Revert "Revert "add chacha20""

This reverts commit 2012e6d3a8.

build-js.sh

@@ -65,11 +65,10 @@ echo "building nntpchan.js ..."
 echo
 initfile "$outfile"
 
-if [ -e ./contrib/js/contrib/*.js ] ; then
+
 for f in ./contrib/js/contrib/*.js ; do
     mini "$f" "$outfile"
 done
-fi
 
 mini ./contrib/js/entry.js "$outfile"
 

contrib/js/contrib/chacha20.js

@@ -0,0 +1,116 @@
+/* chacha20 - 256 bits */
+
+// Written in 2014 by Devi Mandiri. Public domain.
+//
+// Implementation derived from chacha-ref.c version 20080118
+// See for details: http://cr.yp.to/chacha/chacha-20080128.pdf
+
+function U8TO32_LE(x, i) {
+  return x[i] | (x[i+1]<<8) | (x[i+2]<<16) | (x[i+3]<<24);
+}
+
+function U32TO8_LE(x, i, u) {
+  x[i]   = u; u >>>= 8;
+  x[i+1] = u; u >>>= 8;
+  x[i+2] = u; u >>>= 8;
+  x[i+3] = u;
+}
+
+function ROTATE(v, c) {
+  return (v << c) | (v >>> (32 - c));
+}
+
+var Chacha20 = function(key, nonce, counter) {
+  this.input = new Uint32Array(16);
+
+  // https://tools.ietf.org/html/draft-irtf-cfrg-chacha20-poly1305-01#section-2.3
+  this.input[0] = 1634760805;
+  this.input[1] =  857760878;
+  this.input[2] = 2036477234;
+  this.input[3] = 1797285236;
+  this.input[4] = U8TO32_LE(key, 0);
+  this.input[5] = U8TO32_LE(key, 4);
+  this.input[6] = U8TO32_LE(key, 8);
+  this.input[7] = U8TO32_LE(key, 12);
+  this.input[8] = U8TO32_LE(key, 16);
+  this.input[9] = U8TO32_LE(key, 20);
+  this.input[10] = U8TO32_LE(key, 24);
+  this.input[11] = U8TO32_LE(key, 28);
+  // be compatible with the reference ChaCha depending on the nonce size
+  if(nonce.length == 12)
+  {
+    this.input[12] = counter;
+    this.input[13] = U8TO32_LE(nonce, 0);
+    this.input[14] = U8TO32_LE(nonce, 4);
+    this.input[15] = U8TO32_LE(nonce, 8);
+  }else{
+    this.input[12] = counter;
+    this.input[13] = 0;
+    this.input[14] = U8TO32_LE(nonce, 0);
+    this.input[15] = U8TO32_LE(nonce, 4);
+    
+  }
+};
+
+Chacha20.prototype.quarterRound = function(x, a, b, c, d) {
+  x[a] += x[b]; x[d] = ROTATE(x[d] ^ x[a], 16);
+  x[c] += x[d]; x[b] = ROTATE(x[b] ^ x[c], 12);
+  x[a] += x[b]; x[d] = ROTATE(x[d] ^ x[a],  8);
+  x[c] += x[d]; x[b] = ROTATE(x[b] ^ x[c],  7);
+};
+
+Chacha20.prototype.encrypt = function(dst, src, len) {
+  var x = new Uint32Array(16);
+  var output = new Uint8Array(64);
+  var i, dpos = 0, spos = 0;
+
+  while (len > 0 ) {
+    for (i = 16; i--;) x[i] = this.input[i];
+    for (i = 20; i > 0; i -= 2) {
+      this.quarterRound(x, 0, 4, 8,12);
+      this.quarterRound(x, 1, 5, 9,13);
+      this.quarterRound(x, 2, 6,10,14);
+      this.quarterRound(x, 3, 7,11,15);
+      this.quarterRound(x, 0, 5,10,15);
+      this.quarterRound(x, 1, 6,11,12);
+      this.quarterRound(x, 2, 7, 8,13);
+      this.quarterRound(x, 3, 4, 9,14);
+    }
+    for (i = 16; i--;) x[i] += this.input[i];
+    for (i = 16; i--;) U32TO8_LE(output, 4*i, x[i]);
+
+    this.input[12] += 1;
+    if (!this.input[12]) {
+      this.input[13] += 1;
+    }
+    if (len <= 64) {
+      for (i = len; i--;) {
+        dst[i+dpos] = src[i+spos] ^ output[i];
+      }
+      return;
+    }
+    for (i = 64; i--;) {
+      dst[i+dpos] = src[i+spos] ^ output[i];
+    }
+    len -= 64;
+    spos += 64;
+    dpos += 64;
+  }
+};
+
+Chacha20.prototype.keystream = function(dst, len) {
+  for (var i = 0; i < len; ++i) dst[i] = 0;
+  this.encrypt(dst, dst, len);
+};
+
+// additions to make it easier and export it as a module
+
+exports.Cipher = Chacha20;
+
+exports.encrypt = exports.decrypt = function(key, nonce, data)
+{
+  var cipher = new Chacha20(key, nonce);
+  var ret = new Buffer(data.length);
+  cipher.encrypt(ret, data, data.length);
+  return ret;
+}