemize}
+ \item Activation sequence triggers card to send ATR (Answer To Reset)
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Bit transmission level}
+\begin{itemize}
+ \item despite the clock, communication is asynchronous!
+ \item baud rate derived from divided clock
+ \item no defined phase relationship between clock and data
+ \item serial data is just like UART/RS232, ... but:
+ \begin{itemize}
+ \item one line for both Rx and Tx
+ \item direction changes once after every byte (ACK in T=0)
+ \item direction changes every few bytes (TPDU state machine)
+ \item timings are actually not very well specified
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Smart Card Communication}
+\begin{itemize}
+ \item based on APDU (Application Protocol Data Unit) as per ISO 7816-4
+ \begin{itemize}
+ \item CLA (class byte)
+ \item INS (instruction byte)
+ \item P1, P2 (parameter bytes)
+ \item Lc (command length)
+ \item Command data
+ \item Le (expected response length)
+ \item Response data
+ \item SW (status word)
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Smart Card Transmission Protocol}
+\begin{itemize}
+ \item different protocols transceive APDUs from/to cards
+ \item T=0 most commonly used with SIM cards
+ \item T=1 also possible but rarely used in SIM
+ \begin{itemize}
+ \item specs require phones to implement both T=0 and T=1
+ \item SIM card can be either T=0 or T=1
+ \item T=1 more used in banking / crypto smart card world
+ \end{itemize}
+ \item APDU gets mapped to protocol-specific TPDU (Transmission Protocol Data Unit)
+ \begin{itemize}
+ \item: Example Command TPDU: A0 A4 00 00 02 3F 00
+ \item: Example Response TPDU: 90 00 (just status word)
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Card Filesystem}
+\begin{itemize}
+ \item most smart cards contain file system abstraction
+ \item cannot be mounted (not exposed like a block device / USB drive!)
+ \item access based on file-level commands (analogy: more like MTP/PTP)
+ \item some similarities to general-purpose (computer) OS file systems:
+ \begin{itemize}
+ \item MF: Master File (root directory)
+ \item DF: Dedicated File (subdirectory)
+ \item EF: Elementary File (data file)
+ \end{itemize}
+ \item However, much more comprehensive than computer OS file systems, e.g.
+ \begin{itemize}
+ \item {\em transparent EF}: opaque stream of data, like PC
+ \item {\em linear fixed EF}: fixed-size records, seekable
+ \item {\em cyclic fixed EF}: ring buffer of records, seekable
+ \item {\em incrementable}: for monotonically incrementing counters
+ \end{itemize}
+ \item Each file has Access Control Conditions (ACC)
+ \begin{itemize}
+ \item read/write/update only after PIN1/PIN2/ADM-PIN
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Key SIM Card Commands}
+\begin{itemize}
+ \item SELECT (file)
+ \item READ RECORD / UPDATE RECORD
+ \begin{itemize}
+ \item for record-oriented EF
+ \end{itemize}
+ \item READ BINARY / UPDATE BINARY
+ \begin{itemize}
+ \item for transparent EF
+ \end{itemize}
+ \item CHANGE CHV / DISABLE CHV / ENABLE CHV
+ \begin{itemize}
+ \item CHV: Card Holder Verification (PIN)
+ \end{itemize}
+ \item RUN GSM ALGORITHM
+ \begin{itemize}
+ \item ask SIM to execute authentication algorithm in card
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{SIM card filesystem hierarchy}
+\begin{itemize}
+ \item MF (3F00)
+ \begin{itemize}
+ \item DF\_TELECOM (7F10)
+ \begin{itemize}
+ \item EF\_SMS
+ \item EF\_MSISDN
+ \item ...
+ \end{itemize}
+ \item DF\_GSM (7F20)
+ \begin{itemize}
+ \item EF\_IMSI
+ \item EF\_Kc
+ \item ...
+ \end{itemize}
+ \item EF\_ICCID
+ \item ...
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+
+
+\begin{frame}{3G: ETSI UICC and the 3GPP USIM}
+\begin{itemize}
+ \item The GSM SIM was fully specified by ETSI in TS 11.11
+ \item As GSM specs moved from ETSI to 3GPP, card specs were split:
+ \begin{itemize}
+ \item ETSI UICC (Universal Intergrated Circuit Card)
+ \begin{itemize}
+ \item like a {\em base class} abstacting out those parts that are not cellular
+ related, or at very least not 3GPP network related
+ \end{itemize}
+ \item 3GPP USIM Applicaiton on top of UICC
+ \begin{itemize}
+ \item specifies those parts specifically relevant to 3GPP networks
+ \item implemented in ADF\_USIM (Application Dedicated File)
+ \item ADF can be entered via SELECT, similar to classic DF
+ \end{itemize}
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{4G: The ISIM}
+\begin{itemize}
+ \item 3G/LTE reuses the existing 3G Authentication (UMTS AKA)
+ \item 4G/LTE simply resuses existing USIM
+ \item some new optional files were introduced in ADF\_USIM
+ \item IMS (IP Multimedia System used for not only VoLTE) specifies ISIM application
+ \begin{itemize}
+ \item stores additional IMS related parameters like SIP server / user identity
+ \item presence of ISIM not required for IMS to work
+ \item if present, ISIM application present next to USIM (and possibly SIM)
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{SIM cards in 5G}
+\begin{itemize}
+ \item 5G reuses existing 3G/4G USIM
+ \item some new optional files were introduced in ADF\_USIM
+ \item SUCI (Subscriber Concealed Identifier) can optionally be computed by SIM
+ \begin{itemize}
+ \item this is the only feature requiring different card / apps on card
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}{SIM card hardware}
+\begin{itemize}
+ \item processor core
+ \begin{itemize}
+ \item many different vendors and architectures, from 8-bit 8051 to 32bit ARM
+ \item today quite often ARM SCxxx "Secure Core" family
+ \item documentation on hardware, often even simple one-page data sheets not public
+ \end{itemize}
+ \item built-in RAM
+ \item built-in ROM (at leat boot loader, possibly also OS)
+ \item built-in flash (file system storage, possibly also OS, applications)
+ \item contrary to expensive crypto smart cards, SIM card chip mostly selected purely by low cost
+ \begin{itemize}
+ \item blame pre-paid cards for that
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{SIM card software}
+\begin{itemize}
+ \item Every Smart Card has a Card Operating System (COS)
+ \item Cards without COS are simple memory cards (like I2C eeprom), insufficinet for SIM
+ \item Card OS for Crypto Smart Cards (banking, access control) often publicly known
+ \item SIM Card OS are rarely known / publicly documented or even named
+ \item Example: ARM not only offers SIM card CPU core designs, but also OS (Kigen OS)
+ \item SIM Card OS is {\em implementtaion detail}, almost everything relevant is standardized
+ across OS vendors
+\end{itemize}
+\end{frame}
+
+\begin{frame}{SIM card software modularity}
+\begin{itemize}
+ \item Early SIM cards were (likely) monolithic,
+ \begin{itemize}
+ \item no separation between OS and SIM application
+ \end{itemize}
+ \item Today, SIM cards software is modular
+ \begin{itemize}
+ \item Core OS
+ \item Applications (SIM, USIM, ISIM, ...)
+ \end{itemize}
+ \item traditionally, OS very chip/hardware dependent, non-portable
+ \item traditionally, applications very OS dependent, non-portable
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}{Java Cards}
+\begin{itemize}
+ \item independent of SIM cards, Java Smart Cards have been developed
+ \item based on Java Card Platform specifications by Sun (now Oracle)
+ \item first cards in 1996 by Schlumberger (now Gemalto)
+ \item independent of SIM cards, Java Smart Cards have been developed in 1996 by Schlumberger
+ \item most cards implement GlobalPlatform specifications for vendor-independent management
+ \begin{itemize}
+ \item super constrained, weird subset of Java
+ \item special on-card VM (not normal JVM)
+ \item special CAP format (not normal JAR)
+ \item Idea: Portability of Cardlets (card applications)
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Java SIM Cards}
+\begin{itemize}
+ \item There is no functional requirement for a SIM/USIM/ISIM to be a java card
+ \item In reality, most SIM cards probably are Java Cards these days
+ \item Portability is the main driver here
+ \item Operators want to share same applications over multiple vendors/generations of cards
+ \item 3GPP and ETSI specify Java APIs / packages available specifically on Java SIM cards
+\end{itemize}
+\end{frame}
+
+\begin{frame}{SIM Toolkit (STK) / Card Application Toolkit (CAT)}
+\begin{itemize}
+ \item Ability by card to offer applications with UI/menu on the phone
+ \item New APDUs/Instructions
+ \begin{itemize}
+ \item TERMINAL PROFILE
+ \item ENVELOPE
+ \item FETCH
+ \item TERMINAL RESPONSE
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Proactive SIM}
+\begin{itemize}
+ \item SIM cards are "slave" in the 7816 interface
+ \item All actions are triggered by the phone, card can only respond
+ \item Proactive SIM works around this restriction
+ \item Piggy-backs proactive commands to card responses
+ \item Phone can be requested to poll the SIM if it has some proactive commands pending
+ \item Phone can be requested to provide event notifications
+\end{itemize}
+\end{frame}
+
+\begin{frame}{OTA (Over-The-Air)}
+\begin{itemize}
+ \item Ability for operator to transparently communicate with SIM card in the field
+ \item Based on Proactive SIM
+ \item Can use different transport channels, such as
+ \begin{itemize}
+ \item SMS-PP (normal SMS as you know it)
+ \item SMS-CB (bulk update of cards via cell broadcast)
+ \item USSD
+ \item BIP (via CSD, GPRS)
+ \item now also HTTPS
+ \end{itemize}
+ \item Cryptographic security mechanisms specified, but detailed use up to operator
+ \begin{itemize}
+ \item Message Authentication (optional)
+ \item Message Encryption (optional)
+ \item Replay Protection (optional)
+ \end{itemize}
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Remote File Management (RFM)}
+\begin{itemize}
+ \item Common use case of OTA
+ \item Allows remote read / update of files in file system
+ \item Example: Change of preferred/forbidden roaming operator list
+ \item Example (ancient): Backup of phonebook at operator
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Remote Application Management (RAM)}
+\begin{itemize}
+ \item Common use case of OTA
+ \item Allows remote installation / removal of applications on card
+ \item Example: New multi-IMSI application (MVNOs)
+ \item Example: New STK applications
+\end{itemize}
+\end{frame}
+
+\begin{frame}{S@T}
+\begin{itemize}
+ \item a strange beast specified outside of ETSI/3GPP
+ \item allows SIM toolkit applications without writing Java or native applications
+ \item special byte code format interpreted by S@T browser
+ \item to me, one of those WTF? techologies
+\end{itemize}
+\end{frame}
+
+
+\begin{frame}{The CCC event SIM cards}
+\begin{itemize}
+ \item are Java SIM + USIM cards
+ \item support OTA, RAM, RFM
+ \item you can get the ADM PIN and OTA keys from the event GSM team
+ \item a "hello world" Java applet and tools for installation are provided (thanks to shadytel + Dieter Spaar)
+ \item identities and key data can be modified using Osmocom pySim software
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Further Reading}
+\begin{itemize}
+ \item FIXME
+\end{itemize}
+\end{frame}
+
+\begin{frame}{Thanks}
+Thanks for your attention.
+
+ You have a General Public License to ask questions now :)
+\end{frame}
+
+\end{document}
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