NAME

Net::SSH::AuthorizedKey - Virtual Base Class for SSH Public Keys

SYNOPSIS

    use Net::SSH::AuthorizedKey;

      # Either parse a string (without leading whitespace or comments):
    my $key = Net::SSH::AuthorizedKey->parse( $line );

    if(defined $key) {
          # ssh-1 or ssh-2
        print "Key parsed, type is ", $key->type(), "\n";
    } else {
        die "Cannot parse key '$line'";
    }

      # ... or create an object yourself:
    my $pubkey = Net::SSH::AuthorizedKey->new(
        options  => { from                  => 'foo@bar.com', 
                      "no-agent-forwarding" => 1 },
        key      => "123....890",
        keylen   => 1024,
        exponent => 35,
        type     => "ssh-1",
    );

DESCRIPTION

Net::SSH::AuthorizedKey is a virtual base class for ssh public keys. Real implementations of it are Net::SSH::AuthorizedKey::SSH1 and Net::SSH::AuthorizedKey::SSH2.

The only way to using it directly is by calling its parse() method, and passing it an authorized_keys string (aka a line from an authorized_keys file). If it recognizes either a ssh-1 or a ssh-2 type key, it will return a Net::SSH::AuthorizedKey::SSH1 or a Net::SSH::AuthorizedKey::SSH2 object, both of which support the accessor methods defined in the FIELDS section below.

The as_string() method will cobble the (perhaps modified) fields together and return them as a string suitable as a line for an authorized_keys file.

METHODS

"parse( $line )": Reads in a single text line containing a ssh-1 or ssh-2 key. Returns a Net::SSH::AuthorizedKey::SSH1 or a Net::SSH::AuthorizedKey::SSH2 object, or "undef" in case of an error.
"fingerprint()": Returns a MD5 hex hash of the parsed key. The hash is unique for functionally identical keys. Fields not contributing to the key's functional uniqueness are ignored.
"error()": Returns the last parsing error encountered as a text string.
"as_string( )": Return the object as a string suitable as a autorized_keys line.

FIELDS

All of the following fields are available via accessors:

"type": Type of ssh key, usually "ssh-1" or "ssh-2".
"key": Public key, either a long number (ssh-1) or a line of alphanumeric characters (ssh-2).
"keylen": Length of the key in bit (e.g. 1024).
"exponent": Two-digit number in front of the key in ssh-1 authorized_keys lines.
"options": Returns a reference to a hash with options key/value pairs, listed in front of the key.

IMPLEMENTATION REFERENCE

The key parsers implemented in this distribution are implemented similarily as the authorized_keys file parser in the openssh source distribution.

Openssh contains the authorized_keys parser in its auth2_pubkey.c file. The user_key_allowed2() function opens the file and reads it line by line, ignoring leading whitespace, empty and comment lines.

After that, if a line doesn't contain a plain key, the parser skips ahead until the first whitespace (zooming through quoted areas "..." and interpreting '\"' as an escaped quote), then skips this whitespace and tries to read a key one more time.

Regarding options, the Perl parser isn't as elaborate with semantic peculiarities as openssh's auth_parse_options(), but this might be added in the future.

NOTES FOR SUBCLASS DEVELOPERS

If you're just using Net::SSH::AuthorizedKey to parse keys, the following section doesn't concern you. It's only relevant if you add new subclasses to this package, on top of what's already provided.

Net::SSH::AuthorizedKey is a (semi-)virtual base class that implements options handling for its SSH1 and SSH2 subclasses.

SSH key lines can contain options that carry values (like command="ls") and binary options that are either set or unset (like "no_agent_forwarding"). To distinguish the two, and to provide a set of allowed option names, the subclass has to implement the method option_type(), which takes an option name, and returns

undef if the option is not supported
"s" if the option is a "string" option that carries a value
1 if the option is a binary option

The subclasses Net::SSH::AuthorizedKey::SSH1 and Net::SSH::AuthorizedKey::SSH2 are doing this already.

LEGALESE

AUTHOR

2005, Mike Schilli <m@perlmeister.com>