/* * Platform-independent bits of X11 forwarding. */ #include #include #include #include #include "putty.h" #include "ssh.h" #include "sshchan.h" #include "tree234.h" static inline uint16_t GET_16BIT_X11(char endian, const void *p) { return endian == 'B' ? GET_16BIT_MSB_FIRST(p) : GET_16BIT_LSB_FIRST(p); } static inline void PUT_16BIT_X11(char endian, void *p, uint16_t value) { if (endian == 'B') PUT_16BIT_MSB_FIRST(p, value); else PUT_16BIT_LSB_FIRST(p, value); } const char *const x11_authnames[] = { "", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1" }; struct XDMSeen { unsigned int time; unsigned char clientid[6]; }; typedef struct X11Connection { unsigned char firstpkt[12]; /* first X data packet */ tree234 *authtree; struct X11Display *disp; char *auth_protocol; unsigned char *auth_data; int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize; bool verified; bool input_wanted; bool no_data_sent_to_x_client; char *peer_addr; int peer_port; SshChannel *c; /* channel structure held by SSH backend */ Socket *s; Plug plug; Channel chan; } X11Connection; static int xdmseen_cmp(void *a, void *b) { struct XDMSeen *sa = a, *sb = b; return sa->time > sb->time ? 1 : sa->time < sb->time ? -1 : memcmp(sa->clientid, sb->clientid, sizeof(sa->clientid)); } struct X11FakeAuth *x11_invent_fake_auth(tree234 *authtree, int authtype) { struct X11FakeAuth *auth = snew(struct X11FakeAuth); int i; /* * This function has the job of inventing a set of X11 fake auth * data, and adding it to 'authtree'. We must preserve the * property that for any given actual authorisation attempt, _at * most one_ thing in the tree can possibly match it. * * For MIT-MAGIC-COOKIE-1, that's not too difficult: the match * criterion is simply that the entire cookie is correct, so we * just have to make sure we don't make up two cookies the same. * (Vanishingly unlikely, but we check anyway to be sure, and go * round again inventing a new cookie if add234 tells us the one * we thought of is already in use.) * * For XDM-AUTHORIZATION-1, it's a little more fiddly. The setup * with XA1 is that half the cookie is used as a DES key with * which to CBC-encrypt an assortment of stuff. Happily, the stuff * encrypted _begins_ with the other half of the cookie, and the * IV is always zero, which means that any valid XA1 authorisation * attempt for a given cookie must begin with the same cipher * block, consisting of the DES ECB encryption of the first half * of the cookie using the second half as a key. So we compute * that cipher block here and now, and use it as the sorting key * for distinguishing XA1 entries in the tree. */ if (authtype == X11_MIT) { auth->proto = X11_MIT; /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */ auth->datalen = 16; auth->data = snewn(auth->datalen, unsigned char); auth->xa1_firstblock = NULL; while (1) { random_read(auth->data, auth->datalen); if (add234(authtree, auth) == auth) break; } auth->xdmseen = NULL; } else { assert(authtype == X11_XDM); auth->proto = X11_XDM; /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */ auth->datalen = 16; auth->data = snewn(auth->datalen, unsigned char); auth->xa1_firstblock = snewn(8, unsigned char); memset(auth->xa1_firstblock, 0, 8); while (1) { random_read(auth->data, 15); auth->data[15] = auth->data[8]; auth->data[8] = 0; memcpy(auth->xa1_firstblock, auth->data, 8); des_encrypt_xdmauth(auth->data + 9, auth->xa1_firstblock, 8); if (add234(authtree, auth) == auth) break; } auth->xdmseen = newtree234(xdmseen_cmp); } auth->protoname = dupstr(x11_authnames[auth->proto]); auth->datastring = snewn(auth->datalen * 2 + 1, char); for (i = 0; i < auth->datalen; i++) sprintf(auth->datastring + i*2, "%02x", auth->data[i]); auth->disp = NULL; auth->share_cs = NULL; auth->share_chan = NULL; return auth; } void x11_free_fake_auth(struct X11FakeAuth *auth) { if (auth->data) smemclr(auth->data, auth->datalen); sfree(auth->data); sfree(auth->protoname); sfree(auth->datastring); sfree(auth->xa1_firstblock); if (auth->xdmseen != NULL) { struct XDMSeen *seen; while ((seen = delpos234(auth->xdmseen, 0)) != NULL) sfree(seen); freetree234(auth->xdmseen); } sfree(auth); } int x11_authcmp(void *av, void *bv) { struct X11FakeAuth *a = (struct X11FakeAuth *)av; struct X11FakeAuth *b = (struct X11FakeAuth *)bv; if (a->proto < b->proto) return -1; else if (a->proto > b->proto) return +1; if (a->proto == X11_MIT) { if (a->datalen < b->datalen) return -1; else if (a->datalen > b->datalen) return +1; return memcmp(a->data, b->data, a->datalen); } else { assert(a->proto == X11_XDM); return memcmp(a->xa1_firstblock, b->xa1_firstblock, 8); } } struct X11Display *x11_setup_display(const char *display, Conf *conf, char **error_msg) { struct X11Display *disp = snew(struct X11Display); char *localcopy; *error_msg = NULL; if (!display || !*display) { localcopy = platform_get_x_display(); if (!localcopy || !*localcopy) { sfree(localcopy); localcopy = dupstr(":0"); /* plausible default for any platform */ } } else localcopy = dupstr(display); /* * Parse the display name. * * We expect this to have one of the following forms: * * - the standard X format which looks like * [ [ protocol '/' ] host ] ':' displaynumber [ '.' screennumber ] * (X11 also permits a double colon to indicate DECnet, but * that's not our problem, thankfully!) * * - only seen in the wild on MacOS (so far): a pathname to a * Unix-domain socket, which will typically and confusingly * end in ":0", and which I'm currently distinguishing from * the standard scheme by noting that it starts with '/'. */ if (localcopy[0] == '/') { disp->unixsocketpath = localcopy; disp->unixdomain = true; disp->hostname = NULL; disp->displaynum = -1; disp->screennum = 0; disp->addr = NULL; } else { char *colon, *dot, *slash; char *protocol, *hostname; colon = host_strrchr(localcopy, ':'); if (!colon) { *error_msg = dupprintf("display name '%s' has no ':number'" " suffix", localcopy); sfree(disp); sfree(localcopy); return NULL; } *colon++ = '\0'; dot = strchr(colon, '.'); if (dot) *dot++ = '\0'; disp->displaynum = atoi(colon); if (dot) disp->screennum = atoi(dot); else disp->screennum = 0; protocol = NULL; hostname = localcopy; if (colon > localcopy) { slash = strchr(localcopy, '/'); if (slash) { *slash++ = '\0'; protocol = localcopy; hostname = slash; } } disp->hostname = *hostname ? dupstr(hostname) : NULL; if (protocol) disp->unixdomain = (!strcmp(protocol, "local") || !strcmp(protocol, "unix")); else if (!*hostname || !strcmp(hostname, "unix")) disp->unixdomain = platform_uses_x11_unix_by_default; else disp->unixdomain = false; if (!disp->hostname && !disp->unixdomain) disp->hostname = dupstr("localhost"); disp->unixsocketpath = NULL; disp->addr = NULL; sfree(localcopy); } /* * Look up the display hostname, if we need to. */ if (!disp->unixdomain) { const char *err; disp->port = 6000 + disp->displaynum; disp->addr = name_lookup(disp->hostname, disp->port, &disp->realhost, conf, ADDRTYPE_UNSPEC, NULL, NULL); if ((err = sk_addr_error(disp->addr)) != NULL) { *error_msg = dupprintf("unable to resolve host name '%s' in " "display name", disp->hostname); sk_addr_free(disp->addr); sfree(disp->hostname); sfree(disp->unixsocketpath); sfree(disp); return NULL; } } /* * Try upgrading an IP-style localhost display to a Unix-socket * display (as the standard X connection libraries do). */ if (!disp->unixdomain && sk_address_is_local(disp->addr)) { SockAddr *ux = platform_get_x11_unix_address(NULL, disp->displaynum); const char *err = sk_addr_error(ux); if (!err) { /* Create trial connection to see if there is a useful Unix-domain * socket */ Socket *s = sk_new(sk_addr_dup(ux), 0, false, false, false, false, nullplug); err = sk_socket_error(s); sk_close(s); } if (err) { sk_addr_free(ux); } else { sk_addr_free(disp->addr); disp->unixdomain = true; disp->addr = ux; /* Fill in the rest in a moment */ } } if (disp->unixdomain) { if (!disp->addr) disp->addr = platform_get_x11_unix_address(disp->unixsocketpath, disp->displaynum); if (disp->unixsocketpath) disp->realhost = dupstr(disp->unixsocketpath); else disp->realhost = dupprintf("unix:%d", disp->displaynum); disp->port = 0; } /* * Fetch the local authorisation details. */ disp->localauthproto = X11_NO_AUTH; disp->localauthdata = NULL; disp->localauthdatalen = 0; platform_get_x11_auth(disp, conf); return disp; } void x11_free_display(struct X11Display *disp) { sfree(disp->hostname); sfree(disp->unixsocketpath); if (disp->localauthdata) smemclr(disp->localauthdata, disp->localauthdatalen); sfree(disp->localauthdata); sk_addr_free(disp->addr); sfree(disp); } #define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */ static const char *x11_verify(unsigned long peer_ip, int peer_port, tree234 *authtree, char *proto, unsigned char *data, int dlen, struct X11FakeAuth **auth_ret) { struct X11FakeAuth match_dummy; /* for passing to find234 */ struct X11FakeAuth *auth; /* * First, do a lookup in our tree to find the only authorisation * record that _might_ match. */ if (!strcmp(proto, x11_authnames[X11_MIT])) { /* * Just look up the whole cookie that was presented to us, * which x11_authcmp will compare against the cookies we * currently believe in. */ match_dummy.proto = X11_MIT; match_dummy.datalen = dlen; match_dummy.data = data; } else if (!strcmp(proto, x11_authnames[X11_XDM])) { /* * Look up the first cipher block, against the stored first * cipher blocks for the XDM-AUTHORIZATION-1 cookies we * currently know. (See comment in x11_invent_fake_auth.) */ match_dummy.proto = X11_XDM; match_dummy.xa1_firstblock = data; } else { return "Unsupported authorisation protocol"; } if ((auth = find234(authtree, &match_dummy, 0)) == NULL) return "Authorisation not recognised"; /* * If we're using MIT-MAGIC-COOKIE-1, that was all we needed. If * we're doing XDM-AUTHORIZATION-1, though, we have to check the * rest of the auth data. */ if (auth->proto == X11_XDM) { unsigned long t; time_t tim; int i; struct XDMSeen *seen, *ret; if (dlen != 24) return "XDM-AUTHORIZATION-1 data was wrong length"; if (peer_port == -1) return "cannot do XDM-AUTHORIZATION-1 without remote address data"; des_decrypt_xdmauth(auth->data+9, data, 24); if (memcmp(auth->data, data, 8) != 0) return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */ if (GET_32BIT_MSB_FIRST(data+8) != peer_ip) return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */ if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port) return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */ t = GET_32BIT_MSB_FIRST(data+14); for (i = 18; i < 24; i++) if (data[i] != 0) /* zero padding wrong */ return "XDM-AUTHORIZATION-1 data failed check"; tim = time(NULL); if (((unsigned long)t - (unsigned long)tim + XDM_MAXSKEW) > 2*XDM_MAXSKEW) return "XDM-AUTHORIZATION-1 time stamp was too far out"; seen = snew(struct XDMSeen); seen->time = t; memcpy(seen->clientid, data+8, 6); assert(auth->xdmseen != NULL); ret = add234(auth->xdmseen, seen); if (ret != seen) { sfree(seen); return "XDM-AUTHORIZATION-1 data replayed"; } /* While we're here, purge entries too old to be replayed. */ for (;;) { seen = index234(auth->xdmseen, 0); assert(seen != NULL); if (t - seen->time <= XDM_MAXSKEW) break; sfree(delpos234(auth->xdmseen, 0)); } } /* implement other protocols here if ever required */ *auth_ret = auth; return NULL; } ptrlen BinarySource_get_string_xauth(BinarySource *src) { size_t len = get_uint16(src); return get_data(src, len); } #define get_string_xauth(src) \ BinarySource_get_string_xauth(BinarySource_UPCAST(src)) void BinarySink_put_stringpl_xauth(BinarySink *bs, ptrlen pl) { assert((pl.len >> 16) == 0); put_uint16(bs, pl.len); put_datapl(bs, pl); } #define put_stringpl_xauth(bs, ptrlen) \ BinarySink_put_stringpl_xauth(BinarySink_UPCAST(bs),ptrlen) void x11_get_auth_from_authfile(struct X11Display *disp, const char *authfilename) { FILE *authfp; char *buf; int size; BinarySource src[1]; int family, protocol; ptrlen addr, protoname, data; char *displaynum_string; int displaynum; bool ideal_match = false; char *ourhostname; /* A maximally sized (wildly implausible) .Xauthority record * consists of a 16-bit integer to start with, then four strings, * each of which has a 16-bit length field followed by that many * bytes of data (i.e. up to 0xFFFF bytes). */ const size_t MAX_RECORD_SIZE = 2 + 4 * (2+0xFFFF); /* We'll want a buffer of twice that size (see below). */ const size_t BUF_SIZE = 2 * MAX_RECORD_SIZE; /* * Normally we should look for precisely the details specified in * `disp'. However, there's an oddity when the display is local: * displays like "localhost:0" usually have their details stored * in a Unix-domain-socket record (even if there isn't actually a * real Unix-domain socket available, as with OpenSSH's proxy X11 * server). * * This is apparently a fudge to get round the meaninglessness of * "localhost" in a shared-home-directory context -- xauth entries * for Unix-domain sockets already disambiguate this by storing * the *local* hostname in the conveniently-blank hostname field, * but IP "localhost" records couldn't do this. So, typically, an * IP "localhost" entry in the auth database isn't present and if * it were it would be ignored. * * However, we don't entirely trust that (say) Windows X servers * won't rely on a straight "localhost" entry, bad idea though * that is; so if we can't find a Unix-domain-socket entry we'll * fall back to an IP-based entry if we can find one. */ bool localhost = !disp->unixdomain && sk_address_is_local(disp->addr); authfp = fopen(authfilename, "rb"); if (!authfp) return; ourhostname = get_hostname(); /* * Allocate enough space to hold two maximally sized records, so * that a full record can start anywhere in the first half. That * way we avoid the accidentally-quadratic algorithm that would * arise if we moved everything to the front of the buffer after * consuming each record; instead, we only move everything to the * front after our current position gets past the half-way mark. * Before then, there's no need to move anyway; so this guarantees * linear time, in that every byte written into this buffer moves * at most once (because every move is from the second half of the * buffer to the first half). */ buf = snewn(BUF_SIZE, char); size = fread(buf, 1, BUF_SIZE, authfp); BinarySource_BARE_INIT(src, buf, size); while (!ideal_match) { bool match = false; if (src->pos >= MAX_RECORD_SIZE) { size -= src->pos; memcpy(buf, buf + src->pos, size); size += fread(buf + size, 1, BUF_SIZE - size, authfp); BinarySource_BARE_INIT(src, buf, size); } family = get_uint16(src); addr = get_string_xauth(src); displaynum_string = mkstr(get_string_xauth(src)); displaynum = displaynum_string[0] ? atoi(displaynum_string) : -1; sfree(displaynum_string); protoname = get_string_xauth(src); data = get_string_xauth(src); if (get_err(src)) break; /* * Now we have a full X authority record in memory. See * whether it matches the display we're trying to * authenticate to. * * The details we've just read should be interpreted as * follows: * * - 'family' is the network address family used to * connect to the display. 0 means IPv4; 6 means IPv6; * 256 means Unix-domain sockets. * * - 'addr' is the network address itself. For IPv4 and * IPv6, this is a string of binary data of the * appropriate length (respectively 4 and 16 bytes) * representing the address in big-endian format, e.g. * 7F 00 00 01 means IPv4 localhost. For Unix-domain * sockets, this is the host name of the machine on * which the Unix-domain display resides (so that an * .Xauthority file on a shared file system can contain * authority entries for Unix-domain displays on * several machines without them clashing). * * - 'displaynum' is the display number. An empty display * number is a wildcard for any display number. * * - 'protoname' is the authorisation protocol, encoded as * its canonical string name (i.e. "MIT-MAGIC-COOKIE-1", * "XDM-AUTHORIZATION-1" or something we don't recognise). * * - 'data' is the actual authorisation data, stored in * binary form. */ if (disp->displaynum < 0 || (displaynum >= 0 && disp->displaynum != displaynum)) continue; /* not the one */ for (protocol = 1; protocol < lenof(x11_authnames); protocol++) if (ptrlen_eq_string(protoname, x11_authnames[protocol])) break; if (protocol == lenof(x11_authnames)) continue; /* don't recognise this protocol, look for another */ switch (family) { case 0: /* IPv4 */ if (!disp->unixdomain && sk_addrtype(disp->addr) == ADDRTYPE_IPV4) { char buf[4]; sk_addrcopy(disp->addr, buf); if (addr.len == 4 && !memcmp(addr.ptr, buf, 4)) { match = true; /* If this is a "localhost" entry, note it down * but carry on looking for a Unix-domain entry. */ ideal_match = !localhost; } } break; case 6: /* IPv6 */ if (!disp->unixdomain && sk_addrtype(disp->addr) == ADDRTYPE_IPV6) { char buf[16]; sk_addrcopy(disp->addr, buf); if (addr.len == 16 && !memcmp(addr.ptr, buf, 16)) { match = true; ideal_match = !localhost; } } break; case 256: /* Unix-domain / localhost */ if ((disp->unixdomain || localhost) && ourhostname && ptrlen_eq_string(addr, ourhostname)) { /* A matching Unix-domain socket is always the best * match. */ match = true; ideal_match = true; } break; } if (match) { /* Current best guess -- may be overridden if !ideal_match */ disp->localauthproto = protocol; sfree(disp->localauthdata); /* free previous guess, if any */ disp->localauthdata = snewn(data.len, unsigned char); memcpy(disp->localauthdata, data.ptr, data.len); disp->localauthdatalen = data.len; } } fclose(authfp); smemclr(buf, 2 * MAX_RECORD_SIZE); sfree(buf); sfree(ourhostname); } void x11_format_auth_for_authfile( BinarySink *bs, SockAddr *addr, int display_no, ptrlen authproto, ptrlen authdata) { if (sk_address_is_special_local(addr)) { char *ourhostname = get_hostname(); put_uint16(bs, 256); /* indicates Unix-domain socket */ put_stringpl_xauth(bs, ptrlen_from_asciz(ourhostname)); sfree(ourhostname); } else if (sk_addrtype(addr) == ADDRTYPE_IPV4) { char ipv4buf[4]; sk_addrcopy(addr, ipv4buf); put_uint16(bs, 0); /* indicates IPv4 */ put_stringpl_xauth(bs, make_ptrlen(ipv4buf, 4)); } else if (sk_addrtype(addr) == ADDRTYPE_IPV6) { char ipv6buf[16]; sk_addrcopy(addr, ipv6buf); put_uint16(bs, 6); /* indicates IPv6 */ put_stringpl_xauth(bs, make_ptrlen(ipv6buf, 16)); } else { unreachable("Bad address type in x11_format_auth_for_authfile"); } { char *numberbuf = dupprintf("%d", display_no); put_stringpl_xauth(bs, ptrlen_from_asciz(numberbuf)); sfree(numberbuf); } put_stringpl_xauth(bs, authproto); put_stringpl_xauth(bs, authdata); } static void x11_log(Plug *p, PlugLogType type, SockAddr *addr, int port, const char *error_msg, int error_code) { /* We have no interface to the logging module here, so we drop these. */ } static void x11_send_init_error(struct X11Connection *conn, const char *err_message); static void x11_closing(Plug *plug, const char *error_msg, int error_code, bool calling_back) { struct X11Connection *xconn = container_of( plug, struct X11Connection, plug); if (error_msg) { /* * Socket error. If we're still at the connection setup stage, * construct an X11 error packet passing on the problem. */ if (xconn->no_data_sent_to_x_client) { char *err_message = dupprintf("unable to connect to forwarded " "X server: %s", error_msg); x11_send_init_error(xconn, err_message); sfree(err_message); } /* * Whether we did that or not, now we slam the connection * shut. */ sshfwd_initiate_close(xconn->c, error_msg); } else { /* * Ordinary EOF received on socket. Send an EOF on the SSH * channel. */ if (xconn->c) sshfwd_write_eof(xconn->c); } } static void x11_receive(Plug *plug, int urgent, const char *data, size_t len) { struct X11Connection *xconn = container_of( plug, struct X11Connection, plug); xconn->no_data_sent_to_x_client = false; sshfwd_write(xconn->c, data, len); } static void x11_sent(Plug *plug, size_t bufsize) { struct X11Connection *xconn = container_of( plug, struct X11Connection, plug); sshfwd_unthrottle(xconn->c, bufsize); } /* * When setting up X forwarding, we should send the screen number * from the specified local display. This function extracts it from * the display string. */ int x11_get_screen_number(char *display) { int n; n = host_strcspn(display, ":"); if (!display[n]) return 0; n = strcspn(display, "."); if (!display[n]) return 0; return atoi(display + n + 1); } static const PlugVtable X11Connection_plugvt = { .log = x11_log, .closing = x11_closing, .receive = x11_receive, .sent = x11_sent, }; static void x11_chan_free(Channel *chan); static size_t x11_send( Channel *chan, bool is_stderr, const void *vdata, size_t len); static void x11_send_eof(Channel *chan); static void x11_set_input_wanted(Channel *chan, bool wanted); static char *x11_log_close_msg(Channel *chan); static const ChannelVtable X11Connection_channelvt = { .free = x11_chan_free, .open_confirmation = chan_remotely_opened_confirmation, .open_failed = chan_remotely_opened_failure, .send = x11_send, .send_eof = x11_send_eof, .set_input_wanted = x11_set_input_wanted, .log_close_msg = x11_log_close_msg, .want_close = chan_default_want_close, .rcvd_exit_status = chan_no_exit_status, .rcvd_exit_signal = chan_no_exit_signal, .rcvd_exit_signal_numeric = chan_no_exit_signal_numeric, .run_shell = chan_no_run_shell, .run_command = chan_no_run_command, .run_subsystem = chan_no_run_subsystem, .enable_x11_forwarding = chan_no_enable_x11_forwarding, .enable_agent_forwarding = chan_no_enable_agent_forwarding, .allocate_pty = chan_no_allocate_pty, .set_env = chan_no_set_env, .send_break = chan_no_send_break, .send_signal = chan_no_send_signal, .change_window_size = chan_no_change_window_size, .request_response = chan_no_request_response, }; /* * Called to set up the X11Connection structure, though this does not * yet connect to an actual server. */ Channel *x11_new_channel(tree234 *authtree, SshChannel *c, const char *peeraddr, int peerport, bool connection_sharing_possible) { struct X11Connection *xconn; /* * Open socket. */ xconn = snew(struct X11Connection); xconn->plug.vt = &X11Connection_plugvt; xconn->chan.vt = &X11Connection_channelvt; xconn->chan.initial_fixed_window_size = (connection_sharing_possible ? 128 : 0); xconn->auth_protocol = NULL; xconn->authtree = authtree; xconn->verified = false; xconn->data_read = 0; xconn->input_wanted = true; xconn->no_data_sent_to_x_client = true; xconn->c = c; /* * We don't actually open a local socket to the X server just yet, * because we don't know which one it is. Instead, we'll wait * until we see the incoming authentication data, which may tell * us what display to connect to, or whether we have to divert * this X forwarding channel to a connection-sharing downstream * rather than handling it ourself. */ xconn->disp = NULL; xconn->s = NULL; /* * Stash the peer address we were given in its original text form. */ xconn->peer_addr = peeraddr ? dupstr(peeraddr) : NULL; xconn->peer_port = peerport; return &xconn->chan; } static void x11_chan_free(Channel *chan) { assert(chan->vt == &X11Connection_channelvt); X11Connection *xconn = container_of(chan, X11Connection, chan); if (xconn->auth_protocol) { sfree(xconn->auth_protocol); sfree(xconn->auth_data); } if (xconn->s) sk_close(xconn->s); sfree(xconn->peer_addr); sfree(xconn); } static void x11_set_input_wanted(Channel *chan, bool wanted) { assert(chan->vt == &X11Connection_channelvt); X11Connection *xconn = container_of(chan, X11Connection, chan); xconn->input_wanted = wanted; if (xconn->s) sk_set_frozen(xconn->s, !xconn->input_wanted); } static void x11_send_init_error(struct X11Connection *xconn, const char *err_message) { char *full_message; int msglen, msgsize; unsigned char *reply; full_message = dupprintf("%s X11 proxy: %s\n", appname, err_message); msglen = strlen(full_message); reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */ msgsize = (msglen + 3) & ~3; reply[0] = 0; /* failure */ reply[1] = msglen; /* length of reason string */ memcpy(reply + 2, xconn->firstpkt + 2, 4); /* major/minor proto vsn */ PUT_16BIT_X11(xconn->firstpkt[0], reply + 6, msgsize >> 2);/* data len */ memset(reply + 8, 0, msgsize); memcpy(reply + 8, full_message, msglen); sshfwd_write(xconn->c, reply, 8 + msgsize); sshfwd_write_eof(xconn->c); xconn->no_data_sent_to_x_client = false; sfree(reply); sfree(full_message); } static bool x11_parse_ip(const char *addr_string, unsigned long *ip) { /* * See if we can make sense of this string as an IPv4 address, for * XDM-AUTHORIZATION-1 purposes. */ int i[4]; if (addr_string && 4 == sscanf(addr_string, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) { *ip = (i[0] << 24) | (i[1] << 16) | (i[2] << 8) | i[3]; return true; } else { return false; } } /* * Called to send data down the raw connection. */ static size_t x11_send( Channel *chan, bool is_stderr, const void *vdata, size_t len) { assert(chan->vt == &X11Connection_channelvt); X11Connection *xconn = container_of(chan, X11Connection, chan); const char *data = (const char *)vdata; /* * Read the first packet. */ while (len > 0 && xconn->data_read < 12) xconn->firstpkt[xconn->data_read++] = (unsigned char) (len--, *data++); if (xconn->data_read < 12) return 0; /* * If we have not allocated the auth_protocol and auth_data * strings, do so now. */ if (!xconn->auth_protocol) { char endian = xconn->firstpkt[0]; xconn->auth_plen = GET_16BIT_X11(endian, xconn->firstpkt + 6); xconn->auth_dlen = GET_16BIT_X11(endian, xconn->firstpkt + 8); xconn->auth_psize = (xconn->auth_plen + 3) & ~3; xconn->auth_dsize = (xconn->auth_dlen + 3) & ~3; /* Leave room for a terminating zero, to make our lives easier. */ xconn->auth_protocol = snewn(xconn->auth_psize + 1, char); xconn->auth_data = snewn(xconn->auth_dsize, unsigned char); } /* * Read the auth_protocol and auth_data strings. */ while (len > 0 && xconn->data_read < 12 + xconn->auth_psize) xconn->auth_protocol[xconn->data_read++ - 12] = (len--, *data++); while (len > 0 && xconn->data_read < 12 + xconn->auth_psize + xconn->auth_dsize) xconn->auth_data[xconn->data_read++ - 12 - xconn->auth_psize] = (unsigned char) (len--, *data++); if (xconn->data_read < 12 + xconn->auth_psize + xconn->auth_dsize) return 0; /* * If we haven't verified the authorisation, do so now. */ if (!xconn->verified) { const char *err; struct X11FakeAuth *auth_matched = NULL; unsigned long peer_ip; int peer_port; int protomajor, protominor; void *greeting; int greeting_len; unsigned char *socketdata; int socketdatalen; char new_peer_addr[32]; int new_peer_port; char endian = xconn->firstpkt[0]; protomajor = GET_16BIT_X11(endian, xconn->firstpkt + 2); protominor = GET_16BIT_X11(endian, xconn->firstpkt + 4); assert(!xconn->s); xconn->auth_protocol[xconn->auth_plen] = '\0'; /* ASCIZ */ peer_ip = 0; /* placate optimiser */ if (x11_parse_ip(xconn->peer_addr, &peer_ip)) peer_port = xconn->peer_port; else peer_port = -1; /* signal no peer address data available */ err = x11_verify(peer_ip, peer_port, xconn->authtree, xconn->auth_protocol, xconn->auth_data, xconn->auth_dlen, &auth_matched); if (err) { x11_send_init_error(xconn, err); return 0; } assert(auth_matched); /* * If this auth points to a connection-sharing downstream * rather than an X display we know how to connect to * directly, pass it off to the sharing module now. (This will * have the side effect of freeing xconn.) */ if (auth_matched->share_cs) { sshfwd_x11_sharing_handover(xconn->c, auth_matched->share_cs, auth_matched->share_chan, xconn->peer_addr, xconn->peer_port, xconn->firstpkt[0], protomajor, protominor, data, len); return 0; } /* * Now we know we're going to accept the connection, and what * X display to connect to. Actually connect to it. */ xconn->chan.initial_fixed_window_size = 0; sshfwd_window_override_removed(xconn->c); xconn->disp = auth_matched->disp; xconn->s = new_connection(sk_addr_dup(xconn->disp->addr), xconn->disp->realhost, xconn->disp->port, false, true, false, false, &xconn->plug, sshfwd_get_conf(xconn->c)); if ((err = sk_socket_error(xconn->s)) != NULL) { char *err_message = dupprintf("unable to connect to" " forwarded X server: %s", err); x11_send_init_error(xconn, err_message); sfree(err_message); return 0; } /* * Write a new connection header containing our replacement * auth data. */ socketdatalen = 0; /* placate compiler warning */ socketdata = sk_getxdmdata(xconn->s, &socketdatalen); if (socketdata && socketdatalen==6) { sprintf(new_peer_addr, "%d.%d.%d.%d", socketdata[0], socketdata[1], socketdata[2], socketdata[3]); new_peer_port = GET_16BIT_MSB_FIRST(socketdata + 4); } else { strcpy(new_peer_addr, "0.0.0.0"); new_peer_port = 0; } greeting = x11_make_greeting(xconn->firstpkt[0], protomajor, protominor, xconn->disp->localauthproto, xconn->disp->localauthdata, xconn->disp->localauthdatalen, new_peer_addr, new_peer_port, &greeting_len); sk_write(xconn->s, greeting, greeting_len); smemclr(greeting, greeting_len); sfree(greeting); /* * Now we're done. */ xconn->verified = true; } /* * After initialisation, just copy data simply. */ return sk_write(xconn->s, data, len); } static void x11_send_eof(Channel *chan) { assert(chan->vt == &X11Connection_channelvt); X11Connection *xconn = container_of(chan, X11Connection, chan); if (xconn->s) { sk_write_eof(xconn->s); } else { /* * If EOF is received from the X client before we've got to * the point of actually connecting to an X server, then we * should send an EOF back to the client so that the * forwarded channel will be terminated. */ if (xconn->c) sshfwd_write_eof(xconn->c); } } static char *x11_log_close_msg(Channel *chan) { return dupstr("Forwarded X11 connection terminated"); } /* * Utility functions used by connection sharing to convert textual * representations of an X11 auth protocol name + hex cookie into our * usual integer protocol id and binary auth data. */ int x11_identify_auth_proto(ptrlen protoname) { int protocol; for (protocol = 1; protocol < lenof(x11_authnames); protocol++) if (ptrlen_eq_string(protoname, x11_authnames[protocol])) return protocol; return -1; } void *x11_dehexify(ptrlen hexpl, int *outlen) { int len, i; unsigned char *ret; len = hexpl.len / 2; ret = snewn(len, unsigned char); for (i = 0; i < len; i++) { char bytestr[3]; unsigned val = 0; bytestr[0] = ((const char *)hexpl.ptr)[2*i]; bytestr[1] = ((const char *)hexpl.ptr)[2*i+1]; bytestr[2] = '\0'; sscanf(bytestr, "%x", &val); ret[i] = val; } *outlen = len; return ret; } /* * Construct an X11 greeting packet, including making up the right * authorisation data. */ void *x11_make_greeting(int endian, int protomajor, int protominor, int auth_proto, const void *auth_data, int auth_len, const char *peer_addr, int peer_port, int *outlen) { unsigned char *greeting; unsigned char realauthdata[64]; const char *authname; const unsigned char *authdata; int authnamelen, authnamelen_pad; int authdatalen, authdatalen_pad; int greeting_len; authname = x11_authnames[auth_proto]; authnamelen = strlen(authname); authnamelen_pad = (authnamelen + 3) & ~3; if (auth_proto == X11_MIT) { authdata = auth_data; authdatalen = auth_len; } else if (auth_proto == X11_XDM && auth_len == 16) { time_t t; unsigned long peer_ip = 0; x11_parse_ip(peer_addr, &peer_ip); authdata = realauthdata; authdatalen = 24; memset(realauthdata, 0, authdatalen); memcpy(realauthdata, auth_data, 8); PUT_32BIT_MSB_FIRST(realauthdata+8, peer_ip); PUT_16BIT_MSB_FIRST(realauthdata+12, peer_port); t = time(NULL); PUT_32BIT_MSB_FIRST(realauthdata+14, t); des_encrypt_xdmauth((char *)auth_data + 9, realauthdata, authdatalen); } else { authdata = realauthdata; authdatalen = 0; } authdatalen_pad = (authdatalen + 3) & ~3; greeting_len = 12 + authnamelen_pad + authdatalen_pad; greeting = snewn(greeting_len, unsigned char); memset(greeting, 0, greeting_len); greeting[0] = endian; PUT_16BIT_X11(endian, greeting+2, protomajor); PUT_16BIT_X11(endian, greeting+4, protominor); PUT_16BIT_X11(endian, greeting+6, authnamelen); PUT_16BIT_X11(endian, greeting+8, authdatalen); memcpy(greeting+12, authname, authnamelen); memcpy(greeting+12+authnamelen_pad, authdata, authdatalen); smemclr(realauthdata, sizeof(realauthdata)); *outlen = greeting_len; return greeting; }