diff options
author | Alan Coopersmith <alan.coopersmith@oracle.com> | 2013-03-01 21:05:27 -0800 |
---|---|---|
committer | Alan Coopersmith <alan.coopersmith@oracle.com> | 2013-05-09 18:59:50 -0700 |
commit | 5669a220816b7d58fcaf0c302ead16fbe5c87817 (patch) | |
tree | b8c1e6d74eb7472d9a49a6b385608fc1b52a47a5 | |
parent | 6df8a63d34b7514077188e2062a13774f920c085 (diff) |
integer overflow in _XF86BigfontQueryFont() [CVE-2013-1981 2/13]
Similar to _XQueryFont, but with more ways to go wrong and overflow.
Only compiled if libX11 is built with XF86BigFont support.
v2: Fix reply_left calculations, check calculated sizes fit in reply_left
Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
-rw-r--r-- | src/Font.c | 42 |
1 files changed, 25 insertions, 17 deletions
@@ -403,7 +403,8 @@ _XF86BigfontQueryFont ( unsigned long seq) { register XFontStruct *fs; - register long nbytes; + unsigned long nbytes; + unsigned long reply_left; /* unused data left in reply buffer */ xXF86BigfontQueryFontReply reply; register xXF86BigfontQueryFontReq *req; register _XExtension *ext; @@ -456,13 +457,10 @@ _XF86BigfontQueryFont ( DeqAsyncHandler(dpy, &async2); if (seq) DeqAsyncHandler(dpy, &async1); + reply_left = reply.length - + ((SIZEOF(xXF86BigfontQueryFontReply) - SIZEOF(xReply)) >> 2); if (! (fs = (XFontStruct *) Xmalloc (sizeof (XFontStruct)))) { - _XEatData(dpy, - reply.nFontProps * SIZEOF(xFontProp) - + (reply.nCharInfos > 0 && reply.shmid == (CARD32)(-1) - ? reply.nUniqCharInfos * SIZEOF(xCharInfo) - + (reply.nCharInfos+1)/2 * 2 * sizeof(CARD16) - : 0)); + _XEatDataWords(dpy, reply_left); return (XFontStruct *)NULL; } fs->ext_data = NULL; @@ -488,23 +486,32 @@ _XF86BigfontQueryFont ( */ fs->properties = NULL; if (fs->n_properties > 0) { - nbytes = reply.nFontProps * sizeof(XFontProp); - fs->properties = (XFontProp *) Xmalloc ((unsigned) nbytes); + /* nFontProps is a CARD16 */ nbytes = reply.nFontProps * SIZEOF(xFontProp); + if ((nbytes >> 2) <= reply_left) { + size_t pbytes = reply.nFontProps * sizeof(XFontProp); + fs->properties = Xmalloc (pbytes); + } if (! fs->properties) { Xfree((char *) fs); - _XEatData(dpy, - nbytes - + (reply.nCharInfos > 0 && reply.shmid == (CARD32)(-1) - ? reply.nUniqCharInfos * SIZEOF(xCharInfo) - + (reply.nCharInfos+1)/2 * 2 * sizeof(CARD16) - : 0)); + _XEatDataWords(dpy, reply_left); return (XFontStruct *)NULL; } _XRead32 (dpy, (long *)fs->properties, nbytes); + reply_left -= (nbytes >> 2); } fs->per_char = NULL; +#ifndef LONG64 + /* compares each part to half the maximum, which should be far more than + any real font needs, so the combined total doesn't overflow either */ + if (reply.nUniqCharInfos > ((ULONG_MAX / 2) / SIZEOF(xCharInfo)) || + reply.nCharInfos > ((ULONG_MAX / 2) / sizeof(CARD16))) { + Xfree((char *) fs); + _XEatDataWords(dpy, reply_left); + return (XFontStruct *)NULL; + } +#endif if (reply.nCharInfos > 0) { /* fprintf(stderr, "received font metrics, nCharInfos = %d, nUniqCharInfos = %d, shmid = %d\n", reply.nCharInfos, reply.nUniqCharInfos, reply.shmid); */ if (reply.shmid == (CARD32)(-1)) { @@ -518,14 +525,14 @@ _XF86BigfontQueryFont ( if (!pUniqCI) { if (fs->properties) Xfree((char *) fs->properties); Xfree((char *) fs); - _XEatData(dpy, nbytes); + _XEatDataWords(dpy, reply_left); return (XFontStruct *)NULL; } if (! (fs->per_char = (XCharStruct *) Xmalloc (reply.nCharInfos * sizeof(XCharStruct)))) { Xfree((char *) pUniqCI); if (fs->properties) Xfree((char *) fs->properties); Xfree((char *) fs); - _XEatData(dpy, nbytes); + _XEatDataWords(dpy, reply_left); return (XFontStruct *)NULL; } _XRead16 (dpy, (char *) pUniqCI, nbytes); @@ -580,6 +587,7 @@ _XF86BigfontQueryFont ( if (!(extcodes->serverCapabilities & CAP_VerifiedLocal)) { struct shmid_ds buf; if (!(shmctl(reply.shmid, IPC_STAT, &buf) >= 0 + && reply.nCharInfos < (LONG_MAX / sizeof(XCharStruct)) && buf.shm_segsz >= reply.shmsegoffset + reply.nCharInfos * sizeof(XCharStruct) + sizeof(CARD32) && *(CARD32 *)(addr + reply.shmsegoffset + reply.nCharInfos * sizeof(XCharStruct)) == extcodes->serverSignature)) { shmdt(addr); |