Add from_{der,pem}_custom_validator methods

* Allow user to parse otherwise unsupported extensions.
* Retain the custom extensions when parsing.
* Update to latest branch commit
* Ran rustfmt
* Fix clippy
* Add UnsupportedExtension wrapper type

Author: jean-airoldie

rcgen/Cargo.toml

@@ -28,7 +28,8 @@ ring = { workspace = true, optional = true }
 pem = { workspace = true, optional = true }
 pki-types = { workspace = true }
 time = { version = "0.3.6", default-features = false }
-x509-parser = { workspace = true, features = ["verify"], optional = true }
+#x509-parser = { workspace = true, features = ["verify"], optional = true }
+x509-parser = { features = ["verify"], optional = true, git = "https://github.com/jean-airoldie/x509-parser", branch = "custom-extension" }
 zeroize = { version = "1.2", optional = true }
 
 [features]
@@ -51,7 +52,7 @@ allowed_external_types = [
 [dev-dependencies]
 openssl = "0.10"
 pki-types = { package = "rustls-pki-types", version = "1" }
-x509-parser = { workspace = true, features = ["verify"] }
+x509-parser = { features = ["verify"], git = "https://github.com/jean-airoldie/x509-parser", branch = "custom-extension" }
 rustls-webpki = { version = "0.103", features = ["ring", "std"] }
 botan = { version = "0.11", features = ["vendored"] }
 ring = { workspace = true }

rcgen/src/csr.rs

@@ -10,7 +10,7 @@ use crate::{
 	Certificate, CertificateParams, Error, Issuer, PublicKeyData, SignatureAlgorithm, SigningKey,
 };
 #[cfg(feature = "x509-parser")]
-use crate::{DistinguishedName, SanType};
+use crate::{CustomExtension, DistinguishedName, SanType};
 
 /// A public key, extracted from a CSR
 #[derive(Debug, PartialEq, Eq, Hash)]
@@ -65,6 +65,18 @@ impl From<CertificateSigningRequest> for CertificateSigningRequestDer<'static> {
 	}
 }
 
+/// A unsupported extension.
+#[derive(Debug, Clone, Eq, PartialEq)]
+#[cfg(feature = "x509-parser")]
+pub struct UnsupportedExtension<'a> {
+	/// The Object ID of the extension.
+	pub oid: Vec<u64>,
+	/// The unparsed value.
+	pub value: &'a [u8],
+	/// Whether the extension is critical.
+	pub critical: bool,
+}
+
 /// Parameters for a certificate signing request
 #[derive(Debug)]
 pub struct CertificateSigningRequestParams {
@@ -84,6 +96,23 @@ impl CertificateSigningRequestParams {
 		Self::from_der(&csr.contents().into())
 	}
 
+	/// Parse a certificate signing request from the ASCII PEM format
+	/// using the provided validator function to handle unknown extension
+	/// types.
+	///
+	/// The validator function must return an error if the attribute OID or value
+	/// is incorrect.
+	///
+	/// See [`from_der`](Self::from_der) for more details.
+	#[cfg(all(feature = "pem", feature = "x509-parser"))]
+	pub fn from_pem_custom_validator<F>(pem_str: &str, valid_fn: F) -> Result<Self, Error>
+	where
+		F: FnMut(&UnsupportedExtension<'_>) -> Result<(), Error>,
+	{
+		let csr = pem::parse(pem_str).or(Err(Error::CouldNotParseCertificationRequest))?;
+		Self::from_der_custom_validator(&csr.contents().into(), valid_fn)
+	}
+
 	/// Parse a certificate signing request from DER-encoded bytes
 	///
 	/// Currently, this only supports the `Subject Alternative Name` extension.
@@ -96,6 +125,24 @@ impl CertificateSigningRequestParams {
 	/// [`rustls_pemfile::csr()`]: https://docs.rs/rustls-pemfile/latest/rustls_pemfile/fn.csr.html
 	#[cfg(feature = "x509-parser")]
 	pub fn from_der(csr: &CertificateSigningRequestDer<'_>) -> Result<Self, Error> {
+		Self::from_der_custom_validator(csr, |_| Ok(()))
+	}
+
+	/// Parse a certificate signing request from DER-encoded bytes using the provided
+	/// validator function to handle unknown extension types.
+	///
+	/// The validator function must return an error if the attribute OID or value
+	/// is incorrect.
+	///
+	/// See [`from_der`](Self::from_der) for more details.
+	#[cfg(feature = "x509-parser")]
+	pub fn from_der_custom_validator<F>(
+		csr: &CertificateSigningRequestDer<'_>,
+		mut valid_fn: F,
+	) -> Result<Self, Error>
+	where
+		F: FnMut(&UnsupportedExtension<'_>) -> Result<(), Error>,
+	{
 		use crate::KeyUsagePurpose;
 		use x509_parser::prelude::FromDer;
 
@@ -171,7 +218,25 @@ impl CertificateSigningRequestParams {
 							return Err(Error::UnsupportedExtension);
 						}
 					},
-					_ => return Err(Error::UnsupportedExtension),
+					x509_parser::extensions::ParsedExtension::UnsupportedExtension(val) => {
+						let oid: Vec<u64> = match val.oid.iter() {
+							Some(iter) => iter.collect(),
+							None => return Err(Error::UnsupportedExtension),
+						};
+						let ext = UnsupportedExtension {
+							oid,
+							value: val.value,
+							critical: val.critical,
+						};
+						valid_fn(&ext)?;
+						let mut ext =
+							CustomExtension::from_oid_content(&ext.oid, val.value.to_vec());
+						ext.set_criticality(val.critical);
+						params.custom_extensions.push(ext);
+					},
+					_ => {
+						return Err(Error::UnsupportedExtension);
+					},
 				}
 			}
 		}

rcgen/tests/generic.rs

@@ -80,13 +80,11 @@ mod test_x509_custom_ext {
 	fn custom_ext() {
 		// Create an imaginary critical custom extension for testing.
 		let test_oid = asn1_rs::Oid::from(&[2, 5, 29, 999999]).unwrap();
+		let oid_vec = test_oid.iter().unwrap().collect::<Vec<u64>>();
 		let test_ext = yasna::construct_der(|writer| {
 			writer.write_utf8_string("🦀 greetz to ferris 🦀");
 		});
-		let mut custom_ext = CustomExtension::from_oid_content(
-			test_oid.iter().unwrap().collect::<Vec<u64>>().as_slice(),
-			test_ext.clone(),
-		);
+		let mut custom_ext = CustomExtension::from_oid_content(&oid_vec, test_ext.clone());
 		custom_ext.set_criticality(true);
 
 		// Generate a certificate with the custom extension, parse it with x509-parser.
@@ -132,6 +130,20 @@ mod test_x509_custom_ext {
 			.expect("missing requested custom extension");
 		assert!(custom_ext.critical);
 		assert_eq!(custom_ext.value, test_ext);
+
+		let csr_params = rcgen::CertificateSigningRequestParams::from_der_custom_validator(
+			test_cert_csr.der(),
+			|ext| {
+				if &ext.oid != &oid_vec || ext.value != test_ext || !ext.critical {
+					Err(rcgen::Error::UnsupportedExtension)
+				} else {
+					Ok(())
+				}
+			},
+		)
+		.unwrap();
+
+		assert_eq!(csr_params.params, params);
 	}
 }