In June of 2009, I published the first version of Getting the Contents of an Active Directory Integrated DNS Zone. Shortly after that, Chris Dent (chris at highorbit dot co dot uk) published a blog post clarifying the format of the dnsRecord attribute. Most of the time, the difference between the “correct” format and what I had deduced had no effect. But, I recently had to go back to this project and I needed to decode more DNS resource records. Now, using the proper format became important.
Thus, version 2 of the utility was born. I now process A, AAAA, MX, PTR, CNAME, SOA, NS, TXT, SRV, and HINFO resource records.
I hope you’ll enjoy this update. Now, if I can figure out how to determine lame delegations in PowerShell, I can write a PowerShell version of dnswalk!
##
## dns-dump.ps1
##
## Michael B. Smith
## michael at smithcons dot com
## http://TheEssentialExchange.com/blogs/michael
## May/June, 2009
## Updated December, 2009 adding many add'l record types.
##
## Use as you wish, no warranties expressed, implied or explicit.
## Works for me, may not for you.
## If you use it, I would appreciate an attribution.
##
## Thanks to Chris Dent, chris at highorbit dot co dot uk
## for some clarification on the precise format of the
## dnsRecord attribute. See his blog post on the topic at
## http://www.highorbit.co.uk/?p=1097
##
Param(
[string]$zone,
[string]$dc,
[switch]$csv,
[switch]$help
)
function dumpByteArray([System.Byte[]]$array, [int]$width = 9)
{
## this is only used if we run into a record type
## we don't understand.
$hex = ""
$chr = ""
$int = ""
$i = $array.Count
"Array contains {0} elements" -f $i
$index = 0
$count = 0
while ($i-- -gt 0)
{
$val = $array[$index++]
$hex += ("{0} " -f $val.ToString("x2"))
if ([char]::IsLetterOrDigit($val) -or
[char]::IsPunctuation($val) -or
([char]$val -eq " "))
{
$chr += [char]$val
}
else
{
$chr += "."
}
$int += "{0,4:N0}" -f $val
$count++
if ($count -ge $width)
{
"$hex $chr $int"
$hex = ""
$chr = ""
$int = ""
$count = 0
}
}
if ($count -gt 0)
{
if ($count -lt $width)
{
$hex += (" " * (3 * ($width - $count)))
$chr += (" " * (1 * ($width - $count)))
$int += (" " * (4 * ($width - $count)))
}
"$hex $chr $int"
}
}
function dwordLE([System.Byte[]]$arr, [int]$startIndex)
{
## convert four consecutive bytes in $arr into a
## 32-bit integer value... if I had bit-manipulation
## primitives in PowerShell, I'd use them instead
## of the multiply operator.
##
## this routine is for little-endian values.
$res = $arr[$startIndex + 3]
$res = ($res * 256) + $arr[$startIndex + 2]
$res = ($res * 256) + $arr[$startIndex + 1]
$res = ($res * 256) + $arr[$startIndex + 0]
return $res
}
function dwordBE([System.Byte[]]$arr, [int]$startIndex)
{
## convert four consecutive bytes in $arr into a
## 32-bit integer value... if I had bit-manipulation
## primitives in PowerShell, I'd use them instead
## of the multiply operator.
##
## this routine is for big-endian values.
$res = $arr[$startIndex]
$res = ($res * 256) + $arr[$startIndex + 1]
$res = ($res * 256) + $arr[$startIndex + 2]
$res = ($res * 256) + $arr[$startIndex + 3]
return $res
}
function wordLE([System.Byte[]]$arr, [int]$startIndex)
{
## convert two consecutive bytes in $arr into a
## 16-bit integer value... if I had bit-manipulation
## primitives in PowerShell, I'd use them instead
## of the multiply operator.
##
## this routine is for little-endian values.
$res = $arr[$startIndex + 1]
$res = ($res * 256) + $arr[$startIndex]
return $res
}
function wordBE([System.Byte[]]$arr, [int]$startIndex)
{
## convert two consecutive bytes in $arr into a
## 16-bit integer value... if I had bit-manipulation
## primitives in PowerShell, I'd use them instead
## of the multiply operator.
##
## this routine is for big-endian values.
$res = $arr[$startIndex]
$res = ($res * 256) + $arr[$startIndex + 1]
return $res
}
function decodeName([System.Byte[]]$arr, [int]$startIndex)
{
## names in DNS are stored in two formats. one
## format contains a single name and is what we
## called "simple string" in the old days. the
## first byte of a byte array contains the length
## of the string, and the rest of the bytes in
## the array are the data in the string.
##
## a "complex string" is built from simple strings.
## the complex string is prefixed by the total
## length of the complex string in byte 0, and the
## total number of segments in the complex string
## in byte 1, and the first simple string starts
## (with its length byte) in byte 2 of the complex
## string.
[int]$totlen = $arr[$startIndex]
[int]$segments = $arr[$startIndex + 1]
[int]$index = $startIndex + 2
[string]$name = ""
while ($segments-- -gt 0)
{
[int]$segmentLength = $arr[$index++]
while ($segmentLength-- -gt 0)
{
$name += [char]$arr[$index++]
}
$name += "."
}
return $name
}
function analyzeArray([System.Byte[]]$arr, [System.Object]$var)
{
$nameArray = $var.distinguishedname.ToString().Split(",")
$name = $nameArray[0].SubString(3)
## RData Length is the length of the payload in bytes (that is, the variable part of the record)
## Truth be told, we don't use it. The payload starts at $arr[24]. If you are ever concerned
## about corrupt data and running off the end of $arr, then you need to verify against the RData
## Length value.
$rdataLen = wordLE $arr 0
## RData Type is the type of the record
$rdatatype = wordLE $arr 2
## the serial in the SOA where this item was last updated
$updatedAtSerial = dwordLE $arr 8
## TimeToLive
$ttl = dwordBE $arr 12
## $unknown = dword $arr 16
## timestamp of when the record expires, or 0 means "static"
$age = dwordLE $arr 20
if ($age -ne 0)
{
## hours since January 1, 1601 (start of Windows epoch)
## there is a long-and-dreary way to do this manually,
## but get-date makes it trivial to do the conversion.
$timestamp = ((get-date -year 1601 -month 1 -day 1 -hour 0 -minute 0 -second 0).AddHours($age)).ToString()
}
else
{
$timestamp = "[static]"
}
if ($rdatatype -eq 1)
{
# "A" record
$ip = "{0}.{1}.{2}.{3}" -f $arr[24], $arr[25], $arr[26], $arr[27]
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4}"
}
$formatstring -f $name, $timestamp, $ttl, "A", $ip
}
elseif ($rdatatype -eq 2)
{
# "NS" record
$nsname = decodeName $arr 24
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4}"
}
$formatstring -f $name, $timestamp, $ttl, "NS", $nsname
}
elseif ($rdatatype -eq 5)
{
# CNAME record
# canonical name or alias
$alias = decodeName $arr 24
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4}"
}
$formatstring -f $name, $timestamp, $ttl, "CNAME", $alias
}
elseif ($rdatatype -eq 6)
{
# "SOA" record
# "Start-Of-Authority"
$nslen = $arr[44]
$priserver = decodeName $arr 44
$index = 46 + $nslen
# "Primary server: $priserver"
##$index += 1
$resparty = decodeName $arr $index
# "Responsible party: $resparty"
# "TTL: $ttl"
# "Age: $age"
$serial = dwordBE $arr 24
# "Serial: $serial"
$refresh = dwordBE $arr 28
# "Refresh: $refresh"
$retry = dwordBE $arr 32
# "Retry: $retry"
$expires = dwordBE $arr 36
# "Expires: $expires"
$minttl = dwordBE $arr 40
# "Minimum TTL: $minttl"
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4},{5},{6},{7},{8},{9},{10}"
$formatstring -f $name, $timestamp, $ttl, `
"SOA", $priserver, $resparty, `
$serial, $refresh, $retry, `
$expires, $minttl
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}"
$formatstring -f $name, $timestamp, $ttl, "SOA"
(" " * 32) + "Primary server: $priserver"
(" " * 32) + "Responsible party: $resparty"
(" " * 32) + "Serial: $serial"
(" " * 32) + "TTL: $ttl"
(" " * 32) + "Refresh: $refresh"
(" " * 32) + "Retry: $retry"
(" " * 32) + "Expires: $expires"
(" " * 32) + "Minimum TTL (default): $minttl"
}
}
elseif ($rdatatype -eq 12)
{
# "PTR" record
$ptr = decodeName $arr 24
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4}"
}
$formatstring -f $name, $timestamp, $ttl, "PTR", $ptr
}
elseif ($rdatatype -eq 13)
{
# "HINFO" record
[string]$cputype = ""
[string]$ostype = ""
[int]$segmentLength = $arr[24]
$index = 25
while ($segmentLength-- -gt 0)
{
$cputype += [char]$arr[$index++]
}
$index = 24 + $arr[24] + 1
[int]$segmentLength = $index++
while ($segmentLength-- -gt 0)
{
$ostype += [char]$arr[$index++]
}
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4},{5}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4},{5}"
}
$formatstring -f $name, $timestamp, $ttl, "HINFO", $cputype, $ostype
}
elseif ($rdatatype -eq 15)
{
# "MX" record
$priority = wordBE $arr 24
$mxhost = decodeName $arr 26
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4},{5}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4} {5}"
}
$formatstring -f $name, $timestamp, $ttl, "MX", $priority, $mxhost
}
elseif ($rdatatype -eq 16)
{
# "TXT" record
[string]$txt = ""
[int]$segmentLength = $arr[24]
$index = 25
while ($segmentLength-- -gt 0)
{
$txt += [char]$arr[$index++]
}
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4}"
}
$formatstring -f $name, $timestamp, $ttl, "TXT", $txt
}
elseif ($rdatatype -eq 28)
{
# "AAAA" record
### yeah, this doesn't do all the fancy formatting that can be done for IPv6
$str = ""
for ($i = 24; $i -lt 40; $i+=2)
{
$seg = wordBE $arr $i
$str += ($seg).ToString('x4')
if ($i -ne 38) { $str += ':' }
}
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3}`t{4}"
}
$formatstring -f $name, $timestamp, $ttl, "AAAA", $str
}
elseif ($rdatatype -eq 33)
{
# "SRV" record
$port = wordBE $arr 28
$weight = wordBE $arr 26
$pri = wordBE $arr 24
$nsname = decodeName $arr 30
if ($csv)
{
$formatstring = "{0},{1},{2},{3},{4},{5}"
}
else
{
$formatstring = "{0,-30}`t{1,-24}`t{2}`t{3} {4} {5}"
}
$formatstring -f `
$name, $timestamp, `
$ttl, "SRV", `
("[" + $pri.ToString() + "][" + $weight.ToString() + "][" + $port.ToString() + "]"), `
$nsname
}
else
{
$name
"RDataType $rdatatype"
$var.distinguishedname.ToString()
dumpByteArray $arr
}
}
function processAttribute([string]$attrName, [System.Object]$var)
{
$array = $var.$attrName.Value
#### "{0} contains {1} rows of type {2} from {3}" -f $attrName, $array.Count, $array.GetType(), $var.distinguishedName.ToString()
if ($array -is [System.Byte[]])
{
#### dumpByteArray $array
" "
analyzeArray $array $var
" "
}
else
{
for ($i = 0; $i -lt $array.Count; $i++)
{
#### dumpByteArray $array[$i]
" "
analyzeArray $array[$i] $var
" "
}
}
}
function usage
{
"
.\dns-dump -zone [-dc ] [-csv] |
-help
dns-dump will dump, from Active Directory, a particular named zone.
The zone named must be Active Directory integrated.
Zone contents can vary depending on domain controller (in regards
to replication and the serial number of the SOA record). By using
the -dc parameter, you can specify the desired DC to use. Otherwise,
dns-dump uses the default DC.
Usually, output is formatted for display on a workstation. If you
want CSV (comma-separated-value) output, specify the -csv parameter.
Use out-file in the pipeline to save the output to a file.
Finally, to produce this helpful output, you can specify the -help
parameter.
This command is basically equivalent to (but better than) the:
dnscmd /zoneprint
or
dnscmd /enumrecords '@'
commands.
Example 1:
.\dns-dump -zone essential.local -dc win2008-dc-3
Example 2:
.\dns-dump -help
Example 3:
.\dns-dump -zone essential.local -csv |
out-file essential.txt -encoding ascii
Note: the '-encoding ascii' is important if you want to
work with the file within the old cmd.exe shell. Otherwise,
you can usually leave that off.
"
}
##
## Main
##
if ($help)
{
usage
return
}
if ($args.Length -gt 0)
{
write-error "Invalid parameter specified"
usage
return
}
if (!$zone)
{
throw "must specify zone name"
return
}
$root = [ADSI]"LDAP://RootDSE"
$defaultNC = $root.defaultNamingContext
$dn = "LDAP://"
if ($dc) { $dn += $dc + "/" }
$dn += "DC=" + $zone + ",CN=MicrosoftDNS,CN=System," + $defaultNC
$obj = [ADSI]$dn
if ($obj.name)
{
if ($csv)
{
"Name,Timestamp,TTL,RecordType,Param1,Param2"
}
#### dNSProperty has a different format than dNSRecord
#### processAttribute "dNSProperty" $obj
foreach ($record in $obj.psbase.Children)
{
#### if ($record.dNSProperty) { processAttribute "dNSProperty" $record }
if ($record.dnsRecord) { processAttribute "dNSRecord" $record }
}
}
else
{
write-error "Can't open $dn"
}
$obj = $null
Until next time…
If there are things you would like to see written about, please let me know
Follow me on twitter: @EssentialExch
