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nmap/nbase/nbase_rnd.c
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/***************************************************************************
* nbase_rnd.c -- Some simple routines for obtaining random numbers for *
* casual use. These are pretty secure on systems with /dev/urandom, but *
* falls back to poor entropy for seeding on systems without such support. *
* *
* Based on DNET / OpenBSD arc4random(). *
* *
* Copyright (c) 2000 Dug Song <dugsong@monkey.org> *
* Copyright (c) 1996 David Mazieres <dm@lcs.mit.edu> *
* *
***********************IMPORTANT NMAP LICENSE TERMS************************
* *
* The Nmap Security Scanner is (C) 1996-2016 Insecure.Com LLC. Nmap is *
* also a registered trademark of Insecure.Com LLC. This program is free *
* software; you may redistribute and/or modify it under the terms of the *
* GNU General Public License as published by the Free Software *
* Foundation; Version 2 ("GPL"), BUT ONLY WITH ALL OF THE CLARIFICATIONS *
* AND EXCEPTIONS DESCRIBED HEREIN. This guarantees your right to use, *
* modify, and redistribute this software under certain conditions. If *
* you wish to embed Nmap technology into proprietary software, we sell *
* alternative licenses (contact sales@nmap.com). Dozens of software *
* vendors already license Nmap technology such as host discovery, port *
* scanning, OS detection, version detection, and the Nmap Scripting *
* Engine. *
* *
* Note that the GPL places important restrictions on "derivative works", *
* yet it does not provide a detailed definition of that term. To avoid *
* misunderstandings, we interpret that term as broadly as copyright law *
* allows. For example, we consider an application to constitute a *
* derivative work for the purpose of this license if it does any of the *
* following with any software or content covered by this license *
* ("Covered Software"): *
* *
* o Integrates source code from Covered Software. *
* *
* o Reads or includes copyrighted data files, such as Nmap's nmap-os-db *
* or nmap-service-probes. *
* *
* o Is designed specifically to execute Covered Software and parse the *
* results (as opposed to typical shell or execution-menu apps, which will *
* execute anything you tell them to). *
* *
* o Includes Covered Software in a proprietary executable installer. The *
* installers produced by InstallShield are an example of this. Including *
* Nmap with other software in compressed or archival form does not *
* trigger this provision, provided appropriate open source decompression *
* or de-archiving software is widely available for no charge. For the *
* purposes of this license, an installer is considered to include Covered *
* Software even if it actually retrieves a copy of Covered Software from *
* another source during runtime (such as by downloading it from the *
* Internet). *
* *
* o Links (statically or dynamically) to a library which does any of the *
* above. *
* *
* o Executes a helper program, module, or script to do any of the above. *
* *
* This list is not exclusive, but is meant to clarify our interpretation *
* of derived works with some common examples. Other people may interpret *
* the plain GPL differently, so we consider this a special exception to *
* the GPL that we apply to Covered Software. Works which meet any of *
* these conditions must conform to all of the terms of this license, *
* particularly including the GPL Section 3 requirements of providing *
* source code and allowing free redistribution of the work as a whole. *
* *
* As another special exception to the GPL terms, Insecure.Com LLC grants *
* permission to link the code of this program with any version of the *
* OpenSSL library which is distributed under a license identical to that *
* listed in the included docs/licenses/OpenSSL.txt file, and distribute *
* linked combinations including the two. *
* *
* Any redistribution of Covered Software, including any derived works, *
* must obey and carry forward all of the terms of this license, including *
* obeying all GPL rules and restrictions. For example, source code of *
* the whole work must be provided and free redistribution must be *
* allowed. All GPL references to "this License", are to be treated as *
* including the terms and conditions of this license text as well. *
* *
* Because this license imposes special exceptions to the GPL, Covered *
* Work may not be combined (even as part of a larger work) with plain GPL *
* software. The terms, conditions, and exceptions of this license must *
* be included as well. This license is incompatible with some other open *
* source licenses as well. In some cases we can relicense portions of *
* Nmap or grant special permissions to use it in other open source *
* software. Please contact fyodor@nmap.org with any such requests. *
* Similarly, we don't incorporate incompatible open source software into *
* Covered Software without special permission from the copyright holders. *
* *
* If you have any questions about the licensing restrictions on using *
* Nmap in other works, are happy to help. As mentioned above, we also *
* offer alternative license to integrate Nmap into proprietary *
* applications and appliances. These contracts have been sold to dozens *
* of software vendors, and generally include a perpetual license as well *
* as providing for priority support and updates. They also fund the *
* continued development of Nmap. Please email sales@nmap.com for further *
* information. *
* *
* If you have received a written license agreement or contract for *
* Covered Software stating terms other than these, you may choose to use *
* and redistribute Covered Software under those terms instead of these. *
* *
* Source is provided to this software because we believe users have a *
* right to know exactly what a program is going to do before they run it. *
* This also allows you to audit the software for security holes. *
* *
* Source code also allows you to port Nmap to new platforms, fix bugs, *
* and add new features. You are highly encouraged to send your changes *
* to the dev@nmap.org mailing list for possible incorporation into the *
* main distribution. By sending these changes to Fyodor or one of the *
* Insecure.Org development mailing lists, or checking them into the Nmap *
* source code repository, it is understood (unless you specify otherwise) *
* that you are offering the Nmap Project (Insecure.Com LLC) the *
* unlimited, non-exclusive right to reuse, modify, and relicense the *
* code. Nmap will always be available Open Source, but this is important *
* because the inability to relicense code has caused devastating problems *
* for other Free Software projects (such as KDE and NASM). We also *
* occasionally relicense the code to third parties as discussed above. *
* If you wish to specify special license conditions of your *
* contributions, just say so when you send them. *
* *
* This program is distributed in the hope that it will be useful, but *
* WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Nmap *
* license file for more details (it's in a COPYING file included with *
* Nmap, and also available from https://svn.nmap.org/nmap/COPYING) *
* *
***************************************************************************/
/* $Id$ */
#include "nbase.h"
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#if HAVE_SYS_TIME_H
#include <sys/time.h>
#endif /* HAV_SYS_TIME_H */
#ifdef WIN32
#include <wincrypt.h>
#endif /* WIN32 */
/* data for our random state */
struct nrand_handle {
u8 i, j, s[256], *tmp;
int tmplen;
};
typedef struct nrand_handle nrand_h;
static void nrand_addrandom(nrand_h *rand, u8 *buf, int len) {
int i;
u8 si;
/* Mix entropy in buf with s[]...
*
* This is the ARC4 key-schedule. It is rather poor and doesn't mix
* the key in very well. This causes a bias at the start of the stream.
* To eliminate most of this bias, the first N bytes of the stream should
* be dropped.
*/
rand->i--;
for (i = 0; i < 256; i++) {
rand->i = (rand->i + 1);
si = rand->s[rand->i];
rand->j = (rand->j + si + buf[i % len]);
rand->s[rand->i] = rand->s[rand->j];
rand->s[rand->j] = si;
}
rand->j = rand->i;
}
static u8 nrand_getbyte(nrand_h *r) {
u8 si, sj;
/* This is the core of ARC4 and provides the pseudo-randomness */
r->i = (r->i + 1);
si = r->s[r->i];
r->j = (r->j + si);
sj = r->s[r->j];
r->s[r->i] = sj; /* The start of the the swap */
r->s[r->j] = si; /* The other half of the swap */
return (r->s[(si + sj) & 0xff]);
}
int nrand_get(nrand_h *r, void *buf, size_t len) {
u8 *p;
size_t i;
/* Hand out however many bytes were asked for */
for (p = buf, i = 0; i < len; i++) {
p[i] = nrand_getbyte(r);
}
return (0);
}
void nrand_init(nrand_h *r) {
u8 seed[256]; /* Starts out with "random" stack data */
int i;
/* Gather seed entropy with best the OS has to offer */
#ifdef WIN32
HCRYPTPROV hcrypt = 0;
CryptAcquireContext(&hcrypt, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
CryptGenRandom(hcrypt, sizeof(seed), seed);
CryptReleaseContext(hcrypt, 0);
#else
struct timeval *tv = (struct timeval *)seed;
int *pid = (int *)(seed + sizeof(*tv));
int fd;
gettimeofday(tv, NULL); /* fill lowest seed[] with time */
*pid = getpid(); /* fill next lowest seed[] with pid */
/* Try to fill the rest of the state with OS provided entropy */
if ((fd = open("/dev/urandom", O_RDONLY)) != -1 ||
(fd = open("/dev/arandom", O_RDONLY)) != -1) {
ssize_t n;
do {
errno = 0;
n = read(fd, seed + sizeof(*tv) + sizeof(*pid),
sizeof(seed) - sizeof(*tv) - sizeof(*pid));
} while (n < 0 && errno == EINTR);
close(fd);
}
#endif
/* Fill up our handle with starter values */
for (i = 0; i < 256; i++) { r->s[i] = i; };
r->i = r->j = 0;
nrand_addrandom(r, seed, 128); /* lower half of seed data for entropy */
nrand_addrandom(r, seed + 128, 128); /* Now use upper half */
r->tmp = NULL;
r->tmplen = 0;
/* This stream will start biased. Get rid of 1K of the stream */
nrand_get(r, seed, 256); nrand_get(r, seed, 256);
nrand_get(r, seed, 256); nrand_get(r, seed, 256);
}
int get_random_bytes(void *buf, int numbytes) {
static nrand_h state;
static int state_init = 0;
/* Initialize if we need to */
if (!state_init) {
nrand_init(&state);
state_init = 1;
}
/* Now fill our buffer */
nrand_get(&state, buf, numbytes);
return 0;
}
int get_random_int() {
int i;
get_random_bytes(&i, sizeof(int));
return i;
}
unsigned int get_random_uint() {
unsigned int i;
get_random_bytes(&i, sizeof(unsigned int));
return i;
}
u64 get_random_u64() {
u64 i;
get_random_bytes(&i, sizeof(i));
return i;
}
u32 get_random_u32() {
u32 i;
get_random_bytes(&i, sizeof(i));
return i;
}
u16 get_random_u16() {
u16 i;
get_random_bytes(&i, sizeof(i));
return i;
}
u8 get_random_u8() {
u8 i;
get_random_bytes(&i, sizeof(i));
return i;
}
unsigned short get_random_ushort() {
unsigned short s;
get_random_bytes(&s, sizeof(unsigned short));
return s;
}
/* This function is magic ;-)
*
* Sometimes Nmap wants to generate IPs that look random
* but don't have any duplicates. The strong RC4 generator
* can't be used for this purpose because it can generate duplicates
* if you get enough IPs (birthday paradox).
*
* This routine exploits the fact that a LCG won't repeat for the
* entire duration of its period. An LCG has some pretty bad
* properties though so this routine does extra work to try to
* tweak the LCG output so that is has very good statistics but
* doesn't repeat. The tweak used was mostly made up on the spot
* but is generally based on good ideas and has been moderately
* tested. See links and reasoning below.
*/
u32 get_random_unique_u32() {
static u32 state, tweak1, tweak2, tweak3;
static int state_init = 0;
u32 output;
/* Initialize if we need to */
if (!state_init) {
get_random_bytes(&state, sizeof(state));
get_random_bytes(&tweak1, sizeof(tweak1));
get_random_bytes(&tweak2, sizeof(tweak2));
get_random_bytes(&tweak3, sizeof(tweak3));
state_init = 1;
}
/* What is this math crap?
*
* The whole idea behind this generator is that an LCG can be constructed
* with a period of exactly 2^32. As long as the LCG is fed back onto
* itself the period will be 2^32. The tweak after the LCG is just
* a good permutation in GF(2^32).
*
* To accomplish the tweak the notion of rounds and round keys from
* block ciphers has been borrowed. The only special aspect of this
* block cipher is that the first round short-circuits the LCG.
*
* This block cipher uses three rounds. Each round is as follows:
*
* 1) Affine transform in GF(2^32)
* 2) Rotate left by round constant
* 3) XOR with round key
*
* For round one the affine transform is used as an LCG.
*/
/* Reasoning:
*
* Affine transforms were chosen both to make a LCG and also
* to try to introduce non-linearity.
*
* The rotate up each round was borrowed from SHA-1 and was introduced
* to help obscure the obvious short cycles when you truncate an LCG with
* a power-of-two period like the one used.
*
* The XOR with the round key was borrowed from several different
* published functions (but see Xorshift)
* and provides a different sequence for the full LCG.
* There are 3 32 bit round keys. This generator can
* generate 2^96 different sequences of period 2^32.
*
* This generator was tested with Dieharder. It did not fail any test.
*/
/* See:
*
* http://en.wikipedia.org/wiki/Galois_field
* http://en.wikipedia.org/wiki/Affine_cipher
* http://en.wikipedia.org/wiki/Linear_congruential_generator
* http://en.wikipedia.org/wiki/Xorshift
* http://en.wikipedia.org/wiki/Sha-1
*
* http://seclists.org/nmap-dev/2009/q3/0695.html
*/
/* First off, we need to evolve the state with our LCG
* We'll use the LCG from Numerical Recipes (m=2^32,
* a=1664525, c=1013904223). All by itself this generator
* pretty bad. We're going to try to fix that without causing
* duplicates.
*/
state = (((state * 1664525) & 0xFFFFFFFF) + 1013904223) & 0xFFFFFFFF;
output = state;
/* With a normal LCG, we would just output the state.
* In this case, though, we are going to try to destroy the
* linear correlation between IPs by approximating a random permutation
* in GF(2^32) (collision-free)
*/
/* Then rotate and XOR */
output = ((output << 7) | (output >> (32 - 7)));
output = output ^ tweak1; /* This is the round key */
/* End round 1, start round 2 */
/* Then put it through an affine transform (glibc constants) */
output = (((output * 1103515245) & 0xFFFFFFFF) + 12345) & 0xFFFFFFFF;
/* Then rotate and XOR some more */
output = ((output << 15) | (output >> (32 - 15)));
output = output ^ tweak2;
/* End round 2, start round 3 */
/* Then put it through another affine transform (Quick C/C++ constants) */
output = (((output * 214013) & 0xFFFFFFFF) + 2531011) & 0xFFFFFFFF;
/* Then rotate and XOR some more */
output = ((output << 5) | (output >> (32 - 5)));
output = output ^ tweak3;
return output;
}
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