light: ensure trust level is strictly less than 1 (#6447)

light/verifier.go

@@ -167,10 +167,10 @@ func Verify(
 
 // ValidateTrustLevel checks that trustLevel is within the allowed range [1/3,
 // 1]. If not, it returns an error. 1/3 is the minimum amount of trust needed
-// which does not break the security model.
+// which does not break the security model. Must be strictly less than 1.
 func ValidateTrustLevel(lvl tmmath.Fraction) error {
 	if lvl.Numerator*3 < lvl.Denominator || // < 1/3
-		lvl.Numerator > lvl.Denominator || // > 1
+		lvl.Numerator >= lvl.Denominator || // >= 1
 		lvl.Denominator == 0 {
 		return fmt.Errorf("trustLevel must be within [1/3, 1], given %v", lvl)
 	}

light/verifier_test.go

@@ -311,25 +311,26 @@ func TestValidateTrustLevel(t *testing.T) {
 		valid bool
 	}{
 		// valid
-		0: {tmmath.Fraction{Numerator: 1, Denominator: 1}, true},
-		1: {tmmath.Fraction{Numerator: 1, Denominator: 3}, true},
-		2: {tmmath.Fraction{Numerator: 2, Denominator: 3}, true},
-		3: {tmmath.Fraction{Numerator: 3, Denominator: 3}, true},
-		4: {tmmath.Fraction{Numerator: 4, Denominator: 5}, true},
+		0: {tmmath.Fraction{Numerator: 1, Denominator: 3}, true},
+		1: {tmmath.Fraction{Numerator: 2, Denominator: 3}, true},
+		2: {tmmath.Fraction{Numerator: 4, Denominator: 5}, true},
+		3: {tmmath.Fraction{Numerator: 99, Denominator: 100}, true},
 
 		// invalid
+		4: {tmmath.Fraction{Numerator: 3, Denominator: 3}, false},
 		5: {tmmath.Fraction{Numerator: 6, Denominator: 5}, false},
-		6: {tmmath.Fraction{Numerator: 0, Denominator: 1}, false},
-		7: {tmmath.Fraction{Numerator: 0, Denominator: 0}, false},
-		8: {tmmath.Fraction{Numerator: 1, Denominator: 0}, false},
+		6: {tmmath.Fraction{Numerator: 3, Denominator: 10}, false},
+		7: {tmmath.Fraction{Numerator: 0, Denominator: 1}, false},
+		8: {tmmath.Fraction{Numerator: 0, Denominator: 0}, false},
+		9: {tmmath.Fraction{Numerator: 1, Denominator: 0}, false},
 	}
 
-	for _, tc := range testCases {
+	for idx, tc := range testCases {
 		err := light.ValidateTrustLevel(tc.lvl)
 		if !tc.valid {
-			assert.Error(t, err)
+			assert.Error(t, err, idx)
 		} else {
-			assert.NoError(t, err)
+			assert.NoError(t, err, idx)
 		}
 	}
 }