Type Confusion in Chi with Cockroachdb

Type confusion in a Chi application using CockroachDB typically arises when application-level types do not match the expected SQL types returned by CockroachDB, or when interface values are asserted to incorrect concrete types. CockroachDB returns column values with Go types that depend on the column type: for example, a STRING column yields a Go string, a TIMESTAMP column yields a time.Time, and an INT column yields an int64. If the application stores these values in an empty interface (e.g., during dynamic scanning or building a generic map) and later asserts them to a specific type, a mismatch can cause type confusion. This can be exacerbated when using sqlx or custom row scanning into a map[string]interface{} and then asserting values without validating their underlying type.

An attacker may exploit this by manipulating input that changes the expected CockroachDB type. For instance, if a query expects an integer ID but an attacker provides a JSON string that causes the application to store a string in an interface, subsequent type assertions can fail or produce unexpected behavior. In a Chi route that decodes JSON into interface{} and later asserts types to construct queries, this can lead to logic flaws or information exposure. Because Chi is a lightweight router, developers often write concise handlers that skip strict type checks for speed, increasing the risk of unchecked interface assertions. Additionally, CockroachDB’s wire protocol and Go driver behavior can return []byte for certain types; if the application incorrectly asserts []byte to string or numeric types, the confusion can trigger panics or bypass intended validation.

Consider a handler that builds a dynamic filter using interface values from request parameters:

var result map[string]interface{}
if err := conn.Get(&result, "SELECT * FROM accounts WHERE id = $1", id); err != nil {
    http.Error(w, err.Error(), http.StatusInternalServerError)
    return
}
if name, ok := result["name"].(string); ok {
    // use name
}

If the column name returns a different type than expected (for example, due to a view or a computed column), the type assertion fails silently, and the application may proceed with an incorrect type. This is a type confusion vector that could be exploited to bypass intended checks or cause runtime errors. The combination of Chi’s ergonomic routing and CockroachDB’s flexible type system requires disciplined type handling and validation to avoid these pitfalls.

Remediation focuses on ensuring type consistency between what CockroachDB returns and what the Chi handler expects. Use strongly typed structs for scanning rows instead of map[string]interface{}, and validate types before assertions. When dynamic behavior is necessary, check the underlying type using a type switch and handle mismatches gracefully.

Prefer explicit struct scanning with sqlx or database/sql to avoid interface confusion:

type Account struct {
    ID   int64  `db:"id"`
    Name string `db:"name"`
}

var acc Account
err := conn.Get(&acc, "SELECT id, name FROM accounts WHERE id = $1", id)
if err != nil {
    http.Error(w, err.Error(), http.StatusInternalServerError)
    return
}
// Use acc.ID and acc.Name directly; types are guaranteed.

If you must work with interface values, use a type switch to safely handle multiple possible CockroachDB types:

val := result["amount"]
switch v := val.(type) {
case int64:
    // handle int64
    amount = float64(v)
case float64:
    amount = v
case []byte:
    // Attempt to parse if CockroachDB returns bytes
    if parsed, err := strconv.ParseFloat(string(v), 64); err == nil {
        amount = parsed
    } else {
        http.Error(w, "invalid numeric format", http.StatusBadRequest)
        return
    }
default:
    http.Error(w, "unexpected type for amount", http.StatusInternalServerError)
    return
}

Validate incoming request parameters to ensure they match the expected CockroachDB types before constructing queries. For JSON payloads, enforce concrete types rather than decoding into interface{}:

var req struct {
    ID int64 `json:"id"`
}
if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
    http.Error(w, "invalid request", http.StatusBadRequest)
    return
}
// Use req.ID directly; it is already a concrete int64.

When using Chi middleware that modifies context values, keep types explicit and avoid storing CockroachDB rows as untyped maps. If you rely on dynamic scanning for schema discovery, verify each key’s type with a type switch before use, and log warnings for unexpected types to aid detection of potential confusion attempts.