Date: Sun, 23 Dec 2012 18:05:09 +0100 From: magnum <john.magnum@...hmail.com> To: john-dev@...ts.openwall.com Subject: Re: scan-build results, part 1 On 23 Dec, 2012, at 17:54 , Dhiru Kholia <dhiru.kholia@...il.com> wrote: > On Sun, Dec 23, 2012 at 10:14 PM, magnum <john.magnum@...hmail.com> wrote: >> On 23 Dec, 2012, at 17:34 , Dhiru Kholia <dhiru.kholia@...il.com> wrote: >> >>> On Sun, Dec 23, 2012 at 9:46 PM, magnum <john.magnum@...hmail.com> wrote: >>>> Another weird complaint is for MSCHAPv2. The pos pointer is set to non-null in line 429. How could it ever be a null dereference in line 433? >>> >>> I have received an "official" answer on this one. It is *not* a false >>> positive. "ciphertext" can be NULL and we haven't checked for it >>> before doing pointer arithmetic on line 429. >>> gwynne> From the analyzer's point of view, NULL acts like NaN; i.e. >>> "NULL + anything = NULL" in terms of pointer validity. >>> >>> Following patch makes this problem go away. >>> >>> diff --git a/src/MSCHAPv2_fmt_plug.c b/src/MSCHAPv2_fmt_plug.c >>> index d946036..b4c7fcf 100644 >>> --- a/src/MSCHAPv2_fmt_plug.c >>> +++ b/src/MSCHAPv2_fmt_plug.c >>> @@ -44,6 +44,7 @@ >>> >>> #include "sha.h" >>> #include <openssl/des.h> >>> +#include <assert.h> >>> ... >> >> Fair enough. But I think I recall Solar wants to avoid using assert() and in this case, we know (even if scan-build doesn't) that this function will never be called with ciphertext being null. So maybe we should just ignore it. > > Sure, no problem. Just to mute scan-build, we could add this instead of that assertion though: if (!ciphertext) return ciphertext; magnum
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