Re: [RFC v2 4/7] modsig: add integrity_module_check hook

[Kasatkin, Dmitry]

On Wed, Aug 15, 2012 at 11:16 PM, Serge Hallyn
<serge.hallyn@xxxxxxxxxxxxx> wrote:
> Quoting Dmitry Kasatkin (dmitry.kasatkin@xxxxxxxxx):
>> IMA measures/appraises modules when modprobe or insmod opens and read them.
>> Unfortunately, there are no guarantees between what is read by userspace and
>> what is passed to the kernel via load_module system call. This patch adds a
>> hook called integrity_module_check() to verify the integrity of the module
>> being loaded.
>>
>> Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
>> ---
>>  include/linux/integrity.h |   10 ++++++++++
>>  kernel/module.c           |    9 +++++++++
>>  2 files changed, 19 insertions(+)
>>
>> diff --git a/include/linux/integrity.h b/include/linux/integrity.h
>> index 66c5fe9..a80ec06 100644
>> --- a/include/linux/integrity.h
>> +++ b/include/linux/integrity.h
>> @@ -37,4 +37,14 @@ static inline void integrity_inode_free(struct inode *inode)
>>       return;
>>  }
>>  #endif /* CONFIG_INTEGRITY_H */
>> +
>> +#ifdef CONFIG_INTEGRITY_MODULES
>> +int integrity_module_check(const void *hdr, const unsigned long len);
>
> sadly not bisect-safe, since integrity_module_check() is defined in
> the next patch.
>

Ok.. Hooks come after implementation...
Will swap.

Thanks.

>> +#else
>> +static inline int integrity_module_check(const void *buf, unsigned long len)
>> +{
>> +     return 0;
>> +}
>> +#endif
>> +
>>  #endif /* _LINUX_INTEGRITY_H */
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 4edbd9c..791da47 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -58,6 +58,7 @@
>>  #include <linux/jump_label.h>
>>  #include <linux/pfn.h>
>>  #include <linux/bsearch.h>
>> +#include <linux/integrity.h>
>>
>>  #define CREATE_TRACE_POINTS
>>  #include <trace/events/module.h>
>> @@ -2437,6 +2438,14 @@ static int copy_and_check(struct load_info *info,
>>
>>       info->hdr = hdr;
>>       info->len = len;
>> +
>> +     err = integrity_module_check(hdr, len);
>> +     if (err < 0)
>> +             goto free_hdr;
>> +
>> +     /* cut signature tail */
>> +     info->len = err;
>> +
>>       return 0;
>>
>>  free_hdr:
>> --
>> 1.7.9.5
>>
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