Fixed warnings from staticcheck

go.mod

@@ -4,3 +4,5 @@ require (
 	golang.org/x/crypto v0.0.0-20190530122614-20be4c3c3ed5
 	golang.org/x/sys v0.0.0-20190412213103-97732733099d
 )
+
+go 1.13

prime.go

@@ -81,10 +81,8 @@ func isGenerator(g, p *big.Int) bool {
 
 func ok(g, x *big.Int, p *big.Int) bool {
 	z := big.NewInt(0).Exp(g, x, p)
-	if z.Cmp(one) != 0 { // the expmod should NOT be 1
-		return true
-	}
-	return false
+	// the expmod should NOT be 1
+	return z.Cmp(one) != 0
 }
 
 // vim: noexpandtab:sw=8:ts=8:tw=92:

srp.go

@@ -181,14 +181,14 @@ func NewWithHash(h crypto.Hash, bits int) (*SRP, error) {
 func ServerBegin(creds string) (string, *big.Int, error) {
 	v := strings.Split(creds, ":")
 	if len(v) != 2 {
-		return "", nil, fmt.Errorf("invalid client public key")
+		return "", nil, fmt.Errorf("srp: invalid client public key")
 	}
 
 	//fmt.Printf("v0: %s\nv1: %s\n", v[0], v[1])
 
 	A, ok := big.NewInt(0).SetString(v[1], 16)
 	if !ok {
-		return "", nil, fmt.Errorf("Invalid client public key A")
+		return "", nil, fmt.Errorf("srp: invalid client public key A")
 	}
 
 	return v[0], A, nil
@@ -374,29 +374,29 @@ func (c *Client) Credentials() string {
 func (c *Client) Generate(srv string) (string, error) {
 	v := strings.Split(srv, ":")
 	if len(v) != 2 {
-		return "", fmt.Errorf("invalid server public key")
+		return "", fmt.Errorf("srp: invalid server public key")
 	}
 
 	salt, err := hex.DecodeString(v[0])
 	if err != nil {
-		return "", fmt.Errorf("invalid server public key")
+		return "", fmt.Errorf("srp: invalid server public key")
 	}
 
 	B, ok1 := big.NewInt(0).SetString(v[1], 16)
 	if !ok1 {
-		return "", fmt.Errorf("invalid server public key")
+		return "", fmt.Errorf("srp: invalid server public key")
 	}
 
 	pf := c.s.pf
 	zero := big.NewInt(0)
 	z := big.NewInt(0).Mod(B, pf.N)
 	if zero.Cmp(z) == 0 {
-		return "", fmt.Errorf("invalid server public key")
+		return "", fmt.Errorf("srp: invalid server public key")
 	}
 
 	u := c.s.hashint(pad(c.xA, pf.n), pad(B, pf.n))
 	if u.Cmp(zero) == 0 {
-		return "", fmt.Errorf("invalid server public key")
+		return "", fmt.Errorf("srp: invalid server public key")
 	}
 
 	// S := ((B - kg^x) ^ (a + ux)) % N
@@ -457,7 +457,7 @@ func (s *SRP) NewServer(v *Verifier, A *big.Int) (*Server, error) {
 	zero := big.NewInt(0)
 	z := big.NewInt(0).Mod(A, pf.N)
 	if zero.Cmp(z) == 0 {
-		return nil, fmt.Errorf("invalid client public key")
+		return nil, fmt.Errorf("srp: invalid client public key")
 	}
 
 	sx := &Server{
@@ -483,7 +483,7 @@ func (s *SRP) NewServer(v *Verifier, A *big.Int) (*Server, error) {
 
 	u := s.hashint(pad(A, pf.n), pad(B, pf.n))
 	if u.Cmp(zero) == 0 {
-		return nil, fmt.Errorf("Invalid client public key u")
+		return nil, fmt.Errorf("srp: invalid client public key u")
 	}
 
 	t0 = big.NewInt(0).Mul(A, big.NewInt(0).Exp(sx.v, u, pf.N))
@@ -570,7 +570,7 @@ func pad(x *big.Int, n int) []byte {
 	b := x.Bytes()
 	if len(b) < n {
 		z := n - len(b)
-		p := make([]byte, n, n)
+		p := make([]byte, n)
 		for i := 0; i < z; i++ {
 			p[i] = 0
 		}
@@ -595,7 +595,7 @@ func randbytes(n int) []byte {
 // Generate and return a bigInt 'bits' bits in length
 func randBigInt(bits int) *big.Int {
 	n := bits / 8
-	if 0 != bits%8 {
+	if (bits%8) != 0 {
 		n += 1
 	}
 	b := randbytes(n)
@@ -646,7 +646,7 @@ func newPrimeField(nbits int) (*primeField, error) {
 			}
 		}
 	}
-	return nil, fmt.Errorf("can't find generator after 100 tries")
+	return nil, fmt.Errorf("srp: can't find generator after 100 tries")
 }
 
 // Find a pre-generated safe-prime and its generator from our list below.
@@ -685,7 +685,7 @@ func init() {
 			N: atobi(v[2], 0),
 			n: b / 8,
 		}
-		if 0 == big.NewInt(0).Cmp(pf.N) {
+		if big.NewInt(0).Cmp(pf.N) == 0 {
 			panic(fmt.Sprintf("srp init: N (%s) is zero", v[2]))
 		}
 		pflist[b] = pf

srp_test.go

@@ -31,9 +31,6 @@ func newAsserter(t *testing.T) func(cond bool, msg string, args ...interface{})
 	}
 }
 
-type user struct {
-	v *Verifier
-}
 
 type userdb struct {
 	s *SRP
@@ -133,7 +130,7 @@ func (db *userdb) verify(t *testing.T, user, pass []byte, goodPw bool) {
 	kc := c.RawKey()
 	ks := srv.RawKey()
 
-	assert(1 == subtle.ConstantTimeCompare(kc, ks), "key mismatch;\nclient %x, server %x", kc, ks)
+	assert(subtle.ConstantTimeCompare(kc, ks) == 1, "key mismatch;\nclient %x, server %x", kc, ks)
 }
 
 func TestSRP(t *testing.T) {
@@ -154,38 +151,3 @@ func TestSRP(t *testing.T) {
 	}
 }
 
-func mustDecode(s string) []byte {
-	n := len(s)
-	b := make([]byte, 0, n)
-	var z, x byte
-	var shift uint = 4
-	for i := 0; i < n; i++ {
-		c := s[i]
-		switch {
-		case '0' <= c && c <= '9':
-			x = c - '0'
-		case 'a' <= c && c <= 'f':
-			x = c - 'a' + 10
-		case 'A' <= c && c <= 'F':
-			x = c - 'A' + 10
-		case c == ' ' || c == '\n' || c == '\t':
-			continue
-		default:
-			panic(fmt.Sprintf("invalid hex char %c in %s", c, s))
-		}
-
-		if shift == 0 {
-			z |= x
-			b = append(b, z)
-			z = 0
-			shift = 4
-		} else {
-			z |= (x << shift)
-			shift -= 4
-		}
-	}
-	if shift != 4 {
-		b = append(b, z)
-	}
-	return b
-}