csr: use specific error for CSR signature verification failure

Author: djc

rcgen/src/csr.rs

@@ -105,7 +105,8 @@ impl CertificateSigningRequestParams {
 		let csr = x509_parser::certification_request::X509CertificationRequest::from_der(csr)
 			.map_err(|_| Error::CouldNotParseCertificationRequest)?
 			.1;
-		csr.verify_signature().map_err(|_| Error::RingUnspecified)?;
+		csr.verify_signature()
+			.map_err(|_| Error::InvalidRequestSignature)?;
 		let alg_oid = csr
 			.signature_algorithm
 			.algorithm

rcgen/src/error.rs

@@ -10,6 +10,9 @@ pub enum Error {
 	CouldNotParseCertificationRequest,
 	/// The given key pair couldn't be parsed
 	CouldNotParseKeyPair,
+	/// The CSR signature is invalid
+	#[cfg(feature = "x509-parser")]
+	InvalidRequestSignature,
 	#[cfg(feature = "x509-parser")]
 	/// Invalid subject alternative name type
 	InvalidNameType,
@@ -62,6 +65,8 @@ impl fmt::Display for Error {
 			)?,
 			CouldNotParseKeyPair => write!(f, "Could not parse key pair")?,
 			#[cfg(feature = "x509-parser")]
+			InvalidRequestSignature => write!(f, "Invalid CSR signature")?,
+			#[cfg(feature = "x509-parser")]
 			InvalidNameType => write!(f, "Invalid subject alternative name type")?,
 			InvalidAsn1String(e) => write!(f, "{e}")?,
 			InvalidIpAddressOctetLength(actual) => {