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

[Umang Jain]

Hi Laurent,

On 6/17/21 5:15 PM, Laurent Pinchart wrote:
> 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
Thanks 😅
>
> :-)
>
>>> +    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
>>>    }