PKCS#11 keys
Dmitry Belyavskiy
dbelyavs at redhat.com
Sun Feb 14 03:28:38 AEDT 2021
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
> >>>
> > >
> > > _______________________________________________
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> >>
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> > >
> > >
> > >
> > > --
> > > 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
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