diff options
Diffstat (limited to 'static/freebsd/man5/moduli.5')
| -rw-r--r-- | static/freebsd/man5/moduli.5 | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/static/freebsd/man5/moduli.5 b/static/freebsd/man5/moduli.5 new file mode 100644 index 00000000..eead6cd0 --- /dev/null +++ b/static/freebsd/man5/moduli.5 @@ -0,0 +1,123 @@ +.\" $OpenBSD: moduli.5,v 1.16 2011/11/28 08:46:27 eric Exp $ +.\" +.\" Copyright (c) 2008 Damien Miller <djm@mindrot.org> +.\" +.\" 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 July 19, 2012 +.Dt MODULI 5 +.Os +.Sh NAME +.Nm moduli +.Nd Diffie-Hellman moduli +.Sh DESCRIPTION +The +.Pa /etc/ssh/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 -G , +calculates numbers that are likely to be useful. +A second +.Em primality testing +pass, using +.Ic ssh-keygen -T , +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/ssh/moduli +that best meets the size requirement. +.Sh SEE ALSO +.Xr ssh-keygen 1 , +.Xr sshd 8 +.Rs +.%R RFC 4419 +.%T "Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol" +.%D 2006 +.Re |
