diff options
Diffstat (limited to 'tools/plink/x11fwd.c')
| -rw-r--r-- | tools/plink/x11fwd.c | 791 |
1 files changed, 791 insertions, 0 deletions
diff --git a/tools/plink/x11fwd.c b/tools/plink/x11fwd.c new file mode 100644 index 000000000..9f22a2364 --- /dev/null +++ b/tools/plink/x11fwd.c @@ -0,0 +1,791 @@ +/*
+ * Platform-independent bits of X11 forwarding.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <time.h>
+
+#include "putty.h"
+#include "ssh.h"
+#include "tree234.h"
+
+#define GET_16BIT(endian, cp) \
+ (endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
+
+#define PUT_16BIT(endian, cp, val) \
+ (endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
+
+const char *const x11_authnames[] = {
+ "", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1"
+};
+
+struct XDMSeen {
+ unsigned int time;
+ unsigned char clientid[6];
+};
+
+struct X11Private {
+ const struct plug_function_table *fn;
+ /* the above variable absolutely *must* be the first in this structure */
+ unsigned char firstpkt[12]; /* first X data packet */
+ struct X11Display *disp;
+ char *auth_protocol;
+ unsigned char *auth_data;
+ int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
+ int verified;
+ int throttled, throttle_override;
+ unsigned long peer_ip;
+ int peer_port;
+ void *c; /* data used by ssh.c */
+ Socket s;
+};
+
+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));
+}
+
+/* Do-nothing "plug" implementation, used by x11_setup_display() when it
+ * creates a trial connection (and then immediately closes it).
+ * XXX: bit out of place here, could in principle live in a platform-
+ * independent network.c or something */
+static void dummy_plug_log(Plug p, int type, SockAddr addr, int port,
+ const char *error_msg, int error_code) { }
+static int dummy_plug_closing
+ (Plug p, const char *error_msg, int error_code, int calling_back)
+{ return 1; }
+static int dummy_plug_receive(Plug p, int urgent, char *data, int len)
+{ return 1; }
+static void dummy_plug_sent(Plug p, int bufsize) { }
+static int dummy_plug_accepting(Plug p, OSSocket sock) { return 1; }
+static const struct plug_function_table dummy_plug = {
+ dummy_plug_log, dummy_plug_closing, dummy_plug_receive,
+ dummy_plug_sent, dummy_plug_accepting
+};
+
+struct X11Display *x11_setup_display(char *display, int authtype,
+ const Config *cfg)
+{
+ struct X11Display *disp = snew(struct X11Display);
+ char *localcopy;
+ int i;
+
+ 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 = strrchr(localcopy, ':');
+ if (!colon) {
+ sfree(disp);
+ sfree(localcopy);
+ return NULL; /* FIXME: report a specific error? */
+ }
+
+ *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, cfg, ADDRTYPE_UNSPEC);
+
+ if ((err = sk_addr_error(disp->addr)) != NULL) {
+ sk_addr_free(disp->addr);
+ sfree(disp->hostname);
+ sfree(disp->unixsocketpath);
+ return NULL; /* FIXME: report an error */
+ }
+ }
+
+ /*
+ * 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 */
+ const struct plug_function_table *dummy = &dummy_plug;
+ Socket s = sk_new(sk_addr_dup(ux), 0, 0, 0, 0, 0, (Plug)&dummy);
+ 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;
+ }
+
+ /*
+ * Invent the remote authorisation details.
+ */
+ if (authtype == X11_MIT) {
+ disp->remoteauthproto = X11_MIT;
+
+ /* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
+ disp->remoteauthdata = snewn(16, unsigned char);
+ for (i = 0; i < 16; i++)
+ disp->remoteauthdata[i] = random_byte();
+ disp->remoteauthdatalen = 16;
+
+ disp->xdmseen = NULL;
+ } else {
+ assert(authtype == X11_XDM);
+ disp->remoteauthproto = X11_XDM;
+
+ /* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
+ disp->remoteauthdata = snewn(16, unsigned char);
+ for (i = 0; i < 16; i++)
+ disp->remoteauthdata[i] = (i == 8 ? 0 : random_byte());
+ disp->remoteauthdatalen = 16;
+
+ disp->xdmseen = newtree234(xdmseen_cmp);
+ }
+ disp->remoteauthprotoname = dupstr(x11_authnames[disp->remoteauthproto]);
+ disp->remoteauthdatastring = snewn(disp->remoteauthdatalen * 2 + 1, char);
+ for (i = 0; i < disp->remoteauthdatalen; i++)
+ sprintf(disp->remoteauthdatastring + i*2, "%02x",
+ disp->remoteauthdata[i]);
+
+ /*
+ * Fetch the local authorisation details.
+ */
+ disp->localauthproto = X11_NO_AUTH;
+ disp->localauthdata = NULL;
+ disp->localauthdatalen = 0;
+ platform_get_x11_auth(disp, cfg);
+
+ return disp;
+}
+
+void x11_free_display(struct X11Display *disp)
+{
+ if (disp->xdmseen != NULL) {
+ struct XDMSeen *seen;
+ while ((seen = delpos234(disp->xdmseen, 0)) != NULL)
+ sfree(seen);
+ freetree234(disp->xdmseen);
+ }
+ sfree(disp->hostname);
+ sfree(disp->unixsocketpath);
+ if (disp->localauthdata)
+ memset(disp->localauthdata, 0, disp->localauthdatalen);
+ sfree(disp->localauthdata);
+ if (disp->remoteauthdata)
+ memset(disp->remoteauthdata, 0, disp->remoteauthdatalen);
+ sfree(disp->remoteauthdata);
+ sfree(disp->remoteauthprotoname);
+ sfree(disp->remoteauthdatastring);
+ sk_addr_free(disp->addr);
+ sfree(disp);
+}
+
+#define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */
+
+static char *x11_verify(unsigned long peer_ip, int peer_port,
+ struct X11Display *disp, char *proto,
+ unsigned char *data, int dlen)
+{
+ if (strcmp(proto, x11_authnames[disp->remoteauthproto]) != 0)
+ return "wrong authorisation protocol attempted";
+ if (disp->remoteauthproto == X11_MIT) {
+ if (dlen != disp->remoteauthdatalen)
+ return "MIT-MAGIC-COOKIE-1 data was wrong length";
+ if (memcmp(disp->remoteauthdata, data, dlen) != 0)
+ return "MIT-MAGIC-COOKIE-1 data did not match";
+ }
+ if (disp->remoteauthproto == 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(disp->remoteauthdata+9, data, 24);
+ if (memcmp(disp->remoteauthdata, 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 (abs(t - tim) > 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(disp->xdmseen != NULL);
+ ret = add234(disp->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(disp->xdmseen, 0);
+ assert(seen != NULL);
+ if (t - seen->time <= XDM_MAXSKEW)
+ break;
+ sfree(delpos234(disp->xdmseen, 0));
+ }
+ }
+ /* implement other protocols here if ever required */
+ return NULL;
+}
+
+void x11_get_auth_from_authfile(struct X11Display *disp,
+ const char *authfilename)
+{
+ FILE *authfp;
+ char *buf, *ptr, *str[4];
+ int len[4];
+ int family, protocol;
+ int ideal_match = FALSE;
+ char *ourhostname = get_hostname();
+
+ /*
+ * 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.
+ */
+ int localhost = !disp->unixdomain && sk_address_is_local(disp->addr);
+
+ authfp = fopen(authfilename, "rb");
+ if (!authfp)
+ return;
+
+ /* Records in .Xauthority contain four strings of up to 64K each */
+ buf = snewn(65537 * 4, char);
+
+ while (!ideal_match) {
+ int c, i, j, match = FALSE;
+
+#define GET do { c = fgetc(authfp); if (c == EOF) goto done; c = (unsigned char)c; } while (0)
+ /* Expect a big-endian 2-byte number giving address family */
+ GET; family = c;
+ GET; family = (family << 8) | c;
+ /* Then expect four strings, each composed of a big-endian 2-byte
+ * length field followed by that many bytes of data */
+ ptr = buf;
+ for (i = 0; i < 4; i++) {
+ GET; len[i] = c;
+ GET; len[i] = (len[i] << 8) | c;
+ str[i] = ptr;
+ for (j = 0; j < len[i]; j++) {
+ GET; *ptr++ = c;
+ }
+ *ptr++ = '\0';
+ }
+#undef GET
+
+ /*
+ * 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.
+ *
+ * - str[0] 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).
+ *
+ * - str[1] is the display number. I've no idea why
+ * .Xauthority stores this as a string when it has a
+ * perfectly good integer format, but there we go.
+ *
+ * - str[2] is the authorisation method, encoded as its
+ * canonical string name (i.e. "MIT-MAGIC-COOKIE-1",
+ * "XDM-AUTHORIZATION-1" or something we don't
+ * recognise).
+ *
+ * - str[3] is the actual authorisation data, stored in
+ * binary form.
+ */
+
+ if (disp->displaynum < 0 || disp->displaynum != atoi(str[1]))
+ continue; /* not the one */
+
+ for (protocol = 1; protocol < lenof(x11_authnames); protocol++)
+ if (!strcmp(str[2], 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 (len[0] == 4 && !memcmp(str[0], 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 (len[0] == 16 && !memcmp(str[0], buf, 16)) {
+ match = TRUE;
+ ideal_match = !localhost;
+ }
+ }
+ break;
+ case 256: /* Unix-domain / localhost */
+ if ((disp->unixdomain || localhost)
+ && ourhostname && !strcmp(ourhostname, str[0]))
+ /* A matching Unix-domain socket is always the best
+ * match. */
+ match = 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(len[3], unsigned char);
+ memcpy(disp->localauthdata, str[3], len[3]);
+ disp->localauthdatalen = len[3];
+ }
+ }
+
+ done:
+ fclose(authfp);
+ memset(buf, 0, 65537 * 4);
+ sfree(buf);
+ sfree(ourhostname);
+}
+
+static void x11_log(Plug p, int 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 int x11_closing(Plug plug, const char *error_msg, int error_code,
+ int calling_back)
+{
+ struct X11Private *pr = (struct X11Private *) plug;
+
+ /*
+ * We have no way to communicate down the forwarded connection,
+ * so if an error occurred on the socket, we just ignore it
+ * and treat it like a proper close.
+ */
+ sshfwd_close(pr->c);
+ x11_close(pr->s);
+ return 1;
+}
+
+static int x11_receive(Plug plug, int urgent, char *data, int len)
+{
+ struct X11Private *pr = (struct X11Private *) plug;
+
+ if (sshfwd_write(pr->c, data, len) > 0) {
+ pr->throttled = 1;
+ sk_set_frozen(pr->s, 1);
+ }
+
+ return 1;
+}
+
+static void x11_sent(Plug plug, int bufsize)
+{
+ struct X11Private *pr = (struct X11Private *) plug;
+
+ sshfwd_unthrottle(pr->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 = strcspn(display, ":");
+ if (!display[n])
+ return 0;
+ n = strcspn(display, ".");
+ if (!display[n])
+ return 0;
+ return atoi(display + n + 1);
+}
+
+/*
+ * Called to set up the raw connection.
+ *
+ * Returns an error message, or NULL on success.
+ * also, fills the SocketsStructure
+ */
+extern const char *x11_init(Socket *s, struct X11Display *disp, void *c,
+ const char *peeraddr, int peerport,
+ const Config *cfg)
+{
+ static const struct plug_function_table fn_table = {
+ x11_log,
+ x11_closing,
+ x11_receive,
+ x11_sent,
+ NULL
+ };
+
+ const char *err;
+ struct X11Private *pr;
+
+ /*
+ * Open socket.
+ */
+ pr = snew(struct X11Private);
+ pr->fn = &fn_table;
+ pr->auth_protocol = NULL;
+ pr->disp = disp;
+ pr->verified = 0;
+ pr->data_read = 0;
+ pr->throttled = pr->throttle_override = 0;
+ pr->c = c;
+
+ pr->s = *s = new_connection(sk_addr_dup(disp->addr),
+ disp->realhost, disp->port,
+ 0, 1, 0, 0, (Plug) pr, cfg);
+ if ((err = sk_socket_error(*s)) != NULL) {
+ sfree(pr);
+ return err;
+ }
+
+ /*
+ * See if we can make sense of the peer address we were given.
+ */
+ {
+ int i[4];
+ if (peeraddr &&
+ 4 == sscanf(peeraddr, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) {
+ pr->peer_ip = (i[0] << 24) | (i[1] << 16) | (i[2] << 8) | i[3];
+ pr->peer_port = peerport;
+ } else {
+ pr->peer_ip = 0;
+ pr->peer_port = -1;
+ }
+ }
+
+ sk_set_private_ptr(*s, pr);
+ return NULL;
+}
+
+void x11_close(Socket s)
+{
+ struct X11Private *pr;
+ if (!s)
+ return;
+ pr = (struct X11Private *) sk_get_private_ptr(s);
+ if (pr->auth_protocol) {
+ sfree(pr->auth_protocol);
+ sfree(pr->auth_data);
+ }
+
+ sfree(pr);
+
+ sk_close(s);
+}
+
+void x11_unthrottle(Socket s)
+{
+ struct X11Private *pr;
+ if (!s)
+ return;
+ pr = (struct X11Private *) sk_get_private_ptr(s);
+
+ pr->throttled = 0;
+ sk_set_frozen(s, pr->throttled || pr->throttle_override);
+}
+
+void x11_override_throttle(Socket s, int enable)
+{
+ struct X11Private *pr;
+ if (!s)
+ return;
+ pr = (struct X11Private *) sk_get_private_ptr(s);
+
+ pr->throttle_override = enable;
+ sk_set_frozen(s, pr->throttled || pr->throttle_override);
+}
+
+/*
+ * Called to send data down the raw connection.
+ */
+int x11_send(Socket s, char *data, int len)
+{
+ struct X11Private *pr;
+ if (!s)
+ return 0;
+ pr = (struct X11Private *) sk_get_private_ptr(s);
+
+ /*
+ * Read the first packet.
+ */
+ while (len > 0 && pr->data_read < 12)
+ pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
+ if (pr->data_read < 12)
+ return 0;
+
+ /*
+ * If we have not allocated the auth_protocol and auth_data
+ * strings, do so now.
+ */
+ if (!pr->auth_protocol) {
+ pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
+ pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
+ pr->auth_psize = (pr->auth_plen + 3) & ~3;
+ pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
+ /* Leave room for a terminating zero, to make our lives easier. */
+ pr->auth_protocol = snewn(pr->auth_psize + 1, char);
+ pr->auth_data = snewn(pr->auth_dsize, unsigned char);
+ }
+
+ /*
+ * Read the auth_protocol and auth_data strings.
+ */
+ while (len > 0 && pr->data_read < 12 + pr->auth_psize)
+ pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
+ while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
+ pr->auth_data[pr->data_read++ - 12 -
+ pr->auth_psize] = (unsigned char) (len--, *data++);
+ if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
+ return 0;
+
+ /*
+ * If we haven't verified the authorisation, do so now.
+ */
+ if (!pr->verified) {
+ char *err;
+
+ pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */
+ err = x11_verify(pr->peer_ip, pr->peer_port,
+ pr->disp, pr->auth_protocol,
+ pr->auth_data, pr->auth_dlen);
+
+ /*
+ * If authorisation failed, construct and send an error
+ * packet, then terminate the connection.
+ */
+ if (err) {
+ char *message;
+ int msglen, msgsize;
+ unsigned char *reply;
+
+ message = dupprintf("%s X11 proxy: %s", appname, err);
+ msglen = strlen(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, pr->firstpkt + 2, 4); /* major/minor proto vsn */
+ PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
+ memset(reply + 8, 0, msgsize);
+ memcpy(reply + 8, message, msglen);
+ sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
+ sshfwd_close(pr->c);
+ x11_close(s);
+ sfree(reply);
+ sfree(message);
+ return 0;
+ }
+
+ /*
+ * Now we know we're going to accept the connection. Strip
+ * the fake auth data, and optionally put real auth data in
+ * instead.
+ */
+ {
+ char realauthdata[64];
+ int realauthlen = 0;
+ int authstrlen = strlen(x11_authnames[pr->disp->localauthproto]);
+ int buflen = 0; /* initialise to placate optimiser */
+ static const char zeroes[4] = { 0,0,0,0 };
+ void *buf;
+
+ if (pr->disp->localauthproto == X11_MIT) {
+ assert(pr->disp->localauthdatalen <= lenof(realauthdata));
+ realauthlen = pr->disp->localauthdatalen;
+ memcpy(realauthdata, pr->disp->localauthdata, realauthlen);
+ } else if (pr->disp->localauthproto == X11_XDM &&
+ pr->disp->localauthdatalen == 16 &&
+ ((buf = sk_getxdmdata(s, &buflen))!=0)) {
+ time_t t;
+ realauthlen = (buflen+12+7) & ~7;
+ assert(realauthlen <= lenof(realauthdata));
+ memset(realauthdata, 0, realauthlen);
+ memcpy(realauthdata, pr->disp->localauthdata, 8);
+ memcpy(realauthdata+8, buf, buflen);
+ t = time(NULL);
+ PUT_32BIT_MSB_FIRST(realauthdata+8+buflen, t);
+ des_encrypt_xdmauth(pr->disp->localauthdata+9,
+ (unsigned char *)realauthdata,
+ realauthlen);
+ sfree(buf);
+ }
+ /* implement other auth methods here if required */
+
+ PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen);
+ PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen);
+
+ sk_write(s, (char *)pr->firstpkt, 12);
+
+ if (authstrlen) {
+ sk_write(s, x11_authnames[pr->disp->localauthproto],
+ authstrlen);
+ sk_write(s, zeroes, 3 & (-authstrlen));
+ }
+ if (realauthlen) {
+ sk_write(s, realauthdata, realauthlen);
+ sk_write(s, zeroes, 3 & (-realauthlen));
+ }
+ }
+ pr->verified = 1;
+ }
+
+ /*
+ * After initialisation, just copy data simply.
+ */
+
+ return sk_write(s, data, len);
+}
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