[libcamera-devel] [PATCH] libcamera: utils: Support systems that lack secure_getenv and issetugid

[Laurent Pinchart]

Hi Umang,

On Thu, Jun 17, 2021 at 05:13:54PM +0530, Umang Jain wrote:
> Hi Laurent,
> 
> On 6/16/21 9:22 PM, Laurent Pinchart wrote:
> > Android provides neither secure_getenv() nor issetugid(). Enable
> > compilation on that platform by using a plain getenv(), as that seems to
> > be the best we can do.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> First of all, LGTM
> 
> Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>
> 
> with a follow-up question
> 
> > ---
> >   meson.build             | 4 ++++
> >   src/libcamera/utils.cpp | 7 ++++++-
> >   2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/meson.build b/meson.build
> > index f6ab7380f1a5..4d7d936f09e2 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -33,6 +33,10 @@ if cc.has_header_symbol('execinfo.h', 'backtrace')
> >       config_h.set('HAVE_BACKTRACE', 1)
> >   endif
> >   
> > +if cc.has_header_symbol('unistd.h', 'issetugid')
> 
> 
> How does one find out which header to look for issetugid? Is it some 
> libc standard practice? For e.g. my /usr/include/unistd.h doesn't define 
> issetugid,  but stdlib.h does define the secure_getenv.

https://man.openbsd.org/issetugid.2

:-)

> > +    config_h.set('HAVE_ISSETUGID', 1)
> > +endif
> > +
> >   if cc.has_header_symbol('stdlib.h', 'secure_getenv', prefix : '#define _GNU_SOURCE')
> >       config_h.set('HAVE_SECURE_GETENV', 1)
> >   endif
> > diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> > index 24a5c9720fbe..ed7e0177ebe1 100644
> > --- a/src/libcamera/utils.cpp
> > +++ b/src/libcamera/utils.cpp
> > @@ -61,6 +61,10 @@ const char *basename(const char *path)
> >    * avoid vulnerabilities that could occur if set-user-ID or set-group-ID
> >    * programs accidentally trust the environment.
> >    *
> > + * \note Not all platforms may support the features required to implement the
> > + * secure execution check, in which case this function behaves as getenv(). A
> > + * notable exception is Android.
> > + *
> >    * \return A pointer to the value in the environment or NULL if the requested
> >    * environment variable doesn't exist or if secure execution is required.
> >    */
> > @@ -69,9 +73,10 @@ char *secure_getenv(const char *name)
> >   #if HAVE_SECURE_GETENV
> >   	return ::secure_getenv(name);
> >   #else
> > +#if HAVE_ISSETUGID
> >   	if (issetugid())
> >   		return NULL;
> > -
> > +#endif
> >   	return getenv(name);
> >   #endif
> >   }

-- 
Regards,

Laurent Pinchart