VOL-1967 move api-server to separate repository
Change-Id: I21b85be74205805be15f8a85e53a903d16785671
diff --git a/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/nfold.go b/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/nfold.go
new file mode 100644
index 0000000..779d1c6
--- /dev/null
+++ b/vendor/gopkg.in/jcmturner/gokrb5.v7/crypto/rfc3961/nfold.go
@@ -0,0 +1,128 @@
+package rfc3961
+
+/*
+Implementation of the n-fold algorithm as defined in RFC 3961.
+
+n-fold is an algorithm that takes m input bits and "stretches" them
+to form n output bits with equal contribution from each input bit to
+the output, as described in [Blumenthal96]:
+
+We first define a primitive called n-folding, which takes a
+variable-length input block and produces a fixed-length output
+sequence. The intent is to give each input bit approximately
+equal weight in determining the value of each output bit. Note
+that whenever we need to treat a string of octets as a number, the
+assumed representation is Big-Endian -- Most Significant Byte
+first.
+
+To n-fold a number X, replicate the input value to a length that
+is the least common multiple of n and the length of X. Before
+each repetition, the input is rotated to the right by 13 bit
+positions. The successive n-bit chunks are added together using
+1's-complement addition (that is, with end-around carry) to yield
+a n-bit result....
+*/
+
+/* Credits
+This golang implementation of nfold used the following project for help with implementation detail.
+Although their source is in java it was helpful as a reference implementation of the RFC.
+You can find the source code of their open source project along with license information below.
+We acknowledge and are grateful to these developers for their contributions to open source
+
+Project: Apache Directory (http://http://directory.apache.org/)
+https://svn.apache.org/repos/asf/directory/apacheds/tags/1.5.1/kerberos-shared/src/main/java/org/apache/directory/server/kerberos/shared/crypto/encryption/NFold.java
+License: http://www.apache.org/licenses/LICENSE-2.0
+*/
+
+// Nfold expands the key to ensure it is not smaller than one cipher block.
+// Defined in RFC 3961.
+//
+// m input bytes that will be "stretched" to the least common multiple of n bits and the bit length of m.
+func Nfold(m []byte, n int) []byte {
+ k := len(m) * 8
+
+ //Get the lowest common multiple of the two bit sizes
+ lcm := lcm(n, k)
+ relicate := lcm / k
+ var sumBytes []byte
+
+ for i := 0; i < relicate; i++ {
+ rotation := 13 * i
+ sumBytes = append(sumBytes, rotateRight(m, rotation)...)
+ }
+
+ nfold := make([]byte, n/8)
+ sum := make([]byte, n/8)
+ for i := 0; i < lcm/n; i++ {
+ for j := 0; j < n/8; j++ {
+ sum[j] = sumBytes[j+(i*len(sum))]
+ }
+ nfold = onesComplementAddition(nfold, sum)
+ }
+ return nfold
+}
+
+func onesComplementAddition(n1, n2 []byte) []byte {
+ numBits := len(n1) * 8
+ out := make([]byte, numBits/8)
+ carry := 0
+ for i := numBits - 1; i > -1; i-- {
+ n1b := getBit(&n1, i)
+ n2b := getBit(&n2, i)
+ s := n1b + n2b + carry
+
+ if s == 0 || s == 1 {
+ setBit(&out, i, s)
+ carry = 0
+ } else if s == 2 {
+ carry = 1
+ } else if s == 3 {
+ setBit(&out, i, 1)
+ carry = 1
+ }
+ }
+ if carry == 1 {
+ carryArray := make([]byte, len(n1))
+ carryArray[len(carryArray)-1] = 1
+ out = onesComplementAddition(out, carryArray)
+ }
+ return out
+}
+
+func rotateRight(b []byte, step int) []byte {
+ out := make([]byte, len(b))
+ bitLen := len(b) * 8
+ for i := 0; i < bitLen; i++ {
+ v := getBit(&b, i)
+ setBit(&out, (i+step)%bitLen, v)
+ }
+ return out
+}
+
+func lcm(x, y int) int {
+ return (x * y) / gcd(x, y)
+}
+
+func gcd(x, y int) int {
+ for y != 0 {
+ x, y = y, x%y
+ }
+ return x
+}
+
+func getBit(b *[]byte, p int) int {
+ pByte := p / 8
+ pBit := uint(p % 8)
+ vByte := (*b)[pByte]
+ vInt := int(vByte >> (8 - (pBit + 1)) & 0x0001)
+ return vInt
+}
+
+func setBit(b *[]byte, p, v int) {
+ pByte := p / 8
+ pBit := uint(p % 8)
+ oldByte := (*b)[pByte]
+ var newByte byte
+ newByte = byte(v<<(8-(pBit+1))) | oldByte
+ (*b)[pByte] = newByte
+}