/* $NetBSD: nchan.c,v 1.10.2.1 2023/12/25 12:31:05 martin Exp $ */ /* $OpenBSD: nchan.c,v 1.74 2022/02/01 23:32:51 djm Exp $ */ /* * 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. */ #include "includes.h" __RCSID("$NetBSD: nchan.c,v 1.10.2.1 2023/12/25 12:31:05 martin Exp $"); #include #include #include #include #include #include #include "ssh2.h" #include "sshbuf.h" #include "ssherr.h" #include "packet.h" #include "channels.h" #include "compat.h" #include "log.h" /* * SSH Protocol 1.5 aka New Channel Protocol * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored. * Written by Markus Friedl in October 1999 * * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the * tear down of channels: * * 1.3: strict request-ack-protocol: * CLOSE -> * <- CLOSE_CONFIRM * * 1.5: uses variations of: * IEOF -> * <- OCLOSE * <- IEOF * OCLOSE -> * i.e. both sides have to close the channel * * 2.0: the EOF messages are optional * * See the debugging output from 'ssh -v' and 'sshd -d' of * ssh-1.2.27 as an example. * */ /* functions manipulating channel states */ /* * EVENTS update channel input/output states execute ACTIONS */ /* * ACTIONS: should never update the channel states */ static void chan_send_eof2(struct ssh *, Channel *); static void chan_send_eow2(struct ssh *, Channel *); /* helper */ static void chan_shutdown_write(struct ssh *, Channel *); static void chan_shutdown_read(struct ssh *, Channel *); static void chan_shutdown_extended_read(struct ssh *, Channel *); static const char * const ostates[] = { "open", "drain", "wait_ieof", "closed", }; static const char * const istates[] = { "open", "drain", "wait_oclose", "closed", }; static void chan_set_istate(Channel *c, u_int next) { if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED) fatal("chan_set_istate: bad state %d -> %d", c->istate, next); debug2("channel %d: input %s -> %s", c->self, istates[c->istate], istates[next]); c->istate = next; } static void chan_set_ostate(Channel *c, u_int next) { if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED) fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next); debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate], ostates[next]); c->ostate = next; } void chan_read_failed(struct ssh *ssh, Channel *c) { debug2("channel %d: read failed", c->self); switch (c->istate) { case CHAN_INPUT_OPEN: chan_shutdown_read(ssh, c); chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN); break; default: error("channel %d: chan_read_failed for istate %d", c->self, c->istate); break; } } void chan_ibuf_empty(struct ssh *ssh, Channel *c) { debug2("channel %d: ibuf empty", c->self); if (sshbuf_len(c->input)) { error("channel %d: chan_ibuf_empty for non empty buffer", c->self); return; } switch (c->istate) { case CHAN_INPUT_WAIT_DRAIN: if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL))) chan_send_eof2(ssh, c); chan_set_istate(c, CHAN_INPUT_CLOSED); break; default: error("channel %d: chan_ibuf_empty for istate %d", c->self, c->istate); break; } } void chan_obuf_empty(struct ssh *ssh, Channel *c) { debug2("channel %d: obuf empty", c->self); if (sshbuf_len(c->output)) { error("channel %d: chan_obuf_empty for non empty buffer", c->self); return; } switch (c->ostate) { case CHAN_OUTPUT_WAIT_DRAIN: chan_shutdown_write(ssh, c); chan_set_ostate(c, CHAN_OUTPUT_CLOSED); break; default: error("channel %d: internal error: obuf_empty for ostate %d", c->self, c->ostate); break; } } void chan_rcvd_eow(struct ssh *ssh, Channel *c) { debug2("channel %d: rcvd eow", c->self); switch (c->istate) { case CHAN_INPUT_OPEN: chan_shutdown_read(ssh, c); chan_set_istate(c, CHAN_INPUT_CLOSED); break; } } static void chan_send_eof2(struct ssh *ssh, Channel *c) { int r; debug2("channel %d: send eof", c->self); switch (c->istate) { case CHAN_INPUT_WAIT_DRAIN: if (!c->have_remote_id) fatal_f("channel %d: no remote_id", c->self); if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 || (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || (r = sshpkt_send(ssh)) != 0) fatal_fr(r, "send CHANNEL_EOF"); c->flags |= CHAN_EOF_SENT; break; default: error("channel %d: cannot send eof for istate %d", c->self, c->istate); break; } } static void chan_send_close2(struct ssh *ssh, Channel *c) { int r; debug2("channel %d: send close", c->self); if (c->ostate != CHAN_OUTPUT_CLOSED || c->istate != CHAN_INPUT_CLOSED) { error("channel %d: cannot send close for istate/ostate %d/%d", c->self, c->istate, c->ostate); } else if (c->flags & CHAN_CLOSE_SENT) { error("channel %d: already sent close", c->self); } else { if (!c->have_remote_id) fatal_f("channel %d: no remote_id", c->self); if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 || (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || (r = sshpkt_send(ssh)) != 0) fatal_fr(r, "send CHANNEL_EOF"); c->flags |= CHAN_CLOSE_SENT; } } static void chan_send_eow2(struct ssh *ssh, Channel *c) { int r; debug2("channel %d: send eow", c->self); if (c->ostate == CHAN_OUTPUT_CLOSED) { error("channel %d: must not sent eow on closed output", c->self); return; } if (!(ssh->compat & SSH_NEW_OPENSSH)) return; if (!c->have_remote_id) fatal_f("channel %d: no remote_id", c->self); if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 || (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 || (r = sshpkt_put_u8(ssh, 0)) != 0 || (r = sshpkt_send(ssh)) != 0) fatal_fr(r, "send CHANNEL_EOF"); } /* shared */ void chan_rcvd_ieof(struct ssh *ssh, Channel *c) { debug2("channel %d: rcvd eof", c->self); c->flags |= CHAN_EOF_RCVD; if (c->ostate == CHAN_OUTPUT_OPEN) chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN); if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN && sshbuf_len(c->output) == 0 && !CHANNEL_EFD_OUTPUT_ACTIVE(c)) chan_obuf_empty(ssh, c); } void chan_rcvd_oclose(struct ssh *ssh, Channel *c) { debug2("channel %d: rcvd close", c->self); if (!(c->flags & CHAN_LOCAL)) { if (c->flags & CHAN_CLOSE_RCVD) error("channel %d: protocol error: close rcvd twice", c->self); c->flags |= CHAN_CLOSE_RCVD; } if (c->type == SSH_CHANNEL_LARVAL) { /* tear down larval channels immediately */ chan_set_ostate(c, CHAN_OUTPUT_CLOSED); chan_set_istate(c, CHAN_INPUT_CLOSED); return; } switch (c->ostate) { case CHAN_OUTPUT_OPEN: /* * wait until a data from the channel is consumed if a CLOSE * is received */ chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN); break; } switch (c->istate) { case CHAN_INPUT_OPEN: chan_shutdown_read(ssh, c); chan_shutdown_extended_read(ssh, c); chan_set_istate(c, CHAN_INPUT_CLOSED); break; case CHAN_INPUT_WAIT_DRAIN: if (!(c->flags & CHAN_LOCAL)) chan_send_eof2(ssh, c); chan_shutdown_extended_read(ssh, c); chan_set_istate(c, CHAN_INPUT_CLOSED); break; } } void chan_write_failed(struct ssh *ssh, Channel *c) { debug2("channel %d: write failed", c->self); switch (c->ostate) { case CHAN_OUTPUT_OPEN: case CHAN_OUTPUT_WAIT_DRAIN: chan_shutdown_write(ssh, c); if (strcmp(c->ctype, "session") == 0) chan_send_eow2(ssh, c); chan_set_ostate(c, CHAN_OUTPUT_CLOSED); break; default: error("channel %d: chan_write_failed for ostate %d", c->self, c->ostate); break; } } void chan_mark_dead(struct ssh *ssh, Channel *c) { c->type = SSH_CHANNEL_ZOMBIE; } int chan_is_dead(struct ssh *ssh, Channel *c, int do_send) { if (c->type == SSH_CHANNEL_ZOMBIE) { debug2("channel %d: zombie", c->self); return 1; } if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED) return 0; if ((ssh->compat & SSH_BUG_EXTEOF) && c->extended_usage == CHAN_EXTENDED_WRITE && c->efd != -1 && sshbuf_len(c->extended) > 0) { debug2("channel %d: active efd: %d len %zu", c->self, c->efd, sshbuf_len(c->extended)); return 0; } if (c->flags & CHAN_LOCAL) { debug2("channel %d: is dead (local)", c->self); return 1; } if (!(c->flags & CHAN_CLOSE_SENT)) { if (do_send) { chan_send_close2(ssh, c); } else { /* channel would be dead if we sent a close */ if (c->flags & CHAN_CLOSE_RCVD) { debug2("channel %d: almost dead", c->self); return 1; } } } if ((c->flags & CHAN_CLOSE_SENT) && (c->flags & CHAN_CLOSE_RCVD)) { debug2("channel %d: is dead", c->self); return 1; } return 0; } /* helper */ static void chan_shutdown_write(struct ssh *ssh, Channel *c) { sshbuf_reset(c->output); if (c->type == SSH_CHANNEL_LARVAL) return; /* shutdown failure is allowed if write failed already */ debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])", c->self, c->istate, c->ostate, c->sock, c->wfd, c->efd, channel_format_extended_usage(c)); if (c->sock != -1) { if (shutdown(c->sock, SHUT_WR) == -1) { debug2_f("channel %d: shutdown() failed for " "fd %d [i%d o%d]: %.100s", c->self, c->sock, c->istate, c->ostate, strerror(errno)); } } else { if (channel_close_fd(ssh, c, &c->wfd) < 0) { logit_f("channel %d: close() failed for " "fd %d [i%d o%d]: %.100s", c->self, c->wfd, c->istate, c->ostate, strerror(errno)); } } } static void chan_shutdown_read(struct ssh *ssh, Channel *c) { if (c->type == SSH_CHANNEL_LARVAL) return; debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])", c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd, channel_format_extended_usage(c)); if (c->sock != -1) { if (shutdown(c->sock, SHUT_RD) == -1) { error_f("channel %d: shutdown() failed for " "fd %d [i%d o%d]: %.100s", c->self, c->sock, c->istate, c->ostate, strerror(errno)); } } else { if (channel_close_fd(ssh, c, &c->rfd) < 0) { logit_f("channel %d: close() failed for " "fd %d [i%d o%d]: %.100s", c->self, c->rfd, c->istate, c->ostate, strerror(errno)); } } } static void chan_shutdown_extended_read(struct ssh *ssh, Channel *c) { if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1) return; if (c->extended_usage != CHAN_EXTENDED_READ && c->extended_usage != CHAN_EXTENDED_IGNORE) return; debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])", c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd, channel_format_extended_usage(c)); if (channel_close_fd(ssh, c, &c->efd) < 0) { logit_f("channel %d: close() failed for " "extended fd %d [i%d o%d]: %.100s", c->self, c->efd, c->istate, c->ostate, strerror(errno)); } }