add libsodium

Author: Alex Wolden

platformio.ini

@@ -342,6 +342,7 @@ build_flags =
   -D RADIO_CLASS=CustomSX1276
   -D WRAPPER_CLASS=CustomSX1276Wrapper
   -D LORA_TX_POWER=20
+  -D USE_ESP32_ENCRYPTION=true
 
 ; =============
 [LilyGo_T3S3_sx1262]
@@ -376,11 +377,9 @@ build_flags =
   -D ADVERT_LAT=-37.0
   -D ADVERT_LON=145.0
   -D ADMIN_PASSWORD="\"password\""
-  -D MESH_PACKET_LOGGING=1
-  -D MESH_DEBUG=1
-  -D CORE_DEBUG_LEVEL=3
-  -D SPI_MAX_DMA_LEN=1024
-  -D BLE_TASK_SIZE=4096
+;  -D MESH_PACKET_LOGGING=1
+;  -D MESH_DEBUG=1
+;  -D CORE_DEBUG_LEVEL=3
 
 [env:LilyGo_T3_sx1276_terminal_chat]
 extends = LilyGo_T3_sx1276
@@ -417,7 +416,7 @@ build_flags =
   -D MAX_CONTACTS=100
   -D MAX_GROUP_CHANNELS=1
   -D BLE_PIN_CODE=123456
-  -D BLE_DEBUG_LOGGING=1
+;  -D BLE_DEBUG_LOGGING=1
 ;  -D ENABLE_PRIVATE_KEY_IMPORT=1
 ;  -D ENABLE_PRIVATE_KEY_EXPORT=1
 ;  -D MESH_PACKET_LOGGING=1

src/Identity.cpp

@@ -3,6 +3,11 @@
 #define ED25519_NO_SEED  1
 #include <ed_25519.h>
 
+// For ESP32, we use libsodium for cryptographic operations to reduce stack usage
+#ifdef USE_ESP32_ENCRYPTION
+#include <sodium.h>
+#endif
+
 namespace mesh {
 
 Identity::Identity() {
@@ -14,7 +19,14 @@ Identity::Identity(const char* pub_hex) {
 }
 
 bool Identity::verify(const uint8_t* sig, const uint8_t* message, int msg_len) const {
-  return ed25519_verify(sig, message, msg_len, pub_key);
+  #ifdef USE_ESP32_ENCRYPTION
+    // Using libsodium for verification on ESP32 to reduce stack usage
+    // This function performs signature verification with much lower stack requirements
+    // than the default implementation
+    return crypto_sign_ed25519_verify_detached(sig, message, msg_len, pub_key) == 0;
+  #else
+    return ed25519_verify(sig, message, msg_len, pub_key);
+  #endif
 }
 
 bool Identity::readFrom(Stream& s) {
@@ -32,14 +44,29 @@ void Identity::printTo(Stream& s) const {
 LocalIdentity::LocalIdentity() {
   memset(prv_key, 0, sizeof(prv_key));
 }
+
 LocalIdentity::LocalIdentity(const char* prv_hex, const char* pub_hex) : Identity(pub_hex) {
   Utils::fromHex(prv_key, PRV_KEY_SIZE, prv_hex);
 }
 
 LocalIdentity::LocalIdentity(RNG* rng) {
   uint8_t seed[SEED_SIZE];
   rng->random(seed, SEED_SIZE);
-  ed25519_create_keypair(pub_key, prv_key, seed);
+  
+  #ifdef USE_ESP32_ENCRYPTION
+    // Use libsodium for keypair generation on ESP32 to reduce stack usage
+    // NOTE: Format differences between implementations:
+    // - The current ed25519 implementation (orlp/ed25519) uses a 64-byte private key format
+    // - Libsodium also uses a 64-byte format for Ed25519 secret keys, where:
+    //   * First 32 bytes: the actual private key seed
+    //   * Last 32 bytes: the corresponding public key
+    
+    // Generate keypair using libsodium with the provided seed
+    // This avoids the deep stack usage of the default implementation
+    crypto_sign_ed25519_seed_keypair(pub_key, prv_key, seed);
+  #else
+    ed25519_create_keypair(pub_key, prv_key, seed);
+  #endif
 }
 
 bool LocalIdentity::readFrom(Stream& s) {
@@ -77,17 +104,51 @@ void LocalIdentity::readFrom(const uint8_t* src, size_t len) {
     memcpy(pub_key, &src[PRV_KEY_SIZE], PUB_KEY_SIZE);
   } else if (len == PRV_KEY_SIZE) {
     memcpy(prv_key, src, PRV_KEY_SIZE);
-    // now need to re-calculate the pub_key
-    ed25519_derive_pub(pub_key, prv_key);
+    
+  #ifdef USE_ESP32_ENCRYPTION
+      // In libsodium, the private key already contains the public key in its last 32 bytes
+      // We can just extract it directly, avoiding the expensive derivation calculation
+      // This significantly reduces stack usage on ESP32
+      memcpy(pub_key, prv_key + 32, 32);
+  #else
+      // now need to re-calculate the pub_key
+      ed25519_derive_pub(pub_key, prv_key);
+  #endif
   }
 }
 
 void LocalIdentity::sign(uint8_t* sig, const uint8_t* message, int msg_len) const {
-  ed25519_sign(sig, message, msg_len, pub_key, prv_key);
+  #ifdef USE_ESP32_ENCRYPTION
+    // Use libsodium for signing on ESP32 to reduce stack usage
+    // The libsodium implementation uses less stack space than the default ed25519 implementation
+    crypto_sign_ed25519_detached(sig, NULL, message, msg_len, prv_key);
+  #else
+    ed25519_sign(sig, message, msg_len, pub_key, prv_key);
+  #endif
 }
 
 void LocalIdentity::calcSharedSecret(uint8_t* secret, const uint8_t* other_pub_key) {
-  ed25519_key_exchange(secret, other_pub_key, prv_key);
+  #ifdef USE_ESP32_ENCRYPTION
+    // NOTE: To calculate a shared secret with Ed25519 keys and libsodium, we need to:
+    // 1. Convert the Ed25519 keys to Curve25519 (X25519) format
+    // 2. Perform the key exchange using the converted keys
+    //
+    // The default implementation handles this conversion internally,
+    // but with libsodium we need to do these steps explicitly.
+    // This approach uses less stack space compared to the original implementation.
+    
+    unsigned char x25519_pk[crypto_scalarmult_curve25519_BYTES];
+    unsigned char x25519_sk[crypto_scalarmult_curve25519_BYTES];
+    
+    // Convert Ed25519 keys to Curve25519 keys for ECDH
+    crypto_sign_ed25519_pk_to_curve25519(x25519_pk, other_pub_key);
+    crypto_sign_ed25519_sk_to_curve25519(x25519_sk, prv_key);
+    
+    // Calculate shared secret using X25519
+    crypto_scalarmult_curve25519(secret, x25519_sk, x25519_pk);
+  #else
+    ed25519_key_exchange(secret, other_pub_key, prv_key);
+  #endif
 }
 
 }