allow the postgres librry to take an md5 hash

allow the raw md5 password hash to be passed in instead of
a password for md5 authentication in postgres. Adds an extra exception
class for when an md5 hash is given but the server expects
a different form of authentication.

MSP-12244

lib/metasploit/framework/login_scanner/postgres.rb

@@ -62,6 +62,11 @@ module Metasploit
             end
           rescue Rex::ConnectionError, EOFError, Timeout::Error => e
             result_options.merge!(status: Metasploit::Model::Login::Status::UNABLE_TO_CONNECT, proof: e)
+          rescue Msf::Db::PostgresPR::AuthenticationMethodMismatch => e
+            result_options.merge!({
+              status: Metasploit::Model::Login::Status::INCORRECT,
+              proof: e.message
+            })
           end
 
           if pg_conn

lib/postgres/postgres-pr/connection.rb

@@ -19,6 +19,9 @@ module PostgresPR
 
 PROTO_VERSION = 3 << 16   #196608
 
+class AuthenticationMethodMismatch < StandardError
+end
+
 class Connection
 
   # Allow easy access to these instance variables
@@ -58,7 +61,10 @@ class Connection
     @transaction_status = nil
     @params = {}
     establish_connection(uri)
-  
+
+    # Check if the password supplied is a Postgres-style md5 hash
+    md5_hash_match = password.match(/md5([a-f0-9]{32})/)
+
     @conn << StartupMessage.new(PROTO_VERSION, 'user' => user, 'database' => database).dump
 
     loop do
@@ -67,19 +73,24 @@ class Connection
       case msg
       when AuthentificationClearTextPassword
         raise ArgumentError, "no password specified" if password.nil?
+        raise AuthenticationMethodMismatch, "Server expected clear text password auth" if md5_hash_match
         @conn << PasswordMessage.new(password).dump
-
       when AuthentificationCryptPassword
         raise ArgumentError, "no password specified" if password.nil?
+        raise AuthenticationMethodMismatch, "Server expected crypt password auth" if md5_hash_match
         @conn << PasswordMessage.new(password.crypt(msg.salt)).dump
-
       when AuthentificationMD5Password
         raise ArgumentError, "no password specified" if password.nil?
         require 'digest/md5'
 
-        m = Digest::MD5.hexdigest(password + user) 
+        if md5_hash_match
+          m = md5_hash_match[1]
+        else
+          m = Digest::MD5.hexdigest(password + user)
+        end
         m = Digest::MD5.hexdigest(m + msg.salt)
         m = 'md5' + m
+
         @conn << PasswordMessage.new(m).dump
 
       when AuthentificationKerberosV4, AuthentificationKerberosV5, AuthentificationSCMCredential