Add support for QRCode pairing

Makefile.projbuild

@@ -1,6 +1,7 @@
 EXTRA_WOLFSSL_CFLAGS = \
 	-DWOLFCRYPT_HAVE_SRP \
 	-DWOLFSSL_SHA512 \
+	-DWOLFSSL_BASE64_ENCODE \
 	-DNO_MD5 \
 	-DNO_SHA \
 	-DHAVE_HKDF \

component.mk

@@ -39,6 +39,7 @@ ifdef component_compile_rules
     EXTRA_WOLFSSL_CFLAGS = \
         -DWOLFCRYPT_HAVE_SRP \
         -DWOLFSSL_SHA512 \
+        -DWOLFSSL_BASE64_ENCODE \
         -DNO_MD5 \
         -DNO_SHA \
         -DHAVE_HKDF \

include/homekit/homekit.h

@@ -32,6 +32,7 @@ typedef struct {
     char *password;
     void (*password_callback)(const char *password);
 
+    char *setupId;
     // Callback for "POST /resource" to get snapshot image from camera
     void (*on_resource)(const char *body, size_t body_size);
 

src/server.c

@@ -23,6 +23,8 @@
 
 #include <http-parser/http_parser.h>
 #include <cJSON.h>
+#include <wolfssl/wolfcrypt/hash.h>
+#include <wolfssl/wolfcrypt/coding.h>
 
 #include "base64.h"
 #include "crypto.h"
@@ -3292,6 +3294,28 @@ void homekit_setup_mdns(homekit_server_t *server) {
     // accessory category identifier
     homekit_mdns_add_txt("ci", "%d", accessory->category);
 
+    if (server->config->setupId) {
+        DEBUG("Accessory Setup ID = %s", server->config->setupId);
+
+        size_t data_size = strlen(server->config->setupId) + strlen(server->accessory_id) + 1;
+        char *data = malloc(data_size);
+        snprintf(data, data_size, "%s%s", server->config->setupId, server->accessory_id);
+        data[data_size-1] = 0;
+
+        unsigned char shaHash[SHA512_DIGEST_SIZE];
+        wc_Sha512Hash((const unsigned char *)data, data_size-1, shaHash);
+
+        free(data);
+
+        unsigned char encodedHash[9];
+        memset(encodedHash, 0, sizeof(encodedHash));
+
+        word32 len = sizeof(encodedHash);
+        Base64_Encode_NoNl((const unsigned char *)shaHash, 4, encodedHash, &len);
+
+        homekit_mdns_add_txt("sh", "%s", encodedHash);
+    }
+
     homekit_mdns_configure_finalize();
 }
 
@@ -3367,6 +3391,7 @@ void homekit_server_task(void *args) {
 }
 
 #define ISDIGIT(x) isdigit((unsigned char)(x))
+#define ISBASE36(x) (isdigit((unsigned char)(x)) || (x >= 'A' && x <= 'Z'))
 
 void homekit_server_init(homekit_server_config_t *config) {
     if (!config->accessories) {
@@ -3393,6 +3418,16 @@ void homekit_server_init(homekit_server_config_t *config) {
         }
     }
 
+    if (config->setupId) {
+        const char *p = config->setupId;
+        if (strlen(p) != 4 ||
+                !(ISBASE36(p[0]) && ISBASE36(p[1]) && ISBASE36(p[2]) && ISBASE36(p[3]))) {
+            ERROR("Error initializing HomeKit accessory server: "
+                  "invalid setup ID format");
+            return;
+        }
+    }
+
     homekit_accessories_init(config->accessories);
 
     homekit_server_t *server = server_new();

tools/gen_qrcode

@@ -0,0 +1,88 @@
+#!/usr/bin/env python
+import argparse
+import os.path
+import PIL.Image
+import PIL.ImageDraw
+import PIL.ImageFont
+import qrcode
+import re
+import sys
+
+script_dir = os.path.dirname(os.path.realpath(__file__))
+
+BASE36 = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+
+PAYLOAD_VERSION = 0
+PAYLOAD_FLAGS = 2  # 2=IP, 4=BLE, 8=IP_WAC
+
+def gen_homekit_setup_uri(category, password, setup_id, version=0, reserved=0, flags=2):
+    payload = 0
+    payload |= (version & 0x7)
+
+    payload <<= 4
+    payload |=(reserved & 0xf)  # reserved bits
+
+    payload <<= 8
+    payload |= (category & 0xff)
+
+    payload <<= 4
+    payload |= (flags & 0xf)
+
+    payload <<= 27
+    payload |= (int(password.replace('-', '')) & 0x7fffffff)
+
+    encodedPayload = ''
+    for _ in range(9):
+        encodedPayload += BASE36[payload % 36]
+        payload //= 36
+
+    return 'X-HM://%s%s' % (''.join(reversed(encodedPayload)), setup_id)
+
+
+def gen_homekit_qrcode(setup_uri, password):
+    code = qrcode.QRCode(version=2, border=0, box_size=12,
+                         error_correction=qrcode.constants.ERROR_CORRECT_Q)
+    code.add_data(setup_uri)
+
+    # open template
+    img = PIL.Image.open(os.path.join(script_dir, 'qrcode.png'))
+    # add QR code to it
+    img.paste(code.make_image().get_image(), (50, 180))
+
+    # add password digits
+    setup_code = password.replace('-', '')
+
+    font = PIL.ImageFont.truetype(os.path.join(script_dir, 'Arial Bold.ttf'), 56)
+    draw = PIL.ImageDraw.Draw(img)
+
+    for i in range(4):
+        draw.text((170 + i*50, 35), setup_code[i], font=font, fill=(0, 0, 0))
+        draw.text((170 + i*50, 95), setup_code[i+4], font=font, fill=(0, 0, 0))
+
+    return img
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('category', type=int)
+    parser.add_argument('password')
+    parser.add_argument('setup_id')
+    parser.add_argument('output_image')
+
+    args = parser.parse_args()
+
+    if not re.match('\d{3}-\d{2}-\d{3}', args.password):
+        raise ValueError('Invalid password')
+
+    if not re.match('[0-9A-Z]{4}', args.setup_id):
+        raise ValueError('Invalid setup ID')
+
+    setupURI = gen_homekit_setup_uri(args.category, args.password, args.setup_id)
+
+    qrcodeImage = gen_homekit_qrcode(setupURI, args.password)
+
+    qrcodeImage.save(args.output_image)
+
+
+if __name__ == '__main__':
+    main()