csr: support reading key usage from CSR

src/csr.rs

@@ -1,7 +1,7 @@
 #[cfg(feature = "x509-parser")]
 use crate::{
 	BasicConstraints, CustomExtension, DistinguishedName, ExtendedKeyUsagePurpose, GeneralSubtree,
-	IsCa, NameConstraints, SanType,
+	IsCa, KeyUsagePurpose, NameConstraints, SanType,
 };
 #[cfg(feature = "pem")]
 use pem::Pem;
@@ -117,6 +117,41 @@ impl CertificateSigningRequest {
 						};
 						true
 					},
+					x509_parser::extensions::ParsedExtension::KeyUsage(ku) => {
+						let mut usages = Vec::default();
+						if ku.digital_signature() {
+							usages.push(KeyUsagePurpose::DigitalSignature);
+						}
+						// NOTE: x509-parser uses the older "non repudiation" name.
+						//     5280 says "recent editions of X.509 have renamed this bit to
+						//     contentCommitment"
+						if ku.non_repudiation() {
+							usages.push(KeyUsagePurpose::ContentCommitment)
+						}
+						if ku.key_encipherment() {
+							usages.push(KeyUsagePurpose::KeyEncipherment)
+						}
+						if ku.data_encipherment() {
+							usages.push(KeyUsagePurpose::DataEncipherment)
+						}
+						if ku.key_agreement() {
+							usages.push(KeyUsagePurpose::KeyAgreement)
+						}
+						if ku.key_cert_sign() {
+							usages.push(KeyUsagePurpose::KeyCertSign)
+						}
+						if ku.crl_sign() {
+							usages.push(KeyUsagePurpose::CrlSign)
+						}
+						if ku.encipher_only() {
+							usages.push(KeyUsagePurpose::EncipherOnly)
+						}
+						if ku.decipher_only() {
+							usages.push(KeyUsagePurpose::DecipherOnly)
+						}
+						params.key_usages = usages;
+						true
+					},
 					x509_parser::extensions::ParsedExtension::ExtendedKeyUsage(eku) => {
 						let mut usages = Vec::default();
 						if eku.any {