app_wifi: Changes in SSID and PoP generation for Provisioning

- In claiming, change the 4 byte random number to 64 byte and store it
as binary data instead of hex representation.
- Instead of reading PoP as hex string from NVS, read it as binary data
(because of above change) and then convert to hex representation.
- Instead of using mac address, use last 3 bytes of the above random number
number as suffix for SSID.

The last change was made so as to allow generating the QR code completely outside
the device, without knowing its mac address.

Author: shahpiyushv

Diff for: CHANGES.md

@@ -1,5 +1,14 @@
 # Changes
 
+## 16-Oct-2020 (app_wifi: Changes in SSID and PoP generation for Provisioning)
+
+The PoP for Wi-Fi provisioning was being fetched from a random 8 character hex string stored in the fctry partition.
+In this commit, the random 8 character hex string has been replaced by 64 byte random number, which can be used for other purposes as well.
+PoP is now generated by reading the first 4 bytes of this and converting to 8 character hex string.
+Even the SSID now uses the last 3 bytes of this random number as the suffix, instead of last 3 bytes of MAC address.
+With this change, it will now be possible to generate the complete Provisioning QR code payload outside the device,
+without having to know its MAC address.
+
 ## 29-Sep-2020 (esp_rmaker_standard_types: Start default names of all standard params with capital letter)
 
 Default parameter names like name, power, etc. have been changed to Name, Power, etc. respectively, so that they look better in the phone app UIs.

Diff for: cli/rmaker_tools/rmaker_claim/claim.py

@@ -152,7 +152,7 @@ def gen_host_csr(private_key, common_name=None):
     csr = request.public_bytes(serialization.Encoding.PEM).decode("utf-8")
     return csr
 
-def gen_hex_str(octets=4):
+def gen_hex_str(octets=64):
     """
     Generate random hex string, it is used as PoP
 
@@ -188,7 +188,7 @@ def save_random_hex_str(dest_filedir, hex_str):
             info_file.write(hex_str)
 
         with open(dest_filedir + 'node_info.csv', 'a') as info_file:
-            info_file.write('random,file,binary,' +
+            info_file.write('random,file,hex2bin,' +
                             dest_filedir + 'random.info')
             info_file.write('\n')
     except Exception as err:

Diff for: components/esp_rainmaker/src/core/esp_rmaker_claim.c

@@ -44,6 +44,9 @@
 #include "esp_rmaker_claim.h"
 
 static const char *TAG = "esp_claim";
+
+#define ESP_RMAKER_RANDOM_NUMBER_LEN    64
+
 #ifdef CONFIG_ESP_RMAKER_SELF_CLAIM
 #include "soc/soc.h"
 #include "soc/efuse_reg.h"
@@ -785,8 +788,7 @@ static void event_handler(void* arg, esp_event_base_t event_base,
 #endif /* CONFIG_ESP_RMAKER_ASSISTED_CLAIM */
 esp_err_t __esp_rmaker_claim_init(esp_rmaker_claim_data_t *claim_data)
 {
-    char hexstr[9];
-    uint32_t my_random;
+    uint8_t random_bytes[ESP_RMAKER_RANDOM_NUMBER_LEN];
     esp_err_t err;
 
     char *key = esp_rmaker_get_client_key();
@@ -812,15 +814,13 @@ esp_err_t __esp_rmaker_claim_init(esp_rmaker_claim_data_t *claim_data)
             return err;
         }
     }
-    /* Generate random hex string */
-    memset(hexstr, 0, sizeof(hexstr));
-    esp_fill_random(&my_random, sizeof(my_random));
-    snprintf(hexstr, sizeof(hexstr), "%08x", my_random);
+    /* Generate random bytes for general purpose use */
+    esp_fill_random(&random_bytes, sizeof(random_bytes));
 
     /* Store the PoP in the storage */
-    err = esp_rmaker_storage_set(ESP_RMAKER_CLIENT_RANDOM_NVS_KEY, hexstr, strlen(hexstr));
+    err = esp_rmaker_storage_set(ESP_RMAKER_CLIENT_RANDOM_NVS_KEY, random_bytes, sizeof(random_bytes));
     if (err != ESP_OK) {
-        ESP_LOGE(TAG, "Failed to store random number to storage");
+        ESP_LOGE(TAG, "Failed to store random bytes to storage.");
         return err;
     }
 #ifdef CONFIG_ESP_RMAKER_SELF_CLAIM

Diff for: examples/common/app_wifi/app_wifi.c

@@ -120,44 +120,55 @@ static void wifi_init_sta()
     ESP_ERROR_CHECK(esp_wifi_start());
 }
 
-static void get_device_service_name(char *service_name, size_t max)
-{
-    uint8_t eth_mac[6];
-    const char *ssid_prefix = "PROV_";
-    esp_wifi_get_mac(WIFI_IF_STA, eth_mac);
-    snprintf(service_name, max, "%s%02X%02X%02X",
-             ssid_prefix, eth_mac[3], eth_mac[4], eth_mac[5]);
-}
-
 /* free the return value after use. */
-static char *read_random_bytes_from_nvs()
+static esp_err_t read_random_bytes_from_nvs(uint8_t **random_bytes, size_t *len)
 {
     nvs_handle handle;
     esp_err_t err;
-    size_t required_size = 0;
-    void *value;
+    *len = 0;
 
     if ((err = nvs_open_from_partition(CONFIG_ESP_RMAKER_FACTORY_PARTITION_NAME, CREDENTIALS_NAMESPACE,
                                 NVS_READONLY, &handle)) != ESP_OK) {
         ESP_LOGD(TAG, "NVS open for %s %s %s failed with error %d", CONFIG_ESP_RMAKER_FACTORY_PARTITION_NAME, CREDENTIALS_NAMESPACE, RANDOM_NVS_KEY, err);
-        return NULL;
+        return ESP_FAIL;
     }
 
-    if ((err = nvs_get_blob(handle, RANDOM_NVS_KEY, NULL, &required_size)) != ESP_OK) {
-        ESP_LOGD(TAG, "Failed to read key %s with error %d size %d", RANDOM_NVS_KEY, err, required_size);
+    if ((err = nvs_get_blob(handle, RANDOM_NVS_KEY, NULL, len)) != ESP_OK) {
+        ESP_LOGD(TAG, "Error %d. Failed to read key %s.", err, RANDOM_NVS_KEY);
         nvs_close(handle);
-        return NULL;
+        return ESP_ERR_NOT_FOUND;
     }
 
-    value = calloc(required_size + 1, 1); /* + 1 for NULL termination */
-    if (value) {
-        nvs_get_blob(handle, RANDOM_NVS_KEY, value, &required_size);
+    *random_bytes = calloc(*len, 1);
+    if (*random_bytes) {
+        nvs_get_blob(handle, RANDOM_NVS_KEY, *random_bytes, len);
+        nvs_close(handle);
+        return ESP_OK;
     }
-
     nvs_close(handle);
-    return value;
+    return ESP_ERR_NO_MEM;
+}
+
+static esp_err_t get_device_service_name(char *service_name, size_t max)
+{
+    uint8_t *nvs_random;
+    const char *ssid_prefix = "PROV_";
+    size_t nvs_random_size = 0;
+    if ((read_random_bytes_from_nvs(&nvs_random, &nvs_random_size) != ESP_OK) || nvs_random_size < 3) {
+        uint8_t eth_mac[6];
+        esp_wifi_get_mac(WIFI_IF_STA, eth_mac);
+        snprintf(service_name, max, "%s%02x%02x%02x", ssid_prefix, eth_mac[3], eth_mac[4], eth_mac[5]);
+    } else {
+        snprintf(service_name, max, "%s%02x%02x%02x", ssid_prefix, nvs_random[nvs_random_size - 3],
+                nvs_random[nvs_random_size - 2], nvs_random[nvs_random_size - 1]);
+    }
+    if (nvs_random) {
+        free(nvs_random);
+    }
+    return ESP_OK;
 }
 
+
 static esp_err_t get_device_pop(char *pop, size_t max, app_wifi_pop_type_t pop_type)
 {
     if (!pop || !max) {
@@ -174,14 +185,13 @@ static esp_err_t get_device_pop(char *pop, size_t max, app_wifi_pop_type_t pop_t
             return err;
         }
     } else if (pop_type == POP_TYPE_RANDOM) {
-        char *nvs_pop = read_random_bytes_from_nvs();
-        if (!nvs_pop) {
+        uint8_t *nvs_random;
+        size_t nvs_random_size = 0;
+        if ((read_random_bytes_from_nvs(&nvs_random, &nvs_random_size) != ESP_OK) || nvs_random_size < 4) {
             return ESP_ERR_NOT_FOUND;
         } else {
-            strncpy(pop, nvs_pop, max - 1);
-            pop[max - 1] = 0;
-            free(nvs_pop);
-            nvs_pop = NULL;
+            snprintf(pop, max, "%02x%02x%02x%02x", nvs_random[0], nvs_random[1], nvs_random[2], nvs_random[3]);
+            free(nvs_random);
             return ESP_OK;
         }
     } else {