claux 20260724.0.2

Terminal AI coding assistant with tool execution
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use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};

use reqwest::Url;

/// Validate a URL and resolve it to public addresses. The returned addresses
/// are pinned into the request client so DNS cannot change between validation
/// and connection.
pub async fn validate_destination(url: &Url) -> Result<Vec<SocketAddr>, String> {
    if !matches!(url.scheme(), "http" | "https") {
        return Err("URL must use http:// or https://".to_string());
    }
    if !url.username().is_empty() || url.password().is_some() {
        return Err("URLs containing credentials are not allowed".to_string());
    }

    let host = url
        .host_str()
        .ok_or_else(|| "URL must include a host".to_string())?;
    let normalized_host = host.trim_end_matches('.').to_ascii_lowercase();
    if normalized_host == "localhost"
        || normalized_host.ends_with(".localhost")
        || normalized_host.ends_with(".local")
        || normalized_host.ends_with(".internal")
    {
        return Err(format!("Private destination is not allowed: {host}"));
    }

    let port = url
        .port_or_known_default()
        .ok_or_else(|| "URL has no usable port".to_string())?;
    let addresses: Vec<SocketAddr> = tokio::net::lookup_host((host, port))
        .await
        .map_err(|e| format!("Failed to resolve {host}: {e}"))?
        .collect();

    if addresses.is_empty() {
        return Err(format!("Host did not resolve: {host}"));
    }
    if let Some(address) = addresses.iter().find(|addr| !is_public_ip(addr.ip())) {
        return Err(format!(
            "Private or non-public destination is not allowed: {}",
            address.ip()
        ));
    }

    Ok(addresses)
}

fn is_public_ip(ip: IpAddr) -> bool {
    match ip {
        IpAddr::V4(ip) => is_public_ipv4(ip),
        IpAddr::V6(ip) => is_public_ipv6(ip),
    }
}

fn is_public_ipv4(ip: Ipv4Addr) -> bool {
    let [a, b, c, d] = ip.octets();
    !matches!(
        (a, b, c, d),
        (0, _, _, _)
            | (10, _, _, _)
            | (100, 64..=127, _, _)
            | (127, _, _, _)
            | (169, 254, _, _)
            | (172, 16..=31, _, _)
            | (192, 0, 0, _)
            | (192, 0, 2, _)
            | (192, 168, _, _)
            | (198, 18..=19, _, _)
            | (198, 51, 100, _)
            | (203, 0, 113, _)
            | (224..=255, _, _, _)
    )
}

fn is_public_ipv6(ip: Ipv6Addr) -> bool {
    let segments = ip.segments();
    if ip.is_unspecified()
        || ip.is_loopback()
        || ip.is_multicast()
        || (segments[0] & 0xfe00) == 0xfc00
        || (segments[0] & 0xffc0) == 0xfe80
        || (segments[0] == 0x2001 && segments[1] == 0x0db8)
    {
        return false;
    }

    if let Some(ipv4) = ip.to_ipv4_mapped() {
        return is_public_ipv4(ipv4);
    }
    true
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn rejects_non_public_ipv4_ranges() {
        for ip in [
            "0.0.0.0",
            "10.0.0.1",
            "100.64.0.1",
            "127.0.0.1",
            "169.254.1.1",
            "172.16.0.1",
            "192.168.1.1",
            "224.0.0.1",
        ] {
            assert!(!is_public_ip(ip.parse().unwrap()), "{ip}");
        }
        assert!(is_public_ip("8.8.8.8".parse().unwrap()));
    }

    #[test]
    fn rejects_non_public_ipv6_ranges() {
        for ip in [
            "::",
            "::1",
            "fc00::1",
            "fe80::1",
            "2001:db8::1",
            "::ffff:127.0.0.1",
        ] {
            assert!(!is_public_ip(ip.parse().unwrap()), "{ip}");
        }
        assert!(is_public_ip("2606:4700:4700::1111".parse().unwrap()));
    }

    #[tokio::test]
    async fn rejects_loopback_literal_before_connecting() {
        let url = Url::parse("http://127.0.0.1/admin").unwrap();
        let error = validate_destination(&url).await.unwrap_err();
        assert!(error.contains("non-public"));
    }

    #[tokio::test]
    async fn rejects_localhost_name_before_resolving() {
        let url = Url::parse("http://localhost/admin").unwrap();
        let error = validate_destination(&url).await.unwrap_err();
        assert!(error.contains("Private destination"));
    }
}