Migrate PKCS7 backend to Rust (#10228)

* Migrate PKCS7 backend to Rust

* Disable PKCS7 functions under BoringSSL

* Misc PKCS7 fixes

Author: facutuesca

src/cryptography/hazmat/backends/openssl/backend.py

@@ -10,7 +10,7 @@
 import typing
 
 from cryptography import utils, x509
-from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
+from cryptography.exceptions import UnsupportedAlgorithm
 from cryptography.hazmat.backends.openssl import aead
 from cryptography.hazmat.backends.openssl.ciphers import _CipherContext
 from cryptography.hazmat.bindings._rust import openssl as rust_openssl
@@ -863,61 +863,6 @@ def poly1305_supported(self) -> bool:
     def pkcs7_supported(self) -> bool:
         return not self._lib.CRYPTOGRAPHY_IS_BORINGSSL
 
-    def load_pem_pkcs7_certificates(
-        self, data: bytes
-    ) -> list[x509.Certificate]:
-        utils._check_bytes("data", data)
-        bio = self._bytes_to_bio(data)
-        p7 = self._lib.PEM_read_bio_PKCS7(
-            bio.bio, self._ffi.NULL, self._ffi.NULL, self._ffi.NULL
-        )
-        if p7 == self._ffi.NULL:
-            self._consume_errors()
-            raise ValueError("Unable to parse PKCS7 data")
-
-        p7 = self._ffi.gc(p7, self._lib.PKCS7_free)
-        return self._load_pkcs7_certificates(p7)
-
-    def load_der_pkcs7_certificates(
-        self, data: bytes
-    ) -> list[x509.Certificate]:
-        utils._check_bytes("data", data)
-        bio = self._bytes_to_bio(data)
-        p7 = self._lib.d2i_PKCS7_bio(bio.bio, self._ffi.NULL)
-        if p7 == self._ffi.NULL:
-            self._consume_errors()
-            raise ValueError("Unable to parse PKCS7 data")
-
-        p7 = self._ffi.gc(p7, self._lib.PKCS7_free)
-        return self._load_pkcs7_certificates(p7)
-
-    def _load_pkcs7_certificates(self, p7) -> list[x509.Certificate]:
-        nid = self._lib.OBJ_obj2nid(p7.type)
-        self.openssl_assert(nid != self._lib.NID_undef)
-        if nid != self._lib.NID_pkcs7_signed:
-            raise UnsupportedAlgorithm(
-                "Only basic signed structures are currently supported. NID"
-                f" for this data was {nid}",
-                _Reasons.UNSUPPORTED_SERIALIZATION,
-            )
-
-        if p7.d.sign == self._ffi.NULL:
-            raise ValueError(
-                "The provided PKCS7 has no certificate data, but a cert "
-                "loading method was called."
-            )
-
-        sk_x509 = p7.d.sign.cert
-        num = self._lib.sk_X509_num(sk_x509)
-        certs: list[x509.Certificate] = []
-        for i in range(num):
-            x509 = self._lib.sk_X509_value(sk_x509, i)
-            self.openssl_assert(x509 != self._ffi.NULL)
-            cert = self._ossl2cert(x509)
-            certs.append(cert)
-
-        return certs
-
 
 class GetCipherByName:
     def __init__(self, fmt: str):

src/cryptography/hazmat/bindings/_rust/pkcs7.pyi

@@ -13,3 +13,9 @@ def sign_and_serialize(
     encoding: serialization.Encoding,
     options: typing.Iterable[pkcs7.PKCS7Options],
 ) -> bytes: ...
+def load_pem_pkcs7_certificates(
+    data: bytes,
+) -> list[x509.Certificate]: ...
+def load_der_pkcs7_certificates(
+    data: bytes,
+) -> list[x509.Certificate]: ...

src/cryptography/hazmat/primitives/serialization/pkcs7.py

@@ -17,22 +17,12 @@
 from cryptography.hazmat.primitives.asymmetric import ec, padding, rsa
 from cryptography.utils import _check_byteslike
 
+load_pem_pkcs7_certificates = rust_pkcs7.load_pem_pkcs7_certificates
 
-def load_pem_pkcs7_certificates(data: bytes) -> list[x509.Certificate]:
-    from cryptography.hazmat.backends.openssl.backend import backend
-
-    return backend.load_pem_pkcs7_certificates(data)
-
-
-def load_der_pkcs7_certificates(data: bytes) -> list[x509.Certificate]:
-    from cryptography.hazmat.backends.openssl.backend import backend
-
-    return backend.load_der_pkcs7_certificates(data)
-
+load_der_pkcs7_certificates = rust_pkcs7.load_der_pkcs7_certificates
 
 serialize_certificates = rust_pkcs7.serialize_certificates
 
-
 PKCS7HashTypes = typing.Union[
     hashes.SHA224,
     hashes.SHA256,

src/rust/cryptography-openssl/Cargo.toml

@@ -9,6 +9,6 @@ rust-version = "1.63.0"
 
 [dependencies]
 openssl = "0.10.63"
-ffi = { package = "openssl-sys", version = "0.9.91" }
+ffi = { package = "openssl-sys", version = "0.9.99" }
 foreign-types = "0.3"
 foreign-types-shared = "0.1"

src/rust/src/pkcs7.rs

@@ -9,11 +9,17 @@ use std::ops::Deref;
 use cryptography_x509::csr::Attribute;
 use cryptography_x509::{common, oid, pkcs7};
 use once_cell::sync::Lazy;
+#[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))]
+use openssl::pkcs7::Pkcs7;
+#[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))]
+use pyo3::IntoPy;
 
 use crate::asn1::encode_der_data;
 use crate::buf::CffiBuf;
-use crate::error::CryptographyResult;
-use crate::{types, x509};
+use crate::error::{CryptographyError, CryptographyResult};
+#[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))]
+use crate::x509::certificate::load_der_x509_certificate;
+use crate::{exceptions, types, x509};
 
 const PKCS7_CONTENT_TYPE_OID: asn1::ObjectIdentifier = asn1::oid!(1, 2, 840, 113549, 1, 9, 3);
 const PKCS7_MESSAGE_DIGEST_OID: asn1::ObjectIdentifier = asn1::oid!(1, 2, 840, 113549, 1, 9, 4);
@@ -290,11 +296,96 @@ fn smime_canonicalize(data: &[u8], text_mode: bool) -> (Cow<'_, [u8]>, Cow<'_, [
     }
 }
 
+#[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))]
+fn load_pkcs7_certificates(
+    py: pyo3::Python<'_>,
+    pkcs7: Pkcs7,
+) -> CryptographyResult<&pyo3::types::PyList> {
+    let nid = pkcs7.type_().map(|t| t.nid());
+    if nid != Some(openssl::nid::Nid::PKCS7_SIGNED) {
+        let nid_string = nid.map_or("empty".to_string(), |n| n.as_raw().to_string());
+        return Err(CryptographyError::from(
+            exceptions::UnsupportedAlgorithm::new_err((
+                format!("Only basic signed structures are currently supported. NID for this data was {}", nid_string),
+                exceptions::Reasons::UNSUPPORTED_SERIALIZATION,
+            )),
+        ));
+    }
+
+    let signed_certificates = pkcs7.signed().and_then(|x| x.certificates());
+    match signed_certificates {
+        None => Err(CryptographyError::from(
+            pyo3::exceptions::PyValueError::new_err(
+                "The provided PKCS7 has no certificate data, but a cert loading method was called.",
+            ),
+        )),
+        Some(certificates) => {
+            let result = pyo3::types::PyList::empty(py);
+            for c in certificates {
+                let cert_der = pyo3::types::PyBytes::new(py, c.to_der()?.as_slice()).into_py(py);
+                let cert = load_der_x509_certificate(py, cert_der, None)?;
+                result.append(cert.into_py(py))?;
+            }
+            Ok(result)
+        }
+    }
+}
+
+#[pyo3::prelude::pyfunction]
+fn load_pem_pkcs7_certificates<'p>(
+    py: pyo3::Python<'p>,
+    data: &[u8],
+) -> CryptographyResult<&'p pyo3::types::PyList> {
+    cfg_if::cfg_if! {
+        if #[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))] {
+            let pkcs7_decoded = openssl::pkcs7::Pkcs7::from_pem(data).map_err(|_| {
+                CryptographyError::from(pyo3::exceptions::PyValueError::new_err(
+                    "Unable to parse PKCS7 data",
+                ))
+            })?;
+            load_pkcs7_certificates(py, pkcs7_decoded)
+        } else {
+            return Err(CryptographyError::from(
+                exceptions::UnsupportedAlgorithm::new_err((
+                    "PKCS#7 is not supported by this backend.",
+                    exceptions::Reasons::UNSUPPORTED_SERIALIZATION,
+                )),
+            ));
+        }
+    }
+}
+
+#[pyo3::prelude::pyfunction]
+fn load_der_pkcs7_certificates<'p>(
+    py: pyo3::Python<'p>,
+    data: &[u8],
+) -> CryptographyResult<&'p pyo3::types::PyList> {
+    cfg_if::cfg_if! {
+        if #[cfg(not(CRYPTOGRAPHY_IS_BORINGSSL))] {
+            let pkcs7_decoded = openssl::pkcs7::Pkcs7::from_der(data).map_err(|_| {
+                CryptographyError::from(pyo3::exceptions::PyValueError::new_err(
+                    "Unable to parse PKCS7 data",
+                ))
+            })?;
+            load_pkcs7_certificates(py, pkcs7_decoded)
+        } else {
+            return Err(CryptographyError::from(
+                exceptions::UnsupportedAlgorithm::new_err((
+                    "PKCS#7 is not supported by this backend.",
+                    exceptions::Reasons::UNSUPPORTED_SERIALIZATION,
+                )),
+            ));
+        }
+    }
+}
+
 pub(crate) fn create_submodule(py: pyo3::Python<'_>) -> pyo3::PyResult<&pyo3::prelude::PyModule> {
     let submod = pyo3::prelude::PyModule::new(py, "pkcs7")?;
 
     submod.add_function(pyo3::wrap_pyfunction!(serialize_certificates, submod)?)?;
     submod.add_function(pyo3::wrap_pyfunction!(sign_and_serialize, submod)?)?;
+    submod.add_function(pyo3::wrap_pyfunction!(load_pem_pkcs7_certificates, submod)?)?;
+    submod.add_function(pyo3::wrap_pyfunction!(load_der_pkcs7_certificates, submod)?)?;
 
     Ok(submod)
 }

src/rust/src/x509/certificate.rs

@@ -378,7 +378,7 @@ fn load_pem_x509_certificates(
 }
 
 #[pyo3::prelude::pyfunction]
-fn load_der_x509_certificate(
+pub(crate) fn load_der_x509_certificate(
     py: pyo3::Python<'_>,
     data: pyo3::Py<pyo3::types::PyBytes>,
     backend: Option<&pyo3::PyAny>,

tests/hazmat/primitives/test_pkcs7.py

@@ -922,3 +922,16 @@ def test_invalid_types(self):
                 certs,
                 "not an encoding",  # type: ignore[arg-type]
             )
+
+
+@pytest.mark.supported(
+    only_if=lambda backend: not backend.pkcs7_supported(),
+    skip_message="Requires OpenSSL without PKCS7 support (BoringSSL)",
+)
+class TestPKCS7Unsupported:
+    def test_pkcs7_functions_unsupported(self):
+        with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_SERIALIZATION):
+            pkcs7.load_der_pkcs7_certificates(b"nonsense")
+
+        with raises_unsupported_algorithm(_Reasons.UNSUPPORTED_SERIALIZATION):
+            pkcs7.load_pem_pkcs7_certificates(b"nonsense")