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putty/x11fwd.c

1203 строки
39 KiB
C
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/*
* 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 "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 = {
x11_log,
x11_closing,
x11_receive,
x11_sent,
NULL
};
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 struct ChannelVtable X11Connection_channelvt = {
x11_chan_free,
chan_remotely_opened_confirmation,
chan_remotely_opened_failure,
x11_send,
x11_send_eof,
x11_set_input_wanted,
x11_log_close_msg,
chan_default_want_close,
chan_no_exit_status,
chan_no_exit_signal,
chan_no_exit_signal_numeric,
chan_no_run_shell,
chan_no_run_command,
chan_no_run_subsystem,
chan_no_enable_x11_forwarding,
chan_no_enable_agent_forwarding,
chan_no_allocate_pty,
chan_no_set_env,
chan_no_send_break,
chan_no_send_signal,
chan_no_change_window_size,
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;
}
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