all: clean up minor issues found by staticcheck

Use bytes.Equal instead of comparing bytes.Compare results to zero,
avoid Yoda conditions, drop a redundant zero slice capacity, use
strings.ReplaceAll, build acme error strings with a strings.Builder,
and lowercase an error string in ocsp. No behavior changes.

Change-Id: I5d2b3fa5c241adc75e61be0f2d2d7af1eb9e8d66
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/803200
Reviewed-by: Roland Shoemaker <roland@golang.org>
Auto-Submit: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

acme/acme_test.go

@@ -734,7 +734,7 @@ func TestTLSALPN01ChallengeCert(t *testing.T) {
 	if !acmeExts[0].Critical {
 		t.Errorf("acmeExt.Critical = %v; want true", acmeExts[0].Critical)
 	}
-	if bytes.Compare(acmeExts[0].Value, extValue) != 0 {
+	if !bytes.Equal(acmeExts[0].Value, extValue) {
 		t.Errorf("acmeExt.Value = %v; want %v", acmeExts[0].Value, extValue)
 	}
 

acme/types.go

@@ -114,14 +114,15 @@ type Error struct {
 }
 
 func (e *Error) Error() string {
-	str := fmt.Sprintf("%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
+	var sb strings.Builder
+	fmt.Fprintf(&sb, "%d %s: %s", e.StatusCode, e.ProblemType, e.Detail)
 	if len(e.Subproblems) > 0 {
-		str += fmt.Sprintf("; subproblems:")
+		sb.WriteString("; subproblems:")
 		for _, sp := range e.Subproblems {
-			str += fmt.Sprintf("\n\t%s", sp)
+			fmt.Fprintf(&sb, "\n\t%s", sp)
 		}
 	}
-	return str
+	return sb.String()
 }
 
 // AuthorizationError indicates that an authorization for an identifier

ocsp/ocsp.go

@@ -322,7 +322,7 @@ type Request struct {
 func (req *Request) Marshal() ([]byte, error) {
 	hashAlg := getOIDFromHashAlgorithm(req.HashAlgorithm)
 	if hashAlg == nil {
-		return nil, errors.New("Unknown hash algorithm")
+		return nil, errors.New("unknown hash algorithm")
 	}
 	return asn1.Marshal(ocspRequest{
 		TBSRequest: tbsRequest{

ocsp/ocsp_test.go

@@ -195,7 +195,7 @@ func TestOCSPRequest(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if bytes.Compare(expectedBytes, marshaledRequest) != 0 {
+	if !bytes.Equal(expectedBytes, marshaledRequest) {
 		t.Errorf(
 			"Marshaled request doesn't match expected: wanted %x, got %x",
 			expectedBytes,

ssh/agent/keyring.go

@@ -104,7 +104,7 @@ func (r *keyring) Unlock(passphrase []byte) error {
 	if !r.locked {
 		return errors.New("agent: not locked")
 	}
-	if 1 != subtle.ConstantTimeCompare(passphrase, r.passphrase) {
+	if subtle.ConstantTimeCompare(passphrase, r.passphrase) != 1 {
 		return fmt.Errorf("agent: incorrect passphrase")
 	}
 

ssh/buffer_test.go

@@ -38,7 +38,7 @@ func TestBufferReadwrite(t *testing.T) {
 	b.write(alphabet[5:15])
 	r, _ = b.Read(make([]byte, 10))
 	r2, _ := b.Read(make([]byte, 10))
-	if r != 10 || r2 != 5 || 15 != r+r2 {
+	if r != 10 || r2 != 5 || r+r2 != 15 {
 		t.Fatal("Expected written == read == 15")
 	}
 }

ssh/handshake_test.go

@@ -195,7 +195,7 @@ func TestHandshakeBasic(t *testing.T) {
 		}
 
 		want := []byte{msgRequestSuccess, byte(i)}
-		if bytes.Compare(p, want) != 0 {
+		if !bytes.Equal(p, want) {
 			t.Errorf("message %d: got %v, want %v", i, p, want)
 		}
 	}

ssh/keys_test.go

@@ -1014,7 +1014,7 @@ func TestKnownHostsParsing(t *testing.T) {
 		input := test.input
 		if strings.Contains(input, rsaKeyToken) {
 			expectedKey = rsaPub
-			input = strings.Replace(test.input, rsaKeyToken, rsaPubSerialized, -1)
+			input = strings.ReplaceAll(test.input, rsaKeyToken, rsaPubSerialized)
 		}
 
 		marker, hosts, pubKey, comment, rest, err := ParseKnownHosts([]byte(input))

ssh/session_test.go

@@ -745,7 +745,7 @@ func TestSessionID(t *testing.T) {
 
 	s := <-serverID
 	c := <-clientID
-	if bytes.Compare(s, c) != 0 {
+	if !bytes.Equal(s, c) {
 		t.Errorf("server session ID (%x) != client session ID (%x)", s, c)
 	} else if len(s) == 0 {
 		t.Errorf("client and server SessionID were empty.")