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putty/x11fwd.c

537 строки
14 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 "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 X11Auth {
unsigned char fakedata[64], realdata[64];
int fakeproto, realproto;
int fakelen, reallen;
tree234 *xdmseen;
};
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 X11Auth *auth;
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));
}
void *x11_invent_auth(char *proto, int protomaxlen,
char *data, int datamaxlen, int proto_id)
{
struct X11Auth *auth = snew(struct X11Auth);
char ourdata[64];
int i;
if (proto_id == X11_MIT) {
auth->fakeproto = X11_MIT;
/* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
auth->fakelen = 16;
for (i = 0; i < 16; i++)
auth->fakedata[i] = random_byte();
auth->xdmseen = NULL;
} else {
assert(proto_id == X11_XDM);
auth->fakeproto = X11_XDM;
/* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
auth->fakelen = 16;
for (i = 0; i < 16; i++)
auth->fakedata[i] = (i == 8 ? 0 : random_byte());
auth->xdmseen = newtree234(xdmseen_cmp);
}
/* Now format for the recipient. */
strncpy(proto, x11_authnames[auth->fakeproto], protomaxlen);
ourdata[0] = '\0';
for (i = 0; i < auth->fakelen; i++)
sprintf(ourdata + strlen(ourdata), "%02x", auth->fakedata[i]);
strncpy(data, ourdata, datamaxlen);
return auth;
}
void x11_free_auth(void *authv)
{
struct X11Auth *auth = (struct X11Auth *)authv;
struct XDMSeen *seen;
if (auth->xdmseen != NULL) {
while ((seen = delpos234(auth->xdmseen, 0)) != NULL)
sfree(seen);
freetree234(auth->xdmseen);
}
sfree(auth);
}
/*
* Fetch the real auth data for a given display string, and store
* it in an X11Auth structure. Returns NULL on success, or an error
* string.
*/
void x11_get_real_auth(void *authv, char *display)
{
struct X11Auth *auth = (struct X11Auth *)authv;
auth->realproto = X11_NO_AUTH; /* in case next call does nothing */
auth->reallen = sizeof(auth->realdata);
platform_get_x11_auth(display, &auth->realproto,
auth->realdata, &auth->reallen);
}
#define XDM_MAXSKEW 20*60 /* 20 minute clock skew should be OK */
static char *x11_verify(unsigned long peer_ip, int peer_port,
struct X11Auth *auth, char *proto,
unsigned char *data, int dlen)
{
if (strcmp(proto, x11_authnames[auth->fakeproto]) != 0)
return "wrong authentication protocol attempted";
if (auth->fakeproto == X11_MIT) {
if (dlen != auth->fakelen)
return "MIT-MAGIC-COOKIE-1 data was wrong length";
if (memcmp(auth->fakedata, data, dlen) != 0)
return "MIT-MAGIC-COOKIE-1 data did not match";
}
if (auth->fakeproto == 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->fakedata+9, data, 24);
if (memcmp(auth->fakedata, 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(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 */
return NULL;
}
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);
}
/* Find the right display, returns an allocated string */
char *x11_display(const char *display) {
char *ret;
if(!display || !*display) {
/* try to find platform-specific local display */
if((ret = platform_get_x_display())==0)
/* plausible default for all platforms */
ret = dupstr(":0");
} else
ret = dupstr(display);
if(ret[0] == ':') {
/* no transport specified, use whatever we think is best */
char *s = dupcat(platform_x11_best_transport, ret, (char *)0);
sfree(ret);
return s;
} else
return ret;
}
/*
* Called to set up the raw connection.
*
* Returns an error message, or NULL on success.
* also, fills the SocketsStructure
*/
const char *x11_init(Socket * s, char *display, void *c, void *auth,
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
};
SockAddr addr;
int port;
const char *err;
char *dummy_realhost;
char host[128];
int n, displaynum;
struct X11Private *pr;
/* default display */
display = x11_display(display);
/*
* Split up display name into host and display-number parts.
*/
n = strcspn(display, ":");
assert(n != 0); /* x11_display() promises this */
if (display[n])
displaynum = atoi(display + n + 1);
else
displaynum = 0; /* sensible default */
if (n > sizeof(host) - 1)
n = sizeof(host) - 1;
strncpy(host, display, n);
host[n] = '\0';
sfree(display);
if(!strcmp(host, "unix")) {
/* use AF_UNIX sockets (doesn't make sense on all platforms) */
addr = platform_get_x11_unix_address(displaynum,
&dummy_realhost);
port = 0; /* to show we are not confused */
} else {
port = 6000 + displaynum;
/*
* Try to find host.
*/
addr = name_lookup(host, port, &dummy_realhost, cfg, ADDRTYPE_UNSPEC);
if ((err = sk_addr_error(addr)) != NULL) {
sk_addr_free(addr);
return err;
}
}
/*
* Open socket.
*/
pr = snew(struct X11Private);
pr->fn = &fn_table;
pr->auth_protocol = NULL;
pr->auth = (struct X11Auth *)auth;
pr->verified = 0;
pr->data_read = 0;
pr->throttled = pr->throttle_override = 0;
pr->c = c;
pr->s = *s = new_connection(addr, dummy_realhost, 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 authentication, 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->auth, pr->auth_protocol,
pr->auth_data, pr->auth_dlen);
/*
* If authentication failed, construct and send an error
* packet, then terminate the connection.
*/
if (err) {
char *message;
int msglen, msgsize;
unsigned char *reply;
message = dupprintf("PuTTY X11 proxy: %s", 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->auth->realproto]);
int buflen;
static const char zeroes[4] = { 0,0,0,0 };
void *buf;
if (pr->auth->realproto == X11_MIT) {
assert(pr->auth->reallen <= lenof(realauthdata));
realauthlen = pr->auth->reallen;
memcpy(realauthdata, pr->auth->realdata, realauthlen);
} else if (pr->auth->realproto == X11_XDM &&
pr->auth->reallen == 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->auth->realdata, 8);
memcpy(realauthdata+8, buf, buflen);
t = time(NULL);
PUT_32BIT_MSB_FIRST(realauthdata+8+buflen, t);
des_encrypt_xdmauth(pr->auth->realdata+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->auth->realproto], 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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