nRF91 certificate provisioning over RTT

[SenseJo]

Hi,

we would like to provision TLS tags / certificates for cloud authentication over Segger RTT on a custom device. We are using the Golioth cloud with the Golioth Firmware SDK, which supports using the nRF91 Key Management Unit for authentication.

I successfully provisioned TLS certificates using the modem_shell sample from NCS, but only via UART. For this, I entered `at at_cmd_mode start`, and then issued the necessary AT%CMNG commands. Afterwards, a connection to the Golioth cloud using the certificates succeeded.

However, when using RTT, in the modem shell `at_cmd_mode`, I get no responses from the device; and when issuing `at AT%CMNG=1` from the modem shell (mosh), the certificates are not listed.

Is there a way to send the multi-line certificates over RTT? Simply quoting them and then using the mosh at command failed, since a line break is interpreted as the end of the command. I also tried removing the line breaks from the certificate, but in that case, the authentication would fail.

I am using NCS v2.5.0 along with modem firmware v1.3.6.

Any help is appreciated!

[Øyvind]

Hello, 

I'm not able to reproduce the issue. I tested with JLinkRTTViewer and enabled "Send on Enter"

It is also possible to configure the line break / end of line

Does this help in your case?

Kind regards,
Øyvind

[SenseJo]

Hi, thank you – I got it working. Most likely, the way I send the commands over RTT caused issues.

Now, I got it working with a custom Python script, which uses `jlink_dongle.py` from https://github.com/Mcublog/rtt-console/blob/master/src/rtt_console/jlink_dongle.py.

My script initially configures the at command mode from the modem_shell sample to expect CR line breaks (by issuing `at at_cmd_mode term_cr`).
Then, it sends the `AT%CMNG` with LF characters within the certificate, and terminates the AT command with a CR character, like that

```
jlink.write_rtt_sring(f'AT%CMNG=0,{SEC_TAG},0,"{root_cert}"\r')
```