Add SSL configuration API for trusted CA callbacks
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index b793ac0..d1ba608 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2071,6 +2071,63 @@
mbedtls_x509_crt *ca_chain,
mbedtls_x509_crl *ca_crl );
+#if defined(MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK)
+/**
+ * \brief Set the trusted certificate callback.
+ *
+ * This API allows to register the set of trusted certificates
+ * through a callback, instead of a linked list as configured
+ * by mbedtls_ssl_conf_ca_chain().
+ *
+ * This is useful for example in contexts where a large number
+ * of CAs are used, and the inefficiency of maintaining them
+ * in a linked list cannot be tolerated. It is also useful when
+ * the set of trusted CAs needs to be modified frequently.
+ *
+ * See the documentation of `mbedtls_x509_crt_ca_cb_t` for
+ * more information.
+ *
+ * \param conf The SSL configuration to register the callback with.
+ * \param f_ca_cb The trusted certificate callback to use when verifying
+ * certificate chains.
+ * \param p_ca_cb The context to be passed to \p f_ca_cb (for example,
+ * a reference to a trusted CA database).
+ *
+ * \note This API is incompatible with mbedtls_ssl_conf_ca_chain():
+ * Any call to this function overwrites the values set through
+ * earlier calls to mbedtls_ssl_conf_ca_chain() or
+ * mbedtls_ssl_conf_ca_cb().
+ *
+ * \note This API is incompatible with CA indication in
+ * CertificateRequest messages: A server-side SSL context which
+ * is bound to an SSL configuration that uses a CA callback
+ * configured via mbedtls_ssl_conf_ca_cb(), and which requires
+ * client authentication, will send an empty CA list in the
+ * corresponding CertificateRequest message.
+ *
+ * \note This API is incompatible with mbedtls_ssl_set_hs_ca_chain():
+ * If an SSL context is bound to an SSL configuration which uses
+ * CA callbacks configured via mbedtls_ssl_conf_ca_cb(), then
+ * calls to mbedtls_ssl_set_hs_ca_chain() have no effect.
+ *
+ * \note The use of this API disables the use of restartable ECC
+ * during X.509 CRT signature verification (but doesn't affect
+ * other uses).
+ *
+ * \warning This API is incompatible with the use of CRLs. Any call to
+ * mbedtls_ssl_conf_ca_cb() unsets CRLs configured through
+ * earlier calls to mbedtls_ssl_conf_ca_chain().
+ *
+ * \warning In multi-threaded environments, the callback \p f_ca_cb
+ * must be thread-safe, and it is the user's responsibility
+ * to guaranteee this (for example through a mutex
+ * contained in the callback context pointed to by \p p_ca_cb).
+ */
+void mbedtls_ssl_conf_ca_cb( mbedtls_ssl_config *conf,
+ mbedtls_x509_crt_ca_cb_t f_ca_cb,
+ void *p_ca_cb );
+#endif /* MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK */
+
/**
* \brief Set own certificate chain and private key
*