On 2/21/22 13:10, Nicolai Stange wrote:
A subsequent commit will introduce "dh" wrapping templates of the form "ffdhe2048(dh)", "ffdhe3072(dh)" and so on in order to provide built-in support for the well-known safe-prime ffdhe group parameters specified in RFC 7919. Those templates' ->set_secret() will wrap the inner "dh" implementation's ->set_secret() and set the ->p and ->g group parameters as appropriate on the way inwards. More specifically, - A ffdheXYZ(dh) user would call crypto_dh_encode() on a struct dh instance having ->p == ->g == NULL as well as ->p_size == ->g_size == 0 and pass the resulting buffer to the outer ->set_secret(). - This outer ->set_secret() would then decode the struct dh via crypto_dh_decode_key(), set ->p, ->g, ->p_size as well as ->g_size as appropriate for the group in question and encode the struct dh again before passing it further down to the inner "dh"'s ->set_secret(). The problem is that crypto_dh_decode_key() implements some basic checks which would reject parameter sets with ->p_size == 0 and thus, the ffdheXYZ templates' ->set_secret() cannot use it as-is for decoding the passed buffer. As the inner "dh"'s ->set_secret() will eventually conduct said checks on the final parameter set anyway, the outer ->set_secret() really only needs the decoding functionality. Split out the pure struct dh decoding part from crypto_dh_decode_key() into the new __crypto_dh_decode_key(). __crypto_dh_decode_key() gets defined in crypto/dh_helper.c, but will have to get called from crypto/dh.c and thus, its declaration must be somehow made available to the latter. Strictly speaking, __crypto_dh_decode_key() is internal to the dh_generic module, yet it would be a bit over the top to introduce a new header like e.g. include/crypto/internal/dh.h containing just a single prototype. Add the __crypto_dh_decode_key() declaration to include/crypto/dh.h instead. Provide a proper kernel-doc annotation, even though __crypto_dh_decode_key() is purposedly not on the function list specified in Documentation/crypto/api-kpp.rst. Signed-off-by: Nicolai Stange <nstange@xxxxxxx> --- crypto/dh_helper.c | 27 +++++++++++++++++++-------- include/crypto/dh.h | 16 ++++++++++++++++ 2 files changed, 35 insertions(+), 8 deletions(-)
Reviewed-by: Hannes Reinecke <hare@xxxxxxx> Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@xxxxxxx +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer
