starting moduli.c port from OpenSSH

2021-05-04 03:39:43 -04:00
parent d3a5f039c1
commit a31d50359a
11 changed files with 364 additions and 60 deletions
--- a/dh/README
+++ b/dh/README
@@ -0,0 +1,51 @@
+The functions found in this sub-component are ported almost directly from the
+openssh-portable[0]'s `moduli.c`[1] code (with, of course, changes made where
+appropriate to match and take advantage of Golang).
+
+The OpenBSD and OpenSSH(-portable) teams have my gratitude.
+
+OpenSSH/OpenSSH portable are released under a combination of the following licenses[2]:
+
+* public domain
+* "BSD-style"
+* 2-, 3-, and 4-clause BSD
+* Beerware
+
+The license in full for OpenSSH/OpenSSH-Portable can be found at [2].
+
+The license for OpenSSH-Portable's `moduli.c` is as follows:
+
+###########################################################################
+Copyright 1994 Phil Karn <karn@qualcomm.com>
+Copyright 1996-1998, 2003 William Allen Simpson <wsimpson@greendragon.com>
+Copyright 2000 Niels Provos <provos@citi.umich.edu>
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+###########################################################################
+
+
+[0] https://www.openssh.com/portable.html
+    https://anongit.mindrot.org/openssh.git
+
+[1] https://anongit.mindrot.org/openssh.git/tree/moduli.c
+
+[2] https://anongit.mindrot.org/openssh.git/tree/LICENCE
--- a/dh/const.go
+++ b/dh/const.go
@@ -0,0 +1,40 @@
+package dh
+
+const (
+	// QSizeMinimum Specifies the number of the most significant bit (0 to M).
+	// WARNING: internally, usually 1 to N.
+	QSizeMinimum = 511
+
+	// Prime sieving constants
+	// Assuming 8 bit bytes and 32 bit words.
+	ShiftBit = 3
+	ShiftByte = 2
+	ShiftWord = ShiftBit + ShiftByte
+	ShiftMegabyte = 20
+	ShiftMegaWord = ShiftMegabyte - ShiftBit
+
+	// Memory limits.
+	// LargeMinimum is 8 megabytes
+	LargeMinimum = uint32(8) // Originally an 8UL in moduli.c
+	// LargeMaximum is 127MB.
+	LargeMaximum = uint32(127)
+	// The largest sieve prime has to be < 2**32 on 32-bit systems.
+	SmallMaximum = uint32(0xffffffff) // 4294967295
+	// Can sieve all primes less than 2**32, as 65537**2 > 2**32-1.
+	TinyNumber = uint32(1) << 16
+	// Ensure enough bit space for testing 2*q.
+	TestMaximum = uint32(1) << 16
+	TestMinimum = QSizeMinimum + 1 // (uint32(1) << (ShiftWord - TestPower))
+	TestPower = 3 // 2**n, n < ShiftWord
+)
+
+var (
+)
+
+// Bit* functions operate on 32-bit words
+func BitClear(a []uint32, n uint32) (i uint32) {
+
+	i = a[n >> ShiftWord] &= ~(uint32(1) << (n & 31))
+
+	return
+}
--- a/dh/func_gen.go
+++ b/dh/func_gen.go
@@ -0,0 +1,36 @@
+/*
+   SSHSecure - a program to harden OpenSSH from defaults
+   Copyright (C) 2020  Brent Saner
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   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
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package dh
+
+/*
+	OpenSSH does prime generation and primality checking a *little* weird.
+
+	The seemingly go-to package for DH parameter generation in Golang, github.com/Luzifer/go-dhparam,
+	does implement safety checking in a way I believe to be safe (with the huge caveat that I am nowhere
+	near a professional, expert, guru, etc. in mathematics, cryptography, or the like).
+
+	However, it is incompatible with OpenSSH's methodology for DH parameter generation.
+
+	1.) First, primes are generated via the Sieve of Eratosthenes.
+		a.) They must also be Sophie Germain primes (where p is selected prime, 2p+1 is also prime).
+	2.) Then they are filtered via Probabilistic Miller-Rabin primality tests (on both q and p, where q is (p-1)/2).
+	3.) OpenSSH fully supports generators of 2, 3, and 5 whereas go-dhparam only fully supports 2 and 5.
+
+	And that's why I'm a sad panda and porting moduli.c to native Golang.
+*/