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Add a new SSH2 bug: some servers apparently claim to be able to do

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DH group exchange, but choke when you actually try it. Never
automatically enabled; manual control only.

[originally from svn r1982]
This commit is contained in:
Simon Tatham 2002-09-26 18:37:33 +00:00
parent b2c7474747
commit a394f20829
5 changed files with 60 additions and 3 deletions
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21
doc/config.but
View File

@ -1,4 +1,4 @@
\versionid $Id: config.but,v 1.41 2002/09/23 09:55:11 jacob Exp $
\versionid $Id: config.but,v 1.42 2002/09/26 18:37:33 simon Exp $
\C{config} Configuring PuTTY
@ -2005,7 +2005,7 @@ server, communication will fail.
This is an SSH2-specific bug.
\S{config-ssh-bug-ssh} \q{Requires padding on SSH2 RSA signatures}
\S{config-ssh-bug-sig} \q{Requires padding on SSH2 RSA signatures}
\cfg{winhelp-topic}{ssh.bugs.rsapad2}
@ -2024,6 +2024,23 @@ to talking to OpenSSH.
This is an SSH2-specific bug.
\S{config-ssh-bug-dhgex} \q{Chokes on Diffie-Hellman group exchange}
\cfg{winhelp-topic}{ssh.bugs.dhgex2}
We have anecdotal evidence that some SSH servers claim to be able to
perform Diffie-Hellman group exchange, but fail to actually do so
when PuTTY tries to. If your SSH2 sessions spontaneously close
immediately after opening the PuTTY window, it might be worth
enabling the workaround for this bug to see if it helps.
We have no hard evidence that any specific version of specific
server software reliably demonstrates this bug. Therefore, PuTTY
will never \e{assume} a server has this bug; if you want the
workaround, you need to enable it manually.
This is an SSH2-specific bug.
\H{config-file} Storing configuration in a file
PuTTY does not currently support storing its configuration in a file

3
putty.h
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@ -372,7 +372,8 @@ typedef struct {
enum {
BUG_AUTO, BUG_OFF, BUG_ON
} sshbug_ignore1, sshbug_plainpw1, sshbug_rsa1,
sshbug_hmac2, sshbug_derivekey2, sshbug_rsapad2;
sshbug_hmac2, sshbug_derivekey2, sshbug_rsapad2,
sshbug_dhgex2;
} Config;
/*

2
settings.c
View File

@ -309,6 +309,7 @@ void save_settings(char *section, int do_host, Config * cfg)
write_setting_i(sesskey, "BugHMAC2", cfg->sshbug_hmac2);
write_setting_i(sesskey, "BugDeriveKey2", cfg->sshbug_derivekey2);
write_setting_i(sesskey, "BugRSAPad2", cfg->sshbug_rsapad2);
write_setting_i(sesskey, "BugDHGEx2", cfg->sshbug_dhgex2);
close_settings_w(sesskey);
}
@ -583,6 +584,7 @@ void load_settings(char *section, int do_host, Config * cfg)
}
gppi(sesskey, "BugDeriveKey2", BUG_AUTO, &cfg->sshbug_derivekey2);
gppi(sesskey, "BugRSAPad2", BUG_AUTO, &cfg->sshbug_rsapad2);
gppi(sesskey, "BugDHGEx2", BUG_AUTO, &cfg->sshbug_dhgex2);
close_settings_r(sesskey);
}

15
ssh.c
View File

@ -183,6 +183,7 @@ static const char *const ssh2_disconnect_reasons[] = {
#define BUG_CHOKES_ON_RSA 8
#define BUG_SSH2_RSA_PADDING 16
#define BUG_SSH2_DERIVEKEY 32
#define BUG_SSH2_DH_GEX 64
static int ssh_pkt_ctx = 0;
@ -1742,6 +1743,14 @@ static void ssh_detect_bugs(char *vstring)
ssh_remote_bugs |= BUG_SSH2_RSA_PADDING;
logevent("We believe remote version has SSH2 RSA padding bug");
}
if (cfg.sshbug_dhgex2 == BUG_ON) {
/*
* These versions have the SSH2 DH GEX bug.
*/
ssh_remote_bugs |= BUG_SSH2_DH_GEX;
logevent("We believe remote version has SSH2 DH group exchange bug");
}
}
static int do_ssh_init(unsigned char c)
@ -3648,6 +3657,9 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
/* List key exchange algorithms. */
ssh2_pkt_addstring_start();
for (i = 0; i < lenof(kex_algs); i++) {
if (kex_algs[i] == &ssh_diffiehellman_gex &&
(ssh_remote_bugs & BUG_SSH2_DH_GEX))
continue;
ssh2_pkt_addstring_str(kex_algs[i]->name);
if (i < lenof(kex_algs) - 1)
ssh2_pkt_addstring_str(",");
@ -3754,6 +3766,9 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
pktin.savedpos += 16; /* skip garbage cookie */
ssh2_pkt_getstring(&str, &len); /* key exchange algorithms */
for (i = 0; i < lenof(kex_algs); i++) {
if (kex_algs[i] == &ssh_diffiehellman_gex &&
(ssh_remote_bugs & BUG_SSH2_DH_GEX))
continue;
if (in_commasep_string(kex_algs[i]->name, str, len)) {
kex = kex_algs[i];
break;

22
windlg.c
View File

@ -548,6 +548,8 @@ enum { IDCX_ABOUT =
IDC_BUGD_DERIVEKEY2,
IDC_BUGS_RSAPAD2,
IDC_BUGD_RSAPAD2,
IDC_BUGS_DHGEX2,
IDC_BUGD_DHGEX2,
sshbugspanelend,
selectionpanelstart,
@ -1044,6 +1046,9 @@ char *help_context_cmd(int id)
case IDC_BUGS_RSAPAD2:
case IDC_BUGD_RSAPAD2:
return "JI(`',`ssh.bugs.rsapad2')";
case IDC_BUGS_DHGEX2:
case IDC_BUGD_DHGEX2:
return "JI(`',`ssh.bugs.dhgex2')";
default:
return NULL;
@ -1391,6 +1396,13 @@ static void init_dlg_ctrls(HWND hwnd, int keepsess)
SendDlgItemMessage(hwnd, IDC_BUGD_RSAPAD2, CB_SETCURSEL,
cfg.sshbug_rsapad2 == BUG_ON ? 2 :
cfg.sshbug_rsapad2 == BUG_OFF ? 1 : 0, 0);
SendDlgItemMessage(hwnd, IDC_BUGD_DHGEX2, CB_RESETCONTENT, 0, 0);
SendDlgItemMessage(hwnd, IDC_BUGD_DHGEX2, CB_ADDSTRING, 0, (LPARAM)"Auto");
SendDlgItemMessage(hwnd, IDC_BUGD_DHGEX2, CB_ADDSTRING, 0, (LPARAM)"Off");
SendDlgItemMessage(hwnd, IDC_BUGD_DHGEX2, CB_ADDSTRING, 0, (LPARAM)"On");
SendDlgItemMessage(hwnd, IDC_BUGD_DHGEX2, CB_SETCURSEL,
cfg.sshbug_dhgex2 == BUG_ON ? 2 :
cfg.sshbug_dhgex2 == BUG_OFF ? 1 : 0, 0);
}
struct treeview_faff {
@ -1994,6 +2006,8 @@ static void create_controls(HWND hwnd, int dlgtype, int panel)
IDC_BUGS_DERIVEKEY2, IDC_BUGD_DERIVEKEY2, 20);
staticddl(&cp, "Requires &padding on SSH2 RSA signatures",
IDC_BUGS_RSAPAD2, IDC_BUGD_RSAPAD2, 20);
staticddl(&cp, "Chokes on &Diffie-Hellman group exchange",
IDC_BUGS_DHGEX2, IDC_BUGD_DHGEX2, 20);
endbox(&cp);
}
}
@ -3612,6 +3626,14 @@ static int GenericMainDlgProc(HWND hwnd, UINT msg,
index == 1 ? BUG_OFF : BUG_ON);
}
break;
case IDC_BUGD_DHGEX2:
if (HIWORD(wParam) == CBN_SELCHANGE) {
int index = SendDlgItemMessage(hwnd, IDC_BUGD_DHGEX2,
CB_GETCURSEL, 0, 0);
cfg.sshbug_dhgex2 = (index == 0 ? BUG_AUTO :
index == 1 ? BUG_OFF : BUG_ON);
}
break;
}
return 0;
case WM_HELP: