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d515e4f1a3
This is a heavily edited (by me) version of a patch originally due to Nico Williams and Viktor Dukhovni. Their comments: * Don't delegate credentials when rekeying unless there's a new TGT or the old service ticket is nearly expired. * Check for the above conditions more frequently (every two minutes by default) and rekey when we would delegate credentials. * Do not rekey with very short service ticket lifetimes; some GSSAPI libraries may lose the race to use an almost expired ticket. Adjust the timing of rekey checks to try to avoid this possibility. My further comments: The most interesting thing about this patch to me is that the use of GSS key exchange causes a switch over to a completely different model of what host keys are for. This comes from RFC 4462 section 2.1: the basic idea is that when your session is mostly bidirectionally authenticated by the GSSAPI exchanges happening in initial kex and every rekey, host keys become more or less vestigial, and their remaining purpose is to allow a rekey to happen if the requirements of the SSH protocol demand it at an awkward moment when the GSS credentials are not currently available (e.g. timed out and haven't been renewed yet). As such, there's no need for host keys to be _permanent_ or to be a reliable identifier of a particular host, and RFC 4462 allows for the possibility that they might be purely transient and only for this kind of emergency fallback purpose. Therefore, once PuTTY has done a GSS key exchange, it disconnects itself completely from the permanent host key cache functions in storage.h, and instead switches to a _transient_ host key cache stored in memory with the lifetime of just that SSH session. That cache is populated with keys received from the server as a side effect of GSS kex (via the optional SSH2_MSG_KEXGSS_HOSTKEY message), and used if later in the session we have to fall back to a non-GSS key exchange. However, in practice servers we've tested against do not send a host key in that way, so we also have a fallback method of populating the transient cache by triggering an immediate non-GSS rekey straight after userauth (reusing the code path we also use to turn on OpenSSH delayed encryption without the race condition). |
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| .. | ||
| configure | ||
| gtkapp.c | ||
| gtkask.c | ||
| gtkcfg.c | ||
| gtkcols.c | ||
| gtkcols.h | ||
| gtkcomm.c | ||
| gtkcompat.h | ||
| gtkdlg.c | ||
| gtkfont.c | ||
| gtkfont.h | ||
| gtkmain.c | ||
| gtkmisc.c | ||
| gtkmisc.h | ||
| gtkwin.c | ||
| osxlaunch.c | ||
| pterm.bundle | ||
| pterm.plist | ||
| putty.bundle | ||
| putty.plist | ||
| unix.h | ||
| ux_x11.c | ||
| uxagentc.c | ||
| uxcfg.c | ||
| uxcons.c | ||
| uxgen.c | ||
| uxgss.c | ||
| uxmisc.c | ||
| uxnet.c | ||
| uxnogtk.c | ||
| uxnoise.c | ||
| uxpeer.c | ||
| uxpgnt.c | ||
| uxplink.c | ||
| uxprint.c | ||
| uxproxy.c | ||
| uxpterm.c | ||
| uxpty.c | ||
| uxputty.c | ||
| uxsel.c | ||
| uxser.c | ||
| uxsftp.c | ||
| uxshare.c | ||
| uxsignal.c | ||
| uxstore.c | ||
| uxucs.c | ||
| x11misc.c | ||
| x11misc.h | ||
| xkeysym.c | ||
| xpmptcfg.c | ||
| xpmpterm.c | ||
| xpmpucfg.c | ||
| xpmputty.c | ||