Mitigation Strategy: Principle of Least Privilege (Bridge Exposure)
Mitigation Strategy: Minimize Exposed Functionality
* **Description:**
1. **Inventory:** Create a list of *all* functions currently exposed through the `webviewjavascriptbridge` interface.
2. **Justification:** For *each* function, write a clear justification explaining *why* it *must* be accessible from the WebView. Actively consider if the functionality could be implemented entirely within the WebView's JavaScript, eliminating the need for bridge exposure.
3. **Refactor:** If a function's justification is weak, remove it from the bridge. If a function is too broad (e.g., a generic "executeCommand" or "accessResource"), refactor it into multiple, highly specific functions with limited scope (e.g., "getUserDisplayName", "setThemePreference"). The goal is to expose *only* the absolute minimum necessary functionality.
4. **Documentation:** Thoroughly document the purpose, expected input parameters (including types and constraints), and expected return values of *each* remaining exposed function. This documentation is crucial for both developers and security reviewers.
5. **Code Review:** Have another developer (ideally with security experience) review the refactored bridge interface, the justifications, and the documentation.
* **Threats Mitigated:**
* **Arbitrary Code Execution (Severity: Critical):** Directly reduces the attack surface. An attacker who compromises the WebView can only call the limited set of exposed functions, preventing them from executing arbitrary native code.
* **Data Exfiltration (Severity: High):** Limits the attacker's ability to access and steal sensitive data. If no exposed functions provide access to sensitive data, the bridge cannot be used for exfiltration.
* **Privilege Escalation (Severity: High):** Prevents an attacker from gaining unauthorized access to privileged functionality within the native application by limiting the available bridge calls.
* **Impact:**
* **Arbitrary Code Execution:** Significantly reduces risk. The risk is not zero (remaining functions could be abused), but the potential damage is greatly constrained.
* **Data Exfiltration:** Significantly reduces risk, especially if access to sensitive data is completely removed from the bridge.
* **Privilege Escalation:** Significantly reduces risk by limiting access to privileged operations.
* **Currently Implemented:** Partially implemented. The `getUserProfile()` function is exposed, but a generic `executeDatabaseQuery()` function also exists, which should be removed. Documentation is incomplete.
* **Missing Implementation:** The `executeDatabaseQuery()` function needs to be removed and replaced with specific, narrowly-scoped functions (e.g., `getUserPosts()`, `getRecentActivity()`). Complete and up-to-date documentation of all exposed functions is required.
Mitigation Strategy: Strict Input Validation (on the Native Side)
Mitigation Strategy: Strict Input Validation (on the Native Side)
* **Description:**
1. **Identify Inputs:** For *each* exposed `webviewjavascriptbridge` function, identify *all* input parameters.
2. **Define Expected Types:** Determine the *exact* expected data type for each parameter (string, integer, boolean, array, etc.). Leverage the native language's type system (e.g., Swift's strong typing) to enforce this.
3. **Type Validation:** Within the native handler function (the code that *implements* the bridge function), *before any other processing*, rigorously validate that each parameter matches its expected type. If a type mismatch occurs, *immediately* reject the request (return an error, throw an exception). Do *not* attempt to coerce or convert the input.
4. **Length Validation:** For string parameters, define a reasonable maximum length and *strictly* enforce it. Reject any input exceeding this length. This helps prevent buffer overflow vulnerabilities.
5. **Format Validation:** For parameters with specific formats (email addresses, URLs, dates, phone numbers, etc.), use regular expressions or dedicated validation libraries to ensure the input conforms to the expected format. Reject invalid formats.
6. **Range Validation:** For numeric parameters, define acceptable ranges (e.g., a user ID must be a positive integer between 1 and 10000). Validate that the input falls within the defined range. Reject out-of-range values.
7. **Sanitization:** If the input is used in database queries, file system operations, or other security-sensitive contexts, *sanitize* it to prevent injection attacks. For database queries, *always* use parameterized queries or prepared statements; *never* construct queries by concatenating strings. For file paths, carefully validate and sanitize to prevent path traversal vulnerabilities.
8. **Whitelisting:** Whenever feasible, use whitelisting instead of blacklisting. Define precisely what input *is* allowed, rather than trying to list what *isn't*. For example, if a parameter can only be one of a few specific values, use an `enum` or a predefined list of allowed values.
9. **Robust Error Handling:** Implement comprehensive error handling. When validation fails, return a clear and informative error message to the WebView (but *never* reveal sensitive information in the error message). Log the validation failure, including the input that caused the failure, on the native side for auditing and debugging.
* **Threats Mitigated:**
* **SQL Injection (Severity: Critical):** Prevents attackers from injecting malicious SQL code through the bridge by ensuring that all database interactions use parameterized queries and that input is properly sanitized.
* **Buffer Overflow (Severity: Critical):** Prevents attackers from overflowing buffers by strictly enforcing length limits on string inputs.
* **Cross-Site Scripting (XSS) (Indirectly) (Severity: High):** While XSS primarily targets the WebView, strict input validation on the native side prevents an XSS attack in the WebView from escalating into a more severe attack on the native application via the bridge.
* **Invalid Data Handling (Severity: Medium):** Prevents the native application from crashing or behaving unexpectedly due to invalid or malformed input received from the WebView.
* **Code Injection (Severity: Critical):** Prevents attackers from injecting malicious code into parameters that are used to construct commands or scripts on the native side.
* **Impact:**
* **SQL Injection:** Effectively eliminates the risk if parameterized queries and proper sanitization are consistently used.
* **Buffer Overflow:** Effectively eliminates the risk if length validation is rigorously applied.
* **XSS (Indirectly):** Significantly reduces the impact of an XSS attack by preventing it from compromising the native application through the bridge.
* **Invalid Data Handling:** Significantly reduces the risk of crashes and unexpected behavior.
* **Code Injection:** Significantly reduces the risk.
* **Currently Implemented:** Partially implemented. Type validation is present for some functions, but length, format, and range validation are inconsistent. Sanitization is not consistently applied, particularly for database interactions.
* **Missing Implementation:** Comprehensive validation (length, format, range, and sanitization) must be added to *all* exposed `webviewjavascriptbridge` functions. A consistent validation library or framework should be adopted to ensure uniformity and maintainability. Parameterized queries should be used *exclusively* for all database interactions.
Mitigation Strategy: Explicit Handler Registration
Mitigation Strategy: Explicit Handler Registration
* **Description:**
1. **Static Registration:** In your native code (Objective-C, Swift, Java, Kotlin), use the `webviewjavascriptbridge` API to *explicitly* register each handler function. This typically involves associating a specific string identifier (the handler name, as seen by the JavaScript code) with a corresponding native function or method.
2. **Avoid Dynamic Registration:** *Absolutely avoid* any mechanism that allows the JavaScript code to dynamically determine which native function to call. Do *not* use reflection, dynamic dispatch, or any approach where the JavaScript sends a string containing the name of the native function to be executed. The mapping between handler names and native functions must be fixed and predetermined in the native code.
3. **Code Review:** Carefully review the code to ensure there are no "backdoors" or unintended ways for JavaScript to invoke native functions outside of the explicitly registered handlers.
* **Threats Mitigated:**
* **Arbitrary Code Execution (Severity: Critical):** Prevents an attacker from calling arbitrary native functions by manipulating the handler registration process. The attacker is restricted to the functions that have been explicitly registered.
* **Function Name Spoofing (Severity: High):** Prevents an attacker from tricking the bridge into calling a different native function than the one intended by the legitimate JavaScript code.
* **Impact:**
* **Arbitrary Code Execution:** Significantly reduces the risk by ensuring that only explicitly registered handlers can be invoked from JavaScript.
* **Function Name Spoofing:** Effectively eliminates the risk.
* **Currently Implemented:** Fully implemented. All handlers are statically registered using the `registerHandler` method of the `webviewjavascriptbridge` library.
* **Missing Implementation:** None.
Mitigation Strategy: Avoid Sensitive Data in the Bridge
Mitigation Strategy: Avoid Sensitive Data in the Bridge
* **Description:**
1. **Review Data Flow:** Carefully analyze *all* data that is passed between the WebView and the native application through the `webviewjavascriptbridge`.
2. **Identify Sensitive Data:** Identify any sensitive data, including:
* API keys
* User authentication tokens (JWTs, session cookies, etc.)
* Personally Identifiable Information (PII)
* Financial data
* Any other confidential information
3. **Minimize Exposure:** Refactor the application's architecture to *minimize* the amount of sensitive data that *must* be passed through the bridge. The ideal scenario is to pass *no* sensitive data through the bridge.
4. **Native-Side Handling:** Whenever possible, handle sensitive operations (authentication, authorization, data encryption/decryption) *entirely* on the native side. Avoid exposing these operations directly to the WebView.
5. **Indirect Identifiers:** If data *must* be shared between the WebView and the native application, use indirect identifiers instead of raw sensitive values. For example, instead of passing a user's password or full credit card number, pass a user ID or a tokenized representation of the credit card.
6. **Encryption (Last Resort):** If sensitive data *absolutely must* be transmitted through the bridge (and all other options have been exhausted), encrypt it on the sending side and decrypt it on the receiving side. Use a strong, industry-standard encryption algorithm (e.g., AES-256) and a robust key management system. Ensure that the encryption keys are *never* exposed to the WebView.
* **Threats Mitigated:**
* **Data Breach (Severity: High):** Reduces the risk of sensitive data being exposed if the WebView is compromised (e.g., through XSS). If sensitive data is not present in the bridge communication, it cannot be stolen via the bridge.
* **Session Hijacking (Severity: High):** Prevents attackers from stealing authentication tokens that might be passed through the bridge, thus preventing them from impersonating users.
* **Man-in-the-Middle (MitM) Attacks (Severity: High):** If encryption is used (as a last resort), it protects the confidentiality of data in transit, even if the communication channel is compromised.
* **Impact:**
* **Data Breach:** Significantly reduces the risk, ideally to near-zero if sensitive data is completely eliminated from the bridge.
* **Session Hijacking:** Significantly reduces the risk if authentication tokens are not passed through the bridge.
* **Man-in-the-Middle (MitM) Attacks:** Encryption (when used) effectively eliminates the risk of data interception and readability during transit.
* **Currently Implemented:** Partially implemented. User IDs are used instead of passwords, but some API keys are still passed through the bridge for certain operations.
* **Missing Implementation:** The application needs to be refactored to remove API keys from the bridge communication. A mechanism for handling API requests entirely on the native side (without exposing the keys to the WebView) should be implemented. Encryption should be considered for any remaining sensitive data that, as an absolute last resort, must be passed through the bridge.
Mitigation Strategy: Rate Limiting (on the Native Side)
Mitigation Strategy: Rate Limiting (on the Native Side)
* **Description:**
1. **Identify High-Risk Functions:** Identify `webviewjavascriptbridge` functions that could be abused for denial-of-service (DoS) attacks, brute-force attempts, or resource exhaustion. These are typically functions that:
* Perform database queries.
* Make network requests.
* Perform computationally expensive operations.
* Interact with limited resources.
2. **Define Limits:** Determine appropriate rate limits for each identified high-risk function. Consider:
* The expected frequency of legitimate use by the WebView.
* The potential impact of abuse (performance degradation, resource exhaustion).
* The resources consumed by the function's execution.
3. **Implement Tracking:** Implement a mechanism to track the number of calls made to each rate-limited function *from the WebView*. This tracking should be done on the *native* side. Options include:
* In-memory counters (suitable for short-term, simple rate limiting).
* A database or cache (for longer-term or more complex rate limiting).
* A dedicated rate-limiting library or service.
4. **Enforce Limits:** Within the native handler function for each rate-limited bridge function, check if the rate limit has been exceeded. If it has, *immediately* reject the request (return an error, throw an exception). Do *not* process the request.
5. **Error Handling:** Implement clear and informative error handling. When a rate limit is exceeded, return an appropriate error message to the WebView (but avoid revealing sensitive information or implementation details). Log the rate-limiting event on the native side for monitoring and analysis.
6. **Consider User/Origin:** If the WebView provides information about the user or origin making the request, track rate limits *per user* or *per origin*. This prevents a single malicious user or compromised origin from affecting other users or the entire application.
* **Threats Mitigated:**
* **Denial-of-Service (DoS) Attacks (Severity: Medium):** Prevents attackers from overwhelming the native application with a large number of bridge calls, thus preventing legitimate users from accessing the application.
* **Brute-Force Attacks (Severity: Medium):** Prevents attackers from repeatedly calling functions in an attempt to guess passwords, tokens, or other secrets.
* **Resource Exhaustion (Severity: Medium):** Prevents attackers from consuming excessive resources (CPU, memory, database connections, network bandwidth) on the native side by repeatedly calling resource-intensive bridge functions.
* **Impact:**
* **Denial-of-Service (DoS) Attacks:** Significantly reduces the risk.
* **Brute-Force Attacks:** Significantly reduces the risk.
* **Resource Exhaustion:** Significantly reduces the risk.
* **Currently Implemented:** Not implemented.
* **Missing Implementation:** Rate limiting needs to be implemented for all high-risk `webviewjavascriptbridge` functions. A suitable rate-limiting mechanism (library or custom implementation) needs to be chosen and integrated into the native code.
Mitigation Strategy: Auditing and Logging
Mitigation Strategy: Auditing and Logging
* **Description:**
1. **Identify Relevant Data:** Determine what information should be logged for *every* `webviewjavascriptbridge` call. This *must* include:
* The name of the called function (the handler name).
* *All* input parameters passed from the WebView.
* The result of the function call (success or failure).
* Any error messages generated.
* The timestamp of the call.
* The origin of the call (if the WebView provides this information).
* A user identifier (if available and applicable).
2. **Implement Logging Mechanism:** Implement a robust logging mechanism on the *native* side. Use a logging library or framework that supports:
* Different log levels (DEBUG, INFO, WARN, ERROR).
* Log rotation (to prevent log files from growing indefinitely).
* Structured logging (e.g., logging in JSON format for easier parsing and analysis).
3. **Log Bridge Calls:** Within *each* `webviewjavascriptbridge` handler function, log the relevant information *before* and *after* processing the request. This provides a complete record of the interaction.
4. **Secure Storage:** Store the logs securely. Protect them from unauthorized access, modification, and deletion.
5. **Regular Review:** Regularly review the logs (manually or using automated tools) to identify any suspicious activity, potential security issues, or errors.
6. **Alerting:** Consider setting up alerts for specific log events, such as:
* Repeated failed validation attempts.
* Rate-limiting events.
* Errors indicating potential security vulnerabilities.
* **Threats Mitigated:**
* **Intrusion Detection (Severity: High):** Logging provides an audit trail that can be used to detect and investigate security incidents. Anomalous patterns in the logs can indicate malicious activity.
* **Debugging (Severity: Medium):** Detailed logs are essential for debugging issues with the `webviewjavascriptbridge` implementation and identifying the root cause of errors.
* **Non-Repudiation (Severity: Low):** Logs can provide evidence of actions taken through the bridge, which can be useful in case of disputes or legal issues (although logging is not a primary non-repudiation mechanism).
* **Impact:**
* **Intrusion Detection:** Significantly improves the ability to detect and respond to security incidents by providing a detailed record of bridge activity.
* **Debugging:** Greatly simplifies the process of identifying and fixing bugs in the bridge implementation.
* **Non-Repudiation:** Provides some level of non-repudiation.
* **Currently Implemented:** Partially implemented. Basic logging is in place, but it doesn't capture all relevant information (e.g., input parameters are not consistently logged). Log rotation is not implemented, and the logging format is not structured.
* **Missing Implementation:** The logging mechanism needs to be significantly enhanced to capture *all* relevant data for *every* `webviewjavascriptbridge` call, including all input parameters. Log rotation and structured logging (e.g., JSON) should be implemented. Regular log review procedures and alerting mechanisms should be established.