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Message-ID: <5e3edf2a-eb58-a529-c561-1b86f5d8ee08@mirbsd.de>
Date: Fri, 25 Jul 2025 16:35:59 +0200 (CEST)
From: Thorsten Glaser <tg@...bsd.de>
To: musl@...ts.openwall.com
Subject: Re: Bug in IN6_IS_ADDR_V4COMPAT macro for addresses ending
in .1
On Fri, 25 Jul 2025, Yusuke Endoh wrote:
>I suspect the condition in the macro is incorrect.
>Currently it checks if the LSB is "> 1", but it should be ">= 1".
The analysis is correct, the fix is wrong (::172.17.1.0 would still
be misrecognised).
AIUI, the macro needs to check that the address begins with quite a
lot of zeroes but is not exactly ::1 (or ::).
> #define IN6_IS_ADDR_V4COMPAT(a) \
> (((uint32_t *) (a))[0] == 0 && ((uint32_t *) (a))[1] == 0 && \
>- ((uint32_t *) (a))[2] == 0 && ((uint8_t *) (a))[15] > 1)
>+ ((uint32_t *) (a))[2] == 0 && ((uint8_t *) (a))[15] >= 1)
Is that casting well-defined? If so, perhaps:
+ ((uint32_t *) (a))[2] == 0 && ((uint32_t *) (a))[3] > 1)
Untested, and I’ve not yet had enough coffee, so DWIM ☻
bye,
//mirabilos
--
(gnutls can also be used, but if you are compiling lynx for your own use,
there is no reason to consider using that package)
-- Thomas E. Dickey on the Lynx mailing list, about OpenSSL
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