xserver/os/mitauth.c

/*

Copyright 1988, 1998  The Open Group

Permission to use, copy, modify, distribute, and sell this software and its
documentation for any purpose is hereby granted without fee, provided that
the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation.

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

Except as contained in this notice, the name of The Open Group shall
not be used in advertising or otherwise to promote the sale, use or
other dealings in this Software without prior written authorization
from The Open Group.

*/

/*
 * MIT-MAGIC-COOKIE-1 authorization scheme
 * Author:  Keith Packard, MIT X Consortium
 */

#include <dix-config.h>

#include <X11/X.h>
#include "os.h"
#include "osdep.h"
#include "mitauth.h"
#include "dixstruct.h"

static struct auth {
    struct auth *next;
    unsigned short len;
    char *data;
    XID id;
} *mit_auth;

XID
MitAddCookie(unsigned short data_length, const char *data)
{
    struct auth *new;

    // check for possible duplicate and return it instead
    for (struct auth *walk=mit_auth; walk; walk=walk->next) {
        if ((walk->len == data_length) &&
            (memcmp(walk->data, data, data_length) == 0))
            return walk->id;
    }

    new = calloc(1, sizeof(struct auth));
    if (!new)
        return 0;
    new->data = calloc(1, (unsigned) data_length);
    if (!new->data) {
        free(new);
        return 0;
    }
    new->next = mit_auth;
    mit_auth = new;
    memcpy(new->data, data, (size_t) data_length);
    new->len = data_length;
    new->id = FakeClientID(0);
    return new->id;
}

XID
MitCheckCookie(unsigned short data_length,
               const char *data, ClientPtr client, const char **reason)
{
    struct auth *auth;

    for (auth = mit_auth; auth; auth = auth->next) {
        if (data_length == auth->len &&
            timingsafe_memcmp(data, auth->data, (int) data_length) == 0)
            return auth->id;
    }
    *reason = "Invalid MIT-MAGIC-COOKIE-1 key";
    return (XID) -1;
}

int
MitResetCookie(void)
{
    struct auth *auth, *next;

    for (auth = mit_auth; auth; auth = next) {
        next = auth->next;
        free(auth->data);
        free(auth);
    }
    mit_auth = 0;
    return 0;
}

int
MitFromID(XID id, unsigned short *data_lenp, char **datap)
{
    struct auth *auth;

    for (auth = mit_auth; auth; auth = auth->next) {
        if (id == auth->id) {
            *data_lenp = auth->len;
            *datap = auth->data;
            return 1;
        }
    }
    return 0;
}

int
MitRemoveCookie(unsigned short data_length, const char *data)
{
    struct auth *auth, *prev;

    prev = 0;
    for (auth = mit_auth; auth; prev = auth, auth = auth->next) {
        if (data_length == auth->len &&
            memcmp(data, auth->data, data_length) == 0) {
            if (prev)
                prev->next = auth->next;
            else
                mit_auth = auth->next;
            free(auth->data);
            free(auth);
            return 1;
        }
    }
    return 0;
}

static char cookie[16];         /* 128 bits */

static void
GenerateRandomData(int len, char *buf)
{
#ifdef HAVE_ARC4RANDOM_BUF
    arc4random_buf(buf, len);
#else
    int fd;

    fd = open("/dev/urandom", O_RDONLY);
    read(fd, buf, len);
    close(fd);
#endif
}

XID
MitGenerateCookie(unsigned data_length,
                  const char *data,
                  unsigned *data_length_return, char **data_return)
{
    int i = 0;

    while (data_length--) {
        cookie[i++] += *data++;
        if (i >= sizeof(cookie))
            i = 0;
    }
    GenerateRandomData(sizeof(cookie), cookie);
    XID id = MitAddCookie(sizeof(cookie), cookie);
    if (!id)
        return 0;

    *data_return = cookie;
    *data_length_return = sizeof(cookie);
    return id;
}