New function mbedtls_ecp_set_public_key
Set the public key in a key pair. This complements mbedtls_ecp_read_key and
the functions can be used in either order.
Document the need to call check functions separately.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index f169008..96f030d 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -1259,6 +1259,38 @@
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng);
+/** \brief Set the public key in a key pair object.
+ *
+ * \note This function does not check that the point actually
+ * belongs to the given group. Call mbedtls_ecp_check_pubkey()
+ * on \p Q before calling this function to check that.
+ *
+ * \note This function does not check that the public key matches
+ * the private key that is already in \p key, if any.
+ * To check the consistency of the resulting key pair object,
+ * call mbedtls_ecp_check_pub_priv() after setting both
+ * the public key and the private key.
+ *
+ * \param grp_id The ECP group identifier.
+ * \param key The key pair object. It must be initialized.
+ * If its group has already been set, it must match \p grp_id.
+ * If its group has not been set, it will be set to \p grp_id.
+ * If the public key has already been set, it is overwritten.
+ * \param Q The public key to copy. This must be a point on the
+ * curve indicated by \p grp_id.
+ *
+ * \return \c 0 on success.
+ * \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if \p key does not
+ * match \p grp_id.
+ * \return #MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE if the operation for
+ * the group is not implemented.
+ * \return #MBEDTLS_ERR_MPI_ALLOC_FAILED on memory-allocation failure.
+ * \return Another negative error code on other kinds of failure.
+ */
+int mbedtls_ecp_set_public_key(mbedtls_ecp_group_id grp_id,
+ mbedtls_ecp_keypair *key,
+ const mbedtls_ecp_point *Q);
+
/**
* \brief This function reads an elliptic curve private key.
*