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2ca0070f89
I've tried to separate out as many individually coherent changes from
this work as I could into their own commits, but here's where I run
out and have to commit the rest of this major refactoring as a
big-bang change.
Most of ssh.c is now no longer in ssh.c: all five of the main
coroutines that handle layers of the SSH-1 and SSH-2 protocols now
each have their own source file to live in, and a lot of the
supporting functions have moved into the appropriate one of those too.
The new abstraction is a vtable called 'PacketProtocolLayer', which
has an input and output packet queue. Each layer's main coroutine is
invoked from the method ssh_ppl_process_queue(), which is usually
(though not exclusively) triggered automatically when things are
pushed on the input queue. In SSH-2, the base layer is the transport
protocol, and it contains a pair of subsidiary queues by which it
passes some of its packets to the higher SSH-2 layers - first userauth
and then connection, which are peers at the same level, with the
former abdicating in favour of the latter at the appropriate moment.
SSH-1 is simpler: the whole login phase of the protocol (crypto setup
and authentication) is all in one module, and since SSH-1 has no
repeat key exchange, that setup layer abdicates in favour of the
connection phase when it's done.
ssh.c itself is now about a tenth of its old size (which all by itself
is cause for celebration!). Its main job is to set up all the layers,
hook them up to each other and to the BPP, and to funnel data back and
forth between that collection of modules and external things such as
the network and the terminal. Once it's set up a collection of packet
protocol layers, it communicates with them partly by calling methods
of the base layer (and if that's ssh2transport then it will delegate
some functionality to the corresponding methods of its higher layer),
and partly by talking directly to the connection layer no matter where
it is in the stack by means of the separate ConnectionLayer vtable
which I introduced in commit 8001dd4cb, and to which I've now added
quite a few extra methods replacing services that used to be internal
function calls within ssh.c.
(One effect of this is that the SSH-1 and SSH-2 channel storage is now
no longer shared - there are distinct struct types ssh1_channel and
ssh2_channel. That means a bit more code duplication, but on the plus
side, a lot fewer confusing conditionals in the middle of half-shared
functions, and less risk of a piece of SSH-1 escaping into SSH-2 or
vice versa, which I remember has happened at least once in the past.)
The bulk of this commit introduces the five new source files, their
common header sshppl.h and some shared supporting routines in
sshcommon.c, and rewrites nearly all of ssh.c itself. But it also
includes a couple of other changes that I couldn't separate easily
enough:
Firstly, there's a new handling for socket EOF, in which ssh.c sets an
'input_eof' flag in the BPP, and that responds by checking a flag that
tells it whether to report the EOF as an error or not. (This is the
main reason for those new BPP_READ / BPP_WAITFOR macros - they can
check the EOF flag every time the coroutine is resumed.)
Secondly, the error reporting itself is changed around again. I'd
expected to put some data fields in the public PacketProtocolLayer
structure that it could set to report errors in the same way as the
BPPs have been doing, but in the end, I decided propagating all those
data fields around was a pain and that even the BPPs shouldn't have
been doing it that way. So I've reverted to a system where everything
calls back to functions in ssh.c itself to report any connection-
ending condition. But there's a new family of those functions,
categorising the possible such conditions by semantics, and each one
has a different set of detailed effects (e.g. how rudely to close the
network connection, what exit status should be passed back to the
whole application, whether to send a disconnect message and/or display
a GUI error box).
I don't expect this to be immediately perfect: of course, the code has
been through a big upheaval, new bugs are expected, and I haven't been
able to do a full job of testing (e.g. I haven't tested every auth or
kex method). But I've checked that it _basically_ works - both SSH
protocols, all the different kinds of forwarding channel, more than
one auth method, Windows and Linux, connection sharing - and I think
it's now at the point where the easiest way to find further bugs is to
let it out into the wild and see what users can spot.
145 lines
6.0 KiB
C
145 lines
6.0 KiB
C
/*
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* Abstraction of the various layers of SSH packet-level protocol,
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* general enough to take in all three of the main SSH-2 layers and
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* both of the SSH-1 phases.
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*/
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#ifndef PUTTY_SSHPPL_H
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#define PUTTY_SSHPPL_H
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typedef void (*packet_handler_fn_t)(PacketProtocolLayer *ppl, PktIn *pktin);
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typedef void (*add_special_fn_t)(
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void *ctx, const char *text, SessionSpecialCode code, int arg);
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struct PacketProtocolLayerVtable {
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void (*free)(PacketProtocolLayer *);
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void (*process_queue)(PacketProtocolLayer *ppl);
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int (*get_specials)(
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PacketProtocolLayer *ppl, add_special_fn_t add_special, void *ctx);
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void (*special_cmd)(
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PacketProtocolLayer *ppl, SessionSpecialCode code, int arg);
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int (*want_user_input)(PacketProtocolLayer *ppl);
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void (*got_user_input)(PacketProtocolLayer *ppl);
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void (*reconfigure)(PacketProtocolLayer *ppl, Conf *conf);
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/* Protocol-level name of this layer. */
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const char *name;
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};
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struct PacketProtocolLayer {
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const struct PacketProtocolLayerVtable *vt;
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/* Link to the underlying SSH BPP. */
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BinaryPacketProtocol *bpp;
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/* Queue from which the layer receives its input packets, and one
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* to put its output packets on. */
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PktInQueue *in_pq;
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PktOutQueue *out_pq;
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/* Idempotent callback that in_pq will be linked to, causing a
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* call to the process_queue method. in_pq points to this, so it
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* will be automatically triggered by pushing things on the
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* layer's input queue, but it can also be triggered on purpose. */
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IdempotentCallback ic_process_queue;
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/* Owner's pointer to this layer. Permits a layer to unilaterally
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* abdicate in favour of a replacement, by overwriting this
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* pointer and then freeing itself. */
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PacketProtocolLayer **selfptr;
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/* Bufchain of keyboard input from the user, for login prompts and
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* similar. */
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bufchain *user_input;
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/* Logging and error-reporting facilities. */
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void *frontend; /* for logevent, dialog boxes etc */
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Ssh ssh; /* for session termination + assorted connection-layer ops */
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/* Known bugs in the remote implementation. */
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unsigned remote_bugs;
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};
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#define ssh_ppl_process_queue(ppl) ((ppl)->vt->process_queue(ppl))
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#define ssh_ppl_get_specials(ppl, add, ctx) \
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((ppl)->vt->get_specials(ppl, add, ctx))
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#define ssh_ppl_special_cmd(ppl, code, arg) \
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((ppl)->vt->special_cmd(ppl, code, arg))
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#define ssh_ppl_want_user_input(ppl) ((ppl)->vt->want_user_input(ppl))
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#define ssh_ppl_got_user_input(ppl) ((ppl)->vt->got_user_input(ppl))
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#define ssh_ppl_reconfigure(ppl, conf) ((ppl)->vt->reconfigure(ppl, conf))
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/* ssh_ppl_free is more than just a macro wrapper on the vtable; it
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* does centralised parts of the freeing too. */
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void ssh_ppl_free(PacketProtocolLayer *ppl);
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/* Helper routine to point a PPL at its input and output queues. Also
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* sets up the IdempotentCallback on the input queue to trigger a call
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* to process_queue whenever packets are added to it. */
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void ssh_ppl_setup_queues(PacketProtocolLayer *ppl,
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PktInQueue *inq, PktOutQueue *outq);
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/* Routine a PPL can call to abdicate in favour of a replacement, by
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* overwriting ppl->selfptr. Has the side effect of freeing 'old', so
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* if 'old' actually called this (which is likely) then it should
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* avoid dereferencing itself on return from this function! */
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void ssh_ppl_replace(PacketProtocolLayer *old, PacketProtocolLayer *new);
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PacketProtocolLayer *ssh1_login_new(
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Conf *conf, const char *host, int port,
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PacketProtocolLayer *successor_layer);
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PacketProtocolLayer *ssh1_connection_new(
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Ssh ssh, Conf *conf, ConnectionLayer **cl_out);
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struct DataTransferStats;
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struct ssh_connection_shared_gss_state;
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PacketProtocolLayer *ssh2_transport_new(
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Conf *conf, const char *host, int port, const char *fullhostname,
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const char *client_greeting, const char *server_greeting,
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struct ssh_connection_shared_gss_state *shgss,
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struct DataTransferStats *stats,
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PacketProtocolLayer *higher_layer);
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PacketProtocolLayer *ssh2_userauth_new(
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PacketProtocolLayer *successor_layer,
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const char *hostname, const char *fullhostname,
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Filename *keyfile, int tryagent,
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const char *default_username, int change_username,
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int try_ki_auth,
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int try_gssapi_auth, int try_gssapi_kex_auth,
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int gssapi_fwd, struct ssh_connection_shared_gss_state *shgss);
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PacketProtocolLayer *ssh2_connection_new(
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Ssh ssh, ssh_sharing_state *connshare, int is_simple,
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Conf *conf, const char *peer_verstring, ConnectionLayer **cl_out);
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/* Can't put this in the userauth constructor without having a
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* dependency loop at setup time (transport and userauth can't _both_
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* be constructed second and given a pointer to the other). */
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void ssh2_userauth_set_transport_layer(PacketProtocolLayer *userauth,
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PacketProtocolLayer *transport);
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/* Convenience macro for protocol layers to send formatted strings to
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* the Event Log. Assumes a function parameter called 'ppl' is in
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* scope, and takes a double pair of parens because it passes a whole
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* argument list to dupprintf. */
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#define ppl_logevent(params) ( \
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logevent_and_free((ppl)->frontend, dupprintf params))
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/* Convenience macro for protocol layers to send formatted strings to
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* the terminal. Also expects 'ppl' to be in scope and takes double
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* parens. */
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#define ppl_printf(params) \
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ssh_ppl_user_output_string_and_free(ppl, dupprintf params)
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void ssh_ppl_user_output_string_and_free(PacketProtocolLayer *ppl, char *text);
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/* Methods for userauth to communicate back to the transport layer */
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ptrlen ssh2_transport_get_session_id(PacketProtocolLayer *ssh2_transport_ptr);
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void ssh2_transport_notify_auth_done(PacketProtocolLayer *ssh2_transport_ptr);
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/* Methods for ssh1login to pass protocol flags to ssh1connection */
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void ssh1_connection_set_local_protoflags(PacketProtocolLayer *ppl, int flags);
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/* Shared get_specials method between the two ssh1 layers */
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int ssh1_common_get_specials(PacketProtocolLayer *, add_special_fn_t, void *);
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#endif /* PUTTY_SSHPPL_H */
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