Choose from the two sets of instructions below depending on whether you would like the option to submit data to our anonymized research study, the goal of which is to measure the potential dangers of leaving the host names and addresses in your known_hosts files unencrypted. We ask you to consider this now as once you've converted your known_hosts addresses to hashed host format it will no longer be possible to collect this data. Data will not be submitted to our servers without your additional consent during the collection process.

Instructions for patching with the option to contribute to our study:

1. You will need to download:
   • Portable OpenSSH 3.9p1
   • Hashed hosts patch (2005-03-14, with data collection)

   Alternatively, you can download the above files via command line if you have wget:

   wget ftp://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-3.9p1.tar.gz
   wget http://nms.lcs.mit.edu/projects/ssh/openssh-3.9p1-hashed-hosts-COLLECT-20050314.patch.gz
   
   

2. Issue the following commands to unpack the OpenSSH source, apply our patch, and build the patched OpenSSH:

   tar zxf openssh-3.9p1.tar.gz
   gunzip openssh-3.9p1-hashed-hosts-COLLECT-20050314.patch.gz
   patch -p0 < openssh-3.9p1-hashed-hosts-COLLECT-20050314.patch
   cd openssh-3.9p1
   ./configure --prefix=/usr
   make
   
   

3. Install while running as root. This will replace your existing OpenSSH binaries.

   make install
   

4. To obtain the security benefits of the patch, you will need to convert your system's known_hosts files to the hashed hosts format.
   
   The convert_known_hosts.pl script will attempt to locate each user's known_hosts file and convert it to hashed hosts format. In order to do this correctly, the script must be run as root. Backup copies of the original files will be encrypted and placed in the same directory as the originals. You will want to use a pass phrase that is not used elsewhere on your system. Before running convert_known_hosts.pl, you must run the script build-CR.sh in order to build (in place) the Crypt::Rijndael and Digest::SHA1 perl modules if they are not already available on your system. If you need to access the backup files, or if you have any problems running the script, look at the README file and the script's -h (help) option for more information.

   sh build-CR.sh
   perl convert_known_hosts.pl
   

Instructions for patching without contributing to the study (use this option if have already contributed):

1. You will need to download:
   • Portable OpenSSH 3.9p1
   • Hashed hosts patch (2005-02-14, without data collection)

   Alternatively, you can download the above files via command line if you have wget:

   wget ftp://ftp.openbsd.org/pub/OpenBSD/OpenSSH/portable/openssh-3.9p1.tar.gz
   wget http://nms.lcs.mit.edu/projects/ssh/openssh-3.9p1-hashed-hosts-NOCOLLECT-20050214.patch.gz
   
   

2. Issue the following commands to unpack the OpenSSH source, apply our patch, and build the patched OpenSSH:

   tar zxf openssh-3.9p1.tar.gz
   gunzip openssh-3.9p1-hashed-hosts-NOCOLLECT-20050214.patch.gz
   patch -p0 < openssh-3.9p1-hashed-hosts-NOCOLLECT-20050214.patch
   cd openssh-3.9p1
   ./configure --prefix=/usr
   make 
   
   

3. Install while running as root. This will replace your existing OpenSSH binaries.

   make install
   

4. To obtain the security benefits of the patch, you will need to convert your system's known_hosts files to the hashed hosts format.
   
   The convert_known_hosts.pl script will attempt to locate each user's known_hosts file and convert it to hashed hosts format. In order to do this correctly, the script must be run as root. Backup copies of the original files will be encrypted and placed in the same directory as the originals. You will want to use a pass phrase that is not used elsewhere on your system. If you need to access the backup files, or if you have any problems running the script, look at the README file and the script's -h (help) option for more information.

   perl convert_known_hosts.pl