From 0b6b94e6b6152f15cf4c2247c5974f539aae28cd Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 10 Apr 2024 21:49:46 +0200 Subject: Adding upstream version 1:9.6p1. Signed-off-by: Daniel Baumann --- moduli.5 | 126 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 126 insertions(+) create mode 100644 moduli.5 (limited to 'moduli.5') diff --git a/moduli.5 b/moduli.5 new file mode 100644 index 0000000..5086a6d --- /dev/null +++ b/moduli.5 @@ -0,0 +1,126 @@ +.\" $OpenBSD: moduli.5,v 1.19 2022/04/16 04:30:10 dtucker Exp $ +.\" +.\" Copyright (c) 2008 Damien Miller +.\" +.\" Permission to use, copy, modify, and distribute this software for any +.\" purpose with or without fee is hereby granted, provided that the above +.\" copyright notice and this permission notice appear in all copies. +.\" +.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES +.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF +.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR +.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES +.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN +.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF +.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +.Dd $Mdocdate: April 16 2022 $ +.Dt MODULI 5 +.Os +.Sh NAME +.Nm moduli +.Nd Diffie-Hellman moduli +.Sh DESCRIPTION +The +.Pa /etc/moduli +file contains prime numbers and generators for use by +.Xr sshd 8 +in the Diffie-Hellman Group Exchange key exchange method. +.Pp +New moduli may be generated with +.Xr ssh-keygen 1 +using a two-step process. +An initial +.Em candidate generation +pass, using +.Ic ssh-keygen -M generate , +calculates numbers that are likely to be useful. +A second +.Em primality testing +pass, using +.Ic ssh-keygen -M screen , +provides a high degree of assurance that the numbers are prime and are +safe for use in Diffie-Hellman operations by +.Xr sshd 8 . +This +.Nm +format is used as the output from each pass. +.Pp +The file consists of newline-separated records, one per modulus, +containing seven space-separated fields. +These fields are as follows: +.Bl -tag -width Description -offset indent +.It timestamp +The time that the modulus was last processed as YYYYMMDDHHMMSS. +.It type +Decimal number specifying the internal structure of the prime modulus. +Supported types are: +.Pp +.Bl -tag -width 0x00 -compact +.It 0 +Unknown, not tested. +.It 2 +"Safe" prime; (p-1)/2 is also prime. +.It 4 +Sophie Germain; 2p+1 is also prime. +.El +.Pp +Moduli candidates initially produced by +.Xr ssh-keygen 1 +are Sophie Germain primes (type 4). +Further primality testing with +.Xr ssh-keygen 1 +produces safe prime moduli (type 2) that are ready for use in +.Xr sshd 8 . +Other types are not used by OpenSSH. +.It tests +Decimal number indicating the type of primality tests that the number +has been subjected to represented as a bitmask of the following values: +.Pp +.Bl -tag -width 0x00 -compact +.It 0x00 +Not tested. +.It 0x01 +Composite number \(en not prime. +.It 0x02 +Sieve of Eratosthenes. +.It 0x04 +Probabilistic Miller-Rabin primality tests. +.El +.Pp +The +.Xr ssh-keygen 1 +moduli candidate generation uses the Sieve of Eratosthenes (flag 0x02). +Subsequent +.Xr ssh-keygen 1 +primality tests are Miller-Rabin tests (flag 0x04). +.It trials +Decimal number indicating the number of primality trials +that have been performed on the modulus. +.It size +Decimal number indicating the size of the prime in bits. +.It generator +The recommended generator for use with this modulus (hexadecimal). +.It modulus +The modulus itself in hexadecimal. +.El +.Pp +When performing Diffie-Hellman Group Exchange, +.Xr sshd 8 +first estimates the size of the modulus required to produce enough +Diffie-Hellman output to sufficiently key the selected symmetric cipher. +.Xr sshd 8 +then randomly selects a modulus from +.Fa /etc/moduli +that best meets the size requirement. +.Sh SEE ALSO +.Xr ssh-keygen 1 , +.Xr sshd 8 +.Sh STANDARDS +.Rs +.%A M. Friedl +.%A N. Provos +.%A W. Simpson +.%D March 2006 +.%R RFC 4419 +.%T Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol +.Re -- cgit v1.2.3