Re: linux-next: Tree for Aug 22 (evm)

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Hi,

On Mon, Aug 22, 2011 at 10:09 PM, Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 2011-08-22 at 17:49 -0700, Randy Dunlap wrote:
>> On Mon, 22 Aug 2011 20:47:00 -0400 Arnaud Lacombe wrote:
>>
>> > Hi,
>> >
>> > On Mon, Aug 22, 2011 at 3:53 PM, Randy Dunlap <rdunlap@xxxxxxxxxxxx> wrote:
>> > > On Mon, 22 Aug 2011 14:53:04 +1000 Stephen Rothwell wrote:
>> > >
>> > >> Hi all,
>> > >>
>> > >> [The kernel.org mirroring is a bit low today]
>> > >
>> > > (on x86_64:)
>> > >
>> > > When CONFIG_EVM=y, CONFIG_CRYPTO_HASH2=m, CONFIG_TRUSTED_KEYS=m,
>> > > CONFIG_ENCRYPTED_KEYS=m, the build fails with:
>> > >
>> > You did not provide the value of CONFIG_TCG_TPM, I'll assume it was
>> > 'm'. That said, correct me if I'm wrong, but we currently have:
>>
>> Yes, it was 'm'.
>>
>> > menuconfig TCG_TPM
>> >         tristate "TPM Hardware Support"
>> >
>> > [...]
>> >
>> > config EVM
>> >         boolean "EVM support"
>> >         depends on SECURITY && KEYS && TCG_TPM
>> >
>> > which seems terribly broken to me... How can you have a built-in
>> > feature, which depends on another potentially-not-built-in feature ?
>>
>> Yup.
>
> Easy, different use cases. The TPM has been around and used for a while,
> not requiring it to be built-in.  EVM, a new use case, requires it to be
> built-in.
>
What behavior is expected when TPM is built as a module ? Would you
expect EVM to be accessible ?

>> > If you change EVM to 'tristate', you will see that you are not allowed
>> > to make it built-in if TCG_TPM is not built-in.
>>
>> Right.
>
> The TPM, crypto, trusted and encrypted keys are tristate.  Like the
> LSMs, EVM is boolean, which when selected using 'make xconfig', converts
> the tristates to built-in.  The tristate/boolean mismatches aren't
> corrected, when .config is edited directly.
>
well, ... no. 'xconfig' would seem to let you think they have been
changed to 'y', but they have not. I have been able to generate a bad
configuration (TPM module, EVM built-in) using only {menu,x}config.

btw, I never edit the configuration manually, there is a big fat "DO
NOT EDIT" header in the beginning.

Depending on what you expect, one way to fix that is to make EVM
depends on TCG_TPM = y, not just TCG_TPM.

 - Arnaud

> Mimi
>
>> >  - Arnaud
>> >
>> > > (.text+0x378aa): undefined reference to `key_type_encrypted'
>> > > evm_crypto.c:(.text+0x37992): undefined reference to `crypto_alloc_shash'
>> > > evm_crypto.c:(.text+0x37a24): undefined reference to `crypto_shash_setkey'
>> > > evm_crypto.c:(.text+0x37ad9): undefined reference to `crypto_shash_update'
>> > > evm_crypto.c:(.text+0x37aeb): undefined reference to `crypto_shash_final'
>> > > (.text+0x37b4b): undefined reference to `crypto_shash_update'
>> > > (.text+0x37c61): undefined reference to `crypto_shash_update'
>> > > (.text+0x37cb9): undefined reference to `crypto_shash_update'
>> > >
>> > > even though EVM (Kconfig) selects ENCRYPTED_KEYS and TRUSTED_KEYS..
>> > > and even after I add "select CRYPTO_HASH2".
>> > >
>> > > Is this because EVM is bool and kconfig is confused about 'select's
>> > > when a bool is selecting tristates?  Shouldn't the tristates become
>> > > 'y' instead of 'm' if they are selected by a bool that is 'y'?
>> > >
>> > >
>> > > xconfig shows these symbol values:
>> > >
>> > > Symbol: EVM [=y]
>> > > Type : boolean
>> > > Prompt: EVM support
>> > > Defined at security/integrity/evm/Kconfig:1
>> > > Depends on: SECURITY [=y] && KEYS [=y] && TCG_TPM [=m]
>> > > Location:
>> > > -> Security options
>> > > Selects: CRYPTO_HMAC [=m] && CRYPTO_MD5 [=m] && CRYPTO_SHA1 [=m] && CRYPTO_HASH2 [=m] && ENCRYPTED_KEYS [=m] && TRUSTED_KEYS [=m]
>> > >
>> > >
>> > > Hm, changing TCG_TPM to =y also changes TRUSTED_KEYS and ENCRYPTED_KEYS and
>> > > lots of CRYPTO_ symbols from =m to =y.  There must be some kind of min/max
>> > > symbol checking that is confused?
>> > >
>> > there is definitively an underlying min/max, but I would not point
>> > finger too fast.
>>
>>
>> Thanks for your help.
>>
>> ---
>> ~Randy
>> *** Remember to use Documentation/SubmitChecklist when testing your code ***
>
>
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