Hardening Suggestions for: 'Merge Request Test ae9ed373'.

[github-actions]

Introduced protections against system command injection

This change hardens all instances of Runtime#exec() to offer protection against attack.

Left unchecked, Runtime#exec() can execute any arbitrary system command. If an attacker can control part of the strings used to as program paths or arguments, they could execute arbitrary programs, install malware, and anything else they could do if they had a shell open on the application host.

Our change introduces a sandbox which protects the application:

+ import io.github.pixee.security.SystemCommand;
  ...
- Process p = Runtime.getRuntime().exec(command);
+ Process p = SystemCommand.runCommand(Runtime.getRuntime(), command);

The default restrictions applied are the following:

• Prevent command chaining. Many exploits work by injecting command separators and causing the shell to interpret a second, malicious command. The SystemCommand#runCommand() attempts to parse the given command, and throw a SecurityException if multiple commands are present.
• Prevent arguments targeting sensitive files. There is little reason for custom code to target sensitive system files like /etc/passwd, so the sandbox prevents arguments that point to these files that may be targets for exfiltration.

There are more options for sandboxing if you are interested in locking down system commands even more.

Protect readLine() against DoS

This change hardens all BufferedReader#readLine() operations against memory exhaustion.

There is no way to call readLine() safely since it is, by its nature, a read that must be terminated by the stream provider. Furthermore, a stream of data provided by an untrusted source could lead to a denial of service attack, as attackers can provide an infinite stream of bytes until the process runs out of memory.

Fixing it is straightforward using an API which limits the amount of expected characters to some sane limit. This is what our changes look like:

+ import io.github.pixee.security.BoundedLineReader;
  ...
  BufferedReader reader = getReader();
- String line = reader.readLine(); // unlimited read, can lead to DoS
+ String line = BoundedLineReader.readLine(reader, 5_000_000); // limited to 5MB