Add firmware signing and verification

mongoose.c

@@ -1476,6 +1476,10 @@ void mg_error(struct mg_connection *c, const char *fmt, ...) {
 
 
 
+#ifdef MG_OTA_PUBLIC_KEY
+
+
+#endif
 
 #if MG_OTA != MG_OTA_NONE && MG_OTA != MG_OTA_CUSTOM
 
@@ -1533,6 +1537,18 @@ bool mg_ota_flash_end(struct mg_flash *flash) {
     if (size == s_size && crc32 == s_crc32) ok = true;
     MG_DEBUG(("CRC: %x/%x, size: %lu/%lu, status: %s", s_crc32, crc32, s_size,
               size, ok ? "ok" : "fail"));
+#ifdef MG_OTA_PUBLIC_KEY
+    if (ok && s_size > 64) {
+      static const uint8_t s_pubkey[] = MG_OTA_PUBLIC_KEY;
+      uint8_t hash[32];
+      size_t fw_size = s_size - 64;
+      mg_sha256(hash, (uint8_t *) base, fw_size);
+      ok = mg_uecc_verify(s_pubkey, hash, sizeof(hash),
+                          (uint8_t *) base + fw_size,
+                          mg_uecc_secp256r1()) == 1;
+      MG_INFO(("Signature: %s", ok ? "ok" : "fail"));
+    }
+#endif
     s_size = 0;
     if (ok) ok = flash->swap_fn();
   }

resources/sign.js

@@ -0,0 +1,80 @@
+#!/usr/bin/env node
+// OTA firmware signing tool. No npm dependencies required.
+// Usage:
+//   node sign.js keygen            # generate private.pem + print public key #define
+//   node sign.js sign firmware.bin # append 64-byte ECDSA-P256 signature
+
+'use strict';
+
+const crypto = require('crypto');
+const fs = require('fs');
+const path = require('path');
+
+function usage() {
+  console.error('Usage:');
+  console.error('  node sign.js keygen              # generate key pair');
+  console.error('  node sign.js sign FIRMWARE.bin   # sign firmware');
+  process.exit(1);
+}
+
+// DER-encoded ECDSA signature -> raw 64-byte R||S
+function derToRaw(der) {
+  let i = 2;              // skip SEQUENCE tag + length
+  i++;                    // skip INTEGER tag
+  const rLen = der[i++];
+  const r = der.slice(i, i + rLen); i += rLen;
+  i++;                    // skip INTEGER tag
+  const sLen = der[i++];
+  const s = der.slice(i, i + sLen);
+  return Buffer.concat([to32(r), to32(s)]);
+}
+
+// Normalize a DER integer to exactly 32 bytes (strip leading 0x00, zero-pad)
+function to32(b) {
+  while (b.length > 32 && b[0] === 0) b = b.slice(1);
+  const out = Buffer.alloc(32, 0);
+  b.copy(out, 32 - b.length);
+  return out;
+}
+
+function keygen() {
+  const { privateKey, publicKey } = crypto.generateKeyPairSync('ec', {
+    namedCurve: 'P-256',
+  });
+
+  fs.writeFileSync('private.pem', privateKey.export({ type: 'pkcs8', format: 'pem' }));
+  console.log('Wrote private.pem  (keep secret, never ship in firmware)');
+
+  // SPKI DER for P-256 ends with: 04 [X 32 bytes] [Y 32 bytes]
+  // We want the raw 64-byte X||Y (no 0x04 prefix) for mg_uecc_verify
+  const spki = publicKey.export({ type: 'spki', format: 'der' });
+  const raw = spki.slice(-64);
+
+  const hex = Array.from(raw).map(b => '0x' + b.toString(16).padStart(2, '0'));
+  const rows = [];
+  for (let i = 0; i < 64; i += 8)
+    rows.push('  ' + hex.slice(i, i + 8).join(', '));
+
+  console.log('\nAdd to your mongoose_config.h:');
+  console.log(`#define MG_OTA_PUBLIC_KEY { \\\n${rows.join(', \\\n')}, \\\n}`);
+}
+
+function sign(firmware, privateKeyFile = 'private.pem') {
+  const fw = fs.readFileSync(firmware);
+  const privateKey = crypto.createPrivateKey(fs.readFileSync(privateKeyFile));
+  const derSig = crypto.sign('SHA256', fw, privateKey);
+  const raw = derToRaw(derSig);  // 64 bytes: R||S
+
+  const dot = firmware.lastIndexOf('.');
+  const out = dot >= 0
+    ? firmware.slice(0, dot) + '.signed' + firmware.slice(dot)
+    : firmware + '.signed';
+
+  fs.writeFileSync(out, Buffer.concat([fw, raw]));
+  console.log(`Signed: ${out}  (${fw.length} bytes firmware + 64 bytes signature)`);
+}
+
+const [,, cmd, arg1, arg2] = process.argv;
+if      (cmd === 'keygen')          keygen();
+else if (cmd === 'sign' && arg1)    sign(arg1, arg2);
+else                                usage();

src/flash.c

@@ -2,6 +2,10 @@
 #include "flash.h"
 #include "log.h"
 #include "ota.h"
+#ifdef MG_OTA_PUBLIC_KEY
+#include "sha256.h"
+#include "tls_uecc.h"
+#endif
 
 #if MG_OTA != MG_OTA_NONE && MG_OTA != MG_OTA_CUSTOM
 
@@ -59,6 +63,18 @@ bool mg_ota_flash_end(struct mg_flash *flash) {
     if (size == s_size && crc32 == s_crc32) ok = true;
     MG_DEBUG(("CRC: %x/%x, size: %lu/%lu, status: %s", s_crc32, crc32, s_size,
               size, ok ? "ok" : "fail"));
+#ifdef MG_OTA_PUBLIC_KEY
+    if (ok && s_size > 64) {
+      static const uint8_t s_pubkey[] = MG_OTA_PUBLIC_KEY;
+      uint8_t hash[32];
+      size_t fw_size = s_size - 64;
+      mg_sha256(hash, (uint8_t *) base, fw_size);
+      ok = mg_uecc_verify(s_pubkey, hash, sizeof(hash),
+                          (uint8_t *) base + fw_size,
+                          mg_uecc_secp256r1()) == 1;
+      MG_INFO(("Signature: %s", ok ? "ok" : "fail"));
+    }
+#endif
     s_size = 0;
     if (ok) ok = flash->swap_fn();
   }

tutorials/device-dashboard/full/dashboard.html

@@ -622,7 +622,7 @@ a, a:visited, a:link { text-decoration: none; }
                     <path d="M5 21h14" />
                   </svg>
                   Select .bin file
-                  <input type="file" accept=".bin" hidden data-upload="1" />
+                  <input type="file" accept=".bin" hidden data-ota="1" />
                 </label>
 
               </div>

tutorials/stm32/nucleo-h563zi/minimal/Makefile

@@ -12,7 +12,6 @@ SOURCES = main.c hal.c
 SOURCES += cmsis_h5/Source/Templates/gcc/startup_stm32h563xx.s
 SOURCES += mongoose/mongoose.c
 
-
 all build example: firmware.bin
 
 mongoose/mongoose.c mongoose/mongoose.h:
@@ -26,6 +25,9 @@ firmware.bin: firmware.elf
 	@echo
 	@echo "To flash, run 'make flash', or use STM32CubeProgrammer"
 
+sign firmware.signed.bin: firmware.bin
+	node ../../../../resources/sign.js sign firmware.bin private.pem
+
 flash: firmware.bin
 	STM32_Programmer_CLI -c port=swd mode=UR -w firmware.elf -hardRst
 
@@ -37,7 +39,6 @@ CUBEPROG_DIR ?= $(dir $(shell which STM32_Programmer_CLI))
 gdb_server:
 	ST-LINK_gdbserver --port-number 61234 --log-level 1 --swd --verify --stm32cubeprogrammer-path $(CUBEPROG_DIR) --apid 1 --initialize-reset
 
-
 cmsis_core:
 	git clone -q -c advice.detachedHead=false --depth 1 -b 5.9.0 https://github.com/ARM-software/CMSIS_5 $@
 

tutorials/stm32/nucleo-h563zi/minimal/mongoose/mongoose_config.h

@@ -12,6 +12,17 @@
 #define MG_ENABLE_PACKED_FS 1
 #define MG_ENABLE_DRIVER_STM32H 1
 
+#define MG_OTA_PUBLIC_KEY { \
+  0x19, 0x7f, 0xed, 0x81, 0x8b, 0xb7, 0xb2, 0xa5, \
+  0xde, 0xe0, 0xde, 0x04, 0x83, 0x60, 0xc8, 0x69, \
+  0x61, 0x39, 0x30, 0x1f, 0xc1, 0x52, 0x11, 0x4b, \
+  0xb7, 0xa4, 0xd7, 0x52, 0x03, 0x36, 0xc6, 0xc1, \
+  0xbf, 0x22, 0x75, 0x04, 0x49, 0xf8, 0x46, 0x47, \
+  0xec, 0x20, 0xd6, 0x8d, 0x48, 0x29, 0x7d, 0x63, \
+  0xb3, 0xf7, 0x1f, 0x58, 0x44, 0x82, 0xcc, 0x7a, \
+  0x4b, 0x5e, 0x68, 0x98, 0x24, 0x1f, 0x86, 0xf4, \
+}
+
 // #define MG_DRIVER_MDC_CR 4   // RMII MDC clock divider, from 0 to 4
 // #define MG_TCPIP_PHY_ADDR 0  // PHY address
 

tutorials/stm32/nucleo-h563zi/minimal/private.pem

@@ -0,0 +1,5 @@
+-----BEGIN PRIVATE KEY-----
+MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgto6awcVrVzHfgSaD
+WFiy6JrXahab3F5lfGvb7A1XzjShRANCAAQZf+2Bi7eypd7g3gSDYMhpYTkwH8FS
+EUu3pNdSAzbGwb8idQRJ+EZH7CDWjUgpfWOz9x9YRILMekteaJgkH4b0
+-----END PRIVATE KEY-----