drivers: esp32: Fix esp_wifi_drv strncpy warning

[rruuaanng]

issue

#80066

Fixed '-Wstringop-truncation' warning thrown by ssid when using strncpy on esp32.

other code:

zephyr/drivers/wifi/nxp/nxp_wifi_drv.c

Lines 696 to 697 in 6f64f77

	strncpy(wlan_scan_params_v2.ssid[1], params->ssids[1], WIFI_SSID_MAX_LEN);
	wlan_scan_params_v2.ssid[1][WIFI_SSID_MAX_LEN - 1] = 0;

This code does not do this:

zephyr/drivers/wifi/esp32/src/esp_wifi_drv.c

Lines 736 to 740 in 6f64f77

	strncpy(status->ssid, data->status.ssid, WIFI_SSID_MAX_LEN);
	status->ssid_len = strnlen(data->status.ssid, WIFI_SSID_MAX_LEN);
	status->band = WIFI_FREQ_BAND_2_4_GHZ;
	status->link_mode = WIFI_LINK_MODE_UNKNOWN;
	status->mfp = WIFI_MFP_DISABLE;

Fixes: #80066

[brandon-exact]

@jukkar
AFAICT status->ssid is 32 bytes. currently this change gives

/home/brandon/fork/zephyr/drivers/wifi/esp32/src/esp_wifi_drv.c: In function 'esp32_wifi_status':
/home/brandon/fork/zephyr/drivers/wifi/esp32/src/esp_wifi_drv.c:737:21: warning: array subscript 32 is above array bounds of 'char[32]' [-Warray-bounds]
  737 |         status->ssid[WIFI_SSID_MAX_LEN] = '\0';

[rruuaanng]

Actually in my previous submission, it was [WIFI_SSID_MAX_LEN-1]. But it seems the auditors had issues with it, so I changed it

[sylvioalves]

I agree, it should be [WIFI_SSID_MAX_LEN - 1].

@jukkar @krish2718 should we change the API from
char ssid[WIFI_SSID_MAX_LEN]; to
char ssid[WIFI_SSID_MAX_LEN + 1]; as a proper solution instead?

https://github.com/zephyrproject-rtos/zephyr/blob/main/include/zephyr/net/wifi_mgmt.h#L432
https://github.com/zephyrproject-rtos/zephyr/blob/main/include/zephyr/net/wifi_mgmt.h#L432

If yes, I suggest closing this PR and opening another with that solution.

[jukkar]

@jukkar @krish2718 should we change the API from char ssid[WIFI_SSID_MAX_LEN]; to char ssid[WIFI_SSID_MAX_LEN + 1]; as a proper solution instead?

https://github.com/zephyrproject-rtos/zephyr/blob/main/include/zephyr/net/wifi_mgmt.h#L432 https://github.com/zephyrproject-rtos/zephyr/blob/main/include/zephyr/net/wifi_mgmt.h#L432

Yes, that is correct. If we want to store null at the end, there needs to be space for it in the buffer (so +1 is needed).

[rruuaanng]

I think it's good to change it to WIFI_SSID_MAX_LEN-1. Instead of changing the definition, because WIFI_SSID_MAX_LEN already indicates the maximum length. If you +1 to the maximum length, it will make the code extremely difficult to understand.

Edit：
And, in the example I gave, we should keep in sync with him instead of changing the definition at will.

[brandon-exact]

The standard for SSID is 32 bytes long. The way it is now, it will only be 31 bytes due to the '\0' so it must be increased if we want null termination and 32 bytes.

I am surprised this change passed CI, the warning gets created without the CONFIG_SPEED_OPTIMIZATIONS

[rruuaanng]

If it's okay, I'll reopen a PR tomorrow. It'll change the size of the ssid member (even though I’m not a big fan of this, but if the ssid is the standard 32-byte length, then the ssid member has to be 33 bytes).

[sylvioalves]

Making DNM until maintainers reply to the comments above.

[rruuaanng]

I'll close this PR to apply the changes suggested by @brandon-exact.

Thank for your reviewer this :)

[rruuaanng]

#80267