crypto/x509: remove leftover CertificateRequest field

Removes the KeyUsage field that was missed in the rollback in
CL 281235.
Also updates CreateCertificateRequest to reflect that these fields
were removed.

For #43407.
Updates #43477.
Updates #37172.

Change-Id: I6244aed4a3ef3c2460c38af5511e5c2e82546179
Reviewed-on: https://go-review.googlesource.com/c/go/+/287392
Trust: Alexander Rakoczy <alex@golang.org>
Trust: Roland Shoemaker <roland@golang.org>
Trust: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Alexander Rakoczy <alex@golang.org>
Reviewed-by: Alexander Rakoczy <alex@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

src/crypto/x509/x509.go

@@ -1997,15 +1997,6 @@ func buildCSRExtensions(template *CertificateRequest) ([]pkix.Extension, error)
 		})
 	}
 
-	if template.KeyUsage != 0 &&
-		!oidInExtensions(oidExtensionKeyUsage, template.ExtraExtensions) {
-		ext, err := marshalKeyUsage(template.KeyUsage)
-		if err != nil {
-			return nil, err
-		}
-		ret = append(ret, ext)
-	}
-
 	return append(ret, template.ExtraExtensions...), nil
 }
 
@@ -2371,7 +2362,6 @@ type CertificateRequest struct {
 	Version            int
 	Signature          []byte
 	SignatureAlgorithm SignatureAlgorithm
-	KeyUsage           KeyUsage
 
 	PublicKeyAlgorithm PublicKeyAlgorithm
 	PublicKey          interface{}
@@ -2501,15 +2491,6 @@ func parseCSRExtensions(rawAttributes []asn1.RawValue) ([]pkix.Extension, error)
 //  - EmailAddresses
 //  - IPAddresses
 //  - URIs
-//  - KeyUsage
-//  - ExtKeyUsage
-//  - UnknownExtKeyUsage
-//  - BasicConstraintsValid
-//  - IsCA
-//  - MaxPathLen
-//  - MaxPathLenZero
-//  - SubjectKeyId
-//  - PolicyIdentifiers
 //  - ExtraExtensions
 //  - Attributes (deprecated)
 //
@@ -2734,11 +2715,6 @@ func parseCertificateRequest(in *certificateRequest) (*CertificateRequest, error
 			if err != nil {
 				return nil, err
 			}
-		case extension.Id.Equal(oidExtensionKeyUsage):
-			out.KeyUsage, err = parseKeyUsageExtension(extension.Value)
-			if err != nil {
-				return nil, err
-			}
 		}
 	}
 

src/crypto/x509/x509_test.go

@@ -2977,7 +2977,6 @@ func TestCertificateRequestRoundtripFields(t *testing.T) {
 		EmailAddresses: []string{"a@example.com", "b@example.com"},
 		IPAddresses:    []net.IP{net.IPv4(192, 0, 2, 0), net.IPv6loopback},
 		URIs:           []*url.URL{urlA, urlB},
-		KeyUsage:       KeyUsageCertSign,
 	}
 	out := marshalAndParseCSR(t, in)
 
@@ -2995,7 +2994,4 @@ func TestCertificateRequestRoundtripFields(t *testing.T) {
 	if !reflect.DeepEqual(in.URIs, out.URIs) {
 		t.Fatalf("Unexpected URIs: got %v, want %v", out.URIs, in.URIs)
 	}
-	if in.KeyUsage != out.KeyUsage {
-		t.Fatalf("Unexpected KeyUsage: got %v, want %v", out.KeyUsage, in.KeyUsage)
-	}
 }