[RFC PATCH 0/2] rust: crypto: library AES-128 / SHA-256 / HMAC + RSA

[Mike Lothian]

This RFC series adds a small, reusable kernel::crypto module so in-kernel
Rust code can hash, encrypt a single AES block, and do RSA public-key
encryption:

  1/2  sha256(), hmac_sha256(), Aes128 (single-block ECB)
  2/2  Akcipher + rsa_pubkey_encrypt() over crypto_akcipher

Patch 1 binds the library crypto (lib/crypto) functions directly
(SHA-256 / HMAC-SHA256) and uses one rust_helper_ shim for aes_encrypt()
(its transparent union is unbindable). It runs synchronously in the
calling context with no allocation and is the independently-mergeable,
self-contained contribution.

Patch 2 adds crypto::Akcipher, a thin wrapper over the asynchronous
public-key API (crypto_akcipher) driven synchronously, and a
crypto::rsa_pubkey_encrypt() convenience built on it: it DER-encodes the
RSAPublicKey the "rsa" transform expects, runs one encrypt, and leaves
padding to the caller. The request/scatterlist/completion plumbing (all
static-inline or on-stack) plus a kmalloc bounce for the DMA data path
live in one rust_helper_ shim; crypto_free_akcipher() and
crypto_akcipher_set_pub_key() are exposed through 1:1 shims. Going
through crypto_akcipher rather than the MPI math library means it
composes with any registered RSA implementation, including hardware
offload. It is kept a separate patch so the public-key surface can be
reviewed (or deferred) on its own without touching patch 1.

Both were factored out of an out-of-tree in-kernel Rust DisplayLink DL3
dock driver (which needs SHA/HMAC/AES for HDCP 2.2 and RSA for the AKE),
but the module is generic. Compile-tested in-tree against drm-next.

Mike Lothian (2):
  rust: crypto: add library AES-128 / SHA-256 / HMAC-SHA256 bindings
  rust: crypto: add RSA public-key encryption via crypto_akcipher

 rust/bindings/bindings_helper.h |   3 +
 rust/helpers/crypto.c           |  95 +++++++++++++++++++++++++++
 rust/helpers/helpers.c          |   1 +
 rust/kernel/crypto.rs           | 255 ++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |   1 +
 5 files changed, 355 insertions(+)

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2.54.0