[PATCH] cpukit/mghttpd/mongoose: Fix format truncation warning
gedare at rtems.org
Thu Sep 17 19:07:09 UTC 2020
On Wed, Sep 16, 2020 at 7:15 PM Chris Johns <chrisj at rtems.org> wrote:
> On 17/9/20 9:50 am, Joel Sherrill wrote:
> > On Wed, Sep 16, 2020, 6:43 PM Chris Johns <chrisj at rtems.org
> > <mailto:chrisj at rtems.org>> wrote:
> > On 16/9/20 11:42 pm, Joel Sherrill wrote:
> > > snprintf() is a safe method and I strongly disagree with the blanket
> > replacement
> > > of many safe methods with memcpy().
> > >
> > > Based on what POSIX profiles snprintf() is included in and the safety and
> > > security requirements those profiles are designed to meet, snprintf() is
> > > supported by RTOSes that can meet DO-178 Level A.
> > >
> > > If the POSIX method being reviewed is in the FACE Safety Base or Safety
> > Extended
> > > profile, then it is OK to use and has been used in flight qualified
> > > applications. And that is a general statement meaning running on any of a
> > > variety of RTOSes. If the usage is incorrect, let's fix it but blanket
> > changing
> > > them is wrong.
> > This is really good information, thank you.
> > No problem. That doesn't mean you can't do something stupid with it but
> > sprintf() would be discouraged and isn't in those profiles as I recall.
> > I see EPICS is reporting similar issues at the moment and looking to work around
> > them.
> > And no one is questioning why? What's the risk?
> > Is there a history of why this has been added to compilers as a warning?
> > I have no idea..snprintf has a length and avoids overwrites.
> > I would suggest that we find a safety or security coding standard that warns
> > about whatever methods this catches.
> > Personally replacing snprintf and strong operations with memmove is semantically
> > wrong.
> I found this....
> The "Handling Truncation When It Occurs" section in the blog post is something
> worth considering. It seems the return value of call should be checked. That
> seems reasonable.
Nice. *printf also suffer from other security-relevant vulnerabilities
such as the format-string attack:
This means replacing their use with alternatives can be generally more secure.
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