Date: Thu, 28 Feb 2002 15:07:44 +0900 From: Hajimu UMEMOTO <ume@mahoroba.org> To: Rob Braun <bbraun@FreeBSD.ORG> Cc: freebsd-net@FreeBSD.ORG Subject: Re: proposed changes to getnameinfo() implementation Message-ID: <ygewuwyqgun.wl@cheer.mahoroba.org> In-Reply-To: <200202272105.g1RL50J21344@lh.synack.net> References: <200202272105.g1RL50J21344@lh.synack.net>
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Hi,
>>>>> On Wed, 27 Feb 2002 13:04:59 -0800
>>>>> Rob Braun <bbraun@FreeBSD.ORG> said:
bbraun> getnameinfo() takes a struct sockaddr pointer, and a length
bbraun> parameter for the amount of memory pointed to by the struct
bbraun> sockaddr pointer.
No, the second parameter is not the amount of memory pointed to by the
struct sockaddr pointer. It is the size of the struct sockaddr
according to the address family.
bbraun> The current FreeBSD implementation of getnameinfo() does
bbraun> 2 problematic checks against the length parameter. First,
bbraun> it makes sure the length parameter is equal to the length
bbraun> specified in the passed in sockaddr structure. This is
bbraun> problematic because the length parameter refers to the
bbraun> amount of memory pointed to by the first parameter, and
bbraun> the struct sockaddr sa_len field is used to specify the
bbraun> size of the sockaddr structure, since there are different
bbraun> types of sockaddr structures with different lengths.
RFC2553 defines two types of struct sockaddr, one has sa_len and the
other doesn't has it. Though we *BSD has sa_len, non-BSD doesn't have
it.
bbraun> I propose to change this exact match comparison to ensure
bbraun> that the length passed in is at least what the sa_len
bbraun> field is. This will allow a larger structure to be passed
bbraun> in than the size of the sockaddr structure for the desired
bbraun> protocol.
It shouldn't. Though we actually doesn't need the second parameter of
getnameinfo(), it is the alternative of the sa_len for the systems
which don't have sa_len.
To keep the portability of the application, we must set the size of
the struct sockaddr according to the address family correctly. So, we
should do such sanity checking.
Furthermore, all of KAME delivered getnameinfo() including the version
shipped by ISC do the checking. Changing to only FreeBSD will cause
confusion.
Sincerely,
--
Hajimu UMEMOTO @ Internet Mutual Aid Society Yokohama, Japan
ume@mahoroba.org ume@bisd.hitachi.co.jp ume@{,jp.}FreeBSD.org
http://www.imasy.org/~ume/
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