Fun with ldap

class ldap_writes {
   6
   8
   10
   12
}
rule ldap_proxy {
when RULE_INIT {
     Read Pool
    set ::readPool sun_ldap_read
     Write Pool
    set ::writePool sun_ldap_write
     Turn on debugging
    set ::debug 0
     A lookup table for debugging
    array set ::msg_types {
           0 "bind request"
           1 "bind response"
           2 "unbind request"
           3 "search request"
           4 "search response"
           6 "modify request"
           7 "modify response"
           8 "add request"
           9 "add response"
          10 "delete request"
          11 "delete response"
          12 "modifydn request"
          13 "modifydn response"
          14 "compare request"
          15 "compare response"
          16 "abandon request"
          23 "extended request"
          24 "extended response"
    }
}
when CLIENT_ACCEPTED {  
    set rebind 0
    set binding ""
    set replayop ""
    set writing 0
    TCP::collect
}
 
when CLIENT_DATA {
     Grab the current payload collected
    set payload [TCP::payload]
     Pull the first 2 bytes.  
    binary scan $payload H2c ber_t ber_len
     The first byte is the tag signifying an LDAP message, 
     Always is hex 30, if that is not so reject
    if { $ber_t ne "30" } {
        reject
        return
    }
     The second byte is one of two values:
           a) The length of the packet minus the above
              defining byte and the length byte
        OR 
           b) an octet describing how many subsequent bytes
              hold the packet length
     In either case the message type (what we are after)
     follows the message id field which too can be a variable
     number of bytes. 
    set len_bytes 0
    if { [expr [expr ($ber_len + 0x100) % 0x100] & 128] > 0 } {
        set len_bytes [expr [expr ($ber_len + 0x100) % 0x100] & 127]
    }
     How many bytes is the message id
    binary scan $payload x[expr 3 + $len_bytes]c msgid_bytes
     The message type is then 4 bytes + number length bytes + number of
     message id bytes offset.
    binary scan $payload x[expr 4 + $len_bytes + $msgid_bytes]c msgtype
     msgtype - BER encoded value, bits 1-5 are the actual 
     type, 6 is the data type, 7-8 are the data class  
     Here we only care about the lower 5 bits
    set msgtype [expr $msgtype & 31]
    if {$::debug and 
        [catch {
              log local0. "message type is: $::msg_types($msgtype) $msgtype"
         }
        ] 
       } {
       log local. "Bad message type: $msgtype"
       reject
    }
     Each connection should start with a bind request
     We'll save this packet for later rebinding when we 
     flip between servers
    if { $msgtype == 0 } {
       if {$::debug} {log local0. "Bind Request with: ldap_read"}
       set writing 0
       set rebind 0
       set binding $payload
       LB::detach
       pool $::readPool
     If we come across a write request and are currently not 
     sending data to the write pool, detach, and set the rebind 
     flag so we can send the bind packet before we actually send 
     our write request
    } elseif {[matchclass $msgtype equals $::ldap_writes] and $writing != 1} { 
       if {$::debug} {log local0. "Rebinding with: ldap_write"}
       set rebind 1
       set writing 1
       set replayop $payload
       TCP::payload replace 0 [TCP::payload length] $binding
       LB::detach
       pool $::writePool
     If we come across a read request while we are bound to a write server
     we need to detach and rebind with a read server from the read pool
    } elseif {![matchclass $msgtype equals $::ldap_writes] and $writing == 1} {
       if {$::debug} {log local0. "Rebinding with: ldap_read"}
       set rebind 1
       set writing 0
       set replayop $payload
       TCP::payload replace 0 [TCP::payload length] $binding
       LB::detach
       pool $::readPool
    }
    TCP::release
    TCP::collect
}
when SERVER_CONNECTED {
     A change in the type of request has been detected
     requiring a rebind, we've sent the bind now we need to
     wait for the response before we send the actual request
    if { $rebind == 1 } {
        TCP::collect
    }
}
when SERVER_DATA {
    if { $rebind == 1 } {
        set rebind 0
         See above for details on this block.  Stupid iRules, no proc grrrr
        set payload [TCP::payload]
    
         Pull the first 2 bytes.  
        binary scan $payload H2c ber_t ber_len
        set len_bytes 0
        if { [expr [expr ($ber_len + 0x100) % 0x100] & 128] > 0 } {
            set len_bytes [expr [expr ($ber_len + 0x100) % 0x100] & 127]
        }
            
        binary scan $payload x[expr 3 + $len_bytes]c msgid_bytes
        binary scan $payload x[expr 4 + $len_bytes + $msgid_bytes]c msgtype
        set msgtype [expr $msgtype & 31]
         If the msgtype we have here is for a bind response just discard 
         it as we don't need to send it to the client
        if {$msgtype == 1 } {
            TCP::payload replace 0 [TCP::payload length] ""
        }
         Now send the actual read or write op to the server
         It should now have processed the bind
        TCP::respond $replayop
    }
    TCP::release
}
}