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.

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

wat/game.go

@@ -2,6 +2,7 @@ package wat
 
 import (
 	"crypto/rand"
+	"errors"
 	"fmt"
 	"math/big"
 	"strconv"
@@ -121,9 +122,17 @@ func (g *WatGame) help() string {
 	return ret
 }
 
-func (g *WatGame) RandInt(max int64) uint64 {
+func (g *WatGame) RandInt(max int64) (uint64, error) {
-	i, _ := rand.Int(rand.Reader, big.NewInt(max))
+	bi := big.NewInt(max)
-	return i.Uint64()
+	// prevent panic of rand.Int on big numbers
+	if bi.BitLen() < 2 {
+		return 0, errors.New("overflow")
+	}
+	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 +175,11 @@ func (g *WatGame) Dice(player *Player, fields []string) string {
 			roll = i
 		}
 	}
-	answer := g.RandInt(int64(roll)) + 1
+	answer, err := g.RandInt(int64(roll))
-	return fmt.Sprintf("1d%d - %d", roll, answer)
+	if e := handleError(err); e != "" {
+		return e
+	}
+	return fmt.Sprintf("1d%d - %d", roll + 1, answer)
 }
 
 type PositiveError struct{}
@@ -206,12 +218,20 @@ 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 +275,18 @@ 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
+	chance, randErr := g.RandInt(6)
-	dmg := g.RandInt(6) + 1
+	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 +327,11 @@ 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 +366,11 @@ 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 +415,11 @@ 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 +447,11 @@ 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 +478,15 @@ 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
+	weight, randErr := g.RandInt(370)
-	reps := g.RandInt(10)
+	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 +502,10 @@ 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 randErr != nil {
+			return "woops"
+		}
 		if success != 0 {
 			player.Health = 0
 			player.Anarchy -= 10
@@ -475,7 +528,10 @@ 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 +677,21 @@ func PrintTwo(nick string, value uint64) string {
 }
 
 func (g *WatGame) megaWat(player *Player, _ []string) string {
-	mega := g.RandInt(1000000) + 1
+	mega, randErr := g.RandInt(1000000)
-	kilo := g.RandInt(1000) + 1
+	if e := handleError(randErr); e != "" {
-	ten := g.RandInt(100) + 1
+		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

wat/utils.go

@@ -0,0 +1,22 @@
+package wat
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func handleError(err error) string {
+	if err != nil {
+		pc, _, _, ok := runtime.Caller(1)
+		details := runtime.FuncForPC(pc)
+		var cFun string
+		if ok && details != nil {
+			cFun = details.Name()
+		} else {
+			cFun = "???"
+		}
+		fmt.Printf("caught error in %s: %v\n", cFun, err)
+		return "u wat"
+	}
+	return ""
+}