Out Of Bounds Read in Fiber with Cockroachdb
Out Of Bounds Read in Fiber with Cockroachdb — how this specific combination creates or exposes the vulnerability
An Out Of Bounds Read occurs when a program reads memory from a location outside the intended buffer. In a Fiber application using CockroachDB, this typically arises from unsafe handling of row data and request parameters, where unchecked offsets or lengths lead to reads beyond allocated structures.
Consider a handler that parses an integer ID from the URL and uses it to index into a slice derived from a CockroachDB query without validating bounds:
// Example: unsafe index into rows-derived slice in Fiber
app.Get("/users/:id", func(c *fiber.Ctx) error {
idStr := c.Params("id")
id, err := strconv.Atoi(idStr)
if err != nil {
return c.Status(fiber.StatusBadRequest).SendString("invalid id")
}
rows, err := db.Query("SELECT name, email FROM users WHERE id = $1", id)
if err != nil {
return c.Status(fiber.StatusInternalServerError).SendString("db error")
}
defer rows.Close()
var users []User
for rows.Next() {
var u User
if err := rows.Scan(&u.Name, &u.Email); err != nil {
return c.Status(fiber.StatusInternalServerError).SendString("scan error")
}
users = append(users, u)
}
// Bounds issue: id used directly as index
if id < 0 || id >= len(users) {
// Potential out-of-bounds read if used to index users without guard
_ = users[id]
}
return c.JSON(users[id])
})In the above, if The risk is compounded when OpenAPI specs are involved: an Additionally, unbounded request inputs can trigger excessive row fetches or large scans that increase the likelihood of hitting adjacent memory. Even though Fiber is performant, iterating over many rows without paging and then indexing by user input creates a read primitive that may expose sensitive data in memory, aligning with findings from the Data Exposure and Input Validation checks run in parallel by middleBrick. LLM/AI Security checks are relevant when endpoints return structured data consumed by AI agents; out-of-bounds reads can cause model context to include unintended memory, leading to hallucinations or inadvertent data leakage in outputs. middleBrick’s active prompt injection testing and output scanning help detect downstream risks if such corrupted data reaches LLM endpoints.id is not validated against the length of users, the access users[id]
x-internal extension or weak schema may cause the generator to assume a fixed-size array, while runtime rows vary. middleBrick’s OpenAPI/Swagger spec analysis (with full $ref resolution) can highlight mismatches between declared array sizes and actual row iteration patterns, surfacing implicit assumptions that lead to out-of-bounds reads.
Cockroachdb-Specific Remediation in Fiber — concrete code fixes
Remediation centers on strict bounds validation, safe iteration, and defensive use of database results. Always treat rows as an unbounded stream and avoid using request-derived indices directly on in-memory collections built from CockroachDB rows.
Safe pattern: validate index against slice length and return a 404 if out of range:
app.Get("/users/:id", func(c *fiber.Ctx) error {
idStr := c.Params("id")
id, err := strconv.Atoi(idStr)
if err != nil || id < 0 {
return c.Status(fiber.StatusBadRequest).SendString("invalid id")
}
rows, err := db.Query("SELECT name, email FROM users WHERE id = $1", id)
if err != nil {
return c.Status(fiber.StatusInternalServerError).SendString("db error")
}
defer rows.Close()
var users []User
for rows.Next() {
var u User
if err := rows.Scan(&u.Name, &u.Email); err != nil {
return c.Status(fiber.StatusInternalServerError).SendString("scan error")
}
users = append(users, u)
}
if id >= len(users) {
return c.Status(fiber.StatusNotFound).SendString("user not found")
}
return c.JSON(users[id])
})When the ID is meant to map to a single row, avoid collecting all rows into a slice; instead, scan directly:
app.Get("/user/:id", func(c *fiber.Ctx) error {
idStr := c.Params("id")
id, err := strconv.Atoi(idStr)
if err != nil || id < 0 {
return c.Status(fiber.StatusBadRequest).SendString("invalid id")
}
var u User
err = db.QueryRow("SELECT name, email FROM users WHERE id = $1", id).Scan(&u.Name, &u.Email)
if err == sql.ErrNoRows {
return c.Status(fiber.StatusNotFound).SendString("user not found")
}
if err != nil {
return c.Status(fiber.StatusInternalServerError).SendString("db error")
}
return c.JSON(u)
})For list endpoints, enforce server-side pagination to limit row sets and avoid large in-memory slices:
app.Get("/users", func(c *fiber.Ctx) error {
page, _ := strconv.Atoi(c.Query("page", "1"))
pageSize := 20
offset := (page - 1) * pageSize
rows, err := db.Query("SELECT name, email FROM users LIMIT $1 OFFSET $2", pageSize, offset)
if err != nil {
return c.Status(fiber.StatusInternalServerError).SendString("db error")
}
defer rows.Close()
var users []User
for rows.Next() {
var u User
if err := rows.Scan(&u.Name, &u.Email); err != nil {
return c.Status(fiber.StatusInternalServerError).SendString("scan error")
}
users = append(users, u)
}
return c.JSON(users)
})These patterns align with the BOLA/IDOR and Input Validation checks in middleBrick, ensuring that indices and offsets are controlled and that findings include clear remediation guidance. middleBrick’s CLI can be used to verify that such safe patterns are reflected in runtime behavior by running middlebrick scan <url> and reviewing the prioritized findings.
Frequently Asked Questions
How can I detect an out-of-bounds read risk in my Fiber API using CockroachDB?
middlebrick scan <your-url>. The scan includes Input Validation and Data Exposure checks that highlight unsafe indexing of query-derived slices and will surface mismatches in your OpenAPI spec that may imply fixed-size buffers.