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Introduce framework for authenticating with the local X server.

Browse Source 
Windows and Mac backends have acquired auth-finding functions which
do nothing; Unix backend has acquired one which actually works, so
Plink can now do X forwarding believably.
(This checkin stretches into some unlikely parts of the code because
there have been one or two knock-on effects involving `const'. Bah.)

[originally from svn r2536]
This commit is contained in:
Simon Tatham
2003-01-10 18:33:35 +00:00
parent 2e8b94c8d4
commit 86977efa81
14 changed files with 229 additions and 36 deletions
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90
x11fwd.c
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@ -1,5 +1,6 @@
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "putty.h"
#include "ssh.h"
@ -50,11 +51,19 @@
#define PUT_16BIT(endian, cp, val) \
(endian=='B' ? PUT_16BIT_MSB_FIRST(cp, val) : PUT_16BIT_LSB_FIRST(cp, val))
struct X11Auth {
unsigned char data[64];
int len;
const char *const x11_authnames[] = {
"", "MIT-MAGIC-COOKIE-1"
};
struct X11Auth {
unsigned char fakedata[64], realdata[64];
int fakeproto, realproto;
int fakelen, reallen;
};
extern void platform_get_x11_auth(char *display, int *proto,
unsigned char *data, int *datalen);
struct X11Private {
const struct plug_function_table *fn;
/* the above variable absolutely *must* be the first in this structure */
@ -76,30 +85,51 @@ void *x11_invent_auth(char *proto, int protomaxlen,
char ourdata[64];
int i;
auth->fakeproto = X11_MIT;
/* MIT-MAGIC-COOKIE-1. Cookie size is 128 bits (16 bytes). */
auth->len = 16;
auth->fakelen = 16;
for (i = 0; i < 16; i++)
auth->data[i] = random_byte();
auth->fakedata[i] = random_byte();
/* Now format for the recipient. */
strncpy(proto, "MIT-MAGIC-COOKIE-1", protomaxlen);
strncpy(proto, x11_authnames[auth->fakeproto], protomaxlen);
ourdata[0] = '\0';
for (i = 0; i < auth->len; i++)
sprintf(ourdata + strlen(ourdata), "%02x", auth->data[i]);
for (i = 0; i < auth->fakelen; i++)
sprintf(ourdata + strlen(ourdata), "%02x", auth->fakedata[i]);
strncpy(data, ourdata, datamaxlen);
return 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 int x11_verify(struct X11Auth *auth,
char *proto, unsigned char *data, int dlen)
{
if (strcmp(proto, "MIT-MAGIC-COOKIE-1") != 0)
if (strcmp(proto, x11_authnames[auth->fakeproto]) != 0)
return 0; /* wrong protocol attempted */
if (dlen != auth->len)
return 0; /* cookie was wrong length */
if (memcmp(auth->data, data, dlen) != 0)
return 0; /* cookie was wrong cookie! */
if (auth->fakeproto == X11_MIT) {
if (dlen != auth->fakelen)
return 0; /* cookie was wrong length */
if (memcmp(auth->fakedata, data, dlen) != 0)
return 0; /* cookie was wrong cookie! */
}
/* implement other protocols here if ever required */
return 1;
}
@ -344,12 +374,36 @@ int x11_send(Socket s, char *data, int len)
/*
* Now we know we're going to accept the connection. Strip
* the auth data. (TODO: if we ever work out how, we should
* replace some real auth data in here.)
* the fake auth data, and optionally put real auth data in
* instead.
*/
PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 6, 0); /* auth proto */
PUT_16BIT(pr->firstpkt[0], pr->firstpkt + 8, 0); /* auth data */
sk_write(s, (char *)pr->firstpkt, 12);
{
char realauthdata[64];
int realauthlen = 0;
int authstrlen = strlen(x11_authnames[pr->auth->realproto]);
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);
}
/* 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;
}