vulnerabilities-workflow-1.md

Combined Vulnerability List

1. Vulnerability Name: Insufficient JSON Input Validation

- **Description:**
  The library’s JSON unmarshaling routines (in both the generated ffjson code and the jlexer package) perform only minimal input validation for performance reasons. An external attacker who submits JSON that is “almost valid” (for example, with slight deviations in expected keys, minor syntax anomalies, or subtle malformed constructs) may trigger the parser to accept structurally incorrect input. This can result in missing, defaulted, or unvalidated fields.
  **Step-by-step trigger:**
    1. An attacker crafts JSON payloads that are “almost valid” (for example, with keys that deviate slightly from the expected names or with minor syntax anomalies that the lightweight parser accepts).
    2. The attacker submits these payloads to the application endpoint that uses the easyjson-generated unmarshaling routines.
    3. The application endpoint processes the payload.
- **Impact:**
  If downstream application logic assumes that certain fields are non‑null or correctly populated, processing such “almost valid” input could lead to logic errors, bypassed validations, or even security-sensitive decision mistakes (for example, in authentication or access control).
- **Vulnerability Rank:** High
- **Currently Implemented Mitigations:**
  - The generated marshalers/unmarshalers contain lightweight checks that return errors on gross syntax problems.
  - Documentation clearly warns developers that full JSON schema validation is not performed by default.
- **Missing Mitigations:**
  - There is no built‑in strict JSON schema validation to reject subtly malformed JSON input that does not fully conform to the expected object structure.
- **Preconditions:**
  - The unmarshaling routines (generated using easyjson and ffjson) are used in production to process untrusted JSON without additional, custom schema validation.
- **Source Code Analysis:**
  - In the “gen/decoder.go” file the decoder functions traverse JSON tokens using a highly optimized, token‑based approach.
  - While checks such as `in.IsNull()` and proper delimiting are applied, the decoding logic does not enforce complete JSON grammar validation.
  - This minimal‑validation design means that JSON inputs with slight deviations can be parsed without triggering an error.
- **Security Test Case:**
  1. Deploy the application endpoint that uses the easyjson-generated unmarshaling routines.
  2. Craft JSON payloads that are “almost valid” (for example, with keys that deviate slightly from the expected names or with minor syntax anomalies that the lightweight parser accepts).
  3. Submit these payloads to the application endpoint.
  4. Observe whether fields are silently defaulted or missing and whether that causes logic errors (for example, fields assumed to be non‑null are unpopulated).

2. Vulnerability Name: Arbitrary Code Execution in Code Generation Process

- **Description:**
  The easyjson toolchain (including the “bootstrap” and “gen” packages) generates temporary Go source files that are later compiled and executed (for example, via a “go run” command). If an attacker can influence the source files or other inputs (for instance, via a malicious pull request or by injecting untrusted input into the code–generation process), the temporary generated source may include attacker‑controlled code that is executed as part of the build pipeline.
  **Step-by-step trigger:**
    1. An attacker influences the source files or build parameters (for example, via a malicious pull request or through a compromised public CI/CD pipeline) that are used as input to the code–generation tool.
    2. The easyjson toolchain generates temporary Go source files based on the attacker-influenced input.
    3. The build system executes the generated code using `go run`.
- **Impact:**
  Successful code injection during the code–generation phase could lead to arbitrary code execution with the privileges of the build system. This might allow an attacker to compromise the build environment, exfiltrate sensitive credentials, or modify the application’s source code before deployment.
- **Vulnerability Rank:** Critical
- **Currently Implemented Mitigations:**
  - Documentation and build guidelines clearly state that code generation must be run only on trusted source files and within a controlled, isolated environment.
  - The toolchain expects that repository inputs are vetted prior to running code generation (which is typically not accessible to external users).
- **Missing Mitigations:**
  - No additional sandboxing or automated integrity checks (such as cryptographic signature verification of temporary files) are applied before launching the code–generation process.
  - Input values (including build flags) are not subjected to rigorous sanitization before being passed on to “go run” via the bootstrap process.
- **Preconditions:**
  - An attacker must be able to influence the content of files or build parameters (for example, via a malicious pull request or through a compromised public CI/CD pipeline) that are used as input to the code–generation tool.
- **Source Code Analysis:**
  - In “bootstrap/bootstrap.go” the code–generation process writes temporary stub and main files (using functions like `writeStub` and `writeMain`) and then invokes `go run` on the temporary file.
  - The generation code does not enforce sandboxing or further integrity checks on the source files before execution.
  - Flags and build parameters (such as those parsed via `buildFlagsRegexp`) are used directly in the command invocation without additional sanitization.
- **Security Test Case:**
  1. In a controlled CI/CD environment that invokes the easyjson code–generation tool, submit a pull request containing subtle modifications to a Go source file (or adjust build flags) with malicious payloads embedded.
  2. Monitor the build process to detect whether the temporary generated files incorporate the injected payload.
  3. Confirm that the build system eventually compiles and executes the injected code, demonstrating the arbitrary code execution vector.

3. Vulnerability Name: Unsafe Nil Interface Check Using Unsafe Pointers

- **Description:**
  Several functions in packages such as “jlexer” (which is invoked by the generated decoders in “gen/decoder.go”) inspect interface values by directly examining their memory layouts using the “unsafe” package. This approach bypasses standard Go safety checks and relies on assumptions about the internal representation of interface values. If these assumptions are invalid (for example, due to a change in the Go runtime or through attacker-crafted types), the nil‑check could yield an incorrect result.
  **Step-by-step trigger:**
    1. An attacker crafts a custom Go type. This type is designed so that its underlying interface value, although non‑nil, has a memory layout that mimics nil according to the unsafe assumptions of the library.
    2. The attacker provides an instance of this custom type to the easyjson marshaling routine.
    3. The marshaler uses unsafe operations to perform a nil-check on the interface value.
- **Impact:**
  An incorrect nil‑check may cause valid values to be interpreted as nil (or vice‑versa), leading to fields being omitted or defaulted during marshaling/unmarshaling. In security‑sensitive contexts, this can result in unintended behavior or information leakage.
- **Vulnerability Rank:** High
- **Currently Implemented Mitigations:**
  - The unsafe nil‑check is applied uniformly across the library and is documented to work based on the current Go runtime’s internal representation.
  - The approach is adopted as a performance optimization to avoid the overhead of reflection‑based checks.
- **Missing Mitigations:**
  - No fallback or runtime sanity checks exist to validate that the unsafe assumptions about interface layout are still correct.
  - A safer, reflection‑based check is not employed for interface types, making the implementation potentially fragile with future Go runtime changes.
- **Preconditions:**
  - The application must run on a Go runtime whose internal interface representation diverges from the assumptions made by the library, or an attacker must provide a crafted type that deliberately subverts these assumptions.
- **Source Code Analysis:**
  - In the “gen/decoder.go” file and within the jlexer package, conversions such as “unsafe bytesToStr” and related nil‑checks bypass the safe, standard nil‑comparisons in Go.
  - The code relies on direct memory manipulation using the “unsafe” package to achieve performance gains, which inherently introduces fragility in nil‑detection.
- **Security Test Case:**
  1. Create a small external Go program that defines a custom type. This type should be crafted so that its underlying interface value, although non‑nil, has a memory layout that mimics nil.
  2. Pass an instance of this custom type through the easyjson marshaling routine.
  3. Observe whether the marshaler incorrectly treats the value as nil (or non‑nil), such as by omitting a field or defaulting its value unexpectedly.
  4. Compare the behavior with that of a standard, safe nil‑check implementation to confirm the discrepancy.

4. Vulnerability Name: Information Leak via LexerError Data Field

- **Description:**
    The `LexerError` type in `jlexer/error.go` is used to report JSON parsing errors. This error type includes a `Data` field, which stores the portion of the input JSON data that caused the parsing error. The `Error()` method of `LexerError` formats an error message that includes the content of the `Data` field. If an application using `easyjson` encounters a parsing error and logs or exposes this error message, the `Data` field, which might contain sensitive information from the input JSON, will be leaked. An attacker can craft a malicious JSON payload with embedded sensitive data and introduce syntax errors to trigger a `LexerError`. If the application logs or returns the error, the attacker can potentially extract the sensitive data.
    **Step-by-step trigger:**
    1. An attacker sends a crafted JSON payload to an application that uses `easyjson` for parsing.
    2. The crafted JSON payload includes sensitive information (e.g., API keys, personal data) within its structure.
    3. The attacker intentionally introduces a syntax error into the JSON payload (e.g., invalid character, extra comma).
    4. `easyjson`'s parsing logic encounters the syntax error and generates a `LexerError`.
    5. The `LexerError` object is propagated back to the application's error handling.
    6. The application logs or returns the `LexerError` message, which includes the `Data` field containing the problematic part of the JSON input, potentially revealing the sensitive data embedded in the attacker's payload.
- **Impact:**
    Exposure of sensitive information embedded within user-provided JSON input. The leaked information can vary depending on the application's context and the data being processed. It could include API keys, authentication tokens, personal identifiable information (PII), or other confidential data. The severity of the impact depends on the sensitivity of the leaked data and the context of the application.
- **Vulnerability Rank:** High
- **Currently Implemented Mitigations:**
    None. The current implementation of `LexerError` directly includes the potentially sensitive `Data` field in the error message.
- **Missing Mitigations:**
    - Modify the `LexerError` type and its `Error()` method to prevent direct exposure of the raw `Data` field in error messages.
    - Implement sanitization or truncation of the `Data` field before including it in the error message. For example, truncate the `Data` field to a fixed length or replace sensitive parts with placeholders.
    - Alternatively, the error message could be made more generic, indicating a parsing error at a specific offset without revealing the problematic data itself.
    - Consider logging only the error `Reason` and `Offset` for security-sensitive applications, omitting the `Data` field from logs.
- **Preconditions:**
    - The application uses `easyjson` to parse JSON data from external or untrusted sources.
    - The application's error handling mechanism logs or exposes `LexerError` messages, potentially in application logs, error responses, or debugging outputs.
    - The input JSON data processed by the application might contain sensitive information.
- **Source Code Analysis:**
    - File: `/code/jlexer/error.go`
    ```go
    package jlexer

    import "fmt"

    // LexerError implements the error interface and represents all possible errors that can be
    // generated during parsing the JSON data.
    type LexerError struct {
        Reason string
        Offset int
        Data   string // Data field is included in the error message
    }

    func (l *LexerError) Error() string {
        return fmt.Sprintf("parse error: %s near offset %d of '%s'", l.Reason, l.Offset, l.Data) // Data field is directly used in error message
    }
    ```
    - The `LexerError` struct in `jlexer/error.go` defines the error structure for JSON parsing errors.
    - The `Data string` field within `LexerError` is designed to hold the problematic JSON data segment that caused the parsing failure.
    - The `Error()` method of `LexerError` constructs an error message using `fmt.Sprintf`, directly embedding the `l.Data` string into the formatted output.
    - This direct inclusion of `l.Data` in the error message means that if a parsing error occurs, the raw, potentially sensitive, input data segment will be part of the error string.
    - Any logging or error reporting mechanism that uses the `LexerError.Error()` method will inadvertently expose this `Data` field, leading to potential information leakage.
- **Security Test Case:**
    1. **Setup:** Create a Go application that uses `easyjson` to unmarshal JSON into a simple struct. Configure the application to log error messages to a file or console.
    2. **Craft Malicious Payload:** Create a JSON file named `malicious.json` with the following content. This JSON is intentionally malformed and contains a sensitive string "sensitiveAPIKey: mySecret":
        ```json
        {
          "field1": "value1",
          "sensitiveData": "sensitiveAPIKey: mySecret",
          "field2": "value2",,  // Intentional syntax error: extra comma
        }
        ```
    3. **Run Application with Malicious Payload:** Execute the Go application and feed it the `malicious.json` file as input. The application should attempt to unmarshal this JSON.
    4. **Check Error Logs:** Inspect the error logs generated by the application.
    5. **Verify Information Leak:** Confirm that the error log message contains the content of the `Data` field from `LexerError`, which should include parts of the `malicious.json` content, specifically revealing the "sensitiveAPIKey: mySecret" string or a portion of it along with the syntax error.

    **Expected Error Log Example (may vary slightly depending on the exact error and logging format):**
    ```
    parse error: expected '}', but got ',' near offset XXX of '{
      "field1": "value1",
      "sensitiveData": "sensitiveAPIKey: mySecret",
      "field2": "value2",,'
    ```
    In this example, the error message clearly includes a segment of the input data, potentially leaking the sensitive string "sensitiveAPIKey: mySecret".