pe.old/X11FWD.C
/*
* 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);
}