Integer Overflow in Echo Go with Api Keys

An integer overflow in an Echo Go service that uses API keys can arise when user-controlled numeric input (e.g., a count, size, or iteration parameter) is used to compute memory allocations or loop bounds without proper range checks. If the input is large enough to wrap around the integer type’s maximum value, the resulting allocation may be smaller than expected, leading to a buffer overflow when the service copies data into the allocated buffer. When API keys are involved, the vulnerability is often exposed through an endpoint that accepts both an API key for authorization and a numeric parameter that influences memory or processing. For example, an endpoint like /export?api_key=KEY&limit=100 may use limit to allocate a buffer or batch size. An attacker providing a crafted large value (e.g., near the max of uint32) can trigger an overflow, causing the allocation to be much smaller than intended. Because the API key is required for authentication, the request may pass authorization checks before the overflow is reached, but the overflow occurs later during processing, potentially corrupting memory or enabling out-of-bounds reads. In Echo Go, this can manifest when using standard library functions or third-party utilities that do not validate input ranges before using them in arithmetic such as multiplication or bit shifting. The combination of authenticated access via API keys and unchecked numeric inputs increases risk because the API key may allow the attacker to repeatedly probe the endpoint, making it easier to observe side effects or craft payloads that exploit the overflow. This pattern aligns with common weaknesses such as CWE-190 (Integer Overflow or Wraparound) and is relevant to the broader OWASP API Top 10 concern for excessive resource consumption or buffer-related issues. The overflow may not immediately cause crashes; it can lead to incorrect behavior, data corruption, or conditions that facilitate further attacks like injection or information disclosure.

To remediate integer overflow risks in Echo Go when handling API keys, validate and sanitize numeric inputs before using them in arithmetic or memory operations. Use bounded integer types and explicit range checks, and avoid relying on implicit conversions. Below are concrete, working examples that demonstrate safe patterns.

Example 1: Safe limit handling with validation

This handler validates the limit query parameter, ensuring it stays within a safe range before using it to allocate a slice.

import (
    "net/http"
    "strconv"
    "github.com/labstack/echo/v4"
)

const MaxLimit = 1000

func exportHandler(c echo.Context) error {
    apiKey := c.Request().Header.Get("X-API-Key")
    if apiKey == "" {
        return echo.NewHTTPError(http.StatusUnauthorized, "missing api key")
    }
    // Validate API key via your authentication logic here
    // ...

    limitStr := c.QueryParam("limit")
    if limitStr == "" {
        return echo.NewHTTPError(http.StatusBadRequest, "limit parameter is required")
    }
    limit, err := strconv.Atoi(limitStr)
    if err != nil {
        return echo.NewHTTPError(http.StatusBadRequest, "limit must be an integer")
    }
    if limit <= 0 || limit > MaxLimit {
        return echo.NewHTTPError(http.StatusBadRequest, "limit must be between 1 and " strconv.Itoa(MaxLimit))
    }

    // Safe allocation: limit is now bounded
    data := make([]byte, limit)
    // Use data safely...
    return c.JSON(http.StatusOK, map[string]int{"allocated": len(data)})
}

Example 2: Using checked arithmetic to prevent overflow

When performing calculations that could overflow, check for potential wraparound before the operation.

import (
    "errors"
    "math"
)

func safeMultiply(a, b int) (int, error) {
    if a == 0 || b == 0 {
        return 0, nil
    }
    result := a * b
    if a != 0 && result/a != b {
        return 0, errors.New("integer overflow")
    }
    if result < 0 && a > 0 && b > 0 {
        return 0, errors.New("integer overflow")
    }
    return result, nil
}

func process(c echo.Context) error {
    count, err := strconv.Atoi(c.QueryParam("count"))
    if err != nil {
        return echo.NewHTTPError(http.StatusBadRequest, "invalid count")
    }
    size, err := strconv.Atoi(c.QueryParam("size"))
    if err != nil {
        return echo.NewHTTPError(http.StatusBadRequest, "invalid size")
    }

    total, err := safeMultiply(count, size)
    if err != nil || total > 10_000_000 {
        return echo.NewHTTPError(http.StatusBadRequest, "invalid total size")
    }

    buf := make([]byte, total)
    // Process buf safely...
    return c.JSON(http.StatusOK, "ok")  
}

Additional recommendations

• Use constants to define sane limits (e.g., MaxLimit) and enforce them consistently.
• Prefer 64-bit integers for intermediate calculations if needed, but still validate ranges before allocations.
• Centralize input validation where possible to avoid duplicating checks across handlers.
• Leverage Echo’s middleware to enforce API key presence and basic format checks before reaching business logic.