Add unversioned file rand.lua. Fixes #1320

nselib/rand.lua

@@ -0,0 +1,91 @@
+--- Functions for generating random data
+--
+-- The strings generated here are not cryptographically secure, but they should
+-- be sufficient for most purposes.
+--
+-- @author Daniel Miller
+-- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html
+-- @class module
+-- @name rand
+
+local have_openssl, openssl = pcall(require, "openssl")
+
+local math = require "math"
+local random = math.random
+
+local string = require "string"
+local byte = string.byte
+local char = string.char
+local sub = string.sub
+
+local table = require "table"
+local concat = table.concat
+
+local type = type
+local _ENV = {}
+
+--- Generate a random string.
+--
+-- You can either provide your own charset or the function will generate random
+-- bytes, which may include null bytes.
+-- @param len Length of the string we want to generate.
+-- @param charset Charset that will be used to generate the string. String or table
+-- @return A random string of length <code>len</code> consisting of
+-- characters from <code>charset</code> if one was provided, or random bytes otherwise.
+random_string = function(len, charset)
+  local t = {}
+  if charset then
+    if type(charset) == "string" then
+      for i=1,len do
+        local r = random(#charset)
+        t[i] = sub(charset, r, r)
+      end
+    else
+      for i=1,len do
+        t[i]=charset[random(#charset)]
+      end
+    end
+  else
+    if have_openssl then
+      return openssl.rand_pseudo_bytes(len)
+    else
+      for i=1,len do
+        t[i]=char(random(0 ,0xff))
+      end
+    end
+  end
+  return concat(t)
+end
+local random_string = random_string
+
+--- Generate a charset that can be passed to <code>random_string</code>
+--
+-- @param left_bound The lower bound character or byte value of the set
+-- @param right_bound The upper bound character or byte value of the set
+-- @param charset Optional, a charset table to augment. By default a new charset is created.
+-- @return A charset table
+function charset(left_bound, right_bound, charset)
+  local t = charset or {}
+  left_bound = type(left_bound)=="string" and byte(left_bound) or left_bound
+  right_bound = type(right_bound)=="string" and byte(right_bound) or right_bound
+  if left_bound > right_bound then
+    return t
+  end
+  for i=left_bound,right_bound do
+    t[#t+1] = char(i)
+  end
+  return t
+end
+local charset = charset
+
+--- Generate a random alpha word
+--
+-- Convenience wrapper around <code>random_string</code> to generate a random
+-- string of lowercase alphabetic characters.
+-- @param len The length of word to return
+-- @return A string of random characters between 'a' and 'z' inclusive.
+function random_alpha (len)
+  return random_string(len, charset('a', 'z'))
+end
+
+return _ENV