I've been working on a device that includes an ESP32. I set up a secure GATT server similar to the Secure Gatt Server Example with a custom service with Man in the Middle (MITM) based encryption. Currently pairing setup is Just Works, and when a client connects to the device they are prompted to pair and thus are bonded with key exchange (although it looks like Justworks disables MITM when I did more investigation for this question).
We do not have any real IO except for one button on the device, but I would like to limit pairing to a certain window of time after the Pairing button is pressed, or to have a "pairing mode" that the device enters (I have worked on another device that may have more of a classic pairing mode that was easier to work with). I know that's not explicitly part of the IDF API, but I'm looking for some guidance on how to approach something like a "pairing mode."
Would setting the IO capability to ESP_IO_CAP_IO work for using a button for the Yes/No? I don't see anything relevant in the documentation about how to configure this. In fact the enum does not appear elsewhere in the IDF sourcecode, nor does the mentioned relevant file stack/btm_api.h help.
Is there a way to disable / enable pairing on command? Would it be some type of change to advertising?
Related
I want to know if my BLE 5 (low energy, not "typical"/core bluetooth) embedded system uses (preferably asymmetric) encryption, if encrypted at all.
I'm using this ble module that is communicating with an SOC. My SOC is capable of encryption but the FAE of the BLE module product couldn't come up with any useful information.
My program doesn't appear to have a bonding/pairing process, but I could be wrong since I did not take a closer look at the HAL layer program.
My question is, does BLE 5 require encryption?
If not, how do I find out if my connection is encrypted or not, using methods other than sniffers? For example are there any steps which must be gone through to facilitate encryption, in which case I should check if these steps were skipped or not? (If skipped then surely my communication is in plain texts).
ETA: The target BLE module is based on nrf52832, don't know what BLE stack/softdevice they are using. My soc is STM32WB55 series, using a rather comprehensive BLE stack that supports most functions of which name I couldn't recall for the moment.
BLE does not require encryption for a connection to be made.
At first, every BLE connection starts in Security Mode 1, Level 1 which does not use any encryption at all. Every message will be sent in cleartext. To increase the security two devices have to "pair". Security keys are exchange during the pairing process. There are multiple different pairing methods with different requirements. Have a look at this article for a starting point.
The pairing process is usually not started manually but automatically as soon as a device tries to access a secured characteristic. If you are using a phone to access such a characteristic you will be prompted with a pairing request popup. Based on your description I would assume that your connection is currently not encrypted.
To enable encryption on your SoC please have a look at the function aci_gatt_add_char. This document (direct download link) refers to this function on page 55 and shows that it takes Security_Permissions as an argument. The next page states the possible options as:
0x00: ATTR_PERMISSION_NONE
0x01: Need authentication to read
0x02: Need authorization to read
0x04: Link should be encrypted to read
0x08: Need authentication to write
0x10: Need authorization to write
0x20: Link should be encrypted for write
I recently bought a modem that supports CSD (Circuit Switched Data) calls. I put SIM card in it and I am able to make calls via AT commands. But these are always VOICE calls. I have another modem and I need to connect to it via CSD.
I know it is possible because our colleagues are using it this way to access some network.
They are using windows dial-up connection, but I guess that is just something that in the background calls the AT commands.
Nevertheless the dial-up is still giving me "Error 678: Remote computer did not respond". I have tried many settings, but still the same error. I even tried different computer and still got the same error.
So I found out that when I call CSD, then on the receiving side (if AT+CRC=1) it should display +CRING: REL ASYNC. So I setup another modem and called it and it showed +CRING: VOICE.
So how do I convince my modem to call in the REL ASYNC mode?
I already tried:
AT+IPR=115200 or AT+IPR=9600
AT+FCLASS=0 (this is default though)
AT+CSNS=4
AT+CBST=7,0,0 or AT+CBST=71,0,1
AT^SXRAT=0 (this changes the network to GSM)
But still when I do ATDNUMBERIWANTTOCALL; the receiving side shows +CRING: VOICE.
Also my mobile provider ensured me, that the CSD technology is still supported in my country and that I do not need any kind of special SIM card.
You need to remove the semicolon after the phone number in the ATD command: that semicolon is what tells the modem to make a voice call rather than CSD.
Check with your teleoperator does your sim card have separate data number.
Sometimes postpaid (and/or M2M) cards have three different numbers
1. voice
2. fax
3. data
In the end the number could be called normally like it is written in the question, but it only worked in Germany, not abroad...
I am looking for a way to do a active Bluetooth LE Scan for a specific MAC / UUID only. In other words: I want the scanresponse of a specific device only. All other (passively) scanned devices should not be asked for scanresponse (to save power).
I saw that HCI has a Whitelist and a Resolvinglist:
Would a whitelist limit scanresponse to the whitelisted devices?
What is the resolvinglist for?
If none of those options work:
If I start a passive scan, is there a way to request scanresponse for a specific device via HCI?
I'm not sure BLE works that way... Regular bluetooth sends additional requests to get details about a device, but I don't think BLE does that. There's only one type scan and I think that's passive.
As for the whitelist, that's for something else. What you can do with the whitelist is put a list of devices in there that you want to automatically connect to. You can then issue a command to initiate connections with all devices found that are in the whitelist. This saves you manually watching for ad packets and issuing separate commands for each device you want to connect to. The whitelist won't affect what you see when scanning.
I'm not sure what the "Resolving List" does, that may do what you want...
EDIT:
Okay, I did some Google searches and it seems like there's an "active" scan for BLE, but I've never used it. If there's a passive/active difference then there must also be a way to query a single device for additional information after doing a passive scan.
I've been looking for BLE materials to get answer to this. But I could not get in any. Though practically/logically speaking, peripheral should decide I want to see if it is documented some where. Any links with this information will be very helpful.
On iOS, at least, if the peripheral specifies that encryption is required for a characteristic then iOS Central will initiate a pairing operation when access is attempted. If encryption isn't required then no pairing takes place - The central can just initiate a connection.
So, in summary -
The peripheral 'decides' if pairing is required through the definition of its characteristics.
The central manages the pairing process when required.
On "Just Works"; my understanding is that this is pairing where neither device can display a passkey, or allow the user to input one. It is NOT an unencrypted connections.
While your general iOS device can do both, many devices, such as an toothbrush handle, can't, but can still require "just works" pairing and bounding. This is also called unauthenticated pairing with encryption. It appears that iOS will prompt the user to accept a pairing request if the peripheral can't display a passkey.
What all would be the requirements for the following scenario:
A GSM modem connected to a PC running
a web based (ASP.NET) application. In
the application the user selects a
phone number from a list of phone nos.
When he clicks on a button named the
PC should call the selected phone
number. When the person on the phone
responds he should be able to have a
conversation with the PC user.
Similarly there should be a facility
to send SMS.
Now I don't want any code listings. I just need to know what would be the requirements besides asp.net, database for storing phone numbers, and GSM modem.
Any help in terms of reference websites would be highly appreciated.
I'll pick some points of your very broad question and answer them. Note that there are other points where others may be of more help...
First, a GSM modem is probably not the way you'd want to go as they usually don't allow for concurrency. So unless you just want one user at the time to use your service, you'd probably need another solution.
Also, think about cost issues - at least where I live, providing such a service would be prohibitively expensive using a normal GSM modem and a normal contract - but this is drifting into off-topicness.
The next issue will be to get voice data from the client to the server (which will relay it to the phone system - using whatever practical means). Pure browser based functionality won't be of much help, so you would absolutely need something plugin based.
Flash may work, seeing they provide access to the microphone, but please don't ask me about the details. I've never done anything like this.
Also, privacy would be a concern. While GSM data is encrypted, the path between client and server is not per default. And even if you use SSL, you'd have to convince your users trusting you that you don't record all the conversations going on, but this too is more of a political than a coding issue.
Finally, you'd have to think of bandwidth. Voice uses a lot of it and also it requires low latency. If you use a SIP trunk, you'll need the bandwidth twice per user: Once from and to your client and once from and to the SIP trunk. Calculate with 10-64 KBit/s per user and channel.
A feasible architecture would probably be to use a SIP trunk (they optimize on using VoIP as much as possible and thus can provide much lower rates than a GSM provider generally does. Also, they allow for concurrency), an Asterisk box (http://www.asterisk.org - a free PBX), some custom made flash client and a custom made SIP client on the server.
All in all, this is quite the undertaking :-)
You'll need a GSM library. There appear to be a few of these.
e.g. http://www.wirelessdevstudio.com/eng/
Have a look at the Ekiga project at http://www.Ekiga.org.
This provides audio and or video chat between users using the standard SIP (Session Initiation Protocol) over the Internet. Like most SIP clients, it can also be used to make calls to and receive calls from the telephone network, but this requires an account with a commercial service provider (there are many, and fees are quite reasonable compared to normal phone line accounts).
Ekiga uses the open source OPAL library to implement SIP communications (OPAL has support for several VoIP and video over IP standards - see www.opalvoip.org for more info).