Buffer Overflow in Cockroachdb

CockroachDB is written primarily in Go, a language that provides memory safety by default. However, the storage engine relies on cgo to interface with RocksDB, a C++ library. When Go code passes data to RocksDB without proper length checks, a malformed input can trigger a heap‑based buffer overflow in the native code.

An attacker who can send arbitrary SQL statements to an unauthenticated CockroachDB HTTP endpoint (for example, the admin UI or a misconfigured SQL gateway) may overflow the buffer used by RocksDB when encoding a key or value. The overflow can corrupt adjacent memory, leading to crashes, information disclosure, or, in rare cases, arbitrary code execution.

Consider a simplified Go fragment that mimics how a custom CockroachDB extension might pass a user‑supplied string to RocksDB via cgo:

// vulnerable.go
package main

import "C"

//export WriteKey
func WriteKey(key *C.char, keyLen C.int) {
    // RocksDB expects a length‑prefixed buffer; we deliberately ignore keyLen
    C.rocksdb_put(db, nil, unsafe.Pointer(key), C.strlen(key), nil)
}

func main() {}

The function uses C.strlen(key) to determine the length, which stops at the first null byte. If the supplied key contains embedded null bytes, strlen returns a smaller length than the actual buffer size, causing RocksDB to read past the intended boundary and overflow.

Real‑world analogues include CVE-2020-15157 (a heap buffer overflow in RocksDB’s WriteBatch implementation) and CVE-2021-21315, which affected CockroachDB’s use of the RocksDB bindings when processing overly large binary payloads. While no public CVE has been assigned directly to CockroachDB for a buffer overflow, the dependency chain makes the pattern relevant.

middleBrick performs unauthenticated, black‑box scanning of API endpoints. When scanning a CockroachDB instance, it sends a series of crafted payloads to each discoverable endpoint (e.g., the SQL over HTTP interface, the admin UI, or any custom RPC/REST endpoints). For buffer‑overflow testing, middleBrick includes length‑fuzzing probes that transmit progressively larger strings, binary blobs, and inputs containing null bytes.

If a probe causes the service to return an HTTP 5xx error, a sudden latency spike, or a malformed response that indicates a crash (for example, an empty body with a connection reset), middleBrick flags the finding under the "Input Validation" category with a severity of "high". The report includes:

• The exact endpoint and HTTP method that triggered the anomaly.
• The payload size and content that provoked the crash (truncated for readability).
• A remediation guidance note that references the specific CockroachDB code path (e.g., the RocksDB write path) and advises upgrading the underlying RocksDB version or adding length validation before cgo calls.

Because middleBrick does not require agents or credentials, the test can be run against a staging or production CockroachDB URL in 5–15 seconds, providing immediate visibility into whether the service is susceptible to oversized input that could overflow the native storage layer.

Example CLI invocation:

middlebrick scan https://cockroachdb-staging.example.com

The resulting JSON report will contain an entry similar to:

{
  "category": "Input Validation",
  "severity": "high",
  "finding": "Potential buffer overflow detected via oversized key length in RocksDB write path",
  "remediation": "Validate and limit the length of all user‑supplied byte arrays before passing them to cgo/RocksDB. Consider upgrading to RocksDB v6.20+ which includes fixes for CVE‑2020‑15157."
}

Since middleBrick only reports findings, remediation must be applied in the CockroachDB deployment or any custom extensions that interact with RocksDB via cgo. The following steps are concrete, CockroachDB‑specific actions:

1. Upgrade the RocksDB dependency. CockroachDB vendors a specific version of RocksDB; ensure you are using a release that patches known heap overflows (e.g., v6.20.4 or later, which addresses CVE‑2020‑15157).
2. Add explicit length checks before cgo calls. When writing custom Go code that passes data to RocksDB, always use the provided length argument rather than relying on C‑string termination:

// fixed.go
package main

import "unsafe"

//export WriteKeySafe
func WriteKeySafe(key unsafe.Pointer, keyLen C.size_t) {
    // Pass the exact length received from the caller
    C.rocksdb_put(db, nil, key, keyLen, nil)
}

func main() {}

3. Limit input size at the API layer. CockroachDB’s SQL over HTTP endpoint should enforce a maximum statement length (e.g., 16 KB) and reject larger payloads with a 413 error. This can be configured via the --http‑max‑request‑size flag or through a reverse proxy.
4. Use prepared statements or parameterized queries. By separating SQL code from data, the server avoids concatenating user‑provided strings into large buffers that later reach the storage engine.
5. Enable logging and monitoring for aborts. CockroachDB logs panic‑like stack traces when a RocksDB operation fails due to memory corruption. Setting up alerts on these logs helps catch exploitation attempts early.

Applying these mitigations eliminates the unsafe code path that middleBrick would flag, reducing the risk score for the "Input Validation" category from high to low.