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#!/usr/bin/env ruby
require 'openssl'
require 'base64'
# Parse SSH keys to be used by OpenSSL lib
# Taken from Zerg Support project.
# See: https://github.com/pwnall/zerg_support/blob/faaa5dd140c95588a1db2a25f6c9d9cacb4f9b0a/lib/zerg_support/open_ssh.rb
module OpenSSHKeyConverter
# The components in a openssh .pub / known_host RSA public key.
RSA_COMPONENTS = ['ssh-rsa', :e, :n]
# The components in a openssh .pub / known_host DSA public key.
DSA_COMPONENTS = ['ssh-dss', :p, :q, :g, :pub_key]
# Decodes an openssh public key from the format of .pub & known_hosts files.
def self.decode_pubkey(string)
components = unpack_pubkey_components Base64.decode64(string)
case components.first
when RSA_COMPONENTS.first
ops = RSA_COMPONENTS.zip components
key = OpenSSL::PKey::RSA.new
when DSA_COMPONENTS.first
ops = DSA_COMPONENTS.zip components
key = OpenSSL::PKey::DSA.new
else
fail "Unsupported key type #{components.first}"
end
ops.each do |o|
next unless o.first.is_a? Symbol
key.send "#{o.first}=", decode_mpi(o.last)
end
key
end
# Loads a serialized key from an IO instance (File, StringIO).
def self.load_key(io)
serialized_key = io.read
header = first_line serialized_key
if header.index 'RSA'
OpenSSL::PKey::RSA.new serialized_key
elsif header.index 'DSA'
OpenSSL::PKey::DSA.new serialized_key
else
fail 'Unknown key type'
end
end
# Extracts the first line of a string.
def self.first_line(string)
string[0, string.index(/\r|\n/) || string.len]
end
# Unpacks the string components in an openssh-encoded pubkey.
def self.unpack_pubkey_components(str)
cs = []
i = 0
while i < str.length
len = str[i, 4].unpack('N').first
cs << str[i + 4, len]
i += 4 + len
end
cs
end
# Decodes an openssh-mpi-encoded integer.
def self.decode_mpi(mpi_str)
mpi_str.unpack('C*').inject(0) { |a, e| (a << 8) | e }
end
end
path_to_key = ARGV[0]
key = File.read(path_to_key).split[1]
key = OpenSSHKeyConverter.decode_pubkey(key)
key = OpenSSL::PKey::RSA.new(key)
data_string = [7].pack('N') + 'ssh-rsa' + key.public_key.e.to_s(0) + key.public_key.n.to_s(0)
sha_digest = OpenSSL::Digest::SHA256.digest(data_string)
sha_fingerprint = Base64.encode64(sha_digest)
md5_fingerprint = OpenSSL::Digest::MD5.hexdigest(data_string).scan(/../).join(':')
puts('MD5: ' + md5_fingerprint)
puts('SHA256: ' + sha_fingerprint)
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