PKCS#11 keys

Dmitry Belyavskiy dbelyavs at redhat.com
Sun Feb 14 03:39:01 AEDT 2021


Dear Douglas,

I've got it. The index is shared but the stacks are different.
Many thanks for your help!

On Sat, Feb 13, 2021 at 5:28 PM Dmitry Belyavskiy <dbelyavs at redhat.com>
wrote:

> Many thanks!
>
> Will try.
>
> On Sat, Feb 13, 2021 at 4:54 PM Douglas E Engert <deengert at gmail.com>
> wrote:
>
>>
>> The last line:
>> RSA_set_ex_data(rsa, rsa_idx, k11);
>>
>> sets the pointer to the allocated k11 structure into the rsa key at index
>> rsa_idx
>> OpenSSH has allocated an rsa_index, to allow it to store OpenSSH data in
>> any rsa key.
>> The stack allows different components to also hang their own data on any
>> key.
>> (Note when the index was allocated, a free routine to free a k11
>> structure was added.)
>>
>> The rsa_idx is the index into a stack in each RSA structure.
>> The stack allows multiple components add data to a key.
>>
>> Running under a debugger might help show how this works.
>> This is one of the hardest features of OpenSSL to understand.
>>
>> On 2/13/2021 9:37 AM, Dmitry Belyavskiy wrote:
>> > Dear Douglas,
>> >
>> > Sorry, I don't understand how it works.
>> >
>> > The RSA_get_ex_new_index allocates an index in the internal openssl
>> table. This index is a global variable.
>> >
>> > Then on loading a particular key we use a function pkcs11_rsa_wrap that
>> sets a pointer to a pkcs11_key structure identifying that particular key.
>> >
>> https://github.com/openssh/openssh-portable/blob/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L486-L508
>> > <
>> https://github.com/openssh/openssh-portable/blob/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L486-L508
>> >
>> >
>> > The internal openssl implementation that is used for this purpose uses
>> a stack.
>> > So basically all the _set_ex_data functions put a pointer to some data
>> in stack on position with idx:
>> >
>> https://github.com/openssl/openssl/blob/c8c6e7438c03b2fc24e7ead460feeaef04911fb4/crypto/ex_data.c#L369-L388
>> > <
>> https://github.com/openssl/openssl/blob/c8c6e7438c03b2fc24e7ead460feeaef04911fb4/crypto/ex_data.c#L369-L388
>> >
>> >
>> > (see the definition of OPENSSL_sk_set for details
>> >
>> https://github.com/openssl/openssl/blob/c8c6e7438c03b2fc24e7ead460feeaef04911fb4/crypto/stack/stack.c#L392-L399
>> > <
>> https://github.com/openssl/openssl/blob/c8c6e7438c03b2fc24e7ead460feeaef04911fb4/crypto/stack/stack.c#L392-L399
>> >)
>> >
>> > I think, it an easily be checked just by adding a 2nd RSA key to
>> regress/agent-pkcs11.sh test
>> >
>> > On Sat, Feb 13, 2021 at 4:13 PM Douglas E Engert <deengert at gmail.com
>> <mailto:deengert at gmail.com>> wrote:
>> >
>> >     You are partially right.
>> >     The rsa_idx, and ec_key_idx should not be set to 0, but should be
>> set
>> >     using RSA_get_ex_new_index() as is done later in:
>> >
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L471
>> >     <
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L471
>> >
>> >
>> >     rsa_idx = RSA_get_ex_new_index(0, "ssh-pkcs11-rsa",
>> >
>> >     This then allows for multiple components to store data in a key.
>> >     The index is not of the key, but of extra data that can be stored
>> in a key.
>> >     Thus every key can have its own "ssh-pkcs11-rsa" with different
>> data.
>> >
>> >     The ec_key_idx is set in:
>> >
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L587
>> >     <
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L587
>> >
>> >
>> >
>> >
>> https://www.openssl.org/docs/man1.1.1/man3/RSA_get_ex_new_index.html <
>> https://www.openssl.org/docs/man1.1.1/man3/RSA_get_ex_new_index.html>
>> >     and is also in OpenSSL-1.0.2.
>> >
>> >     OpenSC/libp11 examples start here:
>> >     https://github.com/OpenSC/libp11/blob/master/src/p11_rsa.c#L399 <
>> https://github.com/OpenSC/libp11/blob/master/src/p11_rsa.c#L399>
>> >
>> >     https://github.com/OpenSC/libp11/blob/master/src/p11_ec.c#L155 <
>> https://github.com/OpenSC/libp11/blob/master/src/p11_ec.c#L155>
>> >
>> >
>> >     On 2/13/2021 8:22 AM, Dmitry Belyavskiy wrote:
>> >      > Dear Douglas,
>> >      >
>> >      > Everything is fine with methods. But I'm speaking about the
>> variables rsa_idx and ec_key_idx, sorry for being unclear.
>> >      > They serve as handles in a global OpenSSL table and identify a
>> pkcs11_data associated with a particular key, don't they?
>> >      >
>> >      > On Sat, Feb 13, 2021 at 3:07 PM Douglas E Engert <
>> deengert at gmail.com <mailto:deengert at gmail.com> <mailto:deengert at gmail.com
>> <mailto:deengert at gmail.com>>> wrote:
>> >      >
>> >      >     These lines are for METHODS, i.e. RSA_METHOD and
>> EC_KEY_METHOD. RSA keys can share an RSA_METHOD,
>> >      >     and EC keys can share an EC_KEY_METHOD.  A method can be
>> copied, for example an OpenSSL engine
>> >      >     for using PKCS11, would then provide the routines in the
>> method to not use the default software version
>> >      >     of RSA signature or decrypting operations, but use PKCS11 to
>> have these operations done on the token or smart card.
>> >      >     So for RSA keys on the token, all these keys would share a
>> copied and modified RSA_METHOD PKCS11 method
>> >      >     where the rsa_idx in these keys is used to point to key
>> specific data such as PkCS11 slot and KeyIDs.
>> >      >
>> >      >
>> >      >
>> >      >     On 2/12/2021 10:31 AM, Dmitry Belyavskiy wrote:
>> >      >      > Hello,
>> >      >      >
>> >      >      > Do I correctly understand that there can't be more than
>> one key of each
>> >      >      > type of PKCS#11?
>> >      >      >
>> >      >      > The lines
>> >      >      >
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L191-L196
>> >     <
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L191-L196
>> >
>> >      >     <
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L191-L196
>> >     <
>> https://github.com/openssh/openssh-portable/blame/1bb130ed34721d46452529d094d9bbf045607d79/ssh-pkcs11.c#L191-L196
>> >>
>> >      >      > seem to use the global variables for RSA/ECDSA
>> pkcs11-related data
>> >      >      > structures.
>> >      >      >
>> >      >      > Many thanks!
>> >      >      >
>> >      >
>> >      >     --
>> >      >
>> >      >        Douglas E. Engert  <DEEngert at gmail.com <mailto:
>> DEEngert at gmail.com> <mailto:DEEngert at gmail.com <mailto:DEEngert at gmail.com
>> >>>
>> >      >
>> >      >     _______________________________________________
>> >      >     openssh-unix-dev mailing list
>> >      > openssh-unix-dev at mindrot.org <mailto:
>> openssh-unix-dev at mindrot.org> <mailto:openssh-unix-dev at mindrot.org
>> <mailto:openssh-unix-dev at mindrot.org>>
>> >      > https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev <
>> https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev> <
>> https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
>> >     <https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev>>
>> >      >
>> >      >
>> >      >
>> >      > --
>> >      > Dmitry Belyavskiy
>> >
>> >     --
>> >
>> >        Douglas E. Engert  <DEEngert at gmail.com <mailto:
>> DEEngert at gmail.com>>
>> >
>> >
>> >
>> > --
>> > Dmitry Belyavskiy
>>
>> --
>>
>>   Douglas E. Engert  <DEEngert at gmail.com>
>>
>>
>
> --
> Dmitry Belyavskiy
>


-- 
Dmitry Belyavskiy


More information about the openssh-unix-dev mailing list