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BPF crypto was implemented using the lskcipher API, which doesn't seem
to be going anywhere. lskcipher supports only ARC4 and block ciphers in
CBC and ECB mode, and only with unoptimized implementations.
Library APIs also have been found to be a much better approach, for a
variety of reasons, including reduced overhead, greater flexibility, and
having to be explicit about the crypto algorithms that are supported.
We can safely ignore the theoretical ARC4 and non-AES block cipher
support in BPF crypto as unused, which leaves AES-CBC and AES-ECB.
AES-CBC was stated to be needed for decrypting packets using a homebrew
UDP-based protocol
(https://lore.kernel.org/r/d1cdfc23-b336-49a9-8833-29f05b5b9fec@linux.dev/).
AES-ECB is used by the BPF self-tests, and it was stated to maybe be
used in the future for QUIC-LB
(https://lore.kernel.org/r/5f9c3aab-5339-463c-a86d-edac297e1e95@linux.dev/).
Those reasons don't make much sense either, especially AES-ECB which
isn't appropriate in new systems and should be dropped. Regardless,
let's assume that both AES-CBC and AES-ECB need to be kept for now.
There are library APIs for both of these now, which are much easier to
use and more efficient. Reimplement BPF crypto on top of them, greatly
simplifying the code. As part of this, the bpf_crypto_type abstraction
layer is removed, as it's not useful.
This removes the only user of the lskcipher API, so follow-up patches
will be able to remove that code as well.
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20260924184254.142720-1-ebiggers@kernel.org
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