similar to: Openssh, moduli and ssh-keygen

Hi, Can anybody briefly explain the significance of the updated moduli file? Is this a critical update? Should all existing installations update their moduli file? Thanks in advance, -- Dan

Also, how are default moduli shipped with OpenSSH for use in diffie-hellman-group-exchange-sha1/sha256 chosen? Are they chosen randomly by developers or are they chosen for security properties? If they are random, why not use moduli from RFC 7919 instead, like Mozilla recommends? On Fri, Feb 15, 2019 at 3:48 AM Mark D. Baushke <mdb at juniper.net> wrote: > > Yegor Ievlev <koops1997

On 09/24/2017 12:21 AM, Mark D. Baushke wrote: > I suggest you upgrade to a more recent edition of the OpenSSH software. > The most recent release is OpenSSH 7.5 and OpenSSH 7.6 will be released > very soon. This problem is in v7.5 and v7.6. See dh.c:436. > OpenSSH 6.6 was first released on October 6, 2014. I brought up v6.6 to give an example that older clients wouldn't be

Hi, You will be aware of https://weakdh.org/ by now, I presume; the take-home seems to be that 1024-bit DH primes might well be too weak. I'm wondering what (if anything!) you propose to do about this issue, and what Debian might do for our users? openssh already prefers ECDH, which must reduce the impact somewhat, although the main Windows client (PuTTY) doesn't support ECDH yet. But

> Can this be addressed in ssh_config/sshd_config with the KexAlgorithms setting? weakdh.org/sysadmin.html recommends adding: KexAlgorithms curve25519-sha256 at libssh.org But this thread makes it sound as if it's not necessary. Can anyone confirm? Personally I'm on openssh-6.7. - Grant > You will be aware of https://weakdh.org/ by now, I presume; the take-home seems to be

Hi, I'm interested in requiring a minimum of 3072-bit DH moduli when using the "diffie-hellman-group-exchange-sha256" kex, so I edited my /etc/ssh/moduli file such that only 3071+ moduli are left. However, when clients ask for a max of 2048-bit moduli, they actually get one (!). I poked around and found that a fallback mechanism exists (dh.c:185), which returns back the

On 09/22/2017 06:55 PM, Tim Broberg wrote: > Do I understand correctly, that you find the security of group 14 unacceptable and yet you left it enabled? In the end, I'm trying to ensure a minimum equivalent of 128-bits of security. Group14 is 2048-bits, which roughly translates to 112-bits. [1] To this end, I disabled the "diffie-hellman-group14-sha1" and

Greetings, Given the weakness with Diffie-Hellman modp groups less than 2048, is it time to bump the suggested 1024 bit minimum value from the RFC 4419 to a more current 2048 value for OpenSSH 7.0? If so, should this be just a compile-time change, or should there be a new client and server runtime option? Thanks, -- Mark

A few questions regarding the OpenSSH support for the Diffie Hellman key exchange algorithms: (1) Are the diffie-hellman-group-exchange-sha256", "diffie-hellman-group-exchange-sha1" , "diffie-hellman-group14-sha1" "diffie-hellman-group1-sha1" (as defined in RFCs 4253 and RFC 4419) the complete list of key exchange algorithms supported by OpenSSH? (2) Is there a

http://bugzilla.mindrot.org/show_bug.cgi?id=1372 Summary: sshd(8) and ssh-keygen(1) refer to non-existent moduli(5) Product: Portable OpenSSH Version: 4.7p1 Platform: All OS/Version: All Status: NEW Severity: normal Priority: P2 Component: Documentation AssignedTo: bitbucket at

Hello all, I propose the following patch to ssh-keygen.c for openssh version 4.5. It allows to redirect output of the moduli operations to stdout, to do something like e.g.: $ ssh-keygen -G - -b 2048 | ssh-keygen -T - -f - >moduli Best regards, Christian --- ssh/ssh-keygen.c.old 2007-03-01 12:43:06.000000000 +0100 +++ ssh/ssh-keygen.c 2007-03-01 12:47:32.000000000 +0100 @@ -1270,13

https://bugzilla.mindrot.org/show_bug.cgi?id=2302 Bug ID: 2302 Summary: ssh (and sshd) should not fall back to deselected KEX algos Product: Portable OpenSSH Version: 6.7p1 Hardware: All OS: All Status: NEW Severity: security Priority: P5 Component: ssh

https://bugzilla.mindrot.org/show_bug.cgi?id=2302 Bug ID: 2302 Summary: ssh (and sshd) should not fall back to deselected KEX algos Product: Portable OpenSSH Version: 6.7p1 Hardware: All OS: All Status: NEW Severity: security Priority: P5 Component: ssh

After upgrading a Linux system from OpenSSH 6.7 to 6.9, Cisco switches/routers can no longer scp config files to/from the system. The last debug entry before the Cisco device closes the connection is "debug1: server_input_channel_open: confirm session". The next line is "Connection closed by x.x.x.x". Anyone else seen this or know of a fix? The Cisco device gives

Hi, In a recent security review some systems I manage were flagged due to supporting "weak" ciphers, specifically the ones listed below. So first question is are people generally modifying the list of ciphers supported by the ssh client and sshd? On CentOS 6 currently it looks like if I remove all the ciphers they are concerned about then I am left with Ciphers

> Portable OpenSSH is also available via [...] Github: https://github.com/openssh/openssh-portable > > Running the regression tests supplied with Portable OpenSSH does not require installation and is a simply: > > $ ./configure && make tests I was going to try this on Kali Linux (latest version), but ran into trouble right away. No "configure" script exists

On Fri, 2019-02-15 at 15:57 +1100, Darren Tucker wrote: > That was the original intent (and it's mentioned in RFC4419) however > each moduli file we ship (70-80 instances of 6 sizes) takes about 1 > cpu-month to generate on a lowish-power x86-64 machine. Most of it > is > parallelizable, but even then it'd likely take a few hours to > generate > one of each size. I

On 09/22/2017 03:22 PM, Daniel Kahn Gillmor wrote: > On Thu 2017-09-21 18:12:44 -0400, Joseph S Testa II wrote: >> I gotta say... having a fallback mechanism here seems pretty >> strange. The entire point of the group exchange is to use a dynamic >> group and not a static one. > > fwiw, i think dynamic groups for DHE key exchange is intrinsically > problematic

https://bugzilla.mindrot.org/show_bug.cgi?id=2614 Bug ID: 2614 Summary: ssh-keygen: Moduli generation not accepting start line and count options Product: Portable OpenSSH Version: 7.2p1 Hardware: amd64 OS: Linux Status: NEW Severity: normal Priority: P5 Component:

On Fri, May 22, 2015 at 12:27:01, Darren Tucker <dtucker at zip.com.au> wrote: > Note that PuTTY does do Diffie-Hellman Group Exchange, but until very > recently (ie after their 0.64 release) they didn't do the one that was > actually standardized in RFC4419. OpenSSH recently removed support for > that non-standard one and as a result we don't offer DHGEX to PuTTY >