@aikidosec/firewall/vulnerabilities/shell-injection/containsShellSyntax.js

Zen by Aikido is an embedded Web Application Firewall that autonomously protects Node.js apps against common and critical attacks

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.containsShellSyntax = containsShellSyntax;
const escapeStringRegexp_1 = require("../../helpers/escapeStringRegexp");
const dangerousChars = [
    "#",
    "!",
    '"',
    "$",
    "&",
    "'",
    "(",
    ")",
    "*",
    ";",
    "<",
    "=",
    ">",
    "?",
    "[",
    "\\",
    "]",
    "^",
    "`",
    "{",
    "|",
    "}",
    " ",
    "\n",
    "\t",
    "~",
];
const commands = [
    "sleep",
    "shutdown",
    "reboot",
    "poweroff",
    "halt",
    "ifconfig",
    "chmod",
    "chown",
    "ping",
    "ssh",
    "scp",
    "curl",
    "wget",
    "telnet",
    "kill",
    "killall",
    "rm",
    "mv",
    "cp",
    "touch",
    "echo",
    "cat",
    "head",
    "tail",
    "grep",
    "find",
    "awk",
    "sed",
    "sort",
    "uniq",
    "wc",
    "ls",
    "env",
    "ps",
    "who",
    "whoami",
    "id",
    "w",
    "df",
    "du",
    "pwd",
    "uname",
    "hostname",
    "netstat",
    "passwd",
    "arch",
    "printenv",
    "logname",
    "pstree",
    "hostnamectl",
    "set",
    "lsattr",
    "killall5",
    "dmesg",
    "history",
    "free",
    "uptime",
    "finger",
    "top",
    "shopt",
    // Colon is a null command
    // it might occur in URLs that are passed as arguments to a binary
    // we should flag if it's surrounded by separators
    ":",
];
const pathPrefixes = [
    "/bin/",
    "/sbin/",
    "/usr/bin/",
    "/usr/sbin/",
    "/usr/local/bin/",
    "/usr/local/sbin/",
];
const separators = [" ", "\t", "\n", ";", "&", "|", "(", ")", "<", ">"];
// "killall" should be matched before "kill"
function byLength(a, b) {
    return b.length - a.length;
}
const commandsRegex = new RegExp(`([/.]*(${pathPrefixes.map(escapeStringRegexp_1.escapeStringRegexp).join("|")})?(${commands.slice().sort(byLength).join("|")}))`, "gi");
function matchAll(str, regex) {
    // Reset the regex so that the next call to `exec` starts from the beginning
    // As the regex is global, it will remember the last index
    regex.lastIndex = 0;
    const matches = [];
    let match;
    while ((match = regex.exec(str)) !== null) {
        matches.push(match);
    }
    return matches;
}
function containsShellSyntax(command, userInput) {
    const allWhitespace = /^\s*$/.test(userInput);
    if (allWhitespace) {
        return false;
    }
    if (dangerousChars.find((c) => userInput.includes(c))) {
        return true;
    }
    // The command is the same as the user input
    // Rare case, but it's possible
    // e.g. command is `shutdown` and user input is `shutdown`
    // (`shutdown -h now` will be caught by the dangerous chars as it contains a space)
    if (command === userInput) {
        // Reset the regex so that the next call to `exec` starts from the beginning
        // As the regex is global, it will remember the last index
        commandsRegex.lastIndex = 0;
        const match = commandsRegex.exec(command);
        return match
            ? match.index === 0 && match[0].length === command.length
            : false;
    }
    // Check if the command contains a commonly used command
    for (const match of matchAll(command, commandsRegex)) {
        // We found a command like `rm` or `/sbin/shutdown` in the command
        // Check if the command is the same as the user input
        // If it's not the same, continue searching
        if (userInput !== match[0]) {
            continue;
        }
        // Otherwise, we'll check if the command is surrounded by separators
        // These separators are used to separate commands and arguments
        // e.g. `rm<space>-rf`
        // e.g. `ls<newline>whoami`
        // e.g. `echo<tab>hello`
        const charBefore = command[match.index - 1];
        const charAfter = command[match.index + match[0].length];
        // e.g. `<separator>rm<separator>`
        if (separators.includes(charBefore) && separators.includes(charAfter)) {
            return true;
        }
        // e.g. `<separator>rm`
        if (separators.includes(charBefore) && charAfter === undefined) {
            return true;
        }
        // e.g. `rm<separator>`
        if (charBefore === undefined && separators.includes(charAfter)) {
            return true;
        }
    }
    return false;
}