Add Python Attribute Accessors and Cross-Library Compatibility for PkEncryption #15

TrevisGordan · 2024-12-10T14:35:44Z

This PR adds missing Python attribute accessors and improves compatibility with python-olm by enabling cross-library encryption and decryption tests.

Details:

Adds #[pyo3(get)] annotations to the Message struct fields (ciphertext, mac, ephemeral_key), making these attributes accessible from Python.
Implements a Message constructor in Rust (via #[new]), allowing Python code to create Message instances directly.
Introduces tests to verify that attribute access works as intended.
Adds integration tests to ensure PkEncryption is compatible with python-olm. Specifically:
- Encrypt with Olm and decrypt with Vodozemac.
- Encrypt with Vodozemac and decrypt with Olm.

Next Steps:

To achieve seamless compatibility, the user will need to Base64-encode Vodozemac message attributes (ciphertext, mac, ephemeral_key) before passing them to Olm. For example:

vodo_encryption = PkEncryption.from_key(public_key)
vodo_message = vodo_encryption.encrypt(PLAINTEXT).encode())

vodo_mac = base64.b64encode(vodo_message.mac).decode('ascii')
vodo_ciphertext = base64.b64encode(vodo_message.ciphertext).decode('ascii')
vodo_ephemeral_key = base64.b64encode(vodo_message.ephemeral_key).decode('ascii')

A future enhancement could add a Rust helper function to handle this encoding automatically, such as:

(ciphertext, mac, ephemeral_key) = encryption.encrypt(json.dumps(media_body).encode()).to_base64()

Also unpad_base64_encode and pad_base64_decode functions.
This would streamline the process and reduce the amount of Python-side encoding logic required.

Adds python-olm Dependencie (at 3.2.16). Adds PkEncryption (python-olm) compatibility tests.

poljar

Thanks for writing this and sorry for the delay here. I left some small nits.

poljar · 2025-01-08T14:40:35Z

requirements-dev.txt

@@ -1,2 +1,3 @@
 maturin
 pytest>=4.0
+python-olm==3.2.16


Missing newline.

poljar · 2025-01-08T14:40:51Z

src/pk_encryption.rs

    ephemeral_key: Vec<u8>,
 }

+#[pymethods]
+impl Message {
+    #[new]


Please add some documentation for this method.

poljar · 2025-01-08T14:43:44Z

tests/pk_encryption_test.py

+        olm_msg = olm_encrypts.encrypt(CLEARTEXT)
+
+        # Convert the Olm message into a Vodo message structure.
+        def pad_base64_decode(b64_str: str) -> bytes:


I'm fine with adding another constructor to the Message type, i.e. Message.from_base64(ciphertext, mac, key).

The same applies to the other direction: ciphertext, mac, key = message.to_base64().

Yes..., I’ve put this off for now and separated it out in issue #16. My Rust knowledge is currently quite limited, and Vec didn’t work out for me—especially given that the legacy olm.pk.PkEncryption uses a rather creative base64 encoding implementation.

But if you have a direction / idea, I'm happy to continue that part later on!

Ah right, I remember this now. Doesn't https://docs.rs/vodozemac/latest/vodozemac/fn.base64_decode.html just work? As far as I know libolm just uses unpadded base64.

Ah, that’s the missing piece! I wasn’t aware of that function—thank you. Yes, for some (undocumented) reason it does behave that way; I initially only discovered it through trial and error.

With the compatible base64_decode/base64_encode functions, everything works perfectly now. I was able to implement a from_base64class method and a to_base64 method directly. Please take a look. I also removed that hacky b64 padding helper from the tests. Please double-check if everything is solid.

vodozemac-python/src/pk_encryption.rs

Lines 51 to 97 in 81fa809

/// Create a new Message object from unpadded Base64-encoded components.

///

/// This function decodes the given Base64 strings and returns a `Message`

/// with the resulting byte vectors.

///

/// # Arguments

/// * `ciphertext` - Unpadded Base64-encoded ciphertext

/// * `mac` - Unpadded Base64-encoded message authentication code

/// * `ephemeral_key` - Unpadded Base64-encoded ephemeral key

#[classmethod]

fn from_base64(

_cls: &Bound<'_, PyType>,

ciphertext: &str,

mac: &str,

ephemeral_key: &str,

) -> Self {

let decoded_ciphertext =

vodozemac::base64_decode(ciphertext).expect("Failed to decode ciphertext");

let decoded_mac = vodozemac::base64_decode(mac).expect("Failed to decode mac");

let decoded_ephemeral_key =

vodozemac::base64_decode(ephemeral_key).expect("Failed to decode ephemeral_key");

Self {

ciphertext: decoded_ciphertext,

mac: decoded_mac,

ephemeral_key: decoded_ephemeral_key,

}

}

/// Convert the message components to unpadded Base64-encoded strings.

///

/// Returns a tuple of (ciphertext, mac, ephemeral_key) as unpadded Base64 strings.

fn to_base64<'py>(

&self,

py: Python<'py>,

) -> PyResult<(Bound<'py, PyString>, Bound<'py, PyString>, Bound<'py, PyString>)> {

let ciphertext_b64 = vodozemac::base64_encode(&self.ciphertext);

let mac_b64 = vodozemac::base64_encode(&self.mac);

let ephemeral_key_b64 = vodozemac::base64_encode(&self.ephemeral_key);

Ok((

ephemeral_key_b64.into_pyobject(py)?,

mac_b64.into_pyobject(py)?,

ciphertext_b64.into_pyobject(py)?,

))

}

}

Adds a to_base64 conversion message method.

Removes base64 padding conversion helper functions from tests.

poljar

Some two minor things left to do, then I think we can merge.

poljar · 2025-01-10T11:48:22Z

src/pk_encryption.rs

+        ephemeral_key: &str,
+    ) -> Self {
+        let decoded_ciphertext =
+            vodozemac::base64_decode(ciphertext).expect("Failed to decode ciphertext");


Oh no, we can't just expect() here. We should return a proper error. In other words this method needs to return a Result<Self, SomeError> type.

You can probably just extend the PK error type like such:

diff --git a/src/error.rs b/src/error.rs index c91c256..b26716e 100644 --- a/src/error.rs +++ b/src/error.rs @@ -136,6 +136,8 @@ pub enum PkEncryptionError { InvalidKeySize(usize), #[error(transparent)] Decode(#[from] vodozemac::pk_encryption::Error), + #[error(transparent)] + Mac(#[from] vodozemac::Base64DecodeError), } pyo3::create_exception!(module, PkInvalidKeySizeException, pyo3::exceptions::PyValueError); @@ -148,6 +150,7 @@ impl From<PkEncryptionError> for PyErr { PkInvalidKeySizeException::new_err(e.to_string()) } PkEncryptionError::Decode(_) => PkDecodeException::new_err(e.to_string()), + PkEncryptionError::Mac(_) => PkDecodeException::new_err(e.to_string()), } } }

poljar · 2025-01-10T11:52:59Z

src/pk_encryption.rs

+    /// Convert the message components to unpadded Base64-encoded strings.
+    ///
+    /// Returns a tuple of (ciphertext, mac, ephemeral_key) as unpadded Base64 strings.
+    fn to_base64<'py>(


Doesn't this work just as well?

fn to_base64(&self) -> PyResult<(String, String, String)> { let ciphertext_b64 = vodozemac::base64_encode(&self.ciphertext); let mac_b64 = vodozemac::base64_encode(&self.mac); let ephemeral_key_b64 = vodozemac::base64_encode(&self.ephemeral_key); Ok((ephemeral_key_b64, mac_b64, ciphertext_b64)) }

TrevisGordan added 2 commits December 10, 2024 15:01

Adds missing rust message attribute accessibility and test

2ee3052

Adds Message impl (pymethods) to enable object creation from python.

2f309c5

Adds python-olm Dependencie (at 3.2.16). Adds PkEncryption (python-olm) compatibility tests.

TrevisGordan mentioned this pull request Dec 10, 2024

Add Base64 Helper Functions for Vodozemac-Olm Interoperability #16

Open

cargo fmt

beee99f

poljar requested changes Jan 8, 2025

View reviewed changes

TrevisGordan added 4 commits January 9, 2025 11:28

Adds missing newline.

461673f

Adds Missing Message Object Documentation

6ab4c28

Adds a from_base64 message classmethod.

9258ede

Adds a to_base64 conversion message method.

Adds from_base64 and to_base64 message functions to test.

81fa809

Removes base64 padding conversion helper functions from tests.

poljar requested changes Jan 10, 2025

View reviewed changes

re cargo fmt

de4d64b

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Add Python Attribute Accessors and Cross-Library Compatibility for PkEncryption #15

Add Python Attribute Accessors and Cross-Library Compatibility for PkEncryption #15

TrevisGordan commented Dec 10, 2024

poljar left a comment

poljar Jan 8, 2025

poljar Jan 8, 2025

poljar Jan 8, 2025

TrevisGordan Jan 8, 2025

poljar Jan 8, 2025

TrevisGordan Jan 9, 2025

poljar left a comment

poljar Jan 10, 2025

poljar Jan 10, 2025

	/// Create a new Message object from unpadded Base64-encoded components.
	///
	/// This function decodes the given Base64 strings and returns a `Message`
	/// with the resulting byte vectors.
	///
	/// # Arguments
	/// * `ciphertext` - Unpadded Base64-encoded ciphertext
	/// * `mac` - Unpadded Base64-encoded message authentication code
	/// * `ephemeral_key` - Unpadded Base64-encoded ephemeral key
	#[classmethod]
	fn from_base64(
	_cls: &Bound<'_, PyType>,
	ciphertext: &str,
	mac: &str,
	ephemeral_key: &str,
	) -> Self {
	let decoded_ciphertext =
	vodozemac::base64_decode(ciphertext).expect("Failed to decode ciphertext");
	let decoded_mac = vodozemac::base64_decode(mac).expect("Failed to decode mac");
	let decoded_ephemeral_key =
	vodozemac::base64_decode(ephemeral_key).expect("Failed to decode ephemeral_key");

	Self {
	ciphertext: decoded_ciphertext,
	mac: decoded_mac,
	ephemeral_key: decoded_ephemeral_key,
	}
	}

	/// Convert the message components to unpadded Base64-encoded strings.
	///
	/// Returns a tuple of (ciphertext, mac, ephemeral_key) as unpadded Base64 strings.
	fn to_base64<'py>(
	&self,
	py: Python<'py>,
	) -> PyResult<(Bound<'py, PyString>, Bound<'py, PyString>, Bound<'py, PyString>)> {
	let ciphertext_b64 = vodozemac::base64_encode(&self.ciphertext);
	let mac_b64 = vodozemac::base64_encode(&self.mac);
	let ephemeral_key_b64 = vodozemac::base64_encode(&self.ephemeral_key);

	Ok((
	ephemeral_key_b64.into_pyobject(py)?,
	mac_b64.into_pyobject(py)?,
	ciphertext_b64.into_pyobject(py)?,
	))
	}
	}

Add Python Attribute Accessors and Cross-Library Compatibility for PkEncryption #15

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TrevisGordan commented Dec 10, 2024

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