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

[Umang Jain]

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.

> +    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
>   }