> This patch adds basic abstractions for synchronous message digest API,
> wrapping crypto_shash and shash_desc structures.
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxx>
> ---
> rust/bindings/bindings_helper.h | 1 +
> rust/helpers.c | 26 +++++++
> rust/kernel/crypto.rs | 5 ++
> rust/kernel/crypto/hash.rs | 128 ++++++++++++++++++++++++++++++++
> rust/kernel/lib.rs | 2 +
> 5 files changed, 162 insertions(+)
> create mode 100644 rust/kernel/crypto.rs
> create mode 100644 rust/kernel/crypto/hash.rs
>
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index 3e601ce2548d..2f198c6d5de5 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -6,6 +6,7 @@
> * Sorted alphabetically.
> */
>
> +#include <crypto/hash.h>
> #include <linux/errname.h>
> #include <linux/slab.h>
> #include <linux/refcount.h>
> diff --git a/rust/helpers.c b/rust/helpers.c
> index bb594da56137..7966902ed8eb 100644
> --- a/rust/helpers.c
> +++ b/rust/helpers.c
> @@ -18,6 +18,7 @@
> * accidentally exposed.
> */
>
> +#include <crypto/hash.h>
> #include <linux/bug.h>
> #include <linux/build_bug.h>
> #include <linux/err.h>
> @@ -28,6 +29,31 @@
> #include <linux/sched/signal.h>
> #include <linux/wait.h>
>
> +#ifdef CONFIG_CRYPTO
> +void rust_helper_crypto_free_shash(struct crypto_shash *tfm)
> +{
> + crypto_free_shash(tfm);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_crypto_free_shash);
> +
> +unsigned int rust_helper_crypto_shash_digestsize(struct crypto_shash *tfm)
> +{
> + return crypto_shash_digestsize(tfm);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_crypto_shash_digestsize);
> +
> +unsigned int rust_helper_crypto_shash_descsize(struct crypto_shash *tfm)
> +{
> + return crypto_shash_descsize(tfm);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_crypto_shash_descsize);
> +
> +int rust_helper_crypto_shash_init(struct shash_desc *desc) {
> + return crypto_shash_init(desc);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_crypto_shash_init);
> +#endif
> +
> __noreturn void rust_helper_BUG(void)
> {
> BUG();
> diff --git a/rust/kernel/crypto.rs b/rust/kernel/crypto.rs
> new file mode 100644
> index 000000000000..f80dd7bd3381
> --- /dev/null
> +++ b/rust/kernel/crypto.rs
> @@ -0,0 +1,5 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Cryptography.
> +
> +pub mod hash;
> diff --git a/rust/kernel/crypto/hash.rs b/rust/kernel/crypto/hash.rs
> new file mode 100644
> index 000000000000..cdbc8e70e8f5
> --- /dev/null
> +++ b/rust/kernel/crypto/hash.rs
> @@ -0,0 +1,128 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Cryptographic Hash operations.
> +//!
> +//! C headers: [`include/crypto/hash.h`](../../../../include/crypto/hash.h)
> +
> +use crate::{
> + error::{
> + code::{EINVAL, ENOMEM},
> + from_err_ptr, to_result, Result,
> + },
> + str::CStr,
> +};
> +use alloc::alloc::{alloc, dealloc};
> +use core::alloc::Layout;
> +
> +/// Corresponds to the kernel's `struct crypto_shash`.
> +///
> +/// # Invariants
> +///
> +/// The pointer is valid.
> +pub struct Shash(*mut bindings::crypto_shash);
> +
> +impl Drop for Shash {
> + fn drop(&mut self) {
> + // SAFETY: The type invariant guarantees that the pointer is valid.
> + unsafe { bindings::crypto_free_shash(self.0) }
> + }
> +}
> +
> +impl Shash {
> + /// Creates a [`Shash`] object for a message digest handle.
> + pub fn new(name: &CStr, t: u32, mask: u32) -> Result<Shash> {
> + // SAFETY: There are no safety requirements for this FFI call.
> + let ptr =
> + unsafe { from_err_ptr(bindings::crypto_alloc_shash(name.as_char_ptr(), t, mask)) }?;
> + // INVARIANT: `ptr` is valid and non-null since `crypto_alloc_shash`
> + // returned a valid pointer which was null-checked.
> + Ok(Self(ptr))
> + }
> +
> + /// Sets optional key used by the hashing algorithm.
> + pub fn setkey(&mut self, data: &[u8]) -> Result {
> + // SAFETY: The type invariant guarantees that the pointer is valid.
> + to_result(unsafe {
> + bindings::crypto_shash_setkey(self.0, data.as_ptr(), data.len() as u32)
> + })
> + }
> +
> + /// Returns the size of the result of the transformation.
> + pub fn digestsize(&self) -> u32 {
> + // SAFETY: The type invariant guarantees that the pointer is valid.
> + unsafe { bindings::crypto_shash_digestsize(self.0) }
> + }
> +}
> +
> +/// Corresponds to the kernel's `struct shash_desc`.
> +///
> +/// # Invariants
> +///
> +/// The field `ptr` is valid.
> +pub struct ShashDesc<'a> {
> + ptr: *mut bindings::shash_desc,
> + tfm: &'a Shash,
> + size: usize,
> +}
> +
> +impl Drop for ShashDesc<'_> {
> + fn drop(&mut self) {
> + // SAFETY: The type invariant guarantees that the pointer is valid.
> + unsafe {
> + dealloc(
> + self.ptr.cast(),
> + Layout::from_size_align(self.size, 2).unwrap(),
> + );
> + }
> + }
> +}
> +
> +impl<'a> ShashDesc<'a> {
> + /// Creates a [`ShashDesc`] object for a request data structure for message digest.
> + pub fn new(tfm: &'a Shash) -> Result<Self> {
> + // SAFETY: The type invariant guarantees that `tfm.0` pointer is valid.
> + let size = core::mem::size_of::<bindings::shash_desc>()
> + + unsafe { bindings::crypto_shash_descsize(tfm.0) } as usize;
> + let layout = Layout::from_size_align(size, 2)?;
I still do not like this arbitrary `2` constant as the alignment. Why is
this correct? It should be explained in the code. Otherwise use a
different way to compute the layout via `Layout::new()` and/or
`Layout::repeat`/`Layout::extend` etc.
--
Cheers,
Benno
> + // SAFETY: It's safe because layout has non-zero size.
> + let ptr = unsafe { alloc(layout) } as *mut bindings::shash_desc;
> + if ptr.is_null() {
> + return Err(ENOMEM);
> + }
> + // INVARIANT: `ptr` is valid and non-null since `alloc`
> + // returned a valid pointer which was null-checked.
> + let mut desc = ShashDesc { ptr, tfm, size };
> + // SAFETY: `desc.ptr` is valid and non-null since `alloc`
> + // returned a valid pointer which was null-checked.
> + // Additionally, The type invariant guarantees that `tfm.0` is valid.
> + unsafe { (*desc.ptr).tfm = desc.tfm.0 };
> + desc.reset()?;
> + Ok(desc)
> + }
> +
> + /// Re-initializes message digest.
> + pub fn reset(&mut self) -> Result {
> + // SAFETY: The type invariant guarantees that the pointer is valid.
> + to_result(unsafe { bindings::crypto_shash_init(self.ptr) })
> + }
> +
> + /// Adds data to message digest for processing.
> + pub fn update(&mut self, data: &[u8]) -> Result {
> + if data.len() > u32::MAX as usize {
> + return Err(EINVAL);
> + }
> + // SAFETY: The type invariant guarantees that the pointer is valid.
> + to_result(unsafe {
> + bindings::crypto_shash_update(self.ptr, data.as_ptr(), data.len() as u32)
> + })
> + }
> +
> + /// Calculates message digest.
> + pub fn finalize(&mut self, output: &mut [u8]) -> Result {
> + if self.tfm.digestsize() as usize > output.len() {
> + return Err(EINVAL);
> + }
> + // SAFETY: The type invariant guarantees that the pointer is valid.
> + to_result(unsafe { bindings::crypto_shash_final(self.ptr, output.as_mut_ptr()) })
> + }
> +}
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 85b261209977..3cb8bd8a17d9 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -31,6 +31,8 @@
> #[cfg(not(testlib))]
> mod allocator;
> mod build_assert;
> +#[cfg(CONFIG_CRYPTO)]
> +pub mod crypto;
> pub mod error;
> pub mod init;
> pub mod ioctl;
> --
> 2.34.1
>
