Code:

namespace eval ::dccrecv {# change this and make sure the directory existsvariable dir "~/received";bind ctcp - DCC ::dccrecv::ctcpproc ctcp {n u h t a} {variable dirif {![isbotnick $t]} {return 0}if {[scan $a %s]=="SEND"} {set user $n!$uif {![matchattr $h X]} {# access denied (replace this with your own user validation)log "Refused SEND from $user"return 0}if {[scan $a "%s%s%u%u%u" k file ip port size]==5} {# valid ctcp?if {[catch {valid_file $file} err]} {log "SEND request from $user failed: $err"return 0}if {[catch {valid_ip $ip} err]} {log "SEND request from $user failed: $err"return 0}if {$port<1024||$port>65535} {log "SEND request from $user failed: Invalid port"return 0}if {$size<1} {log "SEND request from $user failed: Invalid size"return 0}log "Connecting to [dec2dot $ip]:$port to receive $file from $user..."# merge dir & file nameset file [file join $dir $file]# make sure no file by that name exists...# (remove this if you implement RESUME, of course :)if {[file exists $file]} {set i 0set root [file rootname $file]set ext [file extension $file]set file $root.$i$extwhile {[file exists $file]} {set file $root.[incr i]$ext}log "(new local file name: $file)"}# create socket and wait for connection to completeif {[catch {socket -async $ip $port} sock]} {log "Failed creating socket to receive $file from $user"return 0}fconfigure $sock -blocking 0 -buffering none -buffersize 1000000 -translation binaryfileevent $sock writable [list ::dccrecv::conn $sock $n!$u $file $size]return 1} else {log "Malformed SEND request from $user"return 0}} else {# not DCC SENDreturn 0}}# Connected?proc conn {sock user file size} {if {[set err [fconfigure $sock -error]]!=""} {log "Failed connecting to $user: $err"close $sockreturn}fileevent $sock writable {}fileevent $sock readable [list ::dccrecv::read_first $sock $user $file $size]}# The first packet... create the file if any data is receivedproc read_first {sock user file size} {if {[set err [fconfigure $sock -error]]!=""} {log "Failed reading first packet from $user: $err"close $sockreturn}if {[eof $sock]} {# i'm not sure this will ever happenlog "EOF on connect to $user - no data received"close $sockreturn}if {[catch {set fchan [open $file w]fconfigure $fchan -translation binaryputs -nonewline $fchan [read $sock]puts -nonewline $sock [binary format I [tell $fchan]]} err]} {log "Error reading first packet from $user: $err"close $sockreturn}if {[tell $fchan]>=$size} {close $fchanclose $socklog "Received $file from $user (all in the first packet)"} else {fileevent $sock readable [list ::dccrecv::read_more $sock $user $file $fchan $size]}}# The rest of the file... keep reading and reporting the total size# and check the size to see if we're done.proc read_more {sock user file fchan size} {if {[set err [fconfigure $sock -error]]!=""} {log "Lost connection to $user: $error"close $fchanclose $sock# you might want to [file delete $file] herereturn} elseif {[eof $sock]} {log "DCC SEND from $user incomplete (unexpected EOF)"close $fchanclose $sock# you might want to [file delete $file] herereturn}if {[catch {puts -nonewline $fchan [read $sock]puts -nonewline $sock [binary format I [tell $fchan]]} err]} {log "Error recieving $file from $user: $err"close $fchanclose $sock# you might want to [file delete $file] herereturn}if {[tell $fchan]>=$size} {# you might want to check if the file size > $size (indicating a possible dos attempt)close $fchanclose $socklog "Received $file from $user"}}proc log msg {putlog "\[dccrecv\] $msg"}proc dec2dot ip {join [scan [format %08x $ip] %2x%2x%2x%2x] .}proc valid_ip ip {if {![string is integer -strict $ip]||($ip<0)||($ip>4294967295)} {error "not a valid ipv4 address: $ip"}if {($ip>=2130706432)&&($ip<2147483648)} {error "loopback address: [dec2dot $ip]"}if {(($ip>=167772160)&&($ip<184549376))||\(($ip>=2886729728)&&($ip<2887778304))||\(($ip>=3232235520)&&($ip<3232301056))} {error "private network address: [dec2dot $ip]"}if {($ip>=2851995648)&&($ip<2852061184)} {error "link-local address: [dec2dot $ip]"}}proc valid_file {file {dir {}} {if {[string match {*[/|@&<>]*} $file]} {error "invalid filename (possible exploit attempt?): $file"}if {$dir!={}&&[file isdir [file join $dir $file]]} {error "file is directory: $file}}}