refactor(crypto,core,lagacy): use secp256k1 submodule for ECDH

[no changelog]

core/SConscript.firmware

@@ -188,6 +188,7 @@ if FEATURE_FLAGS["SECP256K1_ZKP"]:
         'ENABLE_MODULE_RECOVERY',
         'ENABLE_MODULE_SCHNORRSIG',
         'ENABLE_MODULE_EXTRAKEYS',
+        'ENABLE_MODULE_ECDH',
     ]
     SOURCE_MOD_SECP256K1_ZKP = [
         'vendor/secp256k1-zkp/src/secp256k1.c',
@@ -779,7 +780,7 @@ obj_program = []
 obj_program.extend(env.Object(source=SOURCE_MOD))
 obj_program.extend(env.Object(source=SOURCE_MOD_CRYPTO, CCFLAGS='$CCFLAGS -ftrivial-auto-var-init=zero'))
 if FEATURE_FLAGS["SECP256K1_ZKP"]:
-    obj_program.extend(env.Object(source=SOURCE_MOD_SECP256K1_ZKP, CCFLAGS='$CCFLAGS -Wno-unused-function'))
+    obj_program.extend(env.Object(source=SOURCE_MOD_SECP256K1_ZKP, CCFLAGS='$CCFLAGS -Wno-unused-function -Wno-maybe-uninitialized'))
     source_files.extend(SOURCE_MOD_SECP256K1_ZKP)
 obj_program.extend(env.Object(source=SOURCE_FIRMWARE))
 obj_program.extend(env.Object(source=SOURCE_MICROPYTHON))

core/SConscript.unix

@@ -189,6 +189,7 @@ if FEATURE_FLAGS["SECP256K1_ZKP"]:
         'ENABLE_MODULE_RECOVERY',
         'ENABLE_MODULE_SCHNORRSIG',
         'ENABLE_MODULE_EXTRAKEYS',
+        'ENABLE_MODULE_ECDH',
     ]
     SOURCE_MOD_SECP256K1_ZKP = [
         'vendor/secp256k1-zkp/src/secp256k1.c',
@@ -824,7 +825,7 @@ source_files = SOURCE_MOD + SOURCE_MOD_CRYPTO + SOURCE_MICROPYTHON + SOURCE_UNIX
 obj_program.extend(env.Object(source=SOURCE_MOD))
 obj_program.extend(env.Object(source=SOURCE_MOD_CRYPTO, CCFLAGS='$CCFLAGS -ftrivial-auto-var-init=zero'))
 if FEATURE_FLAGS["SECP256K1_ZKP"]:
-    obj_program.extend(env.Object(source=SOURCE_MOD_SECP256K1_ZKP, CCFLAGS='$CCFLAGS -Wno-unused-function'))
+    obj_program.extend(env.Object(source=SOURCE_MOD_SECP256K1_ZKP, CCFLAGS='$CCFLAGS -Wno-unused-function -Wno-maybe-uninitialized'))
     source_files.extend(SOURCE_MOD_SECP256K1_ZKP)
 obj_program.extend(env.Object(source=SOURCE_MICROPYTHON))
 obj_program.extend(env.Object(source=SOURCE_UNIX))

crypto/Makefile

@@ -69,7 +69,8 @@ ZKP_CFLAGS = \
 	-DENABLE_MODULE_GENERATOR \
 	-DENABLE_MODULE_RECOVERY \
 	-DENABLE_MODULE_SCHNORRSIG \
-	-DENABLE_MODULE_EXTRAKEYS
+	-DENABLE_MODULE_EXTRAKEYS \
+	-DENABLE_MODULE_ECDH
 ZKP_PATH = ../vendor/secp256k1-zkp
 # this is specific for 64-bit builds
 CFLAGS += -DSECP256K1_CONTEXT_SIZE=208

crypto/ecdsa.c

@@ -635,7 +635,7 @@ int scalar_multiply(const ecdsa_curve *curve, const bignum256 *k,
 
 #endif
 
-int ecdh_multiply(const ecdsa_curve *curve, const uint8_t *priv_key,
+int tc_ecdh_multiply(const ecdsa_curve *curve, const uint8_t *priv_key,
                      const uint8_t *pub_key, uint8_t *session_key) {
   curve_point point = {0};
   if (!ecdsa_read_pubkey(curve, pub_key, &point)) {
@@ -1312,3 +1312,13 @@ int ecdsa_recover_pub_from_sig(const ecdsa_curve *curve, uint8_t *pub_key,
 #endif
   return tc_ecdsa_recover_pub_from_sig(curve, pub_key, sig, digest, recid);
 }
+
+int ecdh_multiply(const ecdsa_curve *curve, const uint8_t *priv_key,
+                  const uint8_t *pub_key, uint8_t *session_key) {
+#ifdef USE_SECP256K1_ZKP_ECDSA
+  if (curve == &secp256k1) {
+    return zkp_ecdh_multiply(curve, priv_key, pub_key, session_key);
+  }
+#endif
+  return tc_ecdh_multiply(curve, priv_key, pub_key, session_key);
+}

crypto/ecdsa_internal.h

@@ -39,5 +39,6 @@ int tc_ecdsa_verify_digest(const ecdsa_curve *curve, const uint8_t *pub_key,
 int tc_ecdsa_recover_pub_from_sig(const ecdsa_curve *curve, uint8_t *pub_key,
                                   const uint8_t *sig, const uint8_t *digest,
                                   int recid);
-
+int tc_ecdh_multiply(const ecdsa_curve *curve, const uint8_t *priv_key,
+                     const uint8_t *pub_key, uint8_t *session_key);
 #endif

crypto/tests/test_check.c

@@ -4426,6 +4426,90 @@ START_TEST(test_aes) {
 }
 END_TEST
 
+static void test_ecdh_multiply_helper(
+    int (*ecdh_multiply_fn)(const ecdsa_curve *curve, const uint8_t *priv_key,
+                            const uint8_t *pub_key, uint8_t *session_key)) {
+  static struct {
+    const char *priv_key;
+    const char *pub_key;
+    int res;
+    const char *session_key;
+  } tests[] = {
+      // Compressed public key
+      {"1618cc490a4a5b38d9f877759a2c312026fe9f459edb9ba49e91b6de4a237cad",
+       "0322c16706cd0d80dbb4e314799ba1323420e7ffa859a0cf0c82a444192bb6c997", 0,
+       "047b27ebb15e8197c9a560afc1bd45e2a78b864829fc1257333a1a2d7d30d79eed17889"
+       "8ad4960f756cf155cf46d22f2e3b21df10ee5bad560c467ae0d79427a70"},
+      // Uncompressed public key
+      {"55b57f9ffc79d206eaa2b25dd5fe5a0be2d9d880ddfa777a3a0f9c0b2d3a191e",
+       "04816c5bb10c97b96a0b02382b8f8c1a8876218af04396976dace353a139752c6baef57"
+       "449121650cefca54cf9ac4e304890ada667512b5d98171b54a5a8347b09",
+       0,
+       "049b3ab299d119eb89b632ff63ed0b3790508a0020fd729bbc35f39d221101ac5edc3be"
+       "e252886ea8f68c835ed410b715d41e967d0bd10a01a4b01eaa2320a7f4d"},
+      // Invalid compressed public key
+      {"d2ffd4daa78a7fb253edb315e27f5841df00a581ab2c3330ffded22be98b7c96",
+       "026a575a9f3d4e945366a78e7961b312018451df8485ee1210767a0575225c2764", 1,
+       ""},
+      // Invalid uncompressed public key
+      {"7da05844e870b1674c14a9a80b45ef36d221680707b727a7b6c70b2a25e99717",
+       "71ebf221ab355d070a570525e4c4bff94b27ca97e67fcdfb993f6546e7e1ead0ea09ed1"
+       "f7e55282f2787c7fc54cc5815660641cd95148a4b56f15818a04c7f72",
+       1, ""},
+      // Invalid compressed public key - the point at infinity
+      {"6753537e70935a9c85b0bad5b2aa54fb565b50bcf086acc7836a94318bc442d4",
+       "000000000000000000000000000000000000000000000000000000000000000000", 1,
+       ""},
+      // Invalid uncompressed public key - the point at infinity
+      {"6753537e70935a9c85b0bad5b2aa54fb565b50bcf086acc7836a94318bc442d4",
+       "0000000000000000000000000000000000000000000000000000000000000000000000"
+       "0"
+       "00000000000000000000000000000000000000000000000000000000000",
+       1, ""},
+      // Invalid private key - the group order
+      {"fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141",
+       "02e38ad3515c21358659ef113864b26e6caaa6bb780ce02daaf1c13f4fe24bb632", 2,
+       ""},
+      // Invalid private key - zero
+      {"0000000000000000000000000000000000000000000000000000000000000000",
+       "038325242a489e883afdc86da5a714e4ffc86530e1b6660ac87ffb87c0045e486c", 2,
+       ""},
+  };
+
+  const ecdsa_curve *curve = &secp256k1;
+  uint8_t priv_key[32] = {0};
+  uint8_t pub_key[65] = {0};
+  uint8_t session_key[65] = {0};
+  uint8_t expected_session_key[65] = {0};
+  int expected_res = 0;
+  int res = 0;
+
+  for (size_t i = 0; i < sizeof(tests) / sizeof(*tests); i++) {
+    memcpy(priv_key, fromhex(tests[i].priv_key), 32);
+    memcpy(pub_key, fromhex(tests[i].pub_key), 65);
+    expected_res = tests[i].res;
+    if (expected_res == 0) {
+      memcpy(expected_session_key, fromhex(tests[i].session_key), 65);
+    }
+
+    res = ecdh_multiply_fn(curve, priv_key, pub_key, session_key);
+    ck_assert_int_eq(expected_res, res);
+    if (expected_res == 0) {
+      ck_assert_mem_eq(expected_session_key, session_key, 65);
+    }
+  }
+}
+
+START_TEST(test_tc_ecdh_multiply) {
+  test_ecdh_multiply_helper(tc_ecdh_multiply);
+}
+END_TEST
+
+START_TEST(test_zkp_ecdh_multiply) {
+  test_ecdh_multiply_helper(zkp_ecdh_multiply);
+}
+END_TEST
+
 // test vectors from
 // https://datatracker.ietf.org/doc/html/rfc3610
 // https://doi.org/10.6028/NIST.SP.800-38C
@@ -11351,10 +11435,12 @@ Suite *test_suite(void) {
   tcase_add_test(tc, test_tc_ecdsa_get_public_key65);
   tcase_add_test(tc, test_tc_ecdsa_recover_pub_from_sig);
   tcase_add_test(tc, test_tc_ecdsa_verify_digest);
+  tcase_add_test(tc, test_tc_ecdh_multiply);
   tcase_add_test(tc, test_zkp_ecdsa_get_public_key33);
   tcase_add_test(tc, test_zkp_ecdsa_get_public_key65);
   tcase_add_test(tc, test_zkp_ecdsa_recover_pub_from_sig);
   tcase_add_test(tc, test_zkp_ecdsa_verify_digest);
+  tcase_add_test(tc, test_zkp_ecdh_multiply);
 #if USE_RFC6979
   tcase_add_test(tc, test_tc_ecdsa_sign_digest_deterministic);
   tcase_add_test(tc, test_zkp_ecdsa_sign_digest_deterministic);

crypto/zkp_ecdsa.c

@@ -29,6 +29,7 @@
 #include "zkp_context.h"
 
 #include "vendor/secp256k1-zkp/include/secp256k1.h"
+#include "vendor/secp256k1-zkp/include/secp256k1_ecdh.h"
 #include "vendor/secp256k1-zkp/include/secp256k1_extrakeys.h"
 #include "vendor/secp256k1-zkp/include/secp256k1_preallocated.h"
 #include "vendor/secp256k1-zkp/include/secp256k1_recovery.h"
@@ -403,3 +404,79 @@ int zkp_ecdsa_verify(const ecdsa_curve *curve, HasherType hasher_type,
   memzero(hash, sizeof(hash));
   return result;
 }
+
+static int plain_hash_function(unsigned char *output, const unsigned char *x32,
+                               const unsigned char *y32, void *data) {
+  (void)data;
+  output[0] = 0x04;
+  memcpy(output + 1, x32, 32);
+  memcpy(output + 33, y32, 32);
+  return 1;
+}
+
+// ECDH multiplication
+// curve has to be &secp256k1
+// private_key_bytes has 32 bytes
+// public_key_bytes has 33 or 65 bytes
+// session key has 65 bytes
+// returns 0 on success
+int zkp_ecdh_multiply(const ecdsa_curve *curve,
+                      const uint8_t *private_key_bytes,
+                      const uint8_t *public_key_bytes, uint8_t *session_key) {
+  assert(curve == &secp256k1);
+  if (curve != &secp256k1) {
+    return 1;
+  }
+
+  int result = 0;
+
+  int public_key_length = 0;
+
+  if (result == 0) {
+    if (public_key_bytes[0] == 0x04) {
+      public_key_length = 65;
+    } else if (public_key_bytes[0] == 0x02 || public_key_bytes[0] == 0x03) {
+      public_key_length = 33;
+    } else {
+      result = 1;
+    }
+  }
+
+  const secp256k1_context *context_read_only = zkp_context_get_read_only();
+  secp256k1_pubkey public_key = {0};
+
+  if (result == 0) {
+    if (secp256k1_ec_pubkey_parse(context_read_only, &public_key,
+                                  public_key_bytes, public_key_length) != 1) {
+      result = 1;
+    }
+  }
+
+  secp256k1_context *context_writable = NULL;
+  if (result == 0) {
+    context_writable = zkp_context_acquire_writable();
+    if (context_writable == NULL) {
+      result = 1;
+    }
+  }
+  if (result == 0) {
+    if (secp256k1_context_writable_randomize(context_writable) != 0) {
+      result = 1;
+    }
+  }
+
+  if (result == 0) {
+    if (secp256k1_ecdh(context_writable, session_key, &public_key,
+                       private_key_bytes, plain_hash_function, NULL) != 1) {
+      result = 2;
+    }
+  }
+
+  if (context_writable) {
+    zkp_context_release_writable();
+    context_writable = NULL;
+  }
+  memzero(&public_key, sizeof(public_key));
+
+  return result;
+}

crypto/zkp_ecdsa.h

@@ -27,4 +27,6 @@ int zkp_ecdsa_verify_digest(const ecdsa_curve *curve,
 int zkp_ecdsa_verify(const ecdsa_curve *curve, HasherType hasher_sign,
                      const uint8_t *pub_key, const uint8_t *sig,
                      const uint8_t *msg, uint32_t msg_len);
+int zkp_ecdh_multiply(const ecdsa_curve *curve, const uint8_t *priv_key,
+                      const uint8_t *pub_key, uint8_t *session_key);
 #endif

legacy/firmware/Makefile

@@ -23,7 +23,8 @@ ZKP_CFLAGS = \
 	-DENABLE_MODULE_GENERATOR \
 	-DENABLE_MODULE_RECOVERY \
 	-DENABLE_MODULE_SCHNORRSIG \
-	-DENABLE_MODULE_EXTRAKEYS
+	-DENABLE_MODULE_EXTRAKEYS \
+	-DENABLE_MODULE_ECDH
 
 OBJS += secp256k1-zkp.o
 OBJS += precomputed_ecmult.o