Two factor authentication support (#630)

* Initial commit for 2FA support

Signed-off-by: Andrew <write@imaginarycode.com>

* Add vendored files

* Add missing depends

* A few clean ups

* Added improvements, proper encryption

* Better encryption key

* Simplify "key" generation

* Make 2FA enrollment page more robust

* Fix typo

* Rename twofa/2FA to TwoFactor

* UNIQUE INDEX -> UNIQUE

vendor/github.com/boombuler/barcode/utils/reedsolomon.go

@@ -0,0 +1,44 @@
+package utils
+
+import (
+	"sync"
+)
+
+type ReedSolomonEncoder struct {
+	gf        *GaloisField
+	polynomes []*GFPoly
+	m         *sync.Mutex
+}
+
+func NewReedSolomonEncoder(gf *GaloisField) *ReedSolomonEncoder {
+	return &ReedSolomonEncoder{
+		gf, []*GFPoly{NewGFPoly(gf, []int{1})}, new(sync.Mutex),
+	}
+}
+
+func (rs *ReedSolomonEncoder) getPolynomial(degree int) *GFPoly {
+	rs.m.Lock()
+	defer rs.m.Unlock()
+
+	if degree >= len(rs.polynomes) {
+		last := rs.polynomes[len(rs.polynomes)-1]
+		for d := len(rs.polynomes); d <= degree; d++ {
+			next := last.Multiply(NewGFPoly(rs.gf, []int{1, rs.gf.ALogTbl[d-1+rs.gf.Base]}))
+			rs.polynomes = append(rs.polynomes, next)
+			last = next
+		}
+	}
+	return rs.polynomes[degree]
+}
+
+func (rs *ReedSolomonEncoder) Encode(data []int, eccCount int) []int {
+	generator := rs.getPolynomial(eccCount)
+	info := NewGFPoly(rs.gf, data)
+	info = info.MultByMonominal(eccCount, 1)
+	_, remainder := info.Divide(generator)
+
+	result := make([]int, eccCount)
+	numZero := int(eccCount) - len(remainder.Coefficients)
+	copy(result[numZero:], remainder.Coefficients)
+	return result
+}