mgmt: hawkbit: add check for valid domain name length

This commit adds a `strnlen` length check for `server_addr` to ensure that
it will not be truncated and result in a silent failure. Instead, the
call to `hawkbit_set_config` will return -EINVAL if the supplied
`server_addr` is too long for the internal buffer.

Signed-off-by: Neal Jackson <neal@blueirislabs.com>

Author: nealjack

include/zephyr/mgmt/hawkbit/config.h

@@ -45,6 +45,7 @@ struct hawkbit_runtime_config {
  * @param config Configuration settings to set.
  * @retval 0 on success.
  * @retval -EAGAIN if probe is currently running.
+ * @retval -EINVAL if config parameters are invalid.
  */
 int hawkbit_set_config(struct hawkbit_runtime_config *config);
 
@@ -61,6 +62,7 @@ struct hawkbit_runtime_config hawkbit_get_config(void);
  * @param addr_str Server address to set.
  * @retval 0 on success.
  * @retval -EAGAIN if probe is currently running.
+ * @retval -EINVAL if config parameters are invalid.
  */
 static inline int hawkbit_set_server_addr(char *addr_str)
 {

subsys/mgmt/hawkbit/hawkbit.c

@@ -780,6 +780,12 @@ int hawkbit_set_config(struct hawkbit_runtime_config *config)
 {
 	if (k_sem_take(&probe_sem, HAWKBIT_SET_SERVER_TIMEOUT) == 0) {
 		if (config->server_addr != NULL) {
+			if (strnlen(config->server_addr, sizeof(hb_cfg.server_addr)) ==
+			    sizeof(hb_cfg.server_addr)) {
+				LOG_ERR("%s too long: %s", "hawkbit/server_addr",
+					config->server_addr);
+				return -EINVAL;
+			}
 			strncpy(hb_cfg.server_addr, config->server_addr,
 				sizeof(hb_cfg.server_addr));
 			LOG_DBG("configured %s: %s", "hawkbit/server_addr", hb_cfg.server_addr);