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refactor cmac so we can use it from rust as well #13807

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Merged
alex merged 1 commit into from
Nov 4, 2025
Merged

refactor cmac so we can use it from rust as well #13807

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38 changes: 25 additions & 13 deletions src/rust/src/backend/cmac.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
// for complete details.

use cryptography_crypto::constant_time;
use pyo3::types::{PyAnyMethods, PyBytesMethods};
use pyo3::types::PyAnyMethods;

use crate::backend::cipher_registry;
use crate::buf::CffiBuf;
Expand All @@ -19,10 +19,26 @@ struct Cmac {
}

impl Cmac {
fn new_bytes(key: &[u8], cipher: &openssl::cipher::CipherRef) -> CryptographyResult<Self> {
let ctx = cryptography_openssl::cmac::Cmac::new(key, cipher)?;
Ok(Cmac { ctx: Some(ctx) })
}

fn update_bytes(&mut self, data: &[u8]) -> CryptographyResult<()> {
self.get_mut_ctx()?.update(data)?;
Ok(())
}

fn finalize_bytes(&mut self) -> CryptographyResult<cryptography_openssl::hmac::DigestBytes> {
let data = self.get_mut_ctx()?.finish()?;
self.ctx = None;
Ok(data)
}

fn get_ctx(&self) -> CryptographyResult<&cryptography_openssl::cmac::Cmac> {
if let Some(ctx) = self.ctx.as_ref() {
return Ok(ctx);
};
}
Err(exceptions::already_finalized_error())
}

Expand Down Expand Up @@ -64,33 +80,29 @@ impl Cmac {
let key = algorithm
.getattr(pyo3::intern!(py, "key"))?
.extract::<CffiBuf<'_>>()?;
let ctx = cryptography_openssl::cmac::Cmac::new(key.as_bytes(), cipher)?;
Ok(Cmac { ctx: Some(ctx) })

Cmac::new_bytes(key.as_bytes(), cipher)
}

fn update(&mut self, data: CffiBuf<'_>) -> CryptographyResult<()> {
self.get_mut_ctx()?.update(data.as_bytes())?;
Ok(())
self.update_bytes(data.as_bytes())
}

fn finalize<'p>(
&mut self,
py: pyo3::Python<'p>,
) -> CryptographyResult<pyo3::Bound<'p, pyo3::types::PyBytes>> {
let data = self.get_mut_ctx()?.finish()?;
self.ctx = None;
let data = self.finalize_bytes()?;
Ok(pyo3::types::PyBytes::new(py, &data))
}

fn verify(&mut self, py: pyo3::Python<'_>, signature: &[u8]) -> CryptographyResult<()> {
let actual = self.finalize(py)?;
let actual = actual.as_bytes();
if !constant_time::bytes_eq(actual, signature) {
fn verify(&mut self, _py: pyo3::Python<'_>, signature: &[u8]) -> CryptographyResult<()> {
let actual = self.finalize_bytes()?;
if !constant_time::bytes_eq(&actual, signature) {
return Err(CryptographyError::from(
exceptions::InvalidSignature::new_err("Signature did not match digest."),
));
}

Ok(())
}

Expand Down
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