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refactor channels.c

Move static state to a "struct ssh_channels" that is allocated at
runtime and tracked as a member of struct ssh.

Explicitly pass "struct ssh" to all channels functions.

Replace use of the legacy packet APIs in channels.c.

Rework sshd_config PermitOpen handling: previously the configuration
parser would call directly into the channels layer. After the refactor
this is not possible, as the channels structures are allocated at
connection time and aren't available when the configuration is parsed.
The server config parser now tracks PermitOpen itself and explicitly
configures the channels code later.

ok markus@

/* $OpenBSD: channels.h,v 1.128 2017/09/12 06:32:07 djm Exp $ */

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */
/*
 * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef CHANNEL_H
#define CHANNEL_H

/* Definitions for channel types. */
#define SSH_CHANNEL_X11_LISTENER	1	/* Listening for inet X11 conn. */
#define SSH_CHANNEL_PORT_LISTENER	2	/* Listening on a port. */
#define SSH_CHANNEL_OPENING		3	/* waiting for confirmation */
#define SSH_CHANNEL_OPEN		4	/* normal open two-way channel */
#define SSH_CHANNEL_CLOSED		5	/* waiting for close confirmation */
#define SSH_CHANNEL_AUTH_SOCKET		6	/* authentication socket */
#define SSH_CHANNEL_X11_OPEN		7	/* reading first X11 packet */
#define SSH_CHANNEL_LARVAL		10	/* larval session */
#define SSH_CHANNEL_RPORT_LISTENER	11	/* Listening to a R-style port  */
#define SSH_CHANNEL_CONNECTING		12
#define SSH_CHANNEL_DYNAMIC		13
#define SSH_CHANNEL_ZOMBIE		14	/* Almost dead. */
#define SSH_CHANNEL_MUX_LISTENER	15	/* Listener for mux conn. */
#define SSH_CHANNEL_MUX_CLIENT		16	/* Conn. to mux slave */
#define SSH_CHANNEL_ABANDONED		17	/* Abandoned session, eg mux */
#define SSH_CHANNEL_UNIX_LISTENER	18	/* Listening on a domain socket. */
#define SSH_CHANNEL_RUNIX_LISTENER	19	/* Listening to a R-style domain socket. */
#define SSH_CHANNEL_MUX_PROXY		20	/* proxy channel for mux-slave */
#define SSH_CHANNEL_MAX_TYPE		21

#define CHANNEL_CANCEL_PORT_STATIC	-1

struct ssh;
struct Channel;
typedef struct Channel Channel;
struct fwd_perm_list;

typedef void channel_open_fn(struct ssh *, int, int, void *);
typedef void channel_callback_fn(struct ssh *, int, void *);
typedef int channel_infilter_fn(struct ssh *, struct Channel *, char *, int);
typedef void channel_filter_cleanup_fn(struct ssh *, int, void *);
typedef u_char *channel_outfilter_fn(struct ssh *, struct Channel *,
    u_char **, size_t *);

/* Channel success/failure callbacks */
typedef void channel_confirm_cb(struct ssh *, int, struct Channel *, void *);
typedef void channel_confirm_abandon_cb(struct ssh *, struct Channel *, void *);
struct channel_confirm {
	TAILQ_ENTRY(channel_confirm) entry;
	channel_confirm_cb *cb;
	channel_confirm_abandon_cb *abandon_cb;
	void *ctx;
};
TAILQ_HEAD(channel_confirms, channel_confirm);

/* Context for non-blocking connects */
struct channel_connect {
	char *host;
	int port;
	struct addrinfo *ai, *aitop;
};

/* Callbacks for mux channels back into client-specific code */
typedef int mux_callback_fn(struct ssh *, struct Channel *);

struct Channel {
	int     type;		/* channel type/state */
	int     self;		/* my own channel identifier */
	int     remote_id;	/* channel identifier for remote peer */
				/* XXX should be uint32_t */
	u_int   istate;		/* input from channel (state of receive half) */
	u_int   ostate;		/* output to channel  (state of transmit half) */
	int     flags;		/* close sent/rcvd */
	int     rfd;		/* read fd */
	int     wfd;		/* write fd */
	int     efd;		/* extended fd */
	int     sock;		/* sock fd */
	int     ctl_chan;	/* control channel (multiplexed connections) */
	int     isatty;		/* rfd is a tty */
	int	client_tty;	/* (client) TTY has been requested */
	int     force_drain;	/* force close on iEOF */
	time_t	notbefore;	/* Pause IO until deadline (time_t) */
	int     delayed;	/* post-select handlers for newly created
				 * channels are delayed until the first call
				 * to a matching pre-select handler.
				 * this way post-select handlers are not
				 * accidentally called if a FD gets reused */
	struct sshbuf *input;	/* data read from socket, to be sent over
				 * encrypted connection */
	struct sshbuf *output;	/* data received over encrypted connection for
				 * send on socket */
	struct sshbuf *extended;

	char    *path;
		/* path for unix domain sockets, or host name for forwards */
	int     listening_port;	/* port being listened for forwards */
	char   *listening_addr;	/* addr being listened for forwards */
	int     host_port;	/* remote port to connect for forwards */
	char   *remote_name;	/* remote hostname */

	u_int	remote_window;
	u_int	remote_maxpacket;
	u_int	local_window;
	u_int	local_window_max;
	u_int	local_consumed;
	u_int	local_maxpacket;
	int     extended_usage;
	int	single_connection;

	char   *ctype;		/* type */

	/* callback */
	channel_open_fn		*open_confirm;
	void			*open_confirm_ctx;
	channel_callback_fn	*detach_user;
	int			detach_close;
	struct channel_confirms	status_confirms;

	/* filter */
	channel_infilter_fn	*input_filter;
	channel_outfilter_fn	*output_filter;
	void			*filter_ctx;
	channel_filter_cleanup_fn *filter_cleanup;

	/* keep boundaries */
	int     		datagram;

	/* non-blocking connect */
	/* XXX make this a pointer so the structure can be opaque */
	struct channel_connect	connect_ctx;

	/* multiplexing protocol hook, called for each packet received */
	mux_callback_fn		*mux_rcb;
	void			*mux_ctx;
	int			mux_pause;
	int     		mux_downstream_id;
};

#define CHAN_EXTENDED_IGNORE		0
#define CHAN_EXTENDED_READ		1
#define CHAN_EXTENDED_WRITE		2

/* default window/packet sizes for tcp/x11-fwd-channel */
#define CHAN_SES_PACKET_DEFAULT	(32*1024)
#define CHAN_SES_WINDOW_DEFAULT	(64*CHAN_SES_PACKET_DEFAULT)
#define CHAN_TCP_PACKET_DEFAULT	(32*1024)
#define CHAN_TCP_WINDOW_DEFAULT	(64*CHAN_TCP_PACKET_DEFAULT)
#define CHAN_X11_PACKET_DEFAULT	(16*1024)
#define CHAN_X11_WINDOW_DEFAULT	(4*CHAN_X11_PACKET_DEFAULT)

/* possible input states */
#define CHAN_INPUT_OPEN			0
#define CHAN_INPUT_WAIT_DRAIN		1
#define CHAN_INPUT_WAIT_OCLOSE		2
#define CHAN_INPUT_CLOSED		3

/* possible output states */
#define CHAN_OUTPUT_OPEN		0
#define CHAN_OUTPUT_WAIT_DRAIN		1
#define CHAN_OUTPUT_WAIT_IEOF		2
#define CHAN_OUTPUT_CLOSED		3

#define CHAN_CLOSE_SENT			0x01
#define CHAN_CLOSE_RCVD			0x02
#define CHAN_EOF_SENT			0x04
#define CHAN_EOF_RCVD			0x08
#define CHAN_LOCAL			0x10

/* Read buffer size */
#define CHAN_RBUF	(16*1024)

/* Hard limit on number of channels */
#define CHANNELS_MAX_CHANNELS	(16*1024)

/* check whether 'efd' is still in use */
#define CHANNEL_EFD_INPUT_ACTIVE(c) \
	(c->extended_usage == CHAN_EXTENDED_READ && \
	(c->efd != -1 || \
	sshbuf_len(c->extended) > 0))
#define CHANNEL_EFD_OUTPUT_ACTIVE(c) \
	(c->extended_usage == CHAN_EXTENDED_WRITE && \
	c->efd != -1 && (!(c->flags & (CHAN_EOF_RCVD|CHAN_CLOSE_RCVD)) || \
	sshbuf_len(c->extended) > 0))

/* Add channel management structures to SSH transport instance */
void channel_init_channels(struct ssh *ssh);

/* channel management */

Channel	*channel_by_id(struct ssh *, int);
Channel	*channel_by_remote_id(struct ssh *, int);
Channel	*channel_lookup(struct ssh *, int);
Channel *channel_new(struct ssh *, char *, int, int, int, int,
	    u_int, u_int, int, char *, int);
void	 channel_set_fds(struct ssh *, int, int, int, int, int,
	    int, int, u_int);
void	 channel_free(struct ssh *, Channel *);
void	 channel_free_all(struct ssh *);
void	 channel_stop_listening(struct ssh *);

void	 channel_send_open(struct ssh *, int);
void	 channel_request_start(struct ssh *, int, char *, int);
void	 channel_register_cleanup(struct ssh *, int,
	    channel_callback_fn *, int);
void	 channel_register_open_confirm(struct ssh *, int,
	    channel_open_fn *, void *);
void	 channel_register_filter(struct ssh *, int, channel_infilter_fn *,
	    channel_outfilter_fn *, channel_filter_cleanup_fn *, void *);
void	 channel_register_status_confirm(struct ssh *, int,
	    channel_confirm_cb *, channel_confirm_abandon_cb *, void *);
void	 channel_cancel_cleanup(struct ssh *, int);
int	 channel_close_fd(struct ssh *, int *);
void	 channel_send_window_changes(struct ssh *);

/* mux proxy support */

int	 channel_proxy_downstream(struct ssh *, Channel *mc);
int	 channel_proxy_upstream(Channel *, int, u_int32_t, struct ssh *);

/* protocol handler */

int	 channel_input_data(int, u_int32_t, struct ssh *);
int	 channel_input_extended_data(int, u_int32_t, struct ssh *);
int	 channel_input_ieof(int, u_int32_t, struct ssh *);
int	 channel_input_oclose(int, u_int32_t, struct ssh *);
int	 channel_input_open_confirmation(int, u_int32_t, struct ssh *);
int	 channel_input_open_failure(int, u_int32_t, struct ssh *);
int	 channel_input_port_open(int, u_int32_t, struct ssh *);
int	 channel_input_window_adjust(int, u_int32_t, struct ssh *);
int	 channel_input_status_confirm(int, u_int32_t, struct ssh *);

/* file descriptor handling (read/write) */

void	 channel_prepare_select(struct ssh *, fd_set **, fd_set **, int *,
	     u_int*, time_t*);
void     channel_after_select(struct ssh *, fd_set *, fd_set *);
void     channel_output_poll(struct ssh *);

int      channel_not_very_much_buffered_data(struct ssh *);
void     channel_close_all(struct ssh *);
int      channel_still_open(struct ssh *);
char	*channel_open_message(struct ssh *);
int	 channel_find_open(struct ssh *);

/* tcp forwarding */
struct Forward;
struct ForwardOptions;
void	 channel_set_af(struct ssh *, int af);
void     channel_permit_all_opens(struct ssh *);
void	 channel_add_permitted_opens(struct ssh *, char *, int);
int	 channel_add_adm_permitted_opens(struct ssh *, char *, int);
void	 channel_copy_adm_permitted_opens(struct ssh *,
	    const struct fwd_perm_list *);
void	 channel_disable_adm_local_opens(struct ssh *);
void	 channel_update_permitted_opens(struct ssh *, int, int);
void	 channel_clear_permitted_opens(struct ssh *);
void	 channel_clear_adm_permitted_opens(struct ssh *);
void 	 channel_print_adm_permitted_opens(struct ssh *);
Channel	*channel_connect_to_port(struct ssh *, const char *, u_short,
	    char *, char *, int *, const char **);
Channel *channel_connect_to_path(struct ssh *, const char *, char *, char *);
Channel	*channel_connect_stdio_fwd(struct ssh *, const char*,
	    u_short, int, int);
Channel	*channel_connect_by_listen_address(struct ssh *, const char *,
	    u_short, char *, char *);
Channel	*channel_connect_by_listen_path(struct ssh *, const char *,
	    char *, char *);
int	 channel_request_remote_forwarding(struct ssh *, struct Forward *);
int	 channel_setup_local_fwd_listener(struct ssh *, struct Forward *,
	    struct ForwardOptions *);
int	 channel_request_rforward_cancel(struct ssh *, struct Forward *);
int	 channel_setup_remote_fwd_listener(struct ssh *, struct Forward *,
	    int *, struct ForwardOptions *);
int	 channel_cancel_rport_listener(struct ssh *, struct Forward *);
int	 channel_cancel_lport_listener(struct ssh *, struct Forward *,
	    int, struct ForwardOptions *);
int	 permitopen_port(const char *);

/* x11 forwarding */

void	 channel_set_x11_refuse_time(struct ssh *, u_int);
int	 x11_connect_display(struct ssh *);
int	 x11_create_display_inet(struct ssh *, int, int, int, u_int *, int **);
void	 x11_request_forwarding_with_spoofing(struct ssh *, int,
	    const char *, const char *, const char *, int);

/* channel close */

int	 chan_is_dead(struct ssh *, Channel *, int);
void	 chan_mark_dead(struct ssh *, Channel *);

/* channel events */

void	 chan_rcvd_oclose(struct ssh *, Channel *);
void	 chan_rcvd_eow(struct ssh *, Channel *);
void	 chan_read_failed(struct ssh *, Channel *);
void	 chan_ibuf_empty(struct ssh *, Channel *);
void	 chan_rcvd_ieof(struct ssh *, Channel *);
void	 chan_write_failed(struct ssh *, Channel *);
void	 chan_obuf_empty(struct ssh *, Channel *);

#endif