Learn in Public unlocks on Jan 1, 2026
This lesson will be public then. Admins can unlock early with a password.
Learn Cybersecurity
Essential Rust Libraries for Cybersecurity (2026)
The must-know Rust crates for scanning, automation, and detection—plus how to spot their misuse.
rust crates tokio reqwest clap serde security engineering
Learn the core Rust crates that power security tools by building a tiny, end-to-end sample and validating each dependency.
What You’ll Build
- A minimal Rust CLI that uses
tokio,reqwest,clap,serde,tracing, andrustlsto fetch JSON safely. - Version pinning and a quick dependency audit check.
- Notes on how defenders spot default fingerprints and how to tune them.
Prerequisites
- macOS or Linux with Rust 1.80+.
- Internet to download crates.
- Authorized targets only; we’ll default to
https://example.com.
Safety and Legal
- Do not point HTTP clients at systems you aren’t allowed to test.
- Keep User-Agent clear and add contact info; avoid high-concurrency defaults.
- Pin versions to avoid supply-chain surprises.
Step 1) Scaffold and add crates
Click to view commands
cargo new rust-crates-demo
cd rust-crates-demo
cat > Cargo.toml <<'TOML'
[package]
name = "rust-crates-demo"
version = "0.1.0"
edition = "2021"
[dependencies]
tokio = { version = "1.40", features = ["full"] }
reqwest = { version = "0.12", features = ["json", "rustls-tls"] }
clap = { version = "4.5", features = ["derive"] }
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
tracing = "0.1"
tracing-subscriber = { version = "0.3", features = ["fmt", "env-filter"] }
anyhow = "1.0"
TOMLStep 2) Implement a small fetcher using all crates
Replace src/main.rs with:
Click to view Rust code
use clap::Parser;
use reqwest::Client;
use serde::Deserialize;
use tracing::{info, warn};
use tracing_subscriber::EnvFilter;
#[derive(Parser, Debug)]
struct Args {
/// URL to fetch JSON from
#[arg(long, default_value = "https://example.com")]
url: String,
/// Request timeout seconds
#[arg(long, default_value_t = 5)]
timeout: u64,
}
#[derive(Deserialize, Debug)]
struct ExampleJson {
#[serde(default)]
title: String,
}
#[tokio::main]
async fn main() -> anyhow::Result<()> {
tracing_subscriber::fmt()
.with_env_filter(EnvFilter::from_default_env().add_directive("info".parse()?))
.init();
let args = Args::parse();
let client = Client::builder()
.user_agent("rust-crates-demo (+you@example.com)")
.timeout(std::time::Duration::from_secs(args.timeout))
.build()?;
info!("fetching {}", args.url);
let resp = client.get(&args.url).send().await?;
if !resp.status().is_success() {
warn!("non-200 status: {}", resp.status());
return Ok(());
}
let body = resp.text().await?;
// example.com is HTML; this shows serde wiring. Replace with real JSON when needed.
let parsed: Result<ExampleJson, _> = serde_json::from_str(&body);
match parsed {
Ok(p) => info!(?p, "parsed JSON"),
Err(_) => info!("response was not JSON (expected for example.com)"),
}
Ok(())
}Click to view commands
cargo run -- --url https://httpbin.org/jsonCommon fixes:
connection refused: check URL or network egress policy.reqwestTLS errors: ensurerustls-tlsis enabled (already in Cargo.toml) and clock is in sync.
Step 3) Pin and audit dependencies
Click to view commands
cargo metadata --format-version=1 | jq '.packages[] | {name,version}' | head
cargo install cargo-audit --locked
cargo auditDefensive angle: reduce your fingerprint
- Customize User-Agent (default
reqwestUA is recognizable). - Add jitter and low concurrency; avoid bursty scans that trip rate limits.
- Rotate TLS fingerprints where allowed (e.g., through proxies) or document expected JA3 so defenders can whitelist sanctioned tools.
Cleanup
Click to view commands
cd ..
rm -rf rust-crates-demoQuick Reference
- Core crates:
tokio,reqwest,clap,serde,tracing,rustls. - Pin versions; audit regularly (
cargo audit). - Identify yourself via UA; keep concurrency low and logged.