how to handle expired SSL CA certificates in nrf9160

Question

Dear Nordic,

The SSL certificate is hard-coded, it means that the certificate is stored in the source code folder and cannot be changed without a firmware update.
This can be problematic because SSL certificates typically have an expiration date, after which they are no longer valid.
If the certificate is expired, the device may not be able to establish a secure connection with the server, which can lead to security issues and service disruptions.

My environment

Device: nrf9160 customized one

SDK - ncs v1.9.1

I would like to know, is there any way to handle expired SSL CA certificate and update it programatically without upgrading the firmware? (FOTA).
Currently our SSL CA cerificate renewed every year.
I also know that, it is recommended to use SSL certificates with a sufficiently long validity period,
so that they do not expire frequently.

carrie_certs.c

#include <stdint.h>
#include <string.h>
#include <toolchain.h>
#include <sys/util.h>
#include <modem/modem_key_mgmt.h>
#include <logging/log.h>

#include "carrier_certs.h"
#include "ex_common.h"

#define TLS_MC_API_SEC_TAG	42
#if 0
#define TLS_FOTA_SEC_TAG	43
#endif //end if 0

#if 0
static int tags[] = { TLS_MC_API_SEC_TAG, TLS_FOTA_SEC_TAG };
#endif //end if 0

static const char ca42[] = {
	/* API certificate */
#if 0	
	#include "./certs/api.cer" 
#else
	#include "./certs/api_2023_12_24.cer"
#endif
};

#if 0
static const char ca43[] = {
	/* FOTA server certificate */
	#include "./certs/fota.cer"
};
#endif //end if 0

BUILD_ASSERT(sizeof(ca42) < KB(4), "Cert is too large");
#if 0
BUILD_ASSERT(sizeof(ca43) < KB(4), "Cert is too large");
#endif //end if 0

static const struct {
	uint16_t tag;
	const char *data;
} certs[] = {
	{
		.tag = TLS_MC_API_SEC_TAG,
		.data = ca42,
	},
	#if 0
	{
		.tag = TLS_FOTA_SEC_TAG,
		.data = ca43,
	}
	#endif //end if 0
};

int carrier_certs_provision()
{
	int err;
	bool mismatch = 0;
	bool provisioned;

	for (int i = 0; i < ARRAY_SIZE(certs); i++) {
		err = modem_key_mgmt_exists(
			certs[i].tag, MODEM_KEY_MGMT_CRED_TYPE_CA_CHAIN, &provisioned);
		if (err) {
			goto cert_exit_empty;
		}

		if (provisioned) {
			err = modem_key_mgmt_cmp(
				certs[i].tag, MODEM_KEY_MGMT_CRED_TYPE_CA_CHAIN,
				certs[i].data, strlen(certs[i].data));

			/* 0 on match, 1 otherwise; like memcmp() */
			mismatch = err;

			LOG_DBG("Certificate found, tag %d: %s", certs[i].tag,
				mismatch ? "mismatch" : "match");
		} else {
			LOG_DBG("Certificate tag %d not found", certs[i].tag);
		}

		if (mismatch || !provisioned) {
			/* overwrite the certificate */
			err = modem_key_mgmt_write(
				certs[i].tag, MODEM_KEY_MGMT_CRED_TYPE_CA_CHAIN,
				certs[i].data, strlen(certs[i].data));
			if (err) {
				MLOG_ERROR("Unable to provision certificate, error: %d", err);		
			}

			LOG_DBG("Certificate provisioned, tag %d", certs[i].tag);
		}
	}

	return 0;

cert_exit_empty:
	return -1;
	
}

Any help will be appreciated.

Best Regards

Praveen Deshmane