From ece51493f1d970f45e53588e33a700464a42fbab Mon Sep 17 00:00:00 2001 From: Mike DePaulo Date: Sun, 8 Feb 2015 22:27:47 -0500 Subject: CVE-2014-0210: unvalidated length fields in fs_read_glyphs() from xorg/lib/libXfont commit 520683652564c2a4e42328ae23eef9bb63271565 fs_read_glyphs() parses a reply from the font server. The reply contains embedded length fields, none of which are validated. This can cause out of bound reads when looping over the glyph bitmaps in the reply. --- nx-X11/lib/font/fc/fserve.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/nx-X11/lib/font/fc/fserve.c b/nx-X11/lib/font/fc/fserve.c index 79de4f352..26218e568 100644 --- a/nx-X11/lib/font/fc/fserve.c +++ b/nx-X11/lib/font/fc/fserve.c @@ -1916,6 +1916,7 @@ fs_read_glyphs(FontPathElementPtr fpe, FSBlockDataPtr blockrec) FontInfoPtr pfi = &pfont->info; fsQueryXBitmaps16Reply *rep; char *buf; + long bufleft; /* length of reply left to use */ fsOffset32 *ppbits; fsOffset32 local_off; char *off_adr; @@ -1947,9 +1948,33 @@ fs_read_glyphs(FontPathElementPtr fpe, FSBlockDataPtr blockrec) buf = (char *) rep; buf += SIZEOF (fsQueryXBitmaps16Reply); + bufleft = rep->length << 2; + bufleft -= SIZEOF (fsQueryXBitmaps16Reply); + + if ((bufleft / SIZEOF (fsOffset32)) < rep->num_chars) + { +#ifdef DEBUG + fprintf(stderr, + "fsQueryXBitmaps16: num_chars (%d) > bufleft (%ld) / %d\n", + rep->num_chars, bufleft, SIZEOF (fsOffset32)); +#endif + err = AllocError; + goto bail; + } ppbits = (fsOffset32 *) buf; buf += SIZEOF (fsOffset32) * (rep->num_chars); + bufleft -= SIZEOF (fsOffset32) * (rep->num_chars); + if (bufleft < rep->nbytes) + { +#ifdef DEBUG + fprintf(stderr, + "fsQueryXBitmaps16: nbytes (%d) > bufleft (%ld)\n", + rep->nbytes, bufleft); +#endif + err = AllocError; + goto bail; + } pbitmaps = (pointer ) buf; if (blockrec->type == FS_LOAD_GLYPHS) @@ -2007,7 +2032,9 @@ fs_read_glyphs(FontPathElementPtr fpe, FSBlockDataPtr blockrec) */ if (NONZEROMETRICS(&fsdata->encoding[minchar].metrics)) { - if (local_off.length) + if (local_off.length && + (local_off.position < rep->nbytes) && + (local_off.length <= (rep->nbytes - local_off.position))) { bits = allbits; allbits += local_off.length; -- cgit v1.2.3