Added RangeUint32 to support 32-bit builds

psiphon/common/prng/prng.go

@@ -283,6 +283,15 @@ func (p *PRNG) Range(min, max int) int {
 	return n
 }
 
+// RangeUint32 selects an unsigned 32-bit random integer in [min, max].
+// If max < min, min is returned.
+func (p *PRNG) RangeUint32(min, max uint32) uint32 {
+	if max < min {
+		return min
+	}
+	return min + uint32(p.rand.Int63n(int64(max-min)+1))
+}
+
 // Bytes returns a new slice containing length random bytes.
 func (p *PRNG) Bytes(length int) []byte {
 	b := make([]byte, length)
@@ -376,6 +385,10 @@ func Range(min, max int) int {
 	return p.Range(min, max)
 }
 
+func RangeUint32(min, max uint32) uint32 {
+	return p.RangeUint32(min, max)
+}
+
 func Bytes(length int) []byte {
 	return p.Bytes(length)
 }

psiphon/common/prng/prng_test.go

@@ -196,6 +196,40 @@ func TestRange(t *testing.T) {
 	}
 }
 
+func TestUint32Range(t *testing.T) {
+
+	p, err := NewPRNG()
+	if err != nil {
+		t.Fatalf("NewPRNG failed: %s", err)
+	}
+
+	var min uint32 = math.MaxUint32 - 19
+	var max uint32 = math.MaxUint32
+	var gotMin, gotMax bool
+	for n := 0; n < 1000; n++ {
+
+		i := p.RangeUint32(min, max)
+
+		if i < min || i > max {
+			t.Error("out of range")
+		}
+
+		if i == min {
+			gotMin = true
+		}
+		if i == max {
+			gotMax = true
+		}
+	}
+
+	if !gotMin {
+		t.Error("missing min")
+	}
+	if !gotMax {
+		t.Error("missing max")
+	}
+}
+
 func TestPeriod(t *testing.T) {
 
 	p, err := NewPRNG()

psiphon/tlsDialer.go

@@ -868,7 +868,8 @@ func getUTLSClientHelloID(
 		// Generates typical PSK extension values.
 		labelLengths := []int{192, 208, 224, 226, 235, 240, 273, 421, 429, 441}
 		label := prng.Bytes(labelLengths[prng.Intn(len(labelLengths))])
-		obfuscatedTicketAge := uint32(prng.Range(13029567, math.MaxUint32))
+		obfuscatedTicketAge := prng.RangeUint32(13029567, math.MaxUint32)
+
 		binder := prng.Bytes(33)
 		binder[0] = 0x20 // Binder's length