152 lines
6.2 KiB
Markdown
152 lines
6.2 KiB
Markdown
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# Interface with Home Connect appliances in Python
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This is a very, very beta interface for Bosch-Siemens Home Connect
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devices through their local network connection. It has some tools
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to find the TLS PSK (Pre-shared Key) that is used to allow local
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access, and a Python script that can construct the proper Websocket
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interface to subscribe to events.
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*WARNING: This is not ready for prime time!*
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The dishwasher has a local HTTPS port open. Attempting to connect to
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the HTTPS port with `curl` results in a cryptic protocol error
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due to the non-standard cipher selection, `ECDHE-PSK-CHACHA20-POLY1305`.
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PSK also requires that both sides agree on a symetric key,
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so it is necessary to figure out what that key is before any
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further progress can be made.
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The clothes washer has a local HTTP port that also responds to websocket
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traffic, although the contents of the frames are AES-CBC encrypted with a key
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derived from the PSK and authenticated with SHA256-HMAC using another
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key derived from the PSK. It is also necessary to find the IV for the AES
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encryption to communicate with the washer.
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Despite the usual reputation for bad IoT security, Bosch-Siemens seem to
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have done a decent job of designing their system, especially since they
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considered a no-cloud local control configuration. The protocols seem
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sound and should prevent most any random attacker on your network from
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being able to take over your appliances to mine cryptocurrency.
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## Finding the PSK (and IV)
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You will need to set the dishwasher to "`Local network only`"
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in the setup application so that your phone will connect
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directly to it, rather than going through the cloud services.
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You'll also need a rooted Android phone running `frida-server`
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and the `find-psk.frida` script. This will hook the callback
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from the OpenSSL library `hcp::client_psk_callback` that is called
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when OpenSSL has made a connection and now needs to establish
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the PSK.
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```
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frida --no-pause -f com.bshg.homeconnect.android.release -U -l find-psk.frida
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```
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It should start the Home Connect application and eventually
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print a message like:
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```
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psk callback hint 'HCCOM_Local_App'
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psk 32 0x6ee63fb2f0
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0 1 2 3 4 5 6 7 8 9 A B C D E F 0123456789ABCDEF
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00000000 0e c8 1f d8 c6 49 fa d8 bc e7 fd 34 33 54 13 d4 .....I.....43T..
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00000010 73 f9 2e 01 fc d8 26 80 49 89 4c 19 d7 2e cd cb s.....&.I.L.....
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```
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Which gives you the 32-byte PSK value to copy into the `hcpy` program.
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## SSL logging
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The Frida script will also dump all of the SSL traffic so that you can
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see different endpoints and things. Not much is documented yet.
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Note that the TX from the phone on the websocket is "masked" with an
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repeating 4-byte XOR that is sent in the first part of each messages.
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The script could be augmented to decode those as well.
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The replies from the device are not masked so they can be read in the clear.
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## Retrieving home appliance configuration
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```
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frida-trace -o initHomeAppliance.log -f "com.bshg.homeconnect.android.release" -U -j '*!initHomeAppliance''
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```
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PSK can also be found in the last section of the config as base64url encoded.
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```
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echo 'Dsgf2MZJ-ti85_00M1QT1HP5LgH82CaASYlMGdcuzcs"' | tr '_\-"' '/+=' | base64 -d | xxd -g1
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```
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The IV is also there for devices that use it. This needs better documentation.
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TODO: document the other frida scripts that do `sendmsg()` and `Encrypt()` / `Decrypt()` tracing
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## hcpy
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The `hcpy` tool can contact your device, and if the PSK is correct, it will
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register for notification of events.
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```
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RX: {'sID': 2354590730, 'msgID': 3734589701, 'resource': '/ei/initialValues', 'version': 2, 'action': 'POST', 'data': [{'edMsgID': 3182729968}]}
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TX: {"sID":2354590730,"msgID":3734589701,"resource":"/ei/initialValues","version":2,"action":"RESPONSE","data":[{"deviceType":"Application","deviceName":"py-hca","deviceID":"1234"}]}
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TX: {"sID":2354590730,"msgID":3182729968,"resource":"/ci/services","version":1,"action":"GET"}
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TX: {"sID":2354590730,"msgID":3182729969,"resource":"/iz/info","version":1,"action":"GET"}
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TX: {"sID":2354590730,"msgID":3182729970,"resource":"/ei/deviceReady","version":2,"action":"NOTIFY"}
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RX: {'sID': 2354590730, 'msgID': 3182729968, 'resource': '/ci/services', 'version': 1, 'action': 'RESPONSE', 'data': [{'service': 'ci', 'version': 3}, {'service': 'ei', 'version': 2}, {'service': 'iz', 'version': 1}, {'service': 'ni', 'version': 1}, {'service': 'ro', 'version': 1}]}
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RX: {'sID': 2354590730, 'msgID': 3182729969, 'resource': '/iz/info', 'version': 1, 'action': 'RESPONSE', 'data': [{'deviceID': '....', 'eNumber': 'SX65EX56CN/11', 'brand': 'SIEMENS', 'vib': 'SX65EX56CN', 'mac': '....', 'haVersion': '1.4', 'swVersion': '3.2.10.20200911163726', 'hwVersion': '2.0.0.2', 'deviceType': 'Dishwasher', 'deviceInfo': '', 'customerIndex': '11', 'serialNumber': '....', 'fdString': '0201', 'shipSki': '....'}]}
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```
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## Feature UID mapping
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There are other things that can be hooked in the application
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to get the mappings of the `uid` to actual menu settings and
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XML files of the configuration parameters.
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In the `xml/` directory are some of the device descriptions
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and feature maps that the app downloads from the Home Connect
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servers. Note that the XML has unadorned hex, while the
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websocket messages are in decimal.
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For instance, when the dishwasher door is closed and then
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re-opened, it sends the messages for `'uid':512`, which is 0x020F hex:
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```
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RX: {... 'data': [{'uid': 527, 'value': 1}]}
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RX: {... 'data': [{'uid': 527, 'value': 0}]}
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```
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In the `xml/dishwasher-description.xml` there is a `statusList`
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that says uid 0x020f is a readonly value that uses enum 0x0201:
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```
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<status access="read" available="true" enumerationType="0201" refCID="03" refDID="80" uid="020F"/>
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```
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In the `xml/dishwasher-featuremap.xml` there is a mapping of feature
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reference UIDs to names:
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```
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<feature refUID="020F">BSH.Common.Status.DoorState</feature>
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```
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as well as mappings of enum ids to enum names and values:
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```
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<enumDescription enumKey="BSH.Common.EnumType.DoorState" refENID="0201">
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<enumMember refValue="0">Open</enumMember>
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<enumMember refValue="1">Closed</enumMember>
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</enumDescription>
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```
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