/* $OpenBSD: channels.h,v 1.158 2024/10/13 22:20:06 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 client */
#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-client */
#define SSH_CHANNEL_RDYNAMIC_OPEN       21      /* reverse SOCKS, parsing request */
#define SSH_CHANNEL_RDYNAMIC_FINISH     22      /* reverse SOCKS, finishing connect */
#define SSH_CHANNEL_MAX_TYPE            23

#define CHANNEL_CANCEL_PORT_STATIC      -1

/* nonblocking flags for channel_new */
#define CHANNEL_NONBLOCK_LEAVE  0 /* don't modify non-blocking state */
#define CHANNEL_NONBLOCK_SET    1 /* set non-blocking state */
#define CHANNEL_NONBLOCK_STDIO  2 /* set non-blocking and restore on close */

/* c->restore_block mask flags */
#define CHANNEL_RESTORE_RFD     0x01
#define CHANNEL_RESTORE_WFD     0x02
#define CHANNEL_RESTORE_EFD     0x04

/* TCP forwarding */
#define FORWARD_DENY            0
#define FORWARD_REMOTE          (1)
#define FORWARD_LOCAL           (1<<1)
#define FORWARD_ALLOW           (FORWARD_REMOTE|FORWARD_LOCAL)

#define FORWARD_ADM             0x100
#define FORWARD_USER            0x101

struct ssh;
struct Channel;
typedef struct Channel Channel;

typedef void channel_open_fn(struct ssh *, int, int, void *);
typedef void channel_callback_fn(struct ssh *, int, 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 *);

/*
 * NB. channel IDs on the wire and in c->remote_id are uint32, but local
 * channel IDs (e.g. c->self) only ever use the int32 subset of this range,
 * because we use local channel ID -1 for housekeeping. Remote channels have
 * a dedicated "have_remote_id" flag to indicate their validity.
 */

struct Channel {
        int     type;           /* channel type/state */

        int     self;           /* my own channel identifier */
        uint32_t remote_id;     /* channel identifier for remote peer */
        int     have_remote_id; /* non-zero if remote_id is valid */

        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 */
        u_int   io_want;        /* bitmask of SSH_CHAN_IO_* */
        u_int   io_ready;       /* bitmask of SSH_CHAN_IO_* */
        int     pfds[4];        /* pollfd entries for rfd/wfd/efd/sock */
        int     ctl_chan;       /* control channel (multiplexed connections) */
        uint32_t ctl_child_id;  /* child session for mux controllers */
        int     have_ctl_child_id;/* non-zero if ctl_child_id is valid */
        int     isatty;         /* rfd is a tty */
#ifdef _AIX
        int     wfd_isatty;     /* wfd is a tty */
#endif
        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-IO handlers for newly created
                                 * channels are delayed until the first call
                                 * to a matching pre-IO handler.
                                 * this way post-IO handlers are not
                                 * accidentally called if a FD gets reused */
        int     restore_block;  /* fd mask to restore blocking status */
        int     restore_flags[3];/* flags to restore */
        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_exceeded;
        u_int   local_window_max;
        u_int   local_consumed;
        u_int   local_maxpacket;
        int     extended_usage;
        int     single_connection;

        char   *ctype;          /* const type - NB. not freed on channel_free */
        char   *xctype;         /* extended 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;

        /* Inactivity timeouts */

        /* Last traffic seen for OPEN channels */
        time_t                  lastused;
        /* Inactivity timeout deadline in seconds (0 = no timeout) */
        int                     inactive_deadline;
};

#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

/* file descriptor events */
#define SSH_CHAN_IO_RFD                 0x01
#define SSH_CHAN_IO_WFD                 0x02
#define SSH_CHAN_IO_EFD_R               0x04
#define SSH_CHAN_IO_EFD_W               0x08
#define SSH_CHAN_IO_EFD                 (SSH_CHAN_IO_EFD_R|SSH_CHAN_IO_EFD_W)
#define SSH_CHAN_IO_SOCK_R              0x10
#define SSH_CHAN_IO_SOCK_W              0x20
#define SSH_CHAN_IO_SOCK                (SSH_CHAN_IO_SOCK_R|SSH_CHAN_IO_SOCK_W)

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

/* Maximum size for direct reads to buffers */
#define CHANNEL_MAX_READ        CHAN_SES_PACKET_DEFAULT

/* Maximum channel input buffer size */
#define CHAN_INPUT_MAX  (16*1024*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 *, u_int);
Channel *channel_lookup(struct ssh *, int);
Channel *channel_new(struct ssh *, char *, int, int, int, int,
            u_int, u_int, int, const 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_force_close(struct ssh *, Channel *, int);
void     channel_set_xtype(struct ssh *, int, const char *);

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 *, Channel *, int *);
void     channel_send_window_changes(struct ssh *);

/* channel inactivity timeouts */
void channel_add_timeout(struct ssh *, const char *, int);
void channel_clear_timeouts(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_window_adjust(int, u_int32_t, struct ssh *);
int      channel_input_status_confirm(int, u_int32_t, struct ssh *);

/* file descriptor handling (read/write) */
struct pollfd;
struct timespec;

void     channel_prepare_poll(struct ssh *, struct pollfd **,
            u_int *, u_int *, u_int, struct timespec *);
void     channel_after_poll(struct ssh *, struct pollfd *, u_int);
int      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 *);
int      channel_tty_open(struct ssh *);
const char *channel_format_extended_usage(const Channel *);
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(struct ssh *, int);
void     channel_add_permission(struct ssh *, int, int, char *, int);
void     channel_clear_permission(struct ssh *, int, int);
void     channel_disable_admin(struct ssh *, int);
void     channel_update_permission(struct ssh *, int, int);
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*,
            int, int, 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 *, time_t);
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);
int      x11_channel_used_recently(struct ssh *ssh);

/* 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