--- Begin Message ---
- To: submit@bugs.debian.org
- Subject: openssh-client: ssh/scp rekey fails when using GSSAPI KEX
- From: Peter Gille <gille.peter@gmail.com>
- Date: Sun, 27 Mar 2016 17:11:43 +0200
- Message-id: <87vb48gdlc.fsf@wintermute.idem.me>
Package: openssh-client
Version: 1:7.2p2-1
Severity: normal
Dear Maintainer,
I get failures during rekey when using ssh with kerberos authentication
and GSSAPI key-exchange. This can be noticed in long-running ssh
sessions or when doing large scp transfers (or triggered manually in the
ssh client, using the ~R escape sequence).
As far as I can make out the ssh client offers a different set of
key-exchange algorithms on initial connection and when doing the
rekeying. Here is an example output:
-------
$ ssh -vvv foo.example.com
[...]
debug1: Authenticating to foo.example.com:22 as 'user'
[...]
debug2: local client KEXINIT proposal
debug2: KEX algorithms: gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-gex-sha1-A/vxljAEU54gt9a48EiANQ==,gss-group1-sha1-A/vxljAEU54gt9a48EiANQ==,gss-group14-sha1-A/vxljAEU54gt9a48EiANQ==,gss-gex-sha1-bontcUwnM6aGfWCP21alxQ==,gss-group1-sha1-bontcUwnM6aGfWCP21alxQ==,gss-group14-sha1-bontcUwnM6aGfWCP21alxQ==,gss-gex-sha1-eipGX3TCiQSrx573bT1o1Q==,gss-group1-sha1-eipGX3TCiQSrx573bT1o1Q==,gss-group14-sha1-eipGX3TCiQSrx573bT1o1Q==,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,ext-info-c
[...]
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
[...]
Last login: Fri Mar 25 09:56:20 2016 from foo
foo% echo "now sending rekey request with ~R"
now sending rekey request with ~R
foo% debug1: need rekeying
debug1: SSH2_MSG_KEXINIT sent
debug1: rekeying in progress
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1
debug2: host key algorithms: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa,null
[...]
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: gss-gex-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==,gss-group14-sha1-toWM5Slw5Ew8Mqkay+al2g==,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
[...]
debug1: kex: algorithm: curve25519-sha256@libssh.org
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: rekeying in progress
debug1: rekeying in progress
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:w7yxbCZNBwQ0S0AgmCrFYa3XUpDjvWiDOw4/YOY9q8E
The authenticity of host 'foo.example.com (10.0.1.2)' can't be established.
ECDSA key fingerprint is SHA256:w7yxbCZNBwQ0S0AgmCrFYa3XUpDjvWiDOw4/YOY9q8E.
Are you sure you want to continue connecting (yes/no)?
Host key verification failed.
-------
So it appears that the client does not see the gss-* methods but the
server still does.
/ Peter
-- System Information:
Debian Release: stretch/sid
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'testing')
Architecture: amd64 (x86_64)
Kernel: Linux 4.3.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=locale: Cannot set LC_ALL to default locale: No such file or directory
UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages openssh-client depends on:
ii adduser 3.114
ii dpkg 1.18.4
ii libc6 2.22-3
ii libedit2 3.1-20150325-1+b1
ii libgssapi-krb5-2 1.13.2+dfsg-5
ii libselinux1 2.4-3+b1
ii libssl1.0.2 1.0.2g-1
ii passwd 1:4.2-3.1
ii zlib1g 1:1.2.8.dfsg-2+b1
Versions of packages openssh-client recommends:
ii xauth 1:1.0.9-1
Versions of packages openssh-client suggests:
pn keychain <none>
pn libpam-ssh <none>
pn monkeysphere <none>
pn ssh-askpass <none>
-- debconf information:
--- End Message ---
--- Begin Message ---
Source: openssh
Source-Version: 1:7.4p1-6
We believe that the bug you reported is fixed in the latest version of
openssh, which is due to be installed in the Debian FTP archive.
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to 819361@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Colin Watson <cjwatson@debian.org> (supplier of updated openssh package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
Format: 1.8
Date: Mon, 16 Jan 2017 15:11:10 +0000
Source: openssh
Binary: openssh-client openssh-client-ssh1 openssh-server openssh-sftp-server ssh ssh-krb5 ssh-askpass-gnome openssh-client-udeb openssh-server-udeb
Architecture: source
Version: 1:7.4p1-6
Distribution: unstable
Urgency: medium
Maintainer: Debian OpenSSH Maintainers <debian-ssh@lists.debian.org>
Changed-By: Colin Watson <cjwatson@debian.org>
Description:
openssh-client - secure shell (SSH) client, for secure access to remote machines
openssh-client-ssh1 - secure shell (SSH) client for legacy SSH1 protocol
openssh-client-udeb - secure shell client for the Debian installer (udeb)
openssh-server - secure shell (SSH) server, for secure access from remote machines
openssh-server-udeb - secure shell server for the Debian installer (udeb)
openssh-sftp-server - secure shell (SSH) sftp server module, for SFTP access from remot
ssh - secure shell client and server (metapackage)
ssh-askpass-gnome - interactive X program to prompt users for a passphrase for ssh-ad
ssh-krb5 - secure shell client and server (transitional package)
Closes: 819361 850275 850614 851573
Changes:
openssh (1:7.4p1-6) unstable; urgency=medium
.
* Remove temporary file on exit from postinst (closes: #850275).
* Remove LOGIN_PROGRAM and LOGIN_NO_ENDOPT definitions, since UseLogin is
gone.
* Document sshd_config changes that may be needed following the removal of
protocol 1 support from sshd (closes: #851573).
* Remove ssh_host_dsa_key from HostKey default (closes: #850614).
* Fix rekeying failure with GSSAPI key exchange (thanks, Harald Barth;
closes: #819361, LP: #1608965).
Checksums-Sha1:
bc3d6bdd8e56c1f39772c34656302b87f964e89a 2956 openssh_7.4p1-6.dsc
76756a0714d77c72a8764d7270015e2ef2078d66 158280 openssh_7.4p1-6.debian.tar.xz
Checksums-Sha256:
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7dd11fd679db97f01f1bf88d269ac0df11d1ff893c85704ee53c8ea862b86c97 158280 openssh_7.4p1-6.debian.tar.xz
Files:
91e91ffa4f31f68ffa9f1780b8fa7a01 2956 net standard openssh_7.4p1-6.dsc
6c7d449bdafc3b584a29432fc68b8bb3 158280 net standard openssh_7.4p1-6.debian.tar.xz
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