UDS Scanning#

Security Access and System States#

System States#

Table 5 Summary of state modifying services in UDS and GMLAN.#

UDS

GMLAN

10h

DiagnosticSessionControl

10h

InitiateDiagnosticOperation

11h

ECUReset

27h

SecurityAccess

27h

SecurityAccess

28h

CommunicationControl

28h

DisableNormalCommunication

31h

RoutineControl

34h

RequestDownload

3Eh

TesterPresent

3Eh

TesterPresent

A5h

ProgrammingMode

Security Access#

A categorization of reverse-engineered security access functions delivered the following groups:

  • Simple Arithmetic Operations This group contains security access algorithms based on single arithmetic operations such as XOR, NOT, or ADD with a fixed value. Examples are given by the work of Dürrwang et al. and Nie et al. [DBR+18, Lab16]:

    \[key = \neg seed\]

    Implemented often because of an example in a older standard.

  • Mathematical Operations The security access mechanism of one analyzed OEM relies on complex mathematical operations. To obtain a key for this ECU, one needs to know five different numeric values which act as a shared secret. With this secret, a random seed has to be multiplied in different ways to obtain a valid key. An example operation for this group can be the following:

    \[key = (seed * secret1 + secret2) \bigoplus (seed * secret3 + secret4) \bigoplus secret5\]
  • Proprietary XOR-Shift-Loop Security access algorithms for this group were analyzed in-depth by Van den Herrewegen et al. [VdHG18]. Their publication provides examples as well as a cryptographic analysis. Another example is the VWAG SA2 algorithm.

  • Cryptographic Operations One analyzed OEM relies on cryptographic authentication mechanisms for its security access algorithms. The following equation shows an example:

    \[key = RSA_{sign}(MD5(seed~|~salt), {private\_key})\]
  • UnlockECU A collection of Security Accesses can be found under UnlockECU.

../../_images/E1-with-labels.png

Fig. 60 Automatically reverse-engineered system state graph of an ECU. Reset through power cycle is represented by the red dotted lines. Blue lines indicate Security Access (SA) authentication. Diagnostic Session Control (DSC) transitions are shown by the green lines. TP stands for Tester Present.#

Your Friend:

scanner.state_graph.render(view=False)

Extracting information from log files#

  • Ecu utility allows to analyze log files

  • verbose prints packet and state

  • logging creates a log with timestamps and packets

  • store_supported_responses creates a list of all answered responses. This can be used to create an EcuAnsweringMachine on the fly.

from scapy.all import *

load_contrib("isotp")
load_contrib("automotive.uds")
load_contrib("automotive.uds_ecu_states")
load_contrib("automotive.uds_logging")
load_contrib("automotive.ecu")

with PcapReader("ecu_trace.pcap.gz") as sock:
    udsmsgs = sniff(session=ISOTPSession(use_ext_address=False, basecls=UDS), count=50, opened_socket=sock)
 
ecu = Ecu(store_supported_responses=False)
ecu.update(udsmsgs)
 <UDS  service=DiagnosticSessionControl |<UDS_DSC  diagnosticSessionType=extendedDiagnosticSession |>>
 <UDS  service=DiagnosticSessionControlPositiveResponse |<UDS_DSCPR  diagnosticSessionType=extendedDiagnosticSession sessionParameterRecord=b'\x002\x01\xf4' |>>
session3 <UDS  service=RoutineControl |<UDS_RC  routineControlType=startRoutine routineIdentifier=0x203 |>>
session3 <UDS  service=RoutineControlPositiveResponse |<UDS_RCPR  routineControlType=startRoutine routineIdentifier=0x203 |>>
session3 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
session3 <UDS  service=ControlDTCSetting |<UDS_CDTCS  DTCSettingType=130 DTCSettingControlOptionRecord=b'\xff\xff\xff' |>>
session3 <UDS  service=NegativeResponse |<UDS_NR  requestServiceId=ControlDTCSetting negativeResponseCode=requestCorrectlyReceived-ResponsePending |>>
session3 <UDS  service=ControlDTCSettingPositiveResponse |<UDS_CDTCSPR  DTCSettingType=off |>>
session3 <UDS  service=CommunicationControl |<UDS_CC  controlType=129 communicationType0=ISOSAEReserved communicationType1=0 communicationType2=Disable/Enable specific subnet |>>
session3 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
session3 <UDS  service=DiagnosticSessionControl |<UDS_DSC  diagnosticSessionType=programmingSession |>>
session3 <UDS  service=NegativeResponse |<UDS_NR  requestServiceId=DiagnosticSessionControl negativeResponseCode=requestCorrectlyReceived-ResponsePending |>>
session3 <UDS  service=DiagnosticSessionControlPositiveResponse |<UDS_DSCPR  diagnosticSessionType=programmingSession sessionParameterRecord=b'\x002\x01\xf4' |>>
session2 <UDS  service=SecurityAccess |<UDS_SA  securityAccessType=17 securityAccessDataRecord=b'' |>>
session2 <UDS  service=SecurityAccessPositiveResponse |<UDS_SAPR  securityAccessType=17 securitySeed=b'\x00\x03.i' |>>
session2 <UDS  service=SecurityAccess |<UDS_SA  securityAccessType=18 securityKey=b'\xd4\xb2f\x82' |>>
session2 <UDS  service=SecurityAccessPositiveResponse |<UDS_SAPR  securityAccessType=18 |>>
security_level18session2 <UDS  service=WriteDataByIdentifier |<UDS_WDBI  dataIdentifier=0xf15a |<Raw  load=b'\x18\x10\x08\x00\x00\x01\x00\x16/' |>>>
security_level18session2 <UDS  service=WriteDataByIdentifierPositiveResponse |<UDS_WDBIPR  dataIdentifier=0xf15a |>>
security_level18session2 <UDS  service=RequestDownload |<UDS_RD  dataFormatIdentifier=noCompressionNoEncryption memorySizeLen=4 memoryAddressLen=1 memoryAddress1=0xa memorySize4=0x100 |>>
security_level18session2 <UDS  service=RequestDownloadPositiveResponse |<UDS_RDPR  memorySizeLen=2 reserved=0 maxNumberOfBlockLength=b'\x0f\xf9' |>>
req_download{'service': 52}security_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
req_download{'service': 52}security_level18session2 <UDS  service=TransferData |<UDS_TD  blockSequenceCounter=1 transferRequestParameterRecord=b'\x19\xb1B\xe2\xael\xabOik>\x9c\xb28#1q\x1ev\x8fk\x92\xe0Y\xc7\xd7\xef\xf6\x1c0\xf0P\xe9\xb7#\x1e\x01\xb0/\xe5\x82\xf4=|\xf3\xd9\xdb/\x9a\xac\xea\xbc"\xdf\xa3\xd1\x84\x83\xad\xc0\xbb\x9b\xf6\x00#\xb3sV0\x1c\x1a$-&\xc1^XkI\xe1\xbbS\x14\xaf@\xf3a\xb4\x14\xab\x17!\x16Y\xd2\xb9@::O\xfb\xcd\x14l\xd3\xc5\x92\xbe\xec[\x828\xb3\xfb\n\xcc\xb8(\x92\x1f8\x8b\ts\xb6k>f\x9d\x00\x8d\xf7S1v\x9egx\x05\xfa\x12\xdb\x18Y\xc0\x9f\xf6\xbf\xea\x11Z\xb9\x93\x87\x81`\xb2\x14\xfa\x97D\xc3\xd7[\x81PlN5C\xa4\x18\xe9\xd6XV9\xf5P)\x11\xca7\x9d8\xd0w\xf9\xb0\xda\xe5\x98+:\x89(\xd7\xc7\x1d\xd9\xc9\xeaYe%\xd4\xef\xfd\x85\x11\x95g/:"\x81\xfe\xa8\xde\x19\xc2:aH\xf8\xdc\xdf\x8bS\xa0\xd4\xc0\xaf\t\x03\xf3\x90\x06\xc5\x0f\x92g\xfd3~\xa6\x9bK_\xc6\xc0\x90\x92A;\'' |>>
req_download{'service': 52}security_level18session2 <UDS  service=TransferDataPositiveResponse |<UDS_TDPR  blockSequenceCounter=1 transferResponseParameterRecord=b'' |>>
req_download{'service': 52}security_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
req_download{'service': 52}security_level18session2 <UDS  service=RequestTransferExit |>
req_download{'service': 52}security_level18session2 <UDS  service=RequestTransferExitPositiveResponse |>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RoutineControl |<UDS_RC  routineControlType=startRoutine routineIdentifier=0x202 |<Raw  load=b"t\xdb\xf3EW\tBEM\xc4\xf6\xd0\xa3h\x11-PqY\xc5\xdc\xa8g\xaaI4;\x13\xf1+#e\xa9'x\xf0\xe2I<xGt\n\xc57\x7fmDe\xf1!\x7f\x91\x89\x83}\x12\x11\xde\x1aSE\x91\x0c]\xcdf\x80_\xa9\xf7+\xe6u$\xa5^\xa3\xd0\xa2\x1a\x0eN\xde/\x14\x19A\xa2\x18bx!!\xac\xfaC.\xd2\xfc\xc6\x82\xee!\xb4\x1a\xe1\x16\x82D\x82a!\x8d\xf5\x86aJ\xb9\xb9\xb5\xcc4`m\xb5V3" |>>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RoutineControlPositiveResponse |<UDS_RCPR  routineControlType=startRoutine routineIdentifier=0x202 |<Raw  load=b'\x00' |>>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RoutineControl |<UDS_RC  routineControlType=startRoutine routineIdentifier=0xff00 |<Raw  load=b'\x01\x05' |>>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RoutineControlPositiveResponse |<UDS_RCPR  routineControlType=startRoutine routineIdentifier=0xff00 |<Raw  load=b'\x00' |>>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RequestDownload |<UDS_RD  dataFormatIdentifier=noCompressionNoEncryption memorySizeLen=4 memoryAddressLen=1 memoryAddress1=0x5 memorySize4=0x4 |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RequestDownloadPositiveResponse |<UDS_RDPR  memorySizeLen=2 reserved=0 maxNumberOfBlockLength=b'\x0f\xf9' |>>
download_complete{'service': 52}req_download{'service': 52}security_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
download_complete{'service': 52}req_download{'service': 52}security_level18session2 <UDS  service=TransferData |<UDS_TD  blockSequenceCounter=1 transferRequestParameterRecord=b'0321' |>>
download_complete{'service': 52}req_download{'service': 52}security_level18session2 <UDS  service=TransferDataPositiveResponse |<UDS_TDPR  blockSequenceCounter=1 transferResponseParameterRecord=b'' |>>
download_complete{'service': 52}req_download{'service': 52}security_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
download_complete{'service': 52}req_download{'service': 52}security_level18session2 <UDS  service=RequestTransferExit |>
download_complete{'service': 52}req_download{'service': 52}security_level18session2 <UDS  service=RequestTransferExitPositiveResponse |>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RoutineControl |<UDS_RC  routineControlType=startRoutine routineIdentifier=0x202 |<Raw  load=b'\r_Q\x0e\x9e\xfd>\xea\x90\x9df3\xa680]\xe0x\xcd8\xcat\x1f\x82s\x99zk(\x127#\xb0X\xa3\xff\x83\xa9Dk\xc6\xb5\xde\x86xT\xb0.V\xbb\xb6\xaf\xbe!\xb9\xbe\xef\xb1\xcd\r^K\xa5\x96\xf0z\xe6\x15q\x15)U\xcdsF\xffR\xbc\x0e\xe5\x1b^\xf9\xcc\x8b\xd2\xa9\xb4\xb1\xd1!\xf5\xd6U]\xccU\x0c\xbf\xe5\xfe\x81\x84\xeau]\x85\x8c\xdb\x84\x0c\x87\xe8\xe01\xeb\x89\xbb\xcae-\xe4\xe8\xe3n\x11p&' |>>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RoutineControlPositiveResponse |<UDS_RCPR  routineControlType=startRoutine routineIdentifier=0x202 |<Raw  load=b'\x00' |>>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=RoutineControl |<UDS_RC  routineControlType=startRoutine routineIdentifier=0xff00 |<Raw  load=b'\x01\x01' |>>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=NegativeResponse |<UDS_NR  requestServiceId=RoutineControl negativeResponseCode=requestCorrectlyReceived-ResponsePending |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=NegativeResponse |<UDS_NR  requestServiceId=RoutineControl negativeResponseCode=requestCorrectlyReceived-ResponsePending |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=NegativeResponse |<UDS_NR  requestServiceId=RoutineControl negativeResponseCode=requestCorrectlyReceived-ResponsePending |>>
download_complete{'service': 52}req_downloadsecurity_level18session2 <UDS  service=TesterPresent |<UDS_TP  subFunction=128 |>>

Attacks on UDS and GMLAN#

From Automated Threat Evaluation of Automotive Diagnostic Protocols:

Abbiveratons:

  • dos-flood, CWE-400, DoS caused by flooding with a large number of legitimately formatted requests/etc.; normally DoS is a crash, or spending a lot more time on a task than it ‘should’

  • infoleak, CWE-205, CWE-212, CWE-203, CWE-209, CWE-207, CWE-200, CWE-215, others, Information leak by a product, which is not the result of another vulnerability; typically by design or by producing different ‘answers’ that suggest the state; often related to configuration / permissions or error reporting/handling.

  • crypt, CWE-310, CWE-311, CWE-347, CWE-320, CWE-325, Cryptographic error (poor design or implementation), including plaintext storage/transmission of sensitive information.

  • pass, CWE-259, Default or hard-coded password

  • rand, CWE-330, CWE-331, CWE-332, CWE-338, CWE-342, CWE-341, CWE-339, others, Generation of insufficiently random numbers, typically by using easily guessable sources of ‘random’ data

  • int-overflow, CWE-190, A numeric value can be incremented to the point where it overflows and begins at the minimum value, with security implications. Overlaps signedness errors.

  • buf, CWE-119, CWE-120, Buffer overflow

  • phys, Custom, indicates that this service of a diagnostic protocol can cause a physical action on a vehicle

  • upload, CWE-434, Product does not restrict the extensions for files that can be uploaded to the web server, leading to code execution if executable extensions are used in filenames, such as .asp, .php, and .shtml.

UDS

GMLAN

Type

Descriptions and references for the combination of flaw types with UDS/GMLAN services

10h

10h, A5h

dos-flood

These commands will change the session of an ECU. This command’s actual impact can reach from no effect in the functionality to the execution of a different firmware or the ECUs bootloader. Miller & Valasek and Nie et al. used this service to disable (DoS) individual ECUs [MV16, SN17].

11h

dos-flood

During a reset, an ECU is unavailable. Researchers from Keen Labs were able to trigger this function at any speed of a vehicle. Unavailability of safety-critical ECUs in extreme driving conditions can cause serious dangers [CWZ19].

19h, 22h, 23h, 24h, 2Ah, 2Ch, 86h

12h, 1Ah, 22h, 23h, 2Ch, 2Dh, A9h, AAh

infoleak

These commands can be used to gather internal information about an ECU. This can be used to obtain static information (VIN, software versions, etc.), dynamic information to understand the internal behavior of an ECU, or even to extract the entire firmware [PC18].

27h

27h

crypt

Van den Herrewegen et al. and Dürrwang et al. demonstrated impacts of weak cryptographic implementations [DBR+18, VdHG18].

pass

Miller & Valasek revealed many hard-coded cryptographic secrets inside an ECUs firmware [MV13].

rand

Nie et al. analyzed weak security access implementations and showed the lack of random seed creation [SN17].

28h

28h

dos-flood

This service grants the total bandwidth of the CAN bus to only one ECU. Attackers can prevent ECUs from communicating, which causes a DoS of the attacked ECU [KoscherCzeskisRoesner+10].

2Dh

int-overflow

his service specification describes two possible use-cases, clearing of non-volatile memory and changing of calibration values [ISOCSecretary12]. Both use-cases can be used to cause program flow corruptions, e. g. integer- or buffer-overflows.

buf

See above. Identical to int-overflow.

2Eh

3Bh

int-overflow

Identifiers can be any payload. The protocol specifications are very generic for these commands. If a data-identifier is mapped to numeric values, it might be possible that these values can trigger execution errors, such as integer overflows.

phys

Cai et al. demonstrated the manipulation of the driver’s seat position through this service [CWZ19].

buf

Payloads can contain complex data, e. g. certificates or ring buffer contents. Increasing data size and complexity leads to more likelihood of security flaws in interpreters and parsers. Additionally, writable memory areas allow attackers to place exploit code into known and defined memory sections.

2Fh

phys

Miller & Valasek demonstrated the control of a vehicle’s pre-collision system seat belt functionality. This proves the possibility to trigger physical actions through this service [MV13].

31h

dos-flood

Miller & Valasek identified sub-functions that allow the erase of an ECUs memory. Such an operation would brick an ECU and lead to the entire vehicle’s unavailability [MV16].

buf

RoutineControl jobs accept individual payloads with various lengths. The more complex data leads to a higher likelihood of implementation flaws. Cai et al. demonstrated an insecure implementation, combined with a TOCTOU attack, which led to code execution [CWZ19].

phys

RoutineControl jobs can be used to control actuators on a vehicle. Miller & Valasek were able to kill a vehicle’s engine [MV13]. Dürrwang et al. showed the deployment of airbags through insecure implementations of RoutineControl jobs [DBR+18].

infoleak

The sub-function requestRoutineResults can potentially leak sensitive data.

34h

34h

upload

These commands are intended to initiate a software update. Miller & Valasek and Van den Herrewegen et al. demonstrated arbitrary code execution by abusing this command [MV16, VdHG18].

35h

infoleak

This command could be used to leak internal information of an ECU.

36h, 84h

36h

buf

These commands are part of the update process. An implementation flaw is unlikely; nevertheless, buffer overflow vulnerabilities are potentially possible.

87h

dos-flood

Allows the modification of communication parameters. Attackers can prevent an ECU from communicating by providing an invalid configuration.

AEh

phys

Koscher et al. demonstrated the possibility of triggering physical actions on ECUs [KoscherCzeskisRoesner+10].

dos-flood

The GMLAN standard describes the possibility to trigger an ECU reset [GMW18].

Scanning#

  • Scapy contains a powerful scanner library for automotive protocols

  • UDS_Scanner or GMLAN_Scanner are the executors of TestCases

  • Enumerators derive from TestCases

  • Every enumerator scans a different UDS or GMLAN service

  • Since some services generate new states, the specific enumerators evaluate an ECUs response and generate a system state graph.

Example#

    from scapy.all import *

    conf.contribs['CANSocket'] = {'use-python-can': False}
    conf.contribs['ISOTP'] = {'use-can-isotp-kernel-module': True}
    from scapy.contrib.isotp import *
    from scapy.contrib.automotive.uds_scan import *

    sock = ISOTPNativeSocket("can0", tx_id=0x6f1, rx_id=0x610, ext_address=0x10, rx_ext_address=0xf1, basecls=UDS)
    s = UDS_Scanner(sock, test_cases=[UDS_ServiceEnumerator])
    s.scan(timeout=10)
    s.show_testcases()

Output:

    ============================================================
         Available services and negative response per state
    ------------------------------------------------------------

    128 requests were sent, 128 answered, 0 unanswered Statistics per state
    -------------------+---------+----------+
                       | all     | session1 | 
    -------------------+---------+----------+
    answertime_avg     | 0.00077 | 0.00077  | 
    answertime_avg_nr  | 0.00077 | 0.00077  | 
    answertime_avg_pr  | -       | -        | 
    answertime_max     | 0.0012  | 0.0012   | 
    answertime_max_nr  | 0.0012  | 0.0012   | 
    answertime_max_pr  | -       | -        | 
    answertime_min     | 0.0007  | 0.0007   | 
    answertime_min_nr  | 0.0007  | 0.0007   | 
    answertime_min_pr  | -       | -        | 
    num_answered       | 128     | 128      | 
    num_negative_resps | 128     | 128      | 
    num_unanswered     | 0       | 0        | 
    -------------------+---------+----------+

    128 negative responses were received

    These negative response codes were received 0x11 0x13 0x7f
        NRC 0x11: serviceNotSupported received 111 times
        NRC 0x13: incorrectMessageLengthOrInvalidFormat received 10 times
        NRC 0x7f: serviceNotSupportedInActiveSession received 7 times


    The following negative response codes are blacklisted: 
        ['generalReject', 'serviceNotSupported']



    ---------------------------------+-------------------------------------------+
                                     | session1                                  | 
    ---------------------------------+-------------------------------------------+
    0x10: DiagnosticSessionControl   | NR: incorrectMessageLengthOrInvalidFormat | 
    0x11: ECUReset                   | NR: incorrectMessageLengthOrInvalidFormat | 
    0x14: ClearDiagnosticInformation | NR: incorrectMessageLengthOrInvalidFormat | 
    0x19: ReadDTCInformation         | NR: incorrectMessageLengthOrInvalidFormat | 
    0x22: ReadDataByIdentifier       | NR: incorrectMessageLengthOrInvalidFormat | 
    0x27: SecurityAccess             | NR: serviceNotSupportedInActiveSession    | 
    0x28: CommunicationControl       | NR: serviceNotSupportedInActiveSession    | 
    0x2e: WriteDataByIdentifier      | NR: incorrectMessageLengthOrInvalidFormat | 
    0x31: RoutineControl             | NR: incorrectMessageLengthOrInvalidFormat | 
    0x34: RequestDownload            | NR: serviceNotSupportedInActiveSession    | 
    0x35: RequestUpload              | NR: serviceNotSupportedInActiveSession    | 
    0x36: TransferData               | NR: serviceNotSupportedInActiveSession    | 
    0x37: RequestTransferExit        | NR: serviceNotSupportedInActiveSession    | 
    0x3e: TesterPresent              | NR: incorrectMessageLengthOrInvalidFormat | 
    0x85: ControlDTCSetting          | NR: serviceNotSupportedInActiveSession    | 
    0x86: ResponseOnEvent            | NR: incorrectMessageLengthOrInvalidFormat | 
    0xbf: 0xbf                       | NR: incorrectMessageLengthOrInvalidFormat | 
    ---------------------------------+-------------------------------------------+

Possible Enumerators:#

Enumerators List