Performing Cloud Storage Forensic Acquisition

Performing Cloud Storage Forensic Acquisition

Overview

Cloud storage forensic acquisition involves collecting digital evidence from services like Google Drive, OneDrive, Dropbox, and Box through both API-based remote acquisition and local endpoint artifact analysis. Modern investigations must address the challenge that cloud-synced files may exist in multiple states: locally synchronized, cloud-only (on-demand), cached, and deleted. Endpoint devices that have synchronized with cloud storage contain a wealth of metadata about locally synced files, files present only in the cloud, and even deleted items recoverable from cache folders. API-based acquisition using service-specific APIs provides direct access to remote data with valid credentials and proper legal authorization.

Prerequisites

• Legal authorization (warrant, consent, or corporate policy) for cloud data access
• Valid user credentials or administrative access tokens
• Magnet AXIOM Cloud, Cellebrite Cloud Analyzer, or equivalent tool
• KAPE with cloud storage target files
• Python 3.8+ with google-api-python-client, msal, dropbox SDK
• Network connectivity for API-based acquisition

Acquisition Methods

Method 1: API-Based Remote Acquisition

Google Drive API Acquisition

from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
from googleapiclient.http import MediaIoBaseDownload
import io
import os
import json
from datetime import datetime


class GoogleDriveForensicAcquisition:
    """Forensically acquire files and metadata from Google Drive via API."""

    def __init__(self, credentials_path: str, output_dir: str):
        self.creds = Credentials.from_authorized_user_file(credentials_path)
        self.service = build("drive", "v3", credentials=self.creds)
        self.output_dir = output_dir
        os.makedirs(output_dir, exist_ok=True)
        self.acquisition_log = []

    def list_all_files(self, include_trashed: bool = True) -> list:
        """List all files including trashed items."""
        files = []
        page_token = None
        query = "" if include_trashed else "trashed = false"

        while True:
            results = self.service.files().list(
                q=query,
                pageSize=1000,
                fields="nextPageToken, files(id, name, mimeType, size, "
                       "createdTime, modifiedTime, trashed, trashedTime, "
                       "owners, sharingUser, permissions, md5Checksum, "
                       "parents, webViewLink, driveId)",
                pageToken=page_token
            ).execute()

            files.extend(results.get("files", []))
            page_token = results.get("nextPageToken")
            if not page_token:
                break

        return files

    def download_file(self, file_id: str, file_name: str, mime_type: str) -> str:
        """Download a file from Google Drive preserving forensic integrity."""
        output_path = os.path.join(self.output_dir, file_name)

        if mime_type.startswith("application/vnd.google-apps"):
            export_formats = {
                "application/vnd.google-apps.document": "application/pdf",
                "application/vnd.google-apps.spreadsheet": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
                "application/vnd.google-apps.presentation": "application/pdf",
            }
            export_mime = export_formats.get(mime_type, "application/pdf")
            request = self.service.files().export_media(fileId=file_id, mimeType=export_mime)
        else:
            request = self.service.files().get_media(fileId=file_id)

        with io.FileIO(output_path, "wb") as fh:
            downloader = MediaIoBaseDownload(fh, request)
            done = False
            while not done:
                _, done = downloader.next_chunk()

        self.acquisition_log.append({
            "timestamp": datetime.utcnow().isoformat(),
            "file_id": file_id,
            "file_name": file_name,
            "output_path": output_path,
            "action": "downloaded"
        })
        return output_path

    def get_activity_log(self, file_id: str) -> list:
        """Retrieve activity/revision history for a specific file."""
        revisions = self.service.revisions().list(
            fileId=file_id,
            fields="revisions(id, modifiedTime, lastModifyingUser, size, md5Checksum)"
        ).execute()
        return revisions.get("revisions", [])

    def export_acquisition_report(self) -> str:
        """Export acquisition log for chain of custody documentation."""
        report_path = os.path.join(self.output_dir, "acquisition_log.json")
        with open(report_path, "w") as f:
            json.dump({
                "acquisition_start": self.acquisition_log[0]["timestamp"] if self.acquisition_log else None,
                "acquisition_end": datetime.utcnow().isoformat(),
                "total_files": len(self.acquisition_log),
                "entries": self.acquisition_log
            }, f, indent=2)
        return report_path

OneDrive / Microsoft 365 API Acquisition

import msal
import requests
import os
import json
from datetime import datetime


class OneDriveForensicAcquisition:
    """Forensically acquire files and metadata from OneDrive via Microsoft Graph API."""

    def __init__(self, client_id: str, tenant_id: str, client_secret: str, output_dir: str):
        self.output_dir = output_dir
        os.makedirs(output_dir, exist_ok=True)

        authority = f"https://login.microsoftonline.com/{tenant_id}"
        self.app = msal.ConfidentialClientApplication(
            client_id, authority=authority, client_credential=client_secret
        )
        token_result = self.app.acquire_token_for_client(
            scopes=["https://graph.microsoft.com/.default"]
        )
        self.access_token = token_result.get("access_token")
        self.headers = {"Authorization": f"Bearer {self.access_token}"}
        self.base_url = "https://graph.microsoft.com/v1.0"

    def list_user_files(self, user_id: str) -> list:
        """List all files in user's OneDrive."""
        url = f"{self.base_url}/users/{user_id}/drive/root/children"
        files = []
        while url:
            response = requests.get(url, headers=self.headers)
            data = response.json()
            files.extend(data.get("value", []))
            url = data.get("@odata.nextLink")
        return files

    def download_file(self, user_id: str, item_id: str, filename: str) -> str:
        """Download a file from OneDrive."""
        url = f"{self.base_url}/users/{user_id}/drive/items/{item_id}/content"
        response = requests.get(url, headers=self.headers, stream=True)
        output_path = os.path.join(self.output_dir, filename)
        with open(output_path, "wb") as f:
            for chunk in response.iter_content(chunk_size=8192):
                f.write(chunk)
        return output_path

    def get_deleted_items(self, user_id: str) -> list:
        """Retrieve items from OneDrive recycle bin."""
        url = f"{self.base_url}/users/{user_id}/drive/special/recyclebin/children"
        response = requests.get(url, headers=self.headers)
        return response.json().get("value", [])

Method 2: Local Endpoint Artifact Collection

KAPE Targets for Cloud Storage

# Collect all cloud storage artifacts using KAPE
kape.exe --tsource C: --tdest C:\Output\CloudArtifacts --target GoogleDrive,OneDrive,Dropbox,Box

# OneDrive artifacts
# %USERPROFILE%\AppData\Local\Microsoft\OneDrive\logs\
# %USERPROFILE%\AppData\Local\Microsoft\OneDrive\settings\
# %USERPROFILE%\OneDrive\

# Google Drive artifacts
# %USERPROFILE%\AppData\Local\Google\DriveFS\
# Contains metadata SQLite databases and cached files

# Dropbox artifacts
# %USERPROFILE%\AppData\Local\Dropbox\
# %USERPROFILE%\Dropbox\.dropbox.cache\
# Contains filecache.dbx (encrypted SQLite), host.dbx, config.dbx

OneDrive Local Database Analysis

import sqlite3
import os

def analyze_onedrive_sync_engine(db_path: str) -> list:
    """Analyze OneDrive SyncEngineDatabase for file metadata."""
    conn = sqlite3.connect(db_path)
    cursor = conn.cursor()

    # Query for all tracked files including cloud-only items
    cursor.execute("""
        SELECT fileName, fileSize, lastChange,
               resourceID, parentResourceID, eTag
        FROM od_ClientFile_Records
        ORDER BY lastChange DESC
    """)

    files = []
    for row in cursor.fetchall():
        files.append({
            "filename": row[0],
            "size": row[1],
            "last_change": row[2],
            "resource_id": row[3],
            "parent_id": row[4],
            "etag": row[5]
        })

    conn.close()
    return files

Cloud Storage Artifacts Summary

References

• SANS Cloud Storage Acquisition: https://www.sans.org/blog/cloud-storage-acquisition-from-endpoint-devices
• Magnet AXIOM Cloud: https://www.magnetforensics.com/blog/how-to-acquire-and-analyze-cloud-data-with-magnet-axiom/
• AWS Cloud Forensics Framework: https://docs.aws.amazon.com/prescriptive-guidance/latest/security-reference-architecture/cyber-forensics.html
• API-Based Forensic Acquisition of Cloud Drives: https://arxiv.org/abs/1603.06542