Re: Crash while trying to destroy memory cache with Heimdal 1.4.1rc2

https://list.sics.se/sympa/info/heimdal-discuss

Love


11 dec 2011 kl. 08:11 skrev Narendra Kumar S.S:

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> Warm Regards,
> Narendra
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> On Sat, Dec 10, 2011 at 10:56 AM, Love Hörnquist Åstrand <[email protected]> wrote:
> Hello,
> 
> Think about krb5_cc_destroy as a krb5_cc_close() combined with delete all data.
> 
>> Hi,
>> 
>> I need some help in understanding the Heimdal KRB5 Memory cache usage.  
>> In the file 'lib/krb5/test_cc.c ', I see the following line in documentation. 
>> 
>>  93 /*
>>  94  * Check that a closed cc still keeps it data and that it's no longer
>>  95  * there when it's destroyed.
>>  96  */
>> 
> 
> This checks that if a credential cache doesn't go away on krb5_cc_close() and that is really gone when calling krb5_cc_destroy().
> 
> 
>> This implies, that a KRB5 cache needs to be destroyed after it is close, or else it will retain the data.
>> But if you look at the code, it suggests that ref counting is done and the data is freed when you do a close.
>> The ref counting can be seen in the file 'lib/krb5/mcache.c ',  in following lines: 
> 
> Reference counting is done on the name, so that multiple holders of the same cache wont destroy the underlaying handle. The credential data can be destroyed though.
> 
>> So I chose to still do a krb5_cc_destroy to make sure I'm not leaking memory in some other scenarios. 
>> But, when my class tries to do a krb5_cc_destroy() in the destructor, it hits an krb5_abortx() in the same file on following line numbers:
>> 
>> 200     if (m->refcnt == 0)
>> 201       krb5_abortx(context, "mcc_destroy: refcnt already 0");
>> 202 
> 
> krb5_cc_destroy() is an implicit krb5_cc_close().
> 
> 
>> I need some help in understanding the use of KRB5 cache of type MEMORY.  Following are the specific questions I need help with:
>> 1] Is Krb5 Mem cache data ref-counted or needs to be explicitly destroyed?
> 
> Its refcounted and the data is destroyed.
> 
>> 2] While destroying the object, should I use krb5_cc_close() or krb5_cc_destroy() or both?
> 
> krb5_cc_destroy(), destroy lead to the marking the object as dead, and when the last reference is dropped, its gone.
> It can be resurected by krb5_cc_initalize().
> 
> Love
> 
> 
> 
>