Date: Thu, 13 Dec 2018 11:39:29 +0100 From: Solar Designer <solar@...nwall.com> To: Pavel Cheremushkin <Pavel.Cheremushkin@...persky.com> Cc: oss-security@...ts.openwall.com Subject: Re: libvnc and tightvnc vulnerabilities On Mon, Dec 10, 2018 at 07:57:21PM +0100, Solar Designer wrote: > https://github.com/LibVNC/libvncserver/issues/247 > > Upstream's fix appears to be to add casts to (uint64_t) before adding 1 > in those many malloc() calls. On platforms with larger than 32-bit > size_t, this should be sufficient against integer overflows since the > sizes are read from 32-bit protocol fields, but it isn't sufficient to > prevent maliciously large memory allocation on the client by a rogue > server. On a platform with 32-bit size_t, this isn't even sufficient to > prevent the integer overflows. If I haven't missed anything, it'd be > great if you open a new issue suggesting introduction of safety limits > prior to those malloc() lines. > [...] per the commits referenced in issue #247 above, there are many more > instances of the "malloc(... + 1)" pattern, which were patched similarly > incompletely. I've just created this issue: SECURITY: malloc((uint64_t)length + 1) is unsafe, especially on 32-bit systems https://github.com/LibVNC/libvncserver/issues/273 Alexander
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