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New SSH bug flag, for 'can't handle SSH2_MSG_IGNORE'. Another user

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today reported an SSH2_MSG_UNIMPLEMENTED from a Cisco router which
looks as if it was triggered by SSH2_MSG_IGNORE, so I'm
experimentally putting this flag in. Currently must be manually
enabled, though if it turns out to solve the user's problem then
I'll probably add at least one version string...

[Edited commit message: actually, I also committed in error a piece
of experimental code as part of this checkin. Serve me right for not
running 'svn diff' first.]

[originally from svn r8926]
This commit is contained in:
Simon Tatham
2010-04-23 18:32:15 +00:00
parent 97ca111e29
commit d5aa23c116
7 changed files with 82 additions and 12 deletions
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36
ssh.c
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@ -194,6 +194,7 @@ static const char *const ssh2_disconnect_reasons[] = {
#define BUG_SSH2_REKEY 64
#define BUG_SSH2_PK_SESSIONID 128
#define BUG_SSH2_MAXPKT 256
#define BUG_CHOKES_ON_SSH2_IGNORE 512
/*
* Codes for terminal modes.
@ -2011,7 +2012,8 @@ static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt, int noignore)
{
int len;
if (ssh->cscipher != NULL && (ssh->cscipher->flags & SSH_CIPHER_IS_CBC) &&
ssh->deferred_len == 0 && !noignore) {
ssh->deferred_len == 0 && !noignore &&
!(ssh->remote_bugs & BUG_CHOKES_ON_SSH2_IGNORE)) {
/*
* Interpose an SSH_MSG_IGNORE to ensure that user data don't
* get encrypted with a known IV.
@ -2141,7 +2143,8 @@ static void ssh2_pkt_send_with_padding(Ssh ssh, struct Packet *pkt,
* unavailable, we don't do this trick at all, because we
* gain nothing by it.)
*/
if (ssh->cscipher) {
if (ssh->cscipher &&
!(ssh->remote_bugs & BUG_CHOKES_ON_SSH2_IGNORE)) {
int stringlen, i;
stringlen = (256 - ssh->deferred_len);
@ -2508,6 +2511,15 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
ssh->remote_bugs |= BUG_SSH2_MAXPKT;
logevent("We believe remote version ignores SSH-2 maximum packet size");
}
if (ssh->cfg.sshbug_ignore2 == FORCE_ON) {
/*
* Servers that don't support SSH2_MSG_IGNORE. Currently,
* none detected automatically.
*/
ssh->remote_bugs |= BUG_CHOKES_ON_SSH2_IGNORE;
logevent("We believe remote version has SSH-2 ignore bug");
}
}
/*
@ -9426,8 +9438,10 @@ static const struct telnet_special *ssh_get_specials(void *handle)
static const struct telnet_special ssh1_ignore_special[] = {
{"IGNORE message", TS_NOP}
};
static const struct telnet_special ssh2_transport_specials[] = {
static const struct telnet_special ssh2_ignore_special[] = {
{"IGNORE message", TS_NOP},
};
static const struct telnet_special ssh2_rekey_special[] = {
{"Repeat key exchange", TS_REKEY},
};
static const struct telnet_special ssh2_session_specials[] = {
@ -9452,7 +9466,8 @@ static const struct telnet_special *ssh_get_specials(void *handle)
{NULL, TS_EXITMENU}
};
/* XXX review this length for any changes: */
static struct telnet_special ssh_specials[lenof(ssh2_transport_specials) +
static struct telnet_special ssh_specials[lenof(ssh2_ignore_special) +
lenof(ssh2_rekey_special) +
lenof(ssh2_session_specials) +
lenof(specials_end)];
Ssh ssh = (Ssh) handle;
@ -9471,7 +9486,10 @@ static const struct telnet_special *ssh_get_specials(void *handle)
if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE))
ADD_SPECIALS(ssh1_ignore_special);
} else if (ssh->version == 2) {
ADD_SPECIALS(ssh2_transport_specials);
if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH2_IGNORE))
ADD_SPECIALS(ssh2_ignore_special);
if (!(ssh->remote_bugs & BUG_SSH2_REKEY))
ADD_SPECIALS(ssh2_rekey_special);
if (ssh->mainchan)
ADD_SPECIALS(ssh2_session_specials);
} /* else we're not ready yet */
@ -9521,9 +9539,11 @@ static void ssh_special(void *handle, Telnet_Special code)
if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE))
send_packet(ssh, SSH1_MSG_IGNORE, PKT_STR, "", PKT_END);
} else {
pktout = ssh2_pkt_init(SSH2_MSG_IGNORE);
ssh2_pkt_addstring_start(pktout);
ssh2_pkt_send_noqueue(ssh, pktout);
if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH2_IGNORE)) {
pktout = ssh2_pkt_init(SSH2_MSG_IGNORE);
ssh2_pkt_addstring_start(pktout);
ssh2_pkt_send_noqueue(ssh, pktout);
}
}
} else if (code == TS_REKEY) {
if (!ssh->kex_in_progress && ssh->version == 2) {