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-rw-r--r--nchan.c443
1 files changed, 443 insertions, 0 deletions
diff --git a/nchan.c b/nchan.c
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+/* $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"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <errno.h>
+#include <string.h>
+#include <stdarg.h>
+
+#include "openbsd-compat/sys-queue.h"
+#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) {
+ /*
+ * shutdown(sock, SHUT_READ) may return ENOTCONN if the
+ * write side has been closed already. (bug on Linux)
+ * HP-UX may return ENOTCONN also.
+ */
+ if (shutdown(c->sock, SHUT_RD) == -1 && errno != ENOTCONN) {
+ 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));
+ }
+}
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