1 files changed, 124 insertions, 0 deletions

diff --git a/main/identity.c b/main/identity.c
new file mode 100644
index 0000000..1dab415
--- /dev/null
+++ b/main/identity.c
@@ -0,0 +1,124 @@
+#include "identity.h"
+#include "config.h"
+#include "esp_log.h"
+#include "lwip/ip4_addr.h"
+#include "mbedtls/md.h"
+#include "secp256k1.h"
+#include "secp256k1_extrakeys.h"
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static const char *TAG = "identity";
+static tollgate_identity_t s_identity;
+
+static int hex_to_bytes(const char *hex, uint8_t *out, size_t out_len)
+{
+    if (strlen(hex) != out_len * 2) return 0;
+    for (size_t i = 0; i < out_len; i++) {
+        unsigned int byte;
+        if (sscanf(hex + i * 2, "%02x", &byte) != 1) return 0;
+        out[i] = (uint8_t)byte;
+    }
+    return 1;
+}
+
+static void bytes_to_hex(const uint8_t *bytes, size_t len, char *hex)
+{
+    for (size_t i = 0; i < len; i++)
+        sprintf(hex + i * 2, "%02x", bytes[i]);
+    hex[len * 2] = '\0';
+}
+
+static void tollgate_derive(const uint8_t nsec[32], const char *label,
+                            uint32_t index, uint8_t *out, size_t out_len)
+{
+    size_t label_len = strlen(label);
+    size_t msg_len = label_len + 4;
+    uint8_t *msg = (uint8_t *)malloc(msg_len);
+    memcpy(msg, label, label_len);
+    msg[label_len]     = (uint8_t)(index & 0xff);
+    msg[label_len + 1] = (uint8_t)((index >> 8) & 0xff);
+    msg[label_len + 2] = (uint8_t)((index >> 16) & 0xff);
+    msg[label_len + 3] = (uint8_t)((index >> 24) & 0xff);
+
+    uint8_t hmac[64];
+    mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA512),
+                    nsec, 32, msg, msg_len, hmac);
+    free(msg);
+
+    memcpy(out, hmac, out_len);
+}
+
+esp_err_t identity_init(const char *nsec_hex)
+{
+    memset(&s_identity, 0, sizeof(s_identity));
+
+    if (!nsec_hex || strlen(nsec_hex) != 64) {
+        ESP_LOGE(TAG, "Invalid nsec: must be 64 hex chars");
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    strncpy(s_identity.nsec_hex, nsec_hex, sizeof(s_identity.nsec_hex) - 1);
+
+    if (!hex_to_bytes(nsec_hex, s_identity.nsec, 32)) {
+        ESP_LOGE(TAG, "Failed to parse nsec hex");
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    if (!ctx) {
+        ESP_LOGE(TAG, "Failed to create secp256k1 context");
+        return ESP_ERR_NO_MEM;
+    }
+
+    secp256k1_pubkey pubkey;
+    if (!secp256k1_ec_pubkey_create(ctx, &pubkey, s_identity.nsec)) {
+        ESP_LOGE(TAG, "Invalid nsec: secp256k1 key creation failed");
+        secp256k1_context_destroy(ctx);
+        return ESP_ERR_INVALID_ARG;
+    }
+
+    secp256k1_xonly_pubkey xonly;
+    secp256k1_xonly_pubkey_from_pubkey(ctx, &xonly, NULL, &pubkey);
+    uint8_t npub_bytes[32];
+    secp256k1_xonly_pubkey_serialize(ctx, npub_bytes, &xonly);
+    bytes_to_hex(npub_bytes, 32, s_identity.npub_hex);
+
+    tollgate_derive(s_identity.nsec, "sta-mac", 0, s_identity.sta_mac, 6);
+    s_identity.sta_mac[0] = (s_identity.sta_mac[0] | 0x02) & 0xFE;
+
+    tollgate_derive(s_identity.nsec, "ap-mac", 0, s_identity.ap_mac, 6);
+    s_identity.ap_mac[0] = (s_identity.ap_mac[0] | 0x02) & 0xFE;
+
+    snprintf(s_identity.ap_ssid, sizeof(s_identity.ap_ssid),
+             "TollGate-%02X%02X%02X",
+             s_identity.ap_mac[3], s_identity.ap_mac[4], s_identity.ap_mac[5]);
+
+    uint8_t b3 = s_identity.ap_mac[3];
+    uint8_t b4 = s_identity.ap_mac[4];
+    uint8_t b5 = s_identity.ap_mac[5];
+    uint8_t subnet = (b4 ^ b5) % 200 + 10;
+    IP4_ADDR(&s_identity.ap_ip, 10, b3, subnet, 1);
+    snprintf(s_identity.ap_ip_str, sizeof(s_identity.ap_ip_str),
+             IPSTR, IP2STR(&s_identity.ap_ip));
+
+    secp256k1_context_destroy(ctx);
+    s_identity.initialized = true;
+
+    ESP_LOGI(TAG, "Identity: npub=%s", s_identity.npub_hex);
+    ESP_LOGI(TAG, "  STA MAC: %02X:%02X:%02X:%02X:%02X:%02X",
+             s_identity.sta_mac[0], s_identity.sta_mac[1], s_identity.sta_mac[2],
+             s_identity.sta_mac[3], s_identity.sta_mac[4], s_identity.sta_mac[5]);
+    ESP_LOGI(TAG, "  AP  MAC: %02X:%02X:%02X:%02X:%02X:%02X",
+             s_identity.ap_mac[0], s_identity.ap_mac[1], s_identity.ap_mac[2],
+             s_identity.ap_mac[3], s_identity.ap_mac[4], s_identity.ap_mac[5]);
+    ESP_LOGI(TAG, "  SSID: %s, AP IP: %s", s_identity.ap_ssid, s_identity.ap_ip_str);
+
+    return ESP_OK;
+}
+
+const tollgate_identity_t *identity_get(void)
+{
+    return &s_identity;
+}