commit 091a85a7624aa452f46d3090718631907c04f215
author Gilles Peskine <Gilles.Peskine@arm.com> Wed Jun 21 19:51:28 2023 +0200
committer Gilles Peskine <Gilles.Peskine@arm.com> Fri Dec 22 21:30:03 2023 +0100
tree d17b2ee8bbfab9864d87757c2df45395758746a4
parent ba5b5d67aa10e3c7dc5d2136efc226368df1b262

Promise mbedtls_ecp_read_key doesn't overwrite the public key

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

include/mbedtls/ecp.h

diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 9effb72..f169008 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -1262,6 +1262,16 @@
 /**
  * \brief           This function reads an elliptic curve private key.
  *
+ * \note            This function does not set the public key in the
+ *                  key pair object. Without a public key, the key pair object
+ *                  cannot be used with operations that require the public key.
+ *
+ * \note            If a public key has already been set in the key pair
+ *                  object, this function does not check that it is consistent
+ *                  with the private key. Call mbedtls_ecp_check_pub_priv()
+ *                  after setting both the public key and the private key
+ *                  to make that check.
+ *
  * \param grp_id    The ECP group identifier.
  * \param key       The destination key.
  * \param buf       The buffer containing the binary representation of the

tests/suites/test_suite_ecp.function

diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index a4c86e2..aefb57a 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -1044,11 +1044,16 @@
 {
     int ret = 0;
     mbedtls_ecp_keypair key;
-    mbedtls_ecp_keypair key2;
-
     mbedtls_ecp_keypair_init(&key);
+    mbedtls_ecp_keypair key2;
     mbedtls_ecp_keypair_init(&key2);
 
+#if defined(MBEDTLS_BIGNUM_C)
+    TEST_EQUAL(mbedtls_mpi_lset(&key.Q.X, 1), 0);
+    TEST_EQUAL(mbedtls_mpi_lset(&key.Q.Y, 2), 0);
+    TEST_EQUAL(mbedtls_mpi_lset(&key.Q.Z, 3), 0);
+#endif
+
     ret = mbedtls_ecp_read_key(grp_id, &key, in_key->x, in_key->len);
     TEST_ASSERT(ret == expected);
 
@@ -1057,6 +1062,12 @@
         ret = mbedtls_ecp_check_privkey(&key.grp, &key.d);
         TEST_ASSERT(ret == 0);
 
+#if defined(MBEDTLS_BIGNUM_C)
+        TEST_EQUAL(mbedtls_mpi_cmp_int(&key.Q.X, 1), 0);
+        TEST_EQUAL(mbedtls_mpi_cmp_int(&key.Q.Y, 2), 0);
+        TEST_EQUAL(mbedtls_mpi_cmp_int(&key.Q.Z, 3), 0);
+#endif
+
         if (canonical) {
             unsigned char buf[MBEDTLS_ECP_MAX_BYTES];