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Message-ID: <0e66197d-9ccd-4e03-948d-e96d2cd2e465@gmail.com>
Date: Thu, 29 May 2025 09:54:18 +0200
From: Gabriel Ravier <gabravier@...il.com>
To: musl@...ts.openwall.com, Rich Felker <dalias@...c.org>,
whistle@...l.ustc.edu.cn
Subject: Re: Potential Injection Vulnerability in _vsyslog Function
On 5/9/25 1:02 AM, Rich Felker wrote:
> On Thu, May 08, 2025 at 11:14:55PM +0800, whistle@...l.ustc.edu.cn wrote:
>> In the current _vsyslog function, if the log contains characters
>> like \r or \n, according to CWE-93: Improper Neutralization of CRLF
>> Sequences ('CRLF Injection'), this could potentially lead to an
>> injection vulnerability.
>>
>>
>> When using musl, would it be safer to explicitly handle \r and \n
>> here as an extra security measure?
> I don't think there's any reason we should be munging the contents of
> the log message here. The syslogd receiving the datagram is free to
> reject embedded newlines (meaning \n; \r is completely irrelevant here
> AFAICT) or store them in some storage-backend-specific way. If it
> stores them in a manner where they can be misinterpreted as the start
> of a new log record with different process credentials, that seems
> like a weakness in the syslogd not in the libc. Especially since
> someone wanting to do that could just write their own client sending
> the datagrams with embedded newlines to /dev/log, no?
>
> Rich
I imagine for the last question the idea is that a program that lets
someone log arbitrary data (or that one can trick into doing so) could
be used for this (I otherwise fully agree with the rest of the analysis
- it doesn't seem like a real concern given it shouldn't matter unless
syslogd is already grievously broken).
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