Formula Injection in Echo Go with Cockroachdb

Formula Injection occurs when user-controlled data is interpreted as formulas by downstream systems, including databases and spreadsheets. In an Echo Go service that uses CockroachDB, the risk emerges when string values from HTTP requests are directly stored and later retrieved for export or reporting. CockroachDB, while PostgreSQL-wire compatible, preserves certain data interpretation behaviors that can amplify the impact of unchecked input.

Consider an endpoint that accepts a query parameter such as value, stores it in a table, and later returns data that is opened in a spreadsheet. If the input begins with characters like =, +, or -, a spreadsheet application may treat the cell content as a formula and execute it. Even though CockroachDB stores the raw string, the vulnerability is realized downstream during data export, making the database layer part of the attack chain.

When using Echo Go, developers might bind query parameters directly into SQL without type validation. An input like =1+2 stored in a text column and later exported to CSV can trigger unintended calculations in tools that open the file. The database does not evaluate the formula, but the data pipeline does, creating a stored cross-component risk. This is especially relevant when the API serves as a data source for business intelligence tools or exported reports.

The Echo Go framework simplifies routing and binding, but does not automatically sanitize inputs for formula context. If the application inserts user input into SQL using string concatenation or improperly parameterized queries, it not only risks SQL Injection but also facilitates Formula Injection through stored values. Cockroachdb’s compatibility with standard SQL drivers means that unsafe practices in Go code translate directly to unsafe data handling at scale.

Additionally, if the API supports querying or filtering by user-supplied column names or expressions, an attacker may supply values like ' OR 1=1; -- combined with formula-like prefixes. While the immediate SQL execution may be safe due to parameterization, the stored payload can later be used in contexts where evaluation occurs outside the database, extending the blast radius of a single untrusted input field.

Remediation focuses on strict input validation, parameterized queries, and output encoding for downstream consumption. Never concatenate user input into SQL strings, and treat all external data as opaque unless explicitly required.

// Safe: using parameterized queries with database/sql in Echo Go
import (
    "database/sql"
    "net/http"
    "github.com/labstack/echo/v4"
)

func createRecord(c echo.Context) error {
    db := c.Get("db").(*sql.DB)
    value := c.QueryParam("value")
    // Validate input: allow only alphanumeric and safe punctuation
    if !isValidInput(value) {
        return echo.NewHTTPError(http.StatusBadRequest, "invalid value")
    }
    result, err := db.Exec("INSERT INTO entries (data) VALUES ($1)", value)
    if err != nil {
        return echo.NewHTTPError(http.StatusInternalServerError, err.Error())
    }
    id, _ := result.LastInsertId()
    return c.JSON(http.StatusCreated, map[string]int64{"id": id})
}

func isValidInput(s string) bool {
    // Example allowlist: letters, numbers, spaces, hyphens, underscores
    for _, r := range s {
        if !(('a' <= r && r <= 'z') || ('A' <= r && r <= 'Z') || ('0' <= r && r <= '9') || r == ' ' || r == '-' || r == '_') {
            return false
        }
    }
    return true
}

For reporting or export endpoints, encode values based on the target format. For CSV, wrap fields in quotes and escape existing quotes to prevent formula interpretation in spreadsheet applications.

// Safe CSV generation with proper quoting
import (
    "encoding/csv"
    "net/http"
)

func exportCSV(c echo.Context) error {
    rows, err := db.Query("SELECT id, data FROM entries")
    if err != nil {
        return err
    }
    defer rows.Close()

    writer := csv.NewWriter(c.Response().Writer)
    defer writer.Flush()

    // Write header
    writer.Write([]string{"id", "data"})

    for rows.Next() {
        var id int
        var data string
        if err := rows.Scan(&id, &data); err != nil {
            return err
        }
        // CSV writer handles quoting automatically when using Write
        writer.Write([]string{string(id), data})
    }
    return nil
}

When using the Cockroachdb-compatible driver in Go, always prefer prepared statements or ORM-level parameterization. Avoid raw string interpolation even for dynamic table or column names; if unavoidable, use strict allowlists.