Prevent dice overflow

rand.Int() would panic when the max value is <= 0, which happens when
big.NewInt() was fed with a too large number. Avoid this by validating
the big.NewInt() return beforehand. Add error handling to all callers to
both gracefully return to IRC and to log an error message.
Rename the shadowed "max" variable whilst at it to avoid confusion.

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

1 files changed, 88 insertions, 21 deletions

diff --git a/wat/game.go b/wat/game.go
index 8de6991..21ac982 100644
--- a/wat/game.go
+++ b/wat/game.go
@@ -121,9 +121,17 @@ func (g *WatGame) help() string {
 	return ret
 }
 
-func (g *WatGame) RandInt(max int64) uint64 {
-	i, _ := rand.Int(rand.Reader, big.NewInt(max))
-	return i.Uint64()
+func (g *WatGame) RandInt(maxx int64) (uint64, error) {
+	bi := big.NewInt(maxx)
+	// prevent panic of rand.Int on big numbers
+	if bi.BitLen() < 2 {
+		return 0, fmt.Errorf("overflow, got %d", bi)
+	}
+	i, err := rand.Int(rand.Reader, bi)
+	if err != nil {
+		return 0, err
+	}
+	return i.Uint64(), nil
 }
 
 func (g *WatGame) Heal(player *Player, fields []string) string {
@@ -166,8 +174,11 @@ func (g *WatGame) Dice(player *Player, fields []string) string {
 			roll = i
 		}
 	}
-	answer := g.RandInt(int64(roll)) + 1
-	return fmt.Sprintf("1d%d - %d", roll, answer)
+	answer, err := g.RandInt(int64(roll))
+	if e := handleError(err); e != "" {
+		return e
+	}
+	return fmt.Sprintf("1d%d - %d", roll + 1, answer)
 }
 
 type PositiveError struct{}
@@ -206,12 +217,20 @@ func (g *WatGame) Roll(player *Player, fields []string) string {
 	}
 	lotteryNum := int64(-1)
 	if dieSize > 100 {
-		lotteryNum = int64(g.RandInt(dieSize)) + 1
+		lotteryNumRand, randErr := g.RandInt(dieSize)
+		if e := handleError(randErr); e != "" {
+			return e
+		}
+		lotteryNum = int64(lotteryNumRand) + 1
 	}
 	if amount > player.Coins {
 		return "wat? brokeass"
 	}
-	n := int64(g.RandInt(dieSize)) + 1
+	nRand, randErr := g.RandInt(dieSize)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
+	n := int64(nRand) + 1
 	ret := fmt.Sprintf("%s rolls the %d sided die... %d! ", player.Nick, dieSize, n)
 	if n == lotteryNum {
 		player.Coins += player.Coins
@@ -255,11 +274,18 @@ func (g *WatGame) Punch(player *Player, fields []string) string {
 	if !target.Conscious() {
 		return "wat? you're punching someone who is already unconscious. u crazy?"
 	}
-	chance := g.RandInt(6) + 1
-	dmg := g.RandInt(6) + 1
+	chance, randErr := g.RandInt(6)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
+	dmg, randErr := g.RandInt(6)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
+	dmg = dmg + 1
 	ret := fmt.Sprintf("%s rolls a d6... %s ", player.Nick, player.Nick)
 	dmg += uint64(player.Level(player.Anarchy))
-	if chance > 3 {
+	if chance + 1 > 3 {
 		ret += fmt.Sprintf("hits %s for %d points of damage! ", target.Nick, dmg)
 		target.Health -= int64(dmg)
 		g.db.Update(target)
@@ -300,7 +326,11 @@ func (g *WatGame) Frame(player *Player, fields []string) string {
 	if target.Coins < amount {
 		return fmt.Sprintf("wat? %s is too poor for this.", target.Nick)
 	}
-	n := g.RandInt(6) + 1
+	n, randErr := g.RandInt(6)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
+	n = n + 1
 	ret := fmt.Sprintf("%s rolls a d6 to frame %s with %d %s: It's a %d! (<3 wins). ", player.Nick, target.Nick, amount, currency, n)
 	if n < 3 {
 		ret += fmt.Sprintf("You frame %s for a minor crime. They pay me %d.", target.Nick, amount)
@@ -335,7 +365,11 @@ func (g *WatGame) Steal(player *Player, fields []string) string {
 	if target.Coins < amount {
 		return fmt.Sprintf("wat? %s is poor and doesn't have that much to steal. (%d %s)", target.Nick, target.Coins, currency)
 	}
-	n := g.RandInt(6) + 1
+	n, randErr := g.RandInt(6)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
+	n = n + 1
 	ret := fmt.Sprintf("%s is trying to steal %d %s from %s... ", player.Nick, amount, currency, target.Nick)
 	if n < 3 {
 		ret += "You did it! Sneaky bastard!"
@@ -380,7 +414,11 @@ func (g *WatGame) Leech(player *Player, fields []string) string {
 	if err != "" {
 		return err
 	}
-	r := g.RandInt(10) + 1
+	r, randErr := g.RandInt(10)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
+	r = r + 1
 	reply := fmt.Sprintf("You muster your wealth and feed it to %s. ", g.bot.Nick)
 	hpDown := amount / divisor
 	player.Coins -= amount
@@ -408,7 +446,11 @@ func (g *WatGame) Rest(player *Player, fields []string) string {
 	} else if delta < minRest {
 		ret = fmt.Sprintf("wat were you thinking, sleeping at a time like this (%d until next rest)", minRest-delta)
 	} else {
-		value := g.RandInt(10) + 1
+		value, randErr := g.RandInt(10)
+		if e := handleError(randErr); e != "" {
+			return e
+		}
+		value = value + 1
 		if player.Health < -5 {
 			player.Health = 1
 			ret = fmt.Sprintf("wow ur beat up. i pity u, ur health is now 1.")
@@ -435,8 +477,15 @@ func (g *WatGame) Bench(player *Player, fields []string) string {
 	if !g.CanAct(player, Action_Lift, minTime) {
 		return "you're tired. no more lifting for now."
 	}
-	weight := g.RandInt(370) + 50
-	reps := g.RandInt(10)
+	weight, randErr := g.RandInt(370)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
+	weight = weight + 50
+	reps, randErr := g.RandInt(10)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
 	value := int64(0)
 	reply := fmt.Sprintf("%s benches %dwatts for %d reps, ", player.Nick, weight, reps)
 	if weight < 150 {
@@ -452,7 +501,10 @@ func (g *WatGame) Bench(player *Player, fields []string) string {
 	}
 	if g.roid[player.Nick] != 0 {
 		delete(g.roid, player.Nick)
-		success := g.RandInt(2)
+		success, randErr := g.RandInt(2)
+		if e := handleError(randErr); e != "" {
+			return e
+		}
 		if success != 0 {
 			player.Health = 0
 			player.Anarchy -= 10
@@ -475,7 +527,10 @@ func (g *WatGame) Riot(player *Player, fields []string) string {
 	if !g.CanAct(player, Action_Riot, int64((48 * time.Hour).Seconds())) {
 		return "Planning a riot takes time and the right circumstances. Be prepared. (nothing happens)"
 	}
-	r := g.RandInt(100)
+	r, randErr := g.RandInt(100)
+	if e := handleError(randErr); e != "" {
+		return e
+	}
 	reply := ""
 	if r > 40 {
 		player.Anarchy += 3
@@ -621,9 +676,21 @@ func PrintTwo(nick string, value uint64) string {
 }
 
 func (g *WatGame) megaWat(player *Player, _ []string) string {
-	mega := g.RandInt(1000000) + 1
-	kilo := g.RandInt(1000) + 1
-	ten := g.RandInt(100) + 1
+	mega, randErr := g.RandInt(1000000)
+	if e := handleError(randErr); e != "" {
+		return e + " mega fail"
+	}
+	mega = mega + 1
+	kilo, randErr := g.RandInt(1000)
+	if e := handleError(randErr); e != "" {
+		return e + " kilo fail"
+	}
+	kilo = kilo + 1
+	ten, randErr := g.RandInt(100)
+	if e := handleError(randErr); e != "" {
+		return e + " ten fail"
+	}
+	ten = ten + 1
 	reply := ""
 	if mega == 23 {
 		player.Coins += 1000000