Am Dienstag, 26. Juli 2016, 13:48:21 CEST schrieb Nicolas Brunie: Hi Nicolas, > Hi All, > I am developping a driver for a crypto offloading solution which > uses the AF_ALG interface. I am trying to stay as close as possible to > the specification but apart from the kernel crypto source code and a few > documents (such as > https://www.kernel.org/doc/htmldocs/crypto-API/ch04s06.html ) I have not > found a lot of details on AF_ALG specification and many points are not > very clear to me, it someone could point me towards reference to answer > the following questions it will be deeply appreciated. See [1] for the library around it. > * > ** > > Socket / Connection : > > Is it legal to open multiple connections on an AF_ALG socket ? How is > the behavior defined Yes, you get a handle (i.e. a file descriptor) for each connection. > > *From what I could test, at least for digests, multiple connections are > OK, but it seems odd to allow multiple connection to a cipher while > using a**shared key and multiple IVs. One of the use I could think of > will be parallelizing several encryption/decryption with the same > symmetric key. It is allowed > * > > Is it true that the key (defined via setsockopt) is common to all the > connections but the IV (defined through message control header) is > specific to each connection ? Yes. > > * > * > > Send/Recv interleaving > > When computing a digest (e.g. sha256) it seems the recv call is > triggering the end of the digest accumulation, such a behavior can be > obtained by using/not using MSG_MORE flags, which *of the two*the > canonical way to compute a hash over several send messages ? It does not > seem possible to compute a partial digest (through a recv call) and then > continue accumulating through other send calls (apart from the security > risk of exposing a te*mporary digest, is there a reason why the recv > ends a digest computation ?)*.* You can read intermediary results. recv does not check for the MSG_MORE flag. > > * > > AES-GCM / AEAD > > Does the aead_assoclen must be set once and for all for each stream or > is it a by message option ? Assoclen is handled like the IV, per message where a message may be sent in multiple chunks. > > Option 0: set aead_assoclen during the first sendmsg and then stream > accross several sendmsg the full AAD and then the full plaintext/ciphertext > > Option 1: set aead_assoclen for each of the first sendmsg containing aad > data. Once the aead_assoclen is strictly less than the msg’s data length > then the next messages must have aead_assoclen set to 0 Option 1, if I read your text right. > > * [1] http://www.chronox.de/libkcapi.html > > best regards, > Nicolas Brunie > -- > To unsubscribe from this list: send the line "unsubscribe linux-crypto" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
