clipboard.md

Clipboard Security

Component Focus: Chromium's Clipboard API implementation in third_party/blink/renderer/modules/clipboard/clipboard.cc. This component handles web page interactions with the system clipboard.

Potential Logic Flaws:

• Data Leakage: Sensitive clipboard data could be leaked through vulnerabilities in the API implementation. The handling of sensitive data types like passwords or credit card information needs careful review, especially in the asynchronous read and readText functions, which handle reading data from the clipboard. These functions should be audited for proper access control, data sanitization, and prevention of unintended data exposure through timing attacks or side channels.
• Clipboard Manipulation or Spoofing: Malicious websites could manipulate or spoof clipboard content. The write and writeText functions, responsible for writing data to the clipboard, are critical. Insufficient input validation or sanitization could allow malicious scripts to modify clipboard content without user consent. The handling of different data types and formats in these functions should be thoroughly reviewed to prevent injection attacks or the insertion of malicious data.
• Unauthorized Clipboard Access: Vulnerabilities could allow unauthorized access to clipboard data. The handling of permissions and timing of access are crucial. The read, readText, write, and writeText functions all interact with the clipboard and should be reviewed for proper permission checks and enforcement. The timing of clipboard access, especially in relation to user gestures and asynchronous operations, is critical for preventing unauthorized access.
• Race Conditions: Race conditions could occur during clipboard operations, particularly with asynchronous read or write operations. The interaction with the Clipboard API, event handling, and callbacks, especially within the ClipboardPromise class, are potential sources of race conditions. The asynchronous nature of clipboard operations and the potential for concurrent access from multiple scripts or frames require careful synchronization to prevent race conditions.

Further Analysis and Potential Issues:

The clipboard.cc file implements the core logic for the Clipboard API in the renderer process. Key areas and functions to investigate include:

• read() and readText(): These asynchronous functions handle reading data from the clipboard. They return a ScriptPromise that resolves with the clipboard data. They should be reviewed for proper access control, data sanitization, and prevention of data leakage through timing attacks or side channels. The interaction with the ClipboardPromise class and the handling of different data formats are crucial for security. The timing of clipboard reads, especially in relation to user permissions and potentially malicious scripts, needs careful analysis.

• write() and writeText(): These asynchronous functions handle writing data to the clipboard. They return a ScriptPromise that resolves when the write operation is complete. They should be thoroughly reviewed for input validation, data sanitization, and prevention of unauthorized clipboard modification. The handling of different data types, formats, and potential injection attacks is critical. The interaction with the ClipboardPromise class and the handling of asynchronous write operations should be analyzed for potential race conditions or unexpected behavior.

• ParseWebCustomFormat(): This function parses custom clipboard formats, which could be a source of vulnerabilities if not handled correctly. It should be reviewed for proper input validation and sanitization to prevent potential bypasses of security checks or unexpected behavior. The handling of MIME types and the interaction with the ui::kWebClipboardFormatPrefix are important for security.

• Permission Checks (within ClipboardPromise): The ClipboardPromise class handles permission checks for clipboard access. The IsReadAllowed and IsWriteAllowed functions within this class should be reviewed for proper handling of permission requests, user prompts, and secure context requirements. The timing of permission checks and their interaction with asynchronous clipboard operations are crucial for security.

• Interaction with Clipboard API and Event Handling (within ClipboardPromise): The ClipboardPromise class interacts with the Clipboard API and handles events and callbacks related to clipboard operations. This interaction, especially the handling of asynchronous read and write operations, should be reviewed for potential race conditions or unexpected behavior. The handling of promise resolutions and rejections, and the timing of these actions, are important for security.

• Secure Contexts and User Interaction (within ClipboardPromise): Clipboard access should be restricted in insecure contexts. The implementation should enforce secure context requirements for sensitive clipboard operations. Clipboard write operations should ideally require a user gesture to prevent unauthorized modification. The ClipboardPromise class should be reviewed for proper handling of secure contexts and user interaction requirements.

Areas Requiring Further Investigation:

• Analyze read and readText for data leakage and access control issues, paying attention to asynchronous behavior and data sanitization.
• Review write and writeText for manipulation/spoofing vulnerabilities, input validation, and secure data handling.
• Investigate ParseWebCustomFormat for input validation and proper MIME type handling.
• Analyze permission checks within ClipboardPromise for proper enforcement and bypass prevention.
• Review the interaction with the Clipboard API and event handling within ClipboardPromise for race conditions.
• Analyze the behavior of ClipboardPromise in secure and insecure contexts.
• Investigate user interaction requirements for clipboard writes.
• Test the Clipboard API implementation with various data types, formats, and scenarios.

Secure Contexts and Clipboard:

Clipboard access should be handled securely in all contexts, especially insecure contexts. Sensitive operations should be restricted or require user consent.

Privacy Implications:

The clipboard can contain sensitive user data. The API implementation should prioritize user privacy and protect clipboard data from unauthorized access or leakage.

Additional Notes:

Files reviewed: third_party/blink/renderer/modules/clipboard/clipboard.cc.