From 967de15331b5a93baa1aff8ca9afecd4801bdc10 Mon Sep 17 00:00:00 2001 From: djm Date: Mon, 4 Sep 2023 00:01:46 +0000 Subject: [PATCH] make channel_output_poll() return a flag indicating whether channel data was enqueued. Will be used to improve keystroke timing obfuscation. Problem spotted by / tested by naddy@ --- usr.bin/ssh/channels.c | 35 ++++++++++++++++++++++------------- usr.bin/ssh/channels.h | 4 ++-- 2 files changed, 24 insertions(+), 15 deletions(-) diff --git a/usr.bin/ssh/channels.c b/usr.bin/ssh/channels.c index 7c43bf38f94..1b310e3c629 100644 --- a/usr.bin/ssh/channels.c +++ b/usr.bin/ssh/channels.c @@ -1,4 +1,4 @@ -/* $OpenBSD: channels.c,v 1.432 2023/07/04 03:59:21 dlg Exp $ */ +/* $OpenBSD: channels.c,v 1.433 2023/09/04 00:01:46 djm Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland @@ -2848,8 +2848,9 @@ channel_after_poll(struct ssh *ssh, struct pollfd *pfd, u_int npfd) /* * Enqueue data for channels with open or draining c->input. + * Returns non-zero if a packet was enqueued. */ -static void +static int channel_output_poll_input_open(struct ssh *ssh, Channel *c) { size_t len, plen; @@ -2872,7 +2873,7 @@ channel_output_poll_input_open(struct ssh *ssh, Channel *c) else chan_ibuf_empty(ssh, c); } - return; + return 0; } if (!c->have_remote_id) @@ -2889,7 +2890,7 @@ channel_output_poll_input_open(struct ssh *ssh, Channel *c) */ if (plen > c->remote_window || plen > c->remote_maxpacket) { debug("channel %d: datagram too big", c->self); - return; + return 0; } /* Enqueue it */ if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_DATA)) != 0 || @@ -2898,7 +2899,7 @@ channel_output_poll_input_open(struct ssh *ssh, Channel *c) (r = sshpkt_send(ssh)) != 0) fatal_fr(r, "channel %i: send datagram", c->self); c->remote_window -= plen; - return; + return 1; } /* Enqueue packet for buffered data. */ @@ -2907,7 +2908,7 @@ channel_output_poll_input_open(struct ssh *ssh, Channel *c) if (len > c->remote_maxpacket) len = c->remote_maxpacket; if (len == 0) - return; + return 0; if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_DATA)) != 0 || (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || (r = sshpkt_put_string(ssh, sshbuf_ptr(c->input), len)) != 0 || @@ -2916,19 +2917,21 @@ channel_output_poll_input_open(struct ssh *ssh, Channel *c) if ((r = sshbuf_consume(c->input, len)) != 0) fatal_fr(r, "channel %i: consume", c->self); c->remote_window -= len; + return 1; } /* * Enqueue data for channels with open c->extended in read mode. + * Returns non-zero if a packet was enqueued. */ -static void +static int channel_output_poll_extended_read(struct ssh *ssh, Channel *c) { size_t len; int r; if ((len = sshbuf_len(c->extended)) == 0) - return; + return 0; debug2("channel %d: rwin %u elen %zu euse %d", c->self, c->remote_window, sshbuf_len(c->extended), c->extended_usage); @@ -2937,7 +2940,7 @@ channel_output_poll_extended_read(struct ssh *ssh, Channel *c) if (len > c->remote_maxpacket) len = c->remote_maxpacket; if (len == 0) - return; + return 0; if (!c->have_remote_id) fatal_f("channel %d: no remote id", c->self); if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA)) != 0 || @@ -2950,15 +2953,20 @@ channel_output_poll_extended_read(struct ssh *ssh, Channel *c) fatal_fr(r, "channel %i: consume", c->self); c->remote_window -= len; debug2("channel %d: sent ext data %zu", c->self, len); + return 1; } -/* If there is data to send to the connection, enqueue some of it now. */ -void +/* + * If there is data to send to the connection, enqueue some of it now. + * Returns non-zero if data was enqueued. + */ +int channel_output_poll(struct ssh *ssh) { struct ssh_channels *sc = ssh->chanctxt; Channel *c; u_int i; + int ret = 0; for (i = 0; i < sc->channels_alloc; i++) { c = sc->channels[i]; @@ -2981,12 +2989,13 @@ channel_output_poll(struct ssh *ssh) /* Get the amount of buffered data for this channel. */ if (c->istate == CHAN_INPUT_OPEN || c->istate == CHAN_INPUT_WAIT_DRAIN) - channel_output_poll_input_open(ssh, c); + ret |= channel_output_poll_input_open(ssh, c); /* Send extended data, i.e. stderr */ if (!(c->flags & CHAN_EOF_SENT) && c->extended_usage == CHAN_EXTENDED_READ) - channel_output_poll_extended_read(ssh, c); + ret |= channel_output_poll_extended_read(ssh, c); } + return ret; } /* -- mux proxy support */ diff --git a/usr.bin/ssh/channels.h b/usr.bin/ssh/channels.h index 36820d3ae9a..7cfba92a8f0 100644 --- a/usr.bin/ssh/channels.h +++ b/usr.bin/ssh/channels.h @@ -1,4 +1,4 @@ -/* $OpenBSD: channels.h,v 1.151 2023/07/04 03:59:21 dlg Exp $ */ +/* $OpenBSD: channels.h,v 1.152 2023/09/04 00:01:46 djm Exp $ */ /* * Author: Tatu Ylonen @@ -332,7 +332,7 @@ 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); -void channel_output_poll(struct ssh *); +int channel_output_poll(struct ssh *); int channel_not_very_much_buffered_data(struct ssh *); void channel_close_all(struct ssh *); -- 2.20.1