[u/mdw/putty] / x11fwd.c

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <time.h>

#include "putty.h"
#include "ssh.h"

#define GET_32BIT_LSB_FIRST(cp) \
  (((unsigned long)(unsigned char)(cp)[0]) | \
  ((unsigned long)(unsigned char)(cp)[1] << 8) | \
  ((unsigned long)(unsigned char)(cp)[2] << 16) | \
  ((unsigned long)(unsigned char)(cp)[3] << 24))

#define PUT_32BIT_LSB_FIRST(cp, value) ( \
  (cp)[0] = (char)(value), \
  (cp)[1] = (char)((value) >> 8), \
  (cp)[2] = (char)((value) >> 16), \
  (cp)[3] = (char)((value) >> 24) )

#define GET_16BIT_LSB_FIRST(cp) \
  (((unsigned long)(unsigned char)(cp)[0]) | \
  ((unsigned long)(unsigned char)(cp)[1] << 8))

#define PUT_16BIT_LSB_FIRST(cp, value) ( \
  (cp)[0] = (char)(value), \
  (cp)[1] = (char)((value) >> 8) )

#define GET_32BIT_MSB_FIRST(cp) \
  (((unsigned long)(unsigned char)(cp)[0] << 24) | \
  ((unsigned long)(unsigned char)(cp)[1] << 16) | \
  ((unsigned long)(unsigned char)(cp)[2] << 8) | \
  ((unsigned long)(unsigned char)(cp)[3]))

#define PUT_32BIT_MSB_FIRST(cp, value) ( \
  (cp)[0] = (char)((value) >> 24), \
  (cp)[1] = (char)((value) >> 16), \
  (cp)[2] = (char)((value) >> 8), \
  (cp)[3] = (char)(value) )

#define GET_16BIT_MSB_FIRST(cp) \
  (((unsigned long)(unsigned char)(cp)[0] << 8) | \
  ((unsigned long)(unsigned char)(cp)[1]))

#define PUT_16BIT_MSB_FIRST(cp, value) ( \
  (cp)[0] = (char)((value) >> 8), \
  (cp)[1] = (char)(value) )

#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 X11Auth {
    unsigned char fakedata[64], realdata[64];
    int fakeproto, realproto;
    int fakelen, reallen;
};

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;
};

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();
    } 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());
    }

    /* 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 *auth)
{

    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);
}

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;

        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) > 20*60)      /* 20 minute clock skew should be OK */
	    return "XDM-AUTHORIZATION-1 time stamp was too far out";
    }
    /* implement other protocols here if ever required */
    return NULL;
}

static int x11_closing(Plug plug, 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
 */
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_closing,
	x11_receive,
	x11_sent,
	NULL
    };

    SockAddr addr;
    int port;
    char *err, *dummy_realhost;
    char host[128];
    int n, displaynum;
    struct X11Private *pr;

    /*
     * Split up display name into host and display-number parts.
     */
    n = strcspn(display, ":");
    if (display[n])
	displaynum = atoi(display + n + 1);
    else
	displaynum = 0;		       /* sensible default */
    if (n > sizeof(host) - 1)
	n = sizeof(host) - 1;
    if (n > 0) {
	strncpy(host, display, n);
	host[n] = '\0';
    } else {
	/*
	 * Local display numbers, particularly on Unix, often omit
	 * the display part completely.
	 */
	strcpy(host, "localhost");
    }

    port = 6000 + displaynum;

    /*
     * Try to find host.
     */
    addr = name_lookup(host, port, &dummy_realhost, cfg);
    if ((err = sk_addr_error(addr)) != NULL)
	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, (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);
    sk_addr_free(addr);
    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]);
	    unsigned long ip;
	    int port;
            static const char zeroes[4] = { 0,0,0,0 };

            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 &&
		       sk_getxdmdata(s, &ip, &port)) {
		time_t t;
                realauthlen = 24;
		memset(realauthdata, 0, 24);
		memcpy(realauthdata, pr->auth->realdata, 8);
		PUT_32BIT_MSB_FIRST(realauthdata+8, ip);
		PUT_16BIT_MSB_FIRST(realauthdata+12, port);
		t = time(NULL);
		PUT_32BIT_MSB_FIRST(realauthdata+14, t);
		des_encrypt_xdmauth(pr->auth->realdata+9,
				    (unsigned char *)realauthdata, 24);
	    }
            /* 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);
}
Commit	Line	Data
9c964e85	1	#include <stdio.h>
9c964e85	2	#include <stdlib.h>
e0e7dff8	3	#include <assert.h>
2f92b717	4	#include <time.h>
9c964e85	5
	6	#include "putty.h"
	7	#include "ssh.h"
	8
9c964e85	9	#define GET_32BIT_LSB_FIRST(cp) \
	10	(((unsigned long)(unsigned char)(cp)[0]) \| \
	11	((unsigned long)(unsigned char)(cp)[1] << 8) \| \
	12	((unsigned long)(unsigned char)(cp)[2] << 16) \| \
	13	((unsigned long)(unsigned char)(cp)[3] << 24))
	14
	15	#define PUT_32BIT_LSB_FIRST(cp, value) ( \
b3ebaa28	16	(cp)[0] = (char)(value), \
	17	(cp)[1] = (char)((value) >> 8), \
	18	(cp)[2] = (char)((value) >> 16), \
	19	(cp)[3] = (char)((value) >> 24) )
9c964e85	20
	21	#define GET_16BIT_LSB_FIRST(cp) \
	22	(((unsigned long)(unsigned char)(cp)[0]) \| \
	23	((unsigned long)(unsigned char)(cp)[1] << 8))
	24
	25	#define PUT_16BIT_LSB_FIRST(cp, value) ( \
b3ebaa28	26	(cp)[0] = (char)(value), \
b3ebaa28	27	(cp)[1] = (char)((value) >> 8) )
9c964e85	28
	29	#define GET_32BIT_MSB_FIRST(cp) \
	30	(((unsigned long)(unsigned char)(cp)[0] << 24) \| \
	31	((unsigned long)(unsigned char)(cp)[1] << 16) \| \
	32	((unsigned long)(unsigned char)(cp)[2] << 8) \| \
	33	((unsigned long)(unsigned char)(cp)[3]))
	34
	35	#define PUT_32BIT_MSB_FIRST(cp, value) ( \
b3ebaa28	36	(cp)[0] = (char)((value) >> 24), \
	37	(cp)[1] = (char)((value) >> 16), \
	38	(cp)[2] = (char)((value) >> 8), \
	39	(cp)[3] = (char)(value) )
9c964e85	40
	41	#define GET_16BIT_MSB_FIRST(cp) \
	42	(((unsigned long)(unsigned char)(cp)[0] << 8) \| \
	43	((unsigned long)(unsigned char)(cp)[1]))
	44
	45	#define PUT_16BIT_MSB_FIRST(cp, value) ( \
b3ebaa28	46	(cp)[0] = (char)((value) >> 8), \
b3ebaa28	47	(cp)[1] = (char)(value) )
9c964e85	48
	49	#define GET_16BIT(endian, cp) \
	50	(endian=='B' ? GET_16BIT_MSB_FIRST(cp) : GET_16BIT_LSB_FIRST(cp))
	51
	52	#define PUT_16BIT(endian, cp, val) \
	53	(endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
	54
e0e7dff8	55	const char *const x11_authnames[] = {
2f92b717	56	"", "MIT-MAGIC-COOKIE-1", "XDM-AUTHORIZATION-1"
e0e7dff8	57	};
e0e7dff8	58
302121de	59	struct X11Auth {
e0e7dff8	60	unsigned char fakedata[64], realdata[64];
	61	int fakeproto, realproto;
	62	int fakelen, reallen;
302121de	63	};
302121de	64
9c964e85	65	struct X11Private {
302121de	66	const struct plug_function_table *fn;
7e78000d	67	/* the above variable absolutely must be the first in this structure */
32874aea	68	unsigned char firstpkt[12]; /* first X data packet */
302121de	69	struct X11Auth *auth;
9c964e85	70	char *auth_protocol;
	71	unsigned char *auth_data;
	72	int data_read, auth_plen, auth_psize, auth_dlen, auth_dsize;
	73	int verified;
5471d09a	74	int throttled, throttle_override;
b3ebaa28	75	unsigned long peer_ip;
b3ebaa28	76	int peer_port;
32874aea	77	void c; / data used by ssh.c */
7e78000d	78	Socket s;
9c964e85	79	};
9c964e85	80
302121de	81	void x11_invent_auth(char proto, int protomaxlen,
b3ebaa28	82	char *data, int datamaxlen, int proto_id)
32874aea	83	{
3d88e64d	84	struct X11Auth *auth = snew(struct X11Auth);
9c964e85	85	char ourdata[64];
	86	int i;
	87
b3ebaa28	88	if (proto_id == X11_MIT) {
b3ebaa28	89	auth->fakeproto = X11_MIT;
e0e7dff8	90
b3ebaa28	91	/* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
	92	auth->fakelen = 16;
	93	for (i = 0; i < 16; i++)
	94	auth->fakedata[i] = random_byte();
	95	} else {
	96	assert(proto_id == X11_XDM);
	97	auth->fakeproto = X11_XDM;
	98
	99	/* XDM-AUTHORIZATION-1. Cookie size is 16 bytes; byte 8 is zero. */
	100	auth->fakelen = 16;
	101	for (i = 0; i < 16; i++)
	102	auth->fakedata[i] = (i == 8 ? 0 : random_byte());
	103	}
9c964e85	104
9c964e85	105	/* Now format for the recipient. */
e0e7dff8	106	strncpy(proto, x11_authnames[auth->fakeproto], protomaxlen);
9c964e85	107	ourdata[0] = '\0';
e0e7dff8	108	for (i = 0; i < auth->fakelen; i++)
e0e7dff8	109	sprintf(ourdata + strlen(ourdata), "%02x", auth->fakedata[i]);
9c964e85	110	strncpy(data, ourdata, datamaxlen);
302121de	111
302121de	112	return auth;
9c964e85	113	}
9c964e85	114
fabd1805	115	void x11_free_auth(void *auth)
	116	{
	117
	118	sfree(auth);
	119	}
	120
e0e7dff8	121	/*
	122	* Fetch the real auth data for a given display string, and store
	123	* it in an X11Auth structure. Returns NULL on success, or an error
	124	* string.
	125	*/
	126	void x11_get_real_auth(void authv, char display)
	127	{
	128	struct X11Auth auth = (struct X11Auth )authv;
	129
	130	auth->realproto = X11_NO_AUTH; /* in case next call does nothing */
	131
	132	auth->reallen = sizeof(auth->realdata);
	133	platform_get_x11_auth(display, &auth->realproto,
	134	auth->realdata, &auth->reallen);
	135	}
	136
b3ebaa28	137	static char *x11_verify(unsigned long peer_ip, int peer_port,
	138	struct X11Auth auth, char proto,
	139	unsigned char *data, int dlen)
32874aea	140	{
e0e7dff8	141	if (strcmp(proto, x11_authnames[auth->fakeproto]) != 0)
b3ebaa28	142	return "wrong authentication protocol attempted";
e0e7dff8	143	if (auth->fakeproto == X11_MIT) {
e0e7dff8	144	if (dlen != auth->fakelen)
b3ebaa28	145	return "MIT-MAGIC-COOKIE-1 data was wrong length";
e0e7dff8	146	if (memcmp(auth->fakedata, data, dlen) != 0)
b3ebaa28	147	return "MIT-MAGIC-COOKIE-1 data did not match";
	148	}
	149	if (auth->fakeproto == X11_XDM) {
	150	unsigned long t;
	151	time_t tim;
	152	int i;
	153
	154	if (dlen != 24)
	155	return "XDM-AUTHORIZATION-1 data was wrong length";
	156	if (peer_port == -1)
	157	return "cannot do XDM-AUTHORIZATION-1 without remote address data";
	158	des_decrypt_xdmauth(auth->fakedata+9, data, 24);
	159	if (memcmp(auth->fakedata, data, 8) != 0)
	160	return "XDM-AUTHORIZATION-1 data failed check"; /* cookie wrong */
	161	if (GET_32BIT_MSB_FIRST(data+8) != peer_ip)
	162	return "XDM-AUTHORIZATION-1 data failed check"; /* IP wrong */
	163	if ((int)GET_16BIT_MSB_FIRST(data+12) != peer_port)
	164	return "XDM-AUTHORIZATION-1 data failed check"; /* port wrong */
	165	t = GET_32BIT_MSB_FIRST(data+14);
	166	for (i = 18; i < 24; i++)
	167	if (data[i] != 0) /* zero padding wrong */
	168	return "XDM-AUTHORIZATION-1 data failed check";
	169	tim = time(NULL);
	170	if (abs(t - tim) > 2060) / 20 minute clock skew should be OK */
	171	return "XDM-AUTHORIZATION-1 time stamp was too far out";
e0e7dff8	172	}
e0e7dff8	173	/* implement other protocols here if ever required */
b3ebaa28	174	return NULL;
9c964e85	175	}
9c964e85	176
32874aea	177	static int x11_closing(Plug plug, char *error_msg, int error_code,
	178	int calling_back)
	179	{
7e78000d	180	struct X11Private pr = (struct X11Private ) plug;
	181
	182	/*
	183	* We have no way to communicate down the forwarded connection,
	184	* so if an error occurred on the socket, we just ignore it
	185	* and treat it like a proper close.
	186	*/
	187	sshfwd_close(pr->c);
	188	x11_close(pr->s);
	189	return 1;
	190	}
	191
32874aea	192	static int x11_receive(Plug plug, int urgent, char *data, int len)
32874aea	193	{
7e78000d	194	struct X11Private pr = (struct X11Private ) plug;
9c964e85	195
5471d09a	196	if (sshfwd_write(pr->c, data, len) > 0) {
	197	pr->throttled = 1;
	198	sk_set_frozen(pr->s, 1);
	199	}
	200
9c964e85	201	return 1;
	202	}
	203
5471d09a	204	static void x11_sent(Plug plug, int bufsize)
	205	{
	206	struct X11Private pr = (struct X11Private ) plug;
	207
	208	sshfwd_unthrottle(pr->c, bufsize);
	209	}
	210
9c964e85	211	/*
421d6835	212	* When setting up X forwarding, we should send the screen number
	213	* from the specified local display. This function extracts it from
	214	* the display string.
	215	*/
	216	int x11_get_screen_number(char *display)
	217	{
	218	int n;
	219
	220	n = strcspn(display, ":");
	221	if (!display[n])
	222	return 0;
	223	n = strcspn(display, ".");
	224	if (!display[n])
	225	return 0;
	226	return atoi(display + n + 1);
	227	}
	228
	229	/*
9c964e85	230	* Called to set up the raw connection.
	231	*
	232	* Returns an error message, or NULL on success.
	233	* also, fills the SocketsStructure
9c964e85	234	*/
b3ebaa28	235	char x11_init(Socket s, char display, void c, void *auth,
e8fa8f62	236	const char peeraddr, int peerport, const Config cfg)
32874aea	237	{
302121de	238	static const struct plug_function_table fn_table = {
7e78000d	239	x11_closing,
5471d09a	240	x11_receive,
	241	x11_sent,
	242	NULL
7e78000d	243	};
7e78000d	244
9c964e85	245	SockAddr addr;
9c964e85	246	int port;
0c6c9a70	247	char err, dummy_realhost;
9c964e85	248	char host[128];
	249	int n, displaynum;
	250	struct X11Private *pr;
	251
	252	/*
	253	* Split up display name into host and display-number parts.
	254	*/
	255	n = strcspn(display, ":");
	256	if (display[n])
32874aea	257	displaynum = atoi(display + n + 1);
9c964e85	258	else
32874aea	259	displaynum = 0; /* sensible default */
	260	if (n > sizeof(host) - 1)
	261	n = sizeof(host) - 1;
ecc0ba5b	262	if (n > 0) {
	263	strncpy(host, display, n);
	264	host[n] = '\0';
	265	} else {
	266	/*
	267	* Local display numbers, particularly on Unix, often omit
	268	* the display part completely.
	269	*/
	270	strcpy(host, "localhost");
	271	}
9c964e85	272
9f2f8ea0	273	port = 6000 + displaynum;
9f2f8ea0	274
9c964e85	275	/*
	276	* Try to find host.
	277	*/
e8fa8f62	278	addr = name_lookup(host, port, &dummy_realhost, cfg);
6518ea7b	279	if ((err = sk_addr_error(addr)) != NULL)
9c964e85	280	return err;
9c964e85	281
9c964e85	282	/*
	283	* Open socket.
	284	*/
3d88e64d	285	pr = snew(struct X11Private);
7e78000d	286	pr->fn = &fn_table;
9c964e85	287	pr->auth_protocol = NULL;
302121de	288	pr->auth = (struct X11Auth *)auth;
9c964e85	289	pr->verified = 0;
9c964e85	290	pr->data_read = 0;
5471d09a	291	pr->throttled = pr->throttle_override = 0;
9c964e85	292	pr->c = c;
9c964e85	293
e8fa8f62	294	pr->s = *s = new_connection(addr, dummy_realhost, port,
e8fa8f62	295	0, 1, 0, (Plug) pr, cfg);
6518ea7b	296	if ((err = sk_socket_error(*s)) != NULL) {
32874aea	297	sfree(pr);
7e78000d	298	return err;
	299	}
	300
b3ebaa28	301	/*
	302	* See if we can make sense of the peer address we were given.
	303	*/
	304	{
	305	int i[4];
	306	if (peeraddr &&
	307	4 == sscanf(peeraddr, "%d.%d.%d.%d", i+0, i+1, i+2, i+3)) {
	308	pr->peer_ip = (i[0] << 24) \| (i[1] << 16) \| (i[2] << 8) \| i[3];
	309	pr->peer_port = peerport;
	310	} else {
	311	pr->peer_ip = 0;
	312	pr->peer_port = -1;
	313	}
	314	}
	315
9c964e85	316	sk_set_private_ptr(*s, pr);
	317	sk_addr_free(addr);
	318	return NULL;
	319	}
	320
32874aea	321	void x11_close(Socket s)
	322	{
	323	struct X11Private *pr;
d74d141c	324	if (!s)
	325	return;
	326	pr = (struct X11Private *) sk_get_private_ptr(s);
9c964e85	327	if (pr->auth_protocol) {
32874aea	328	sfree(pr->auth_protocol);
32874aea	329	sfree(pr->auth_data);
9c964e85	330	}
	331
	332	sfree(pr);
	333
	334	sk_close(s);
	335	}
	336
5471d09a	337	void x11_unthrottle(Socket s)
	338	{
	339	struct X11Private *pr;
	340	if (!s)
	341	return;
	342	pr = (struct X11Private *) sk_get_private_ptr(s);
	343
	344	pr->throttled = 0;
	345	sk_set_frozen(s, pr->throttled \|\| pr->throttle_override);
	346	}
	347
	348	void x11_override_throttle(Socket s, int enable)
	349	{
	350	struct X11Private *pr;
	351	if (!s)
	352	return;
	353	pr = (struct X11Private *) sk_get_private_ptr(s);
	354
	355	pr->throttle_override = enable;
	356	sk_set_frozen(s, pr->throttled \|\| pr->throttle_override);
	357	}
	358
9c964e85	359	/*
	360	* Called to send data down the raw connection.
	361	*/
5471d09a	362	int x11_send(Socket s, char *data, int len)
32874aea	363	{
970f2b02	364	struct X11Private *pr;
970f2b02	365	if (!s)
5471d09a	366	return 0;
970f2b02	367	pr = (struct X11Private *) sk_get_private_ptr(s);
9c964e85	368
	369	/*
	370	* Read the first packet.
	371	*/
	372	while (len > 0 && pr->data_read < 12)
32874aea	373	pr->firstpkt[pr->data_read++] = (unsigned char) (len--, *data++);
9c964e85	374	if (pr->data_read < 12)
5471d09a	375	return 0;
9c964e85	376
	377	/*
	378	* If we have not allocated the auth_protocol and auth_data
	379	* strings, do so now.
	380	*/
	381	if (!pr->auth_protocol) {
32874aea	382	pr->auth_plen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 6);
	383	pr->auth_dlen = GET_16BIT(pr->firstpkt[0], pr->firstpkt + 8);
	384	pr->auth_psize = (pr->auth_plen + 3) & ~3;
	385	pr->auth_dsize = (pr->auth_dlen + 3) & ~3;
	386	/* Leave room for a terminating zero, to make our lives easier. */
3d88e64d	387	pr->auth_protocol = snewn(pr->auth_psize + 1, char);
92d60585	388	pr->auth_data = snewn(pr->auth_dsize, unsigned char);
9c964e85	389	}
	390
	391	/*
	392	* Read the auth_protocol and auth_data strings.
	393	*/
	394	while (len > 0 && pr->data_read < 12 + pr->auth_psize)
32874aea	395	pr->auth_protocol[pr->data_read++ - 12] = (len--, *data++);
9c964e85	396	while (len > 0 && pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
32874aea	397	pr->auth_data[pr->data_read++ - 12 -
32874aea	398	pr->auth_psize] = (unsigned char) (len--, *data++);
9c964e85	399	if (pr->data_read < 12 + pr->auth_psize + pr->auth_dsize)
5471d09a	400	return 0;
9c964e85	401
	402	/*
	403	* If we haven't verified the authentication, do so now.
	404	*/
	405	if (!pr->verified) {
b3ebaa28	406	char *err;
32874aea	407
32874aea	408	pr->auth_protocol[pr->auth_plen] = '\0'; /* ASCIZ */
b3ebaa28	409	err = x11_verify(pr->peer_ip, pr->peer_port,
b3ebaa28	410	pr->auth, pr->auth_protocol,
302121de	411	pr->auth_data, pr->auth_dlen);
32874aea	412
	413	/*
	414	* If authentication failed, construct and send an error
	415	* packet, then terminate the connection.
	416	*/
b3ebaa28	417	if (err) {
	418	char *message;
	419	int msglen, msgsize;
	420	unsigned char *reply;
	421
	422	message = dupprintf("PuTTY X11 proxy: %s", err);
	423	msglen = strlen(message);
3d88e64d	424	reply = snewn(8 + msglen+1 + 4, unsigned char); /* include zero */
b3ebaa28	425	msgsize = (msglen + 3) & ~3;
32874aea	426	reply[0] = 0; /* failure */
	427	reply[1] = msglen; /* length of reason string */
	428	memcpy(reply + 2, pr->firstpkt + 2, 4); /* major/minor proto vsn */
75105663	429	PUT_16BIT(pr->firstpkt[0], reply + 6, msgsize >> 2);/* data len */
32874aea	430	memset(reply + 8, 0, msgsize);
32874aea	431	memcpy(reply + 8, message, msglen);
f28e6b7c	432	sshfwd_write(pr->c, (char *)reply, 8 + msgsize);
32874aea	433	sshfwd_close(pr->c);
32874aea	434	x11_close(s);
b3ebaa28	435	sfree(reply);
b3ebaa28	436	sfree(message);
5471d09a	437	return 0;
32874aea	438	}
	439
	440	/*
	441	* Now we know we're going to accept the connection. Strip
e0e7dff8	442	* the fake auth data, and optionally put real auth data in
e0e7dff8	443	* instead.
32874aea	444	*/
e0e7dff8	445	{
	446	char realauthdata[64];
	447	int realauthlen = 0;
	448	int authstrlen = strlen(x11_authnames[pr->auth->realproto]);
2f92b717	449	unsigned long ip;
2f92b717	450	int port;
e0e7dff8	451	static const char zeroes[4] = { 0,0,0,0 };
	452
	453	if (pr->auth->realproto == X11_MIT) {
	454	assert(pr->auth->reallen <= lenof(realauthdata));
	455	realauthlen = pr->auth->reallen;
	456	memcpy(realauthdata, pr->auth->realdata, realauthlen);
2f92b717	457	} else if (pr->auth->realproto == X11_XDM &&
	458	pr->auth->reallen == 16 &&
	459	sk_getxdmdata(s, &ip, &port)) {
	460	time_t t;
	461	realauthlen = 24;
	462	memset(realauthdata, 0, 24);
	463	memcpy(realauthdata, pr->auth->realdata, 8);
	464	PUT_32BIT_MSB_FIRST(realauthdata+8, ip);
	465	PUT_16BIT_MSB_FIRST(realauthdata+12, port);
	466	t = time(NULL);
	467	PUT_32BIT_MSB_FIRST(realauthdata+14, t);
6e7f5aee	468	des_encrypt_xdmauth(pr->auth->realdata+9,
6e7f5aee	469	(unsigned char *)realauthdata, 24);
2f92b717	470	}
e0e7dff8	471	/* implement other auth methods here if required */
	472
	473	PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, authstrlen);
	474	PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, realauthlen);
	475
	476	sk_write(s, (char *)pr->firstpkt, 12);
	477
	478	if (authstrlen) {
	479	sk_write(s, x11_authnames[pr->auth->realproto], authstrlen);
	480	sk_write(s, zeroes, 3 & (-authstrlen));
	481	}
	482	if (realauthlen) {
	483	sk_write(s, realauthdata, realauthlen);
	484	sk_write(s, zeroes, 3 & (-realauthlen));
	485	}
	486	}
32874aea	487	pr->verified = 1;
9c964e85	488	}
	489
	490	/*
	491	* After initialisation, just copy data simply.
	492	*/
	493
5471d09a	494	return sk_write(s, data, len);
9c964e85	495	}