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Message-ID: <20250225140915.GM1827@brightrain.aerifal.cx>
Date: Tue, 25 Feb 2025 09:09:15 -0500
From: Rich Felker <dalias@...c.org>
To: Anton Moryakov <ant.v.moryakov@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] src: network: replace unsafe strcat with strncat
in getnameinfo.c
On Tue, Feb 25, 2025 at 04:26:46PM +0300, Anton Moryakov wrote:
> Replaced the vulnerable `strcat` function with `strncat` to prevent
> potential buffer overflow. The new implementation limits the number
> of characters copied to the remaining space in the destination buffer,
> ensuring safe string concatenation.
>
> The change addresses the following warning:
> /.build/src/network/getnameinfo.c:178
> Use of vulnerable function 'strcat' at getnameinfo.c:178. This function
> is unsafe, use strncat instead.
>
> While it is unclear if the static analyzer correctly identified this
> as a vulnerability, it is better to err on the side of caution and
> make the code safer by using `strncat`. The fix calculates the
> available space in the buffer using `sizeof(buf) - strlen(buf) - 1`
> to leave room for the null terminator.
>
> Triggers found by static analyzer Svace.
>
> Signed-off-by: Anton Moryakov <ant.v.moryakov@...il.com>
>
> ---
> src/network/getnameinfo.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/network/getnameinfo.c b/src/network/getnameinfo.c
> index 133c15b3..e15f4457 100644
> --- a/src/network/getnameinfo.c
> +++ b/src/network/getnameinfo.c
> @@ -179,7 +179,7 @@ int getnameinfo(const struct sockaddr *restrict sa, socklen_t sl,
> if (!p)
> p = itoa(num, scopeid);
> *--p = '%';
> - strcat(buf, p);
> + strncat(buf, p, sizeof(buf) - strlen(buf) - 1);
> }
> }
> if (strlen(buf) >= nodelen) return EAI_OVERFLOW;
> --
> 2.30.2
buf is 256 bytes. inet_ntop returns at most INET6_ADDRSTRLEN (46)
bytes. p points to a string of length at most IF_NAMESIZE+1 (17) or
3*sizeof(int) (12) bytes.
Rich
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