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[NSE] Added an enhancement to ssh-hostkey that makes a comparison with your known-hosts file. http://seclists.org/nmap-dev/2013/q3/587

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sophron
2013-10-16 18:32:44 +00:00
parent 27af1d09df
commit a7b0fea687
2 changed files with 206 additions and 10 deletions
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165
scripts/ssh-hostkey.nse
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@@ -1,3 +1,4 @@
local base64 = require "base64"
local ipOps = require "ipOps"
local nmap = require "nmap"
local shortport = require "shortport"
@@ -14,14 +15,16 @@ Shows SSH hostkeys.
Shows the target SSH server's key fingerprint and (with high enough verbosity level) the public key itself. It records the discovered host keys in <code>nmap.registry</code> for use by other scripts. Output can be controlled with the <code>ssh_hostkey</code> script argument.
You may also compare the retrieved key with the keys in your known-hosts file using the <code>known-hosts</code> argument.
The script also includes a postrule that check for duplicate hosts using the gathered keys.
]]
---
--@usage
-- nmap host --script SSH-hostkey --script-args ssh_hostkey=full
-- nmap host --script SSH-hostkey --script-args ssh_hostkey=all
-- nmap host --script SSH-hostkey --script-args ssh_hostkey='visual bubble'
-- nmap host --script ssh-hostkey --script-args ssh_hostkey=full
-- nmap host --script ssh-hostkey --script-args ssh_hostkey=all
-- nmap host --script ssh-hostkey --script-args ssh_hostkey='visual bubble'
--
--@args ssh_hostkey Controls the output format of keys. Multiple values may be
-- given, separated by spaces. Possible values are
@@ -29,7 +32,13 @@ The script also includes a postrule that check for duplicate hosts using the gat
-- * <code>"bubble"</code>: Bubble Babble output,
-- * <code>"visual"</code>: Visual ASCII art representation.
-- * <code>"all"</code>: All of the above.
-- @args ssh-hostkey.known-hosts If this is set, the script will check if the
-- known hosts file contains a key for the host being scanned and will compare
-- it with the keys that have been found by the script. The script will try to
-- detect your known-hosts file but you can, optionally, pass the path of the
-- file to this option.
--
-- @args ssh-hostkey.known-hosts-path. Path to a known_hosts file.
--@output
-- 22/tcp open ssh
-- | ssh-hostkey: 2048 f0:58:ce:f4:aa:a4:59:1c:8e:dd:4d:07:44:c8:25:11 (RSA)
@@ -46,9 +55,18 @@ The script also includes a postrule that check for duplicate hosts using the gat
-- | | = . |
-- | | o . |
-- |_ +-----------------+
-- 22/tcp open ssh
-- | ssh-hostkey: 2048 xuvah-degyp-nabus-zegah-hebur-nopig-bubig-difeg-hisym-rumef-cuxex (RSA)
-- |_ ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAwVuv2gcr0maaKQ69VVIEv2ob4OxnuI64fkeOnCXD1lUx5tTA+vefXUWEMxgMuA7iX4irJHy2zer0NQ3Z3yJvr5scPgTYIaEOp5Uo/eGFG9Agpk5wE8CoF0e47iCAPHqzlmP2V7aNURLMODb3jVZuI07A2ZRrMGrD8d888E2ORVORv1rYeTYCqcMMoVFmX9l3gWEdk4yx3w5sD8v501Iuyd1v19mPfyhrI5E1E1nl/Xjp5N0/xP2GUBrdkDMxKaxqTPMie/f0dXBUPQQN697a5q+5lBRPhKYOtn6yQKCd9s1Q22nxn72Jmi1RzbMyYJ52FosDT755Qmb46GLrDMaZMQ==
-- 22/tcp open ssh syn-ack
-- | ssh-hostkey: Key comparison with known_hosts file:
-- | GOOD Matches in known_hosts file:
-- | L7: 199.19.117.60
-- | L11: foo
-- | L15: bar
-- | L19: <unknown>
-- | WRONG Matches in known_hosts file:
-- | L3: 199.19.117.60
-- | ssh-hostkey: 2048 xuvah-degyp-nabus-zegah-hebur-nopig-bubig-difeg-hisym-rumef-cuxex (RSA)
-- |_ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAwVuv2gcr0maaKQ69VVIEv2ob4OxnuI64fkeOnCXD1lUx5tTA+vefXUWEMxgMuA7iX4irJHy2zer0NQ3Z3yJvr5scPgTYIaEOp5Uo/eGFG9Agpk5wE8CoF0e47iCAPHqzlmP2V7aNURLMODb3jVZuI07A2ZRrMGrD8d888E2ORVORv1rYeTYCqcMMoVFmX9l3gWEdk4yx3w5sD8v501Iuyd1v19mPfyhrI5E1E1nl/Xjp5N0/xP2GUBrdkDMxKaxqTPMie/f0dXBUPQQN697a5q+5lBRPhKYOtn6yQKCd9s1Q22nxn72Jmi1RzbMyYJ52FosDT755Qmb46GLrDMaZMQ==
--
--@output
-- Post-scan script results:
@@ -98,7 +116,7 @@ The script also includes a postrule that check for duplicate hosts using the gat
-- </table>
-- </table>
author = "Sven Klemm"
author = "Sven Klemm" -- comparing keys from known_hosts file added by Piotr Olma and George Chatzisofroniou
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"
categories = {"safe","default","discovery"}
@@ -107,6 +125,19 @@ portrule = shortport.port_or_service(22, "ssh")
postrule = function() return (nmap.registry.sshhostkey ~= nil) end
--- check for the presence of a value in a table
--@param tab the table to search into
--@param item the searched value
--@return a boolean indicating whether the value has been found or not
local function contains(tab, item)
for _, val in pairs(tab) do
if val == item then
return true
end
end
return false
end
--- put hostkey in the nmap registry for usage by other scripts
--@param host nmap host table
--@param key host key table
@@ -116,6 +147,114 @@ local add_key_to_registry = function( host, key )
table.insert( nmap.registry.sshhostkey[host.ip], key )
end
--- check if there is a key in known_hosts file for the host that's being scanned
--- and if there is, compare the keys
local function check_keys(host, keys, f)
local keys_found = {}
for _,k in ipairs(keys) do
table.insert(keys_found, k.full_key)
end
local keys_from_file = {}
local same_key, same_key_hashed = {}, {}
local hostname = host.name == "" and nil or host.name
local possible_host_names = {hostname or nil, host.ip or nil, (hostname and host.ip) and ("%s,%s"):format(hostname, host.ip) or nil}
for _p, parts in ipairs(f) do
lnumber = parts.linenumber
parts = parts.entry
local foundhostname = false
if #parts >= 3 then
-- the line might be hashed
if string.match(parts[1], "^|") then
-- split the first part of the line - it contains base64'ed salt and hashed hostname
local parts_hostname = stdnse.strsplit("|", parts[1])
if #parts_hostname == 4 then
-- check if the hash corresponds to the host being scanned
local salt = base64.dec(parts_hostname[3])
for _,name in ipairs(possible_host_names) do
local hash = base64.enc(openssl.hmac("SHA1", salt, name))
if parts_hostname[4] == hash then
stdnse.print_debug(2, "%s: found a hash that matches: %s for hostname: %s", SCRIPT_NAME, hash, name)
foundhostname = true
table.insert(keys_from_file, {name=name, key=("%s %s"):format(parts[2], parts[3]), lnumber=lnumber})
end
end
-- Is the key the same but the hashed hostname isn't?
if not foundhostname then
for _, k in ipairs(keys_found) do
if ("%s %s"):format(parts[2], parts[3]) == k then
table.insert(same_key_hashed, {lnumber = lnumber})
end
end
end
end
else
if contains(possible_host_names, parts[1]) then
stdnse.print_debug(2, "Found an entry that matches: %s", parts[1])
table.insert(keys_from_file, ("%s %s"):format(parts[2], parts[3]))
else
-- Is the key the same but the clear text hostname isn't?
for _, k in ipairs(keys_found) do
if ("%s %s"):format(parts[2], parts[3]) == k then
table.insert(same_key, {name=parts[1], key=("%s %s"):format(parts[2], parts[3]), lnumber=lnumber})
end
end
end
end
end
end
local matched_keys, different_keys = {}, {}
local matched
-- Compare the keys found for this hostname and update the counts.
for _,k in ipairs(keys_from_file) do
matched = false
for __,l in ipairs(keys_found) do
if l == k.key then
table.insert(matched_keys, k)
matched = true
end
end
if not matched then
table.insert(different_keys, k)
end
end
-- Start making output.
local return_string = "Key comparison with known_hosts file: "
if #keys_from_file == 0 then
return_string = return_string .. "\n\t" .. "No entry for scanned host found in known_hosts file."
else
if next(matched_keys) or next(same_key_hashed) or next(same_key) then
return_string = return_string .. "\n\tGOOD Matches in known_hosts file: "
if next(matched_keys) then
for __, gm in ipairs(matched_keys) do
return_string = return_string .. "\n\t\tL" .. gm.lnumber .. ": " .. gm.name
end
end
if next(same_key) then
for __, gm in ipairs(same_key) do
return_string = return_string .. "\n\t\tL" .. gm.lnumber .. ": " .. gm.name
end
end
if next(same_key_hashed) then
for __, gm in ipairs(same_key_hashed) do
return_string = return_string .. "\n\t\tL" .. gm.lnumber .. ": <unknown>"
end
end
if different_keys ~= 0 then
return_string = return_string .. "\n\tWRONG Matches in known_hosts file: "
for __, gm in ipairs(different_keys) do
return_string = return_string .. "\n\t\tL" .. gm.lnumber .. ": " .. gm.name
end
end
end
end
return true, return_string
end
--- gather host keys
--@param host nmap host table
--@param port nmap port table of the currently probed port
@@ -151,7 +290,7 @@ local function portaction(host, port)
fingerprint=stdnse.tohex(key.fingerprint),
type=key.key_type,
bits=key.bits,
key=key.key,
key=base64.enc(key.key),
})
if format:find( 'hex', 1, true ) or all_formats then
table.insert( output, ssh1.fingerprint_hex( key.fingerprint, key.algorithm, key.bits ) )
@@ -170,6 +309,16 @@ local function portaction(host, port)
end
end
-- if a known_hosts file was given, then check if it contains a key for the host being scanned
local known_hosts = stdnse.get_script_args("ssh-hostkey.known-hosts") or false
if known_hosts then
known_hosts = ssh1.parse_known_hosts_file(known_hosts)
local res, status
res, status = check_keys(host, keys, known_hosts)
table.insert(output, 1, status)
end
if #output > 0 then
return output_tab, table.concat( output, '\n' )
end