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package scoring
import (
"fmt"
"github.com/nbutton23/zxcvbn-go/entropy"
"github.com/nbutton23/zxcvbn-go/match"
"github.com/nbutton23/zxcvbn-go/utils/math"
"math"
"sort"
)
const (
START_UPPER string = `^[A-Z][^A-Z]+$`
END_UPPER string = `^[^A-Z]+[A-Z]$'`
ALL_UPPER string = `^[A-Z]+$`
//for a hash function like bcrypt/scrypt/PBKDF2, 10ms per guess is a safe lower bound.
//(usually a guess would take longer -- this assumes fast hardware and a small work factor.)
//adjust for your site accordingly if you use another hash function, possibly by
//several orders of magnitude!
SINGLE_GUESS float64 = 0.010
NUM_ATTACKERS float64 = 100 //Cores used to make guesses
SECONDS_PER_GUESS float64 = SINGLE_GUESS / NUM_ATTACKERS
)
type MinEntropyMatch struct {
Password string
Entropy float64
MatchSequence []match.Match
CrackTime float64
CrackTimeDisplay string
Score int
CalcTime float64
}
/*
Returns minimum entropy
Takes a list of overlapping matches, returns the non-overlapping sublist with
minimum entropy. O(nm) dp alg for length-n password with m candidate matches.
*/
func MinimumEntropyMatchSequence(password string, matches []match.Match) MinEntropyMatch {
bruteforceCardinality := float64(entropy.CalcBruteForceCardinality(password))
upToK := make([]float64, len(password))
backPointers := make([]match.Match, len(password))
for k := 0; k < len(password); k++ {
upToK[k] = get(upToK, k-1) + math.Log2(bruteforceCardinality)
for _, match := range matches {
if match.J != k {
continue
}
i, j := match.I, match.J
//see if best entropy up to i-1 + entropy of match is less that current min at j
upTo := get(upToK, i-1)
candidateEntropy := upTo + match.Entropy
if candidateEntropy < upToK[j] {
upToK[j] = candidateEntropy
match.Entropy = candidateEntropy
backPointers[j] = match
}
}
}
//walk backwards and decode the best sequence
var matchSequence []match.Match
passwordLen := len(password)
passwordLen--
for k := passwordLen; k >= 0; {
match := backPointers[k]
if match.Pattern != "" {
matchSequence = append(matchSequence, match)
k = match.I - 1
} else {
k--
}
}
sort.Sort(match.Matches(matchSequence))
makeBruteForceMatch := func(i, j int) match.Match {
return match.Match{Pattern: "bruteforce",
I: i,
J: j,
Token: password[i : j+1],
Entropy: math.Log2(math.Pow(bruteforceCardinality, float64(j-i)))}
}
k := 0
var matchSequenceCopy []match.Match
for _, match := range matchSequence {
i, j := match.I, match.J
if i-k > 0 {
matchSequenceCopy = append(matchSequenceCopy, makeBruteForceMatch(k, i-1))
}
k = j + 1
matchSequenceCopy = append(matchSequenceCopy, match)
}
if k < len(password) {
matchSequenceCopy = append(matchSequenceCopy, makeBruteForceMatch(k, len(password)-1))
}
var minEntropy float64
if len(password) == 0 {
minEntropy = float64(0)
} else {
minEntropy = upToK[len(password)-1]
}
crackTime := roundToXDigits(entropyToCrackTime(minEntropy), 3)
return MinEntropyMatch{Password: password,
Entropy: roundToXDigits(minEntropy, 3),
MatchSequence: matchSequenceCopy,
CrackTime: crackTime,
CrackTimeDisplay: displayTime(crackTime),
Score: crackTimeToScore(crackTime)}
}
func get(a []float64, i int) float64 {
if i < 0 || i >= len(a) {
return float64(0)
}
return a[i]
}
func entropyToCrackTime(entropy float64) float64 {
crackTime := (0.5 * math.Pow(float64(2), entropy)) * SECONDS_PER_GUESS
return crackTime
}
func roundToXDigits(number float64, digits int) float64 {
return zxcvbn_math.Round(number, .5, digits)
}
func displayTime(seconds float64) string {
formater := "%.1f %s"
minute := float64(60)
hour := minute * float64(60)
day := hour * float64(24)
month := day * float64(31)
year := month * float64(12)
century := year * float64(100)
if seconds < minute {
return "instant"
} else if seconds < hour {
return fmt.Sprintf(formater, (1 + math.Ceil(seconds/minute)), "minutes")
} else if seconds < day {
return fmt.Sprintf(formater, (1 + math.Ceil(seconds/hour)), "hours")
} else if seconds < month {
return fmt.Sprintf(formater, (1 + math.Ceil(seconds/day)), "days")
} else if seconds < year {
return fmt.Sprintf(formater, (1 + math.Ceil(seconds/month)), "months")
} else if seconds < century {
return fmt.Sprintf(formater, (1 + math.Ceil(seconds/century)), "years")
} else {
return "centuries"
}
}
func crackTimeToScore(seconds float64) int {
if seconds < math.Pow(10, 2) {
return 0
} else if seconds < math.Pow(10, 4) {
return 1
} else if seconds < math.Pow(10, 6) {
return 2
} else if seconds < math.Pow(10, 8) {
return 3
}
return 4
}
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