Rust 硬拦截 + Qwen3Guard 语义研判：双层安全风控如何落地

请求
  │
  ├─ 输入规范化与大小检查
  │
  ├─ Rust 硬规则命中 ───────────> 立即拒绝
  │
  ├─ Qwen3Guard 语义研判
  │      ├─ 高风险 ─────────────> 拒绝或转人工
  │      ├─ 中风险 ─────────────> 降权、限流或复核
  │      └─ 低风险 ─────────────> 放行
  │
  └─ 业务服务

cargo new guard-gateway
cd guard-gateway

[package]
name = "guard-gateway"
version = "0.1.0"
edition = "2021"

[dependencies]
anyhow = "1"
regex = "1"
reqwest = { version = "0.12", features = ["json", "rustls-tls"] }
serde_json = "1"
tokio = { version = "1", features = ["macros", "rt-multi-thread"] }

use anyhow::{bail, Context, Result};
use regex::Regex;
use reqwest::Client;
use serde_json::{json, Value};
use std::{env, time::Duration};

fn hard_block(text: &str) -> Result<Option<&'static str>> {
    if text.len() > 8_000 {
        return Ok(Some("input_too_long"));
    }

    if text.chars().any(|c| c == '\0') {
        return Ok(Some("nul_byte"));
    }

    // 演示规则：生产环境应从版本化配置加载，而不是硬编码。
    let blocked = Regex::new(r"(?i)example-forbidden-token")?;
    if blocked.is_match(text) {
        return Ok(Some("blocked_pattern"));
    }

    Ok(None)
}

async fn semantic_check(client: &Client, text: &str) -> Result<Value> {
    let url = env::var("QWEN_GUARD_URL")
        .context("missing QWEN_GUARD_URL")?;
    let token = env::var("QWEN_GUARD_TOKEN")
        .context("missing QWEN_GUARD_TOKEN")?;
    let model = env::var("QWEN_GUARD_MODEL")
        .unwrap_or_else(|_| "qwen3guard".to_string());

    let response = client
        .post(url)
        .bearer_auth(token)
        .json(&json!({
            "model": model,
            "temperature": 0,
            "messages": [
                {
                    "role": "system",
                    "content": "Classify the text. Return JSON only: {\"risk\":\"low|medium|high\",\"category\":\"...\",\"reason\":\"...\"}."
                },
                {"role": "user", "content": text}
            ]
        }))
        .send()
        .await
        .context("guard request failed")?
        .error_for_status()
        .context("guard returned an error status")?;

    let body: Value = response.json().await?;
    let content = body
        .pointer("/choices/0/message/content")
        .and_then(Value::as_str)
        .context("unexpected guard response")?;

    serde_json::from_str(content).context("guard did not return valid JSON")
}

#[tokio::main]
async fn main() -> Result<()> {
    let text = env::args().skip(1).collect::<Vec<_>>().join(" ");
    if text.is_empty() {
        bail!("usage: cargo run -- 'text to inspect'");
    }

    if let Some(reason) = hard_block(&text)? {
        println!("{}", json!({"action": "block", "layer": "rust", "reason": reason}));
        return Ok(());
    }

    let client = Client::builder()
        .timeout(Duration::from_millis(1500))
        .build()?;
    let result = semantic_check(&client, &text).await?;
    let risk = result.get("risk").and_then(Value::as_str).unwrap_or("unknown");

    let action = match risk {
        "high" => "block",
        "medium" => "review",
        "low" => "allow",
        _ => "review",
    };

    println!("{}", json!({"action": action, "layer": "qwen3guard", "result": result}));
    Ok(())
}

export QWEN_GUARD_URL='https://your-provider.example/v1/chat/completions'
export QWEN_GUARD_TOKEN='replace-me'
export QWEN_GUARD_MODEL='replace-with-your-model-id'

cargo run -- '需要检查的多语言用户输入'