Class/DhcpPacket.psm1
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using module '.\Enums.psm1' using module '.\DhcpOptionObject.psm1' <# DHCP Packet Format (RFC 2131 - http://www.ietf.org/rfc/rfc2131.txt): 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | op (1) | htype (1) | hlen (1) | hops (1) | +---------------+---------------+---------------+---------------+ | xid (4) | +-------------------------------+-------------------------------+ | secs (2) | flags (2) | +-------------------------------+-------------------------------+ | ciaddr (4) | +---------------------------------------------------------------+ | yiaddr (4) | +---------------------------------------------------------------+ | siaddr (4) | +---------------------------------------------------------------+ | giaddr (4) | +---------------------------------------------------------------+ | | | chaddr (16) | | | | | +---------------------------------------------------------------+ | | | sname (64) | +---------------------------------------------------------------+ | | | file (128) | +---------------------------------------------------------------+ | | | options (variable) | +---------------------------------------------------------------+ FIELD OCTETS DESCRIPTION ----- ------ ----------- op 1 Message op code / message type. 1 = BOOTREQUEST, 2 = BOOTREPLY htype 1 Hardware address type, see ARP section in "Assigned Numbers" RFC; e.g., '1' = 10mb ethernet. hlen 1 Hardware address length (e.g. '6' for 10mb ethernet). hops 1 Client sets to zero, optionally used by relay agents when booting via a relay agent. xid 4 Transaction ID, a random number chosen by the client, used by the client and server to associate messages and responses between a client and a server. secs 2 Filled in by client, seconds elapsed since client began address acquisition or renewal process. flags 2 Flags (see figure 2). ciaddr 4 Client IP address; only filled in if client is in BOUND, RENEW or REBINDING state and can respond to ARP requests. yiaddr 4 'your' (client) IP address. siaddr 4 IP address of next server to use in bootstrap; returned in DHCPOFFER, DHCPACK by server. giaddr 4 Relay agent IP address, used in booting via a relay agent. chaddr 16 Client hardware address. sname 64 Optional server host name, null terminated string. file 128 Boot file name, null terminated string; "generic" name or null in DHCPDISCOVER, fully qualified directory-path name in DHCPOFFER. options var Optional parameters field. See the options documents for a list of defined options. #> # DHCP Packet class class DhcpPacket { [OpCode]$OpCode = [OpCode]::BOOTREQUEST [byte]$HType = 1 [byte]$HLen = 6 [byte]$Hops = 0 [byte[]]$XID = (New-Object Byte[] 4) [UInt16]$Secs = 0 [UInt16]$Flags = 0 [ipaddress]$CIAddr = [ipaddress]::Any [ipaddress]$YIAddr = [ipaddress]::Any [ipaddress]$SIAddr = [ipaddress]::Any [ipaddress]$GIAddr = [ipaddress]::Any [PhysicalAddress]$CHAddr = [PhysicalAddress]::new((New-Object Byte[] 6)) [string]$SName = '' [string]$File = '' [byte[]]$MagicCookie = [byte[]](0x63, 0x82, 0x53, 0x63) Hidden $_DhcpOptionsList = [System.Collections.Generic.SortedList[[byte], [DhcpOptionObject]]]::new() DhcpPacket() { # Options property (Read-only) $this | Add-Member ScriptProperty 'Options' { # Getter $this._DhcpOptionsList.Values | select OptionCode, Name, Value, Length } # MessageType property $this | Add-Member ScriptProperty 'MessageType' { # Getter [DhcpMessageType]($this._DhcpOptionsList[[DhcpOption]::DHCPMessageType]._Value) } { # Setter param([DhcpMessageType]$MsgType) $this.AddDhcpOptions( [DhcpOptionObject]::new([DhcpOption]::DHCPMessageType, $MsgType) ) } } [void]AddDhcpOptions([DhcpOptionObject[]]$Options) { foreach ($op in $Options) { $this._DhcpOptionsList[$op.OptionCode] = $op } } [void]AddDhcpOption([byte]$OptionCode, [byte[]]$Value) { $op = [DhcpOptionObject]::new([byte]$OptionCode, [byte[]]$Value) $this._DhcpOptionsList[$op.OptionCode] = $op } static [DhcpPacket]Parse([byte[]]$Packet) { $Reader = [System.IO.BinaryReader]::new((New-Object IO.MemoryStream(@(, $Packet)))) $DhcpResponse = [DhcpPacket]::new() # Headers $DhcpResponse.OpCode = $Reader.ReadByte() $DhcpResponse.HType = $Reader.ReadByte() $DhcpResponse.HLen = $Reader.ReadByte() $DhcpResponse.Hops = $Reader.ReadByte() $DhcpResponse.XID = $Reader.ReadBytes(4) $DhcpResponse.Secs = $Reader.ReadUInt16() $DhcpResponse.Flags = $Reader.ReadUInt16() # IP address $DhcpResponse.CIAddr = [ipaddress]::new($Reader.ReadBytes(4)) $DhcpResponse.YIAddr = [ipaddress]::new($Reader.ReadBytes(4)) $DhcpResponse.SIAddr = [ipaddress]::new($Reader.ReadBytes(4)) $DhcpResponse.GIAddr = [ipaddress]::new($Reader.ReadBytes(4)) # MAC address $DhcpResponse.CHAddr = [PhysicalAddress]::new(($Reader.ReadBytes(16))[0..5]) # SName & File $DhcpResponse.SName = [string]::new($Reader.ReadChars(64)).Trim("`0").TrimEnd() $DhcpResponse.File = [string]::new($Reader.ReadChars(128)).Trim("`0").TrimEnd() # MagicCookie $DhcpResponse.MagicCookie = $Reader.ReadBytes(4) # Options while ($Reader.BaseStream.Position -lt $Reader.BaseStream.Length) { $OpNumber = $Reader.ReadByte() if ($OpNumber -eq [DhcpOption]::End) { $OpsObj = [DhcpOptionObject]::new([DhcpOption]::End, $null) $DhcpResponse.AddDhcpOptions($OpsObj) break } else { $OpLength = $Reader.ReadByte() $OpValue = $Reader.ReadBytes($OpLength) $OpsObj = [DhcpOptionObject]::new($OpNumber, $OpValue) $DhcpResponse.AddDhcpOptions($OpsObj) } } return $DhcpResponse } [byte[]]GetPacketBytes() { $ByteArray = New-Object 'System.Collections.Generic.List[byte]' # Headers $ByteArray.Add($this.OpCode) $ByteArray.Add($this.HType) $ByteArray.Add($this.HLen) $ByteArray.Add($this.Hops) $ByteArray.AddRange($this.XID) $ByteArray.AddRange([System.BitConverter]::GetBytes($this.Secs)) $ByteArray.AddRange([System.BitConverter]::GetBytes($this.Flags)) # IP address $ByteArray.AddRange($this.CIAddr.GetAddressBytes()) $ByteArray.AddRange($this.YIAddr.GetAddressBytes()) $ByteArray.AddRange($this.SIAddr.GetAddressBytes()) $ByteArray.AddRange($this.GIAddr.GetAddressBytes()) # MAC address $ByteArray.AddRange($this.CHAddr.GetAddressBytes()) $ByteArray.AddRange((New-Object Byte[] 10)) # SName [byte[]]$SNameBytes = [System.Text.Encoding]::UTF8.GetBytes($this.SName) if ($SNameBytes.Count -gt 64) { $SNameBytes = $SNameBytes[0..63] } else { # Padding $SNameBytes += (New-Object byte[] (64 - $SNameBytes.Count)) } $ByteArray.AddRange($SNameBytes) # File [byte[]]$FileBytes = [System.Text.Encoding]::UTF8.GetBytes($this.SName) if ($FileBytes.Count -gt 128) { $FileBytes = $FileBytes[0..127] } else { # Padding $FileBytes += (New-Object byte[] (128 - $FileBytes.Count)) } $ByteArray.AddRange($FileBytes) # Magic Cookie $ByteArray.AddRange($this.MagicCookie) # Options foreach ($option in $this._DhcpOptionsList.Values) { $ByteArray.AddRange($option.GetBytes()) } return $ByteArray.ToArray() } } |