From: jacob Date: Fri, 4 Mar 2011 22:34:47 +0000 (+0000) Subject: Implement zlib@openssh.com, using the rekey-after-userauth method suggested in X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/commitdiff_plain/ab18ccfffb5274281362d41829fa924f0a964168 Implement zlib@openssh.com, using the rekey-after-userauth method suggested in the wishlist entry. git-svn-id: svn://svn.tartarus.org/sgt/putty@9120 cda61777-01e9-0310-a592-d414129be87e --- diff --git a/ssh.c b/ssh.c index a7f1c6b2..95fa2f2c 100644 --- a/ssh.c +++ b/ssh.c @@ -544,7 +544,7 @@ static int ssh_comp_none_disable(void *handle) return 0; } const static struct ssh_compress ssh_comp_none = { - "none", + "none", NULL, ssh_comp_none_init, ssh_comp_none_cleanup, ssh_comp_none_block, ssh_comp_none_init, ssh_comp_none_cleanup, ssh_comp_none_block, ssh_comp_none_disable, NULL @@ -5422,6 +5422,8 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen, int n_preferred_ciphers; const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX]; const struct ssh_compress *preferred_comp; + int userauth_succeeded; /* for delayed compression */ + int pending_compression; int got_session_id, activated_authconn; struct Packet *pktout; int dlgret; @@ -5437,6 +5439,8 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen, s->cscomp_tobe = s->sccomp_tobe = NULL; s->got_session_id = s->activated_authconn = FALSE; + s->userauth_succeeded = FALSE; + s->pending_compression = FALSE; /* * Be prepared to work around the buggy MAC problem. @@ -5601,26 +5605,32 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen, if (i < s->nmacs - 1) ssh2_pkt_addstring_str(s->pktout, ","); } - /* List client->server compression algorithms. */ - ssh2_pkt_addstring_start(s->pktout); - assert(lenof(compressions) > 1); - ssh2_pkt_addstring_str(s->pktout, s->preferred_comp->name); - for (i = 0; i < lenof(compressions); i++) { - const struct ssh_compress *c = compressions[i]; - if (c != s->preferred_comp) { + /* List client->server compression algorithms, + * then server->client compression algorithms. (We use the + * same set twice.) */ + for (j = 0; j < 2; j++) { + ssh2_pkt_addstring_start(s->pktout); + assert(lenof(compressions) > 1); + /* Prefer non-delayed versions */ + ssh2_pkt_addstring_str(s->pktout, s->preferred_comp->name); + /* We don't even list delayed versions of algorithms until + * they're allowed to be used, to avoid a race. See the end of + * this function. */ + if (s->userauth_succeeded && s->preferred_comp->delayed_name) { ssh2_pkt_addstring_str(s->pktout, ","); - ssh2_pkt_addstring_str(s->pktout, c->name); + ssh2_pkt_addstring_str(s->pktout, + s->preferred_comp->delayed_name); } - } - /* List server->client compression algorithms. */ - ssh2_pkt_addstring_start(s->pktout); - assert(lenof(compressions) > 1); - ssh2_pkt_addstring_str(s->pktout, s->preferred_comp->name); - for (i = 0; i < lenof(compressions); i++) { - const struct ssh_compress *c = compressions[i]; - if (c != s->preferred_comp) { - ssh2_pkt_addstring_str(s->pktout, ","); - ssh2_pkt_addstring_str(s->pktout, c->name); + for (i = 0; i < lenof(compressions); i++) { + const struct ssh_compress *c = compressions[i]; + if (c != s->preferred_comp) { + ssh2_pkt_addstring_str(s->pktout, ","); + ssh2_pkt_addstring_str(s->pktout, c->name); + if (s->userauth_succeeded && c->delayed_name) { + ssh2_pkt_addstring_str(s->pktout, ","); + ssh2_pkt_addstring_str(s->pktout, c->delayed_name); + } + } } } /* List client->server languages. Empty list. */ @@ -5769,6 +5779,13 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen, if (in_commasep_string(c->name, str, len)) { s->cscomp_tobe = c; break; + } else if (in_commasep_string(c->delayed_name, str, len)) { + if (s->userauth_succeeded) { + s->cscomp_tobe = c; + break; + } else { + s->pending_compression = TRUE; /* try this later */ + } } } ssh_pkt_getstring(pktin, &str, &len); /* server->client compression */ @@ -5778,8 +5795,19 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen, if (in_commasep_string(c->name, str, len)) { s->sccomp_tobe = c; break; + } else if (in_commasep_string(c->delayed_name, str, len)) { + if (s->userauth_succeeded) { + s->sccomp_tobe = c; + break; + } else { + s->pending_compression = TRUE; /* try this later */ + } } } + if (s->pending_compression) { + logevent("Server supports delayed compression; " + "will try this later"); + } ssh_pkt_getstring(pktin, &str, &len); /* client->server language */ ssh_pkt_getstring(pktin, &str, &len); /* server->client language */ s->ignorepkt = ssh2_pkt_getbool(pktin) && !s->guessok; @@ -6315,19 +6343,52 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen, * start. * * We _also_ go back to the start if we see pktin==NULL and - * inlen==-1, because this is a special signal meaning + * inlen negative, because this is a special signal meaning * `initiate client-driven rekey', and `in' contains a message * giving the reason for the rekey. + * + * inlen==-1 means always initiate a rekey; + * inlen==-2 means that userauth has completed successfully and + * we should consider rekeying (for delayed compression). */ while (!((pktin && pktin->type == SSH2_MSG_KEXINIT) || - (!pktin && inlen == -1))) { + (!pktin && inlen < 0))) { wait_for_rekey: crReturn(1); } if (pktin) { logevent("Server initiated key re-exchange"); } else { + if (inlen == -2) { + /* + * authconn has seen a USERAUTH_SUCCEEDED. Time to enable + * delayed compression, if it's available. + * + * draft-miller-secsh-compression-delayed-00 says that you + * negotiate delayed compression in the first key exchange, and + * both sides start compressing when the server has sent + * USERAUTH_SUCCESS. This has a race condition -- the server + * can't know when the client has seen it, and thus which incoming + * packets it should treat as compressed. + * + * Instead, we do the initial key exchange without offering the + * delayed methods, but note if the server offers them; when we + * get here, if a delayed method was available that was higher + * on our list than what we got, we initiate a rekey in which we + * _do_ list the delayed methods (and hopefully get it as a + * result). Subsequent rekeys will do the same. + */ + assert(!s->userauth_succeeded); /* should only happen once */ + s->userauth_succeeded = TRUE; + if (!s->pending_compression) + /* Can't see any point rekeying. */ + goto wait_for_rekey; /* this is utterly horrid */ + /* else fall through to rekey... */ + s->pending_compression = FALSE; + } /* + * Now we've decided to rekey. + * * Special case: if the server bug is set that doesn't * allow rekeying, we give a different log message and * continue waiting. (If such a server _initiates_ a rekey, @@ -6345,7 +6406,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen, schedule_timer(ssh->cfg.ssh_rekey_time*60*TICKSPERSEC, ssh2_timer, ssh); } - goto wait_for_rekey; /* this is utterly horrid */ + goto wait_for_rekey; /* this is still utterly horrid */ } else { logeventf(ssh, "Initiating key re-exchange (%s)", (char *)in); } @@ -7256,7 +7317,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int tried_gssapi; #endif int kbd_inter_refused; - int we_are_in; + int we_are_in, userauth_success; prompts_t *cur_prompt; int num_prompts; char username[100]; @@ -7292,7 +7353,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, crBegin(ssh->do_ssh2_authconn_crstate); s->done_service_req = FALSE; - s->we_are_in = FALSE; + s->we_are_in = s->userauth_success = FALSE; #ifndef NO_GSSAPI s->tried_gssapi = FALSE; #endif @@ -7582,7 +7643,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, } if (pktin->type == SSH2_MSG_USERAUTH_SUCCESS) { logevent("Access granted"); - s->we_are_in = TRUE; + s->we_are_in = s->userauth_success = TRUE; break; } @@ -8590,6 +8651,20 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, if (s->agent_response) sfree(s->agent_response); + if (s->userauth_success) { + /* + * We've just received USERAUTH_SUCCESS, and we haven't sent any + * packets since. Signal the transport layer to consider enacting + * delayed compression. + * + * (Relying on we_are_in is not sufficient, as + * draft-miller-secsh-compression-delayed is quite clear that it + * triggers on USERAUTH_SUCCESS specifically, and we_are_in can + * become set for other reasons.) + */ + do_ssh2_transport(ssh, "enabling delayed compression", -2, NULL); + } + /* * Now the connection protocol has started, one way or another. */ diff --git a/ssh.h b/ssh.h index 6acd8780..90dafed1 100644 --- a/ssh.h +++ b/ssh.h @@ -251,6 +251,9 @@ struct ssh_signkey { struct ssh_compress { char *name; + /* For zlib@openssh.com: if non-NULL, this name will be considered once + * userauth has completed successfully. */ + char *delayed_name; void *(*compress_init) (void); void (*compress_cleanup) (void *); int (*compress) (void *, unsigned char *block, int len, diff --git a/sshzlib.c b/sshzlib.c index cc287240..25ccd259 100644 --- a/sshzlib.c +++ b/sshzlib.c @@ -1371,6 +1371,7 @@ int main(int argc, char **argv) const struct ssh_compress ssh_zlib = { "zlib", + "zlib@openssh.com", /* delayed version */ zlib_compress_init, zlib_compress_cleanup, zlib_compress_block,