text: /**
   * \file session_client.h
   * \author Michal Vasko <mvasko@cesnet.cz>
   * \brief libnetconf2 session client manipulation
   *
   * Copyright (c) 2015 CESNET, z.s.p.o.
   *
   * This source code is licensed under BSD 3-Clause License (the "License").
   * You may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     https://opensource.org/licenses/BSD-3-Clause
   */
  
  #ifndef NC_SESSION_CLIENT_H_
  #define NC_SESSION_CLIENT_H_
  
  #include <libyang/libyang.h>
  
  #ifdef NC_ENABLED_SSH
  
  #include <libssh/libssh.h>
  
  #endif
  
  #ifdef NC_ENABLED_TLS
  
  #include <openssl/ssl.h>
  
  #endif
  
  #include "session.h"
  #include "netconf.h"
  #include "messages_client.h"
  
  /**
   * @brief Set location where libnetconf tries to search for YANG/YIN schemas.
   *
   * The location is searched when connecting to a NETCONF server and building
   * YANG context for further processing of the NETCONF messages and data.
   *
   * @param[in] path Directory where to search for YANG/YIN schemas.
   * @return 0 on success, 1 on (memory allocation) failure.
   */
  int nc_client_set_schema_searchpath(const char *path);
  
  /**
   * @brief Get schema searchpath that was set by nc_client_set_schema_searchpath().
   *
   * @return Schema searchpath directory, NULL if not set.
   */
  const char *nc_client_get_schema_searchpath(void);
  
  /**
   * @brief Initialize libssh and/or libssl/libcrypto for use in the client.
   */
  void nc_client_init(void);
  
  /**
   * @brief Destroy all libssh and/or libssl/libcrypto dynamic memory and
   *        the client options, for both SSH and TLS, and for Call Home too.
   */
  void nc_client_destroy(void);
  
  /**
   * @brief Connect to the NETCONF server via proviaded input/output file descriptors.
   *
   * Transport layer is supposed to be already set. Function do not cover authentication
   * or any other manipulation with the transport layer, it only establish NETCONF session
   * by sending and processing NETCONF \<hello\> messages.
   *
   * @param[in] fdin Input file descriptor for reading (clear) data from NETCONF server.
   * @param[in] fdout Output file descriptor for writing (clear) data for NETCONF server.
   * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
   *                (ignoring what is actually supported by the server side). If not set,
   *                YANG context is created for the session using \<get-schema\> (if supported
   *                by the server side) or/and by searching for YANG schemas in the searchpath
   *                (see nc_client_schema_searchpath()). In every case except not providing context
   *                to connect to a server supporting \<get-schema\> it is possible that
   *                the session context will not include all the models supported by the server.
   * @return Created NETCONF session object or NULL in case of error.
   */
  struct nc_session *nc_connect_inout(int fdin, int fdout, struct ly_ctx *ctx);
  
  #ifdef NC_ENABLED_SSH
  
  /**
   * @brief Set SSH authentication hostkey check (knownhosts) callback.
   *
   * @param[in] auth_hostkey_check Function to call, returns 0 on success, non-zero in error.
   *                               If NULL, the default callback is set.
   */
  void nc_client_ssh_set_auth_hostkey_check_clb(int (*auth_hostkey_check)(const char *hostname, ssh_session session));
  
  /**
   * @brief Set SSH password authentication callback.
   *
   * @param[in] auth_password Function to call, returns the password for username\@hostname.
   *                          If NULL, the default callback is set.
   */
  void nc_client_ssh_set_auth_password_clb(char *(*auth_password)(const char *username, const char *hostname));
  
  /**
   * @brief Set SSH interactive authentication callback.
   *
   * @param[in] auth_interactive Function to call for every question, returns the answer for
   *                             authentication name with instruction and echoing prompt.
   *                             If NULL, the default callback is set.
   */
  void nc_client_ssh_set_auth_interactive_clb(char *(*auth_interactive)(const char *auth_name, const char *instruction,
                                                                        const char *prompt, int echo));
  
  /**
   * @brief Set SSH publickey authentication encrypted private key passphrase callback.
   *
   * @param[in] auth_privkey_passphrase Function to call for every question, returns
   *                                    the passphrase for the specific private key.
   */
  void nc_client_ssh_set_auth_privkey_passphrase_clb(char *(*auth_privkey_passphrase)(const char *privkey_path));
  
  /**
   * @brief Add an SSH public and private key pair to be used for client authentication.
   *
   * Private key can be encrypted, the passphrase will be asked for before using it.
   *
   * @param[in] pub_key Path to the public key.
   * @param[in] priv_key Path to the private key.
   * @return 0 on success, -1 on error.
   */
  int nc_client_ssh_add_keypair(const char *pub_key, const char *priv_key);
  
  /**
   * @brief Remove an SSH public and private key pair that was used for client authentication.
   *
   * @param[in] idx Index of the keypair starting with 0.
   * @return 0 on success, -1 on error.
   */
  int nc_client_ssh_del_keypair(int idx);
  
  /**
   * @brief Get the number of public an private key pairs set to be used for client authentication.
   *
   * @return Keypair count.
   */
  int nc_client_ssh_get_keypair_count(void);
  
  /**
   * @brief Get a specific keypair set to be used for client authentication.
   *
   * @param[in] idx Index of the specific keypair.
   * @param[out] pub_key Path to the public key.
   * @param[out] priv_key Path to the private key.
   * @return 0 on success, -1 on error.
   */
  int nc_client_ssh_get_keypair(int idx, const char **pub_key, const char **priv_key);
  
  /**
   * @brief Set SSH authentication method preference.
   *
   * @param[in] auth_type Authentication method to modify the prefrence of.
   * @param[in] pref Preference of \p auth_type. Negative values disable the method.
   */
  void nc_client_ssh_set_auth_pref(NC_SSH_AUTH_TYPE auth_type, int16_t pref);
  
  /**
   * @brief Get SSH authentication method preference.
   *
   * @param[in] auth_type Authentication method to retrieve the prefrence of.
   * @return Preference of the \p auth_type.
   */
  int16_t nc_client_ssh_get_auth_pref(NC_SSH_AUTH_TYPE auth_type);
  
  /**
   * @brief Set client SSH username used for authentication.
   *
   * @param[in] username Username to use.
   * @return 0 on success, -1 on error.
   */
  int nc_client_ssh_set_username(const char *username);
  
  /**
   * @brief Get client SSH username used for authentication.
   *
   * @return Username used.
   */
  const char *nc_client_ssh_get_username(void);
  
  /**
   * @brief Connect to the NETCONF server using SSH transport (via libssh).
   *
   * SSH session is created with default options. If the caller needs to use specific SSH session properties,
   * they are supposed to use nc_connect_libssh().
   *
   * @param[in] host Hostname or address (both Ipv4 and IPv6 are accepted) of the target server.
   *                 'localhost' is used by default if NULL is specified.
   * @param[in] port Port number of the target server. Default value 830 is used if 0 is specified.
   * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
   *                (ignoring what is actually supported by the server side). If not set,
   *                YANG context is created for the session using \<get-schema\> (if supported
   *                by the server side) or/and by searching for YANG schemas in the searchpath
   *                (see nc_client_schema_searchpath()). In every case except not providing context
   *                to connect to a server supporting \<get-schema\> it is possible that
   *                the session context will not include all the models supported by the server.
   * @return Created NETCONF session object or NULL on error.
   */
  struct nc_session *nc_connect_ssh(const char *host, uint16_t port, struct ly_ctx *ctx);
  
  /**
   * @brief Connect to the NETCONF server using the provided SSH (libssh) session.
   *
   * SSH session can have any options set, they will not be modified. If no options were set,
   * host 'localhost', port 22, and the username detected from the EUID is used. If socket is
   * set and connected only the host and the username must be set/is detected. Or the \p ssh_session
   * can already be authenticated in which case it is used directly.
   *
   * @param[in] ssh_session libssh structure representing SSH session object. After passing it
   *                        to libnetconf2 this way, it is fully managed by it (including freeing!).
   * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
   *                (ignoring what is actually supported by the server side). If not set,
   *                YANG context is created for the session using \<get-schema\> (if supported
   *                by the server side) or/and by searching for YANG schemas in the searchpath
   *                (see nc_client_schema_searchpath()). In every case except not providing context
   *                to connect to a server supporting \<get-schema\> it is possible that
   *                the session context will not include all the models supported by the server.
   * @return Created NETCONF session object or NULL on error.
   */
  struct nc_session *nc_connect_libssh(ssh_session ssh_session, struct ly_ctx *ctx);
  
  /**
   * @brief Create another NETCONF session on existing SSH session using separated SSH channel.
   *
   * @param[in] session Existing NETCONF session. The session has to be created on SSH transport layer using libssh -
   *                    it has to be created by nc_connect_ssh(), nc_connect_libssh() or nc_connect_ssh_channel().
   * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
   *                (ignoring what is actually supported by the server side). If not set,
   *                YANG context is created for the session using \<get-schema\> (if supported
   *                by the server side) or/and by searching for YANG schemas in the searchpath
   *                (see nc_client_schema_searchpath()). In every case except not providing context
   *                to connect to a server supporting \<get-schema\> it is possible that
   *                the session context will not include all the models supported by the server.
   * @return Created NETCONF session object or NULL on error.
   */
  struct nc_session *nc_connect_ssh_channel(struct nc_session *session, struct ly_ctx *ctx);
  
  #endif /* NC_ENABLED_SSH */
  
  #ifdef NC_ENABLED_TLS
  
  /**
   * @brief Set client authentication identity - a certificate and a private key.
   *
   * @param[in] client_cert Path to the file containing the client certificate.
   * @param[in] client_key Path to the file containing the private key for the \p client_cert.
   *                       If NULL, key is expected to be stored with \p client_cert.
   * @return 0 on success, -1 on error.
   */
  int nc_client_tls_set_cert_key_paths(const char *client_cert, const char *client_key);
  
  /**
   * @brief Get client authentication identity - a certificate and a private key.
   *
   * @param[out] client_cert Path to the file containing the client certificate. Can be NULL.
   * @param[out] client_key Path to the file containing the private key for the \p client_cert. Can be NULL.
   */
  void nc_client_tls_get_cert_key_paths(const char **client_cert, const char **client_key);
  
  /**
   * @brief Set client trusted CA certificates paths.
   *
   * @param[in] ca_file Location of the CA certificate file used to verify server certificates.
   *                    For more info, see the documentation for SSL_CTX_load_verify_locations() from OpenSSL.
   * @param[in] ca_dir Location of the CA certificates directory used to verify the server certificates.
   *                   For more info, see the documentation for SSL_CTX_load_verify_locations() from OpenSSL.
   * @return 0 on success, -1 on error.
   */
  int nc_client_tls_set_trusted_ca_paths(const char *ca_file, const char *ca_dir);
  
  /**
   * @brief Get client trusted CA certificates paths.
   *
   * @param[out] ca_file Location of the CA certificate file used to verify server certificates.
   *                     Can be NULL.
   * @param[out] ca_dir Location of the CA certificates directory used to verify the server certificates.
   *                    Can be NULL.
   */
  void nc_client_tls_get_trusted_ca_paths(const char **ca_file, const char **ca_dir);
  
  /**
   * @brief Set client Certificate Revocation List paths.
   *
   * @param[in] crl_file Location of the CRL certificate file used to check for revocated certificates.
   * @param[in] crl_dir Location of the CRL certificate directory used to check for revocated certificates.
   * @return 0 on success, -1 on error.
   */
  int nc_client_tls_set_crl_paths(const char *crl_file, const char *crl_dir);
  
  /**
   * @brief Get client Certificate Revocation List paths.
   *
   * @param[out] crl_file Location of the CRL certificate file used to check for revocated certificates.
   * @param[out] crl_dir Location of the CRL certificate directory used to check for revocated certificates.
   */
  void nc_client_tls_get_crl_paths(const char **crl_file, const char **crl_dir);
  
  /**
   * @brief Connect to the NETCONF server using TLS transport (via libssl)
   *
   * TLS session is created with the certificates set using nc_client_tls_* functions, which must be called beforehand!
   * If the caller needs to use specific TLS session properties, they are supposed to use nc_connect_libssl().
   *
   * @param[in] host Hostname or address (both Ipv4 and IPv6 are accepted) of the target server.
   *                 'localhost' is used by default if NULL is specified.
   * @param[in] port Port number of the target server. Default value 6513 is used if 0 is specified.
   * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
   *                (ignoring what is actually supported by the server side). If not set,
   *                YANG context is created for the session using \<get-schema\> (if supported
   *                by the server side) or/and by searching for YANG schemas in the searchpath
   *                (see nc_client_schema_searchpath()). In every case except not providing context
   *                to connect to a server supporting \<get-schema\> it is possible that
   *                the session context will not include all the models supported by the server.
   * @return Created NETCONF session object or NULL on error.
   */
  struct nc_session *nc_connect_tls(const char *host, uint16_t port, struct ly_ctx *ctx);
  
  /**
   * @brief Connect to the NETCONF server using the provided TLS (libssl) session.
   *
   * The TLS session supplied is expected to be fully connected and authenticated!
   *
   * @param[in] tls libssl structure representing the TLS session object.
   * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
   *                (ignoring what is actually supported by the server side). If not set,
   *                YANG context is created for the session using \<get-schema\> (if supported
   *                by the server side) or/and by searching for YANG schemas in the searchpath
   *                (see nc_client_schema_searchpath()). In every case except not providing context
   *                to connect to a server supporting \<get-schema\> it is possible that
   *                the session context will not include all the models supported by the server.
   * @return Created NETCONF session object or NULL on error.
   */
  struct nc_session *nc_connect_libssl(SSL *tls, struct ly_ctx *ctx);
  
  #endif /* NC_ENABLED_TLS */
  
  /**
   * @brief Get session capabilities.
   *
   * @param[in] session Session to get the information from.
   * @return Session capabilities.
   */
  const char **nc_session_get_cpblts(const struct nc_session *session);
  
  /**
   * @brief Check capability presence in a session.
   *
   * @param[in] session Session to check.
   * @param[in] capab Capability to look for, capability with any additional suffix will match.
   * @return Matching capability, NULL if none found.
   */
  const char *nc_session_cpblt(const struct nc_session *session, const char *capab);
  
  /**
   * @brief Check whether the session has a notification thread running.
   *
   * @param[in] session Session to check.
   * @return 1 if notfication thread is running, 0 otherwise.
   */
  int nc_session_ntf_thread_running(const struct nc_session *session);
  
  /**
   * @brief Receive NETCONF RPC reply.
   *
   * If a reply to \<get\> or \<get-config\> RPCs is received, the data are the whole configuration
   * parsed (usually results in more top-level nodes), not just a single 'data' anyxml node with
   * the configuration unparsed inside (which would strictly be according to the model).
   *
   * @param[in] session NETCONF session from which the function gets data. It must be the
   *            client side session object.
   * @param[in] rpc Original RPC this should be the reply to.
   * @param[in] msgid Expected message ID of the reply.
   * @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
   *            waiting and 0 for immediate return if data are not available on the wire.
   * @param[in] parseroptions libyang parseroptions flags, do not set the data type, it is set
   *            internally. LYD_OPT_DESTRUCT and LYD_OPT_NOSIBLINGS is ignored.
   * @param[out] reply Resulting object of NETCONF RPC reply.
   * @return #NC_MSG_REPLY for success,
   *         #NC_MSG_WOULDBLOCK if \p timeout has elapsed,
   *         #NC_MSG_ERROR if reading has failed,
   *         #NC_MSG_NOTIF if a notification was read instead (call this function again to get the reply), and
   *         #NC_MSG_REPLY_ERR_MSGID if a reply with missing or wrong message-id was received.
   */
  NC_MSG_TYPE nc_recv_reply(struct nc_session *session, struct nc_rpc *rpc, uint64_t msgid, int timeout,
                            int parseroptions, struct nc_reply **reply);
  
  /**
   * @brief Receive NETCONF Notification.
   *
   * @param[in] session NETCONF session from which the function gets data. It must be the
   *            client side session object.
   * @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
   *            waiting and 0 for immediate return if data are not available on the wire.
   * @param[out] notif Resulting object of NETCONF Notification.
   * @return #NC_MSG_NOTIF for success,
   *         #NC_MSG_WOULDBLOCK if \p timeout has elapsed,
   *         #NC_MSG_ERROR if reading has failed, and
   *         #NC_MSG_REPLY if a reply was read instead (call this function again to get a notification).
   */
  NC_MSG_TYPE nc_recv_notif(struct nc_session* session, int timeout, struct nc_notif **notif);
  
  /**
   * @brief Receive NETCONF Notifications in a separate thread until the session is terminated
   *        or \<notificationComplete\> is received.
   *
   * @param[in] session Netconf session to read notifications from.
   * @param[in] notif_clb Function that is called for every received notification (including
   *            \<notificationComplete\>). Parameters are the session the notification was received on
   *            and the notification itself.
   * @return 0 if the thread was successfully created, -1 on error.
   */
  int nc_recv_notif_dispatch(struct nc_session *session,
                             void (*notif_clb)(struct nc_session *session, const struct nc_notif *notif));
  
  /**
   * @brief Send NETCONF RPC message via the session.
   *
   * @param[in] session NETCONF session where the RPC will be written.
   * @param[in] rpc NETCOFN RPC object to send via specified session. Object can be created by
   *            nc_rpc_lock(), nc_rpc_unlock() and nc_rpc_generic() functions.
   * @param[in] timeout Timeout for writing in milliseconds. Use negative value for infinite
   *            waiting and 0 for return if data cannot be sent immediately.
   * @param[out] msgid If RPC was successfully sent, this is it's message ID.
   * @return #NC_MSG_RPC on success,
   *         #NC_MSG_WOULDBLOCK in case of a busy session, and
   *         #NC_MSG_ERROR on error.
   */
  NC_MSG_TYPE nc_send_rpc(struct nc_session *session, struct nc_rpc *rpc, int timeout, uint64_t *msgid);
  
  #endif /* NC_SESSION_CLIENT_H_ */
  