3571e53040
patches for easier mirroring, to eliminate a special copy, to make www.freebsd.org/security a full copy of security.freebsd.org and be eventually be the same. For now files are just sitting there. The symlinks are missing. Discussed on: www (repository location) Discussed with: simon (so)
260 lines
10 KiB
Text
260 lines
10 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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=============================================================================
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FreeBSD-SA-01:24 Security Advisory
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FreeBSD, Inc.
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Topic: SSH1 implementations may allow remote system, data compromise
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Category: core/ports
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Module: openssh, ssh
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Announced: 2001-02-12
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Credits: Michal Zalewski <lcamtuf@razor.bindview.com> (Vulnerability 1)
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Core-SDI (http://www.core-sdi.com) (Vulnerability 2)
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Affects: FreeBSD 4.x, 4.2-STABLE prior to the correction date
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Ports collection prior to the correction date.
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Corrected: OpenSSH [FreeBSD 4.x base system]:
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2000-12-05 (Vulnerability 1)
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2001-02-11 (Vulnerability 2)
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OpenSSH [ports]:
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2001-02-09 (Vulnerability 1)
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2001-02-11 (Vulnerability 2)
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ssh [ports]:
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2001-02-09 (Vulnerability 1)
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2001-02-09 (Vulnerability 2)
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Vendor status: Patches released.
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FreeBSD only: NO
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I. Background
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OpenSSH is an implementation of the SSH1 and SSH2 secure shell
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protocols for providing encrypted and authenticated network access,
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which is available free for unrestricted use.
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An SSH1 client/server (ssh) from ssh.com is included in the ports
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collection. This software is not available free of charge for all
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uses, and the FreeBSD Security Officer does not recommend its use.
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II. Problem Description
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There are two flaws in the SSH1 protocol as implemented by OpenSSH and
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ssh.
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Vulnerability 1:
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An integer overflow may allow arbitrary remote users to obtain root
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permissions on the server running sshd. This is due to a coding
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mistake in code intended to work around a protocol flaw in the SSH1
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protocol. This vulnerability was corrected in OpenSSH 2.3.0, which
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was committed to FreeBSD 4.2-STABLE on 2000-12-05.
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Vulnerability 2;
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Remote attackers who can observe the encrypted contents of a user's
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SSH1 session, and who have the ability to mount large numbers of
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connections fo the SSH1 server may be able to break the transient
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server key used by the server to negotiate encryption parameters for
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the session, and from there can decrypt the entire contents of the
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snooped connection. The transient key has a lifetime of only one
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hour by default, but all snooped SSH1 sessions captured within this
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timeframe may be broken if the attack is successful.
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This attack is mitigated by the requirement to initiate large
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numbers of SSH1 protocol connections to the server during the
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lifetime of the key. On average a sustained connection rate of
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around 400 connections and SSH1 protocol handshakes must be carried
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out per second to have a high chance of succeeding within the 1 hour
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lifetime of the server key. OpenSSH contains rate-limiting code
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which will limit the number of outstanding connections to a fraction
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of this number in the default configuration, and computational and
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network limitations may reduce this number still further.
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Therefore, though the potential impact of this flaw is great, it is
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made very difficult to exploit in practice. However, note that even
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though the chances of success are reduced, the vulnerability is not
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eliminated.
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OpenSSH is installed if you chose to install the 'crypto' distribution
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at install-time or when compiling from source, and is installed and
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enabled by default as of FreeBSD 4.1.1-RELEASE. By default SSH1
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protocol support is enabled.
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If SSH1 protocol support has been disabled in OpenSSH, it is not
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vulnerable to these attacks. They do not affect implementations of
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the SSH2 protocol, such as OpenSSH run in SSH2-only mode.
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Versions of the OpenSSH port prior to openssh-2.2.0_2, and versions
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of the ssh port prior to ssh-1.2.27_3 are vulnerable to these attacks.
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III. Impact
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Arbitrary remote users may be able to execute arbitrary code as root
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on an SSH1 server accepting connections via the SSH1 protocol.
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Remote users who can snoop the encrypted contents of SSH1 sessions
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belonging to other users, and who can mount a very high rate of
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connections to the server may be able to mount an attack leading to
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the ability to decrypt these sessions. This attack may disclose
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account password details as well as other sensitive data.
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IV. Workaround
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If you are running sshd, disable the use of the SSH1 protocol in
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OpenSSH. SSH1 contains inherent protocol deficiencies and is not
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recommended for use in high-security environments. Note that some
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third-party SSH clients are not capable of using the SSH2 protocol,
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however the OpenSSH client (version 2.1 and later) included in FreeBSD
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is SSH2-capable.
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To disable SSH1, add the following line to the /etc/ssh/sshd_config
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file (/usr/local/etc/sshd_config for the OpenSSH port):
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Protocol 2
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and remove any other "Protocol" directives from that file.
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Execute the following command as root:
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# kill -HUP `cat /var/run/sshd.pid`
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This will cause the parent process to reread its configuration file,
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and should not interfere with existing SSH sessions.
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V. Solution
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- --[OpenSSH - base system]-----
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One of the following:
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1) Upgrade to FreeBSD 4.2-STABLE after the correction date. Note that
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these versions of FreeBSD contain a newer version of OpenSSH (version
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2.3.0) than was in 4.2-RELEASE (version 2.2.0).
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2) Download the patch and detached PGP signature from the following
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location:
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The following patch applies to FreeBSD 4.2-RELEASE.
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# fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:24/sshd-4.2-release.patch
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# fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:24/sshd-4.2-release.patch.asc
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The folllowing patch applies to FreeBSD 4.2-STABLE which is running
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OpenSSH 2.3.0 (4.2-STABLE dated after 2000-12-05)
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# fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:24/sshd-4.2-stable.patch
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# fetch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-01:24/sshd-4.2-stable.patch.asc
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Verify the detached signature using your PGP utility.
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Issue the following commands as root:
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# cd /usr/src/crypto/openssh
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# patch -p < /path/to/patch
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# cd /usr/src/secure/lib/libssh
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# make all
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# cd /usr/src/secure/usr.bin/ssh-agent
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# make all install
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# cd /usr/src/secure/usr.sbin/sshd
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# make all install
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Finally, if sshd is already running then kill and restart the sshd
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daemon: perform the following command as root:
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# kill -KILL `cat /var/run/sshd.pid` && /usr/sbin/sshd
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This will not affect sessions in progress.
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- --[OpenSSH - port]-----
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Use one of the following options to upgrade the OpenSSH software, then
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kill and restart the sshd daemon if it is already running. This will
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not affect sessions in progress.
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To kill and restart the sshd daemon, perform the following command as
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root:
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# kill -KILL `cat /var/run/sshd.pid` && /usr/local/sbin/sshd
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1) Upgrade your entire ports collection and rebuild the OpenSSH port.
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2) Deinstall the old package and install a new package dated after the
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correction date, obtained from:
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[i386]
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/security/openssh-2.2.0_2.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/security/openssh-2.2.0_2.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/security/openssh-2.2.0_2.tgz
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NOTE: It may be several days before updated packages are available.
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[alpha]
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Packages are not automatically generated for the alpha architecture at
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this time due to lack of build resources.
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3) download a new port skeleton for the OpenSSH port from:
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http://www.freebsd.org/ports/
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and use it to rebuild the port.
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4) Use the portcheckout utility to automate option (3) above. The
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portcheckout port is available in /usr/ports/devel/portcheckout or the
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package can be obtained from:
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/devel/portcheckout-2.0.tgz
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- --[ssh - port]-----
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Use one of the following options to upgrade the ssh software, then
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kill and restart the sshd daemon if it is already running. This will
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not affect sessions in progress.
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To kill and restart the sshd daemon, perform the following command as
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root:
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# kill -KILL `cat /var/run/sshd.pid` && /usr/local/sbin/sshd
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1) Upgrade your entire ports collection and rebuild the ssh port.
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2) Deinstall the old package and install a new package dated after the
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correction date, obtained from:
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[i386]
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/security/ssh-1.2.27_3.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/security/ssh-1.2.27_3.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/security/ssh-1.2.27_3.tgz
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NOTE: It may be several days before updated packages are available.
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[alpha]
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Packages are not automatically generated for the alpha architecture at
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this time due to lack of build resources.
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3) download a new port skeleton for the OpenSSH port from:
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http://www.freebsd.org/ports/
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and use it to rebuild the port.
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4) Use the portcheckout utility to automate option (3) above. The
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portcheckout port is available in /usr/ports/devel/portcheckout or the
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package can be obtained from:
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-3-stable/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-4-stable/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-4-stable/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/i386/packages-5-current/devel/portcheckout-2.0.tgz
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ftp://ftp.FreeBSD.org/pub/FreeBSD/ports/alpha/packages-5-current/devel/portcheckout-2.0.tgz
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-----BEGIN PGP SIGNATURE-----
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Version: GnuPG v1.0.4 (FreeBSD)
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Comment: For info see http://www.gnupg.org
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