Fix ECC validation regression

Author: Frauschi

tests/api/test_ecc.c

@@ -772,6 +772,55 @@ int test_wc_ecc_import_x963(void)
     return EXPECT_RESULT();
 } /* END wc_ecc_import_x963 */
 
+/*
+ * testing wc_ecc_import_x963() rejects an off-curve public point.
+ *
+ * Regression coverage for the invalid-curve attack: the legacy wrapper
+ * wc_ecc_import_x963_ex must pass untrusted=1 to wc_ecc_import_x963_ex2
+ * so that ECIES, PKCS#7 KARI, and EVP ECDH callers validate that the
+ * imported point actually lies on the curve. Without that, an attacker
+ * can feed a point from a weak twist and leak the victim's private
+ * scalar modulo small primes (Biehl-Meyer-Mueller).
+ */
+int test_wc_ecc_import_x963_off_curve(void)
+{
+    EXPECT_DECLS;
+#if defined(HAVE_ECC) && defined(HAVE_ECC_KEY_IMPORT) && \
+    !defined(NO_ECC256) && !defined(NO_ECC_SECP)
+    ecc_key pubKey;
+    /* Uncompressed X9.63 P-256 point: 0x04 || Gx || Gy with the last byte
+     * of Gy flipped by 1. Gx/Gy are the NIST P-256 generator coordinates;
+     * modifying a single bit of Gy produces a point that is not on the
+     * curve, so wc_ecc_import_x963 must reject it. */
+    static const byte offCurveX963[] = {
+        0x04,
+        0x6B, 0x17, 0xD1, 0xF2, 0xE1, 0x2C, 0x42, 0x47,
+        0xF8, 0xBC, 0xE6, 0xE5, 0x63, 0xA4, 0x40, 0xF2,
+        0x77, 0x03, 0x7D, 0x81, 0x2D, 0xEB, 0x33, 0xA0,
+        0xF4, 0xA1, 0x39, 0x45, 0xD8, 0x98, 0xC2, 0x96,
+        0x4F, 0xE3, 0x42, 0xE2, 0xFE, 0x1A, 0x7F, 0x9B,
+        0x8E, 0xE7, 0xEB, 0x4A, 0x7C, 0x0F, 0x9E, 0x16,
+        0x2B, 0xCE, 0x33, 0x57, 0x6B, 0x31, 0x5E, 0xCE,
+        0xCB, 0xB6, 0x40, 0x68, 0x37, 0xBF, 0x51, 0xF4
+    };
+
+    XMEMSET(&pubKey, 0, sizeof(ecc_key));
+
+    ExpectIntEQ(wc_ecc_init(&pubKey), 0);
+
+    /* Importing an off-curve point must fail. */
+    ExpectIntNE(wc_ecc_import_x963(offCurveX963, (word32)sizeof(offCurveX963),
+                                   &pubKey), 0);
+
+    wc_ecc_free(&pubKey);
+
+#ifdef FP_ECC
+    wc_ecc_fp_free();
+#endif
+#endif
+    return EXPECT_RESULT();
+} /* END test_wc_ecc_import_x963_off_curve */
+
 /*
  * testing wc_ecc_import_private_key()
  */

tests/api/test_ecc.h

@@ -39,6 +39,7 @@ int test_wc_ecc_shared_secret(void);
 int test_wc_ecc_export_x963(void);
 int test_wc_ecc_export_x963_ex(void);
 int test_wc_ecc_import_x963(void);
+int test_wc_ecc_import_x963_off_curve(void);
 int test_wc_ecc_import_private_key(void);
 int test_wc_ecc_export_private_only(void);
 int test_wc_ecc_rs_to_sig(void);
@@ -76,6 +77,7 @@ int test_wc_EccPrivateKeyToDer(void);
     TEST_DECL_GROUP("ecc", test_wc_ecc_export_x963),                    \
     TEST_DECL_GROUP("ecc", test_wc_ecc_export_x963_ex),                 \
     TEST_DECL_GROUP("ecc", test_wc_ecc_import_x963),                    \
+    TEST_DECL_GROUP("ecc", test_wc_ecc_import_x963_off_curve),          \
     TEST_DECL_GROUP("ecc", test_wc_ecc_import_private_key),             \
     TEST_DECL_GROUP("ecc", test_wc_ecc_export_private_only),            \
     TEST_DECL_GROUP("ecc", test_wc_ecc_rs_to_sig),                      \

wolfcrypt/src/ecc.c

@@ -11217,7 +11217,8 @@ int wc_ecc_import_x963_ex2(const byte* in, word32 inLen, ecc_key* key,
 int wc_ecc_import_x963_ex(const byte* in, word32 inLen, ecc_key* key,
                           int curve_id)
 {
-    return wc_ecc_import_x963_ex2(in, inLen, key, curve_id, 0);
+    /* treat as untrusted: validate the point is on the curve */
+    return wc_ecc_import_x963_ex2(in, inLen, key, curve_id, 1);
 }
 
 WOLFSSL_ABI