conduit/src/database/proxy.rs

use reqwest::{Proxy, Url};
use serde::Deserialize;

use crate::Result;

/// ## Examples:
/// - No proxy (default):
/// ```toml
/// proxy ="none"
/// ```
/// - Global proxy
/// ```toml
/// [proxy]
/// global = { url = "socks5h://localhost:9050" }
/// ```
/// - Proxy some domains
/// ```toml
/// [proxy]
/// [[proxy.by_domain]]
/// url = "socks5h://localhost:9050"
/// include = ["*.onion", "matrix.myspecial.onion"]
/// exclude = ["*.myspecial.onion"]
/// ```
/// ## Include vs. Exclude
/// If include is an empty list, it is assumed to be `["*"]`.
///
/// If a domain matches both the exclude and include list, the proxy will only be used if it was
/// included because of a more specific rule than it was excluded. In the above example, the proxy
/// would be used for `ordinary.onion`, `matrix.myspecial.onion`, but not `hello.myspecial.onion`.
#[derive(Clone, Debug, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ProxyConfig {
    None,
    Global {
        #[serde(deserialize_with = "crate::utils::deserialize_from_str")]
        url: Url,
    },
    ByDomain(Vec<PartialProxyConfig>),
}
impl ProxyConfig {
    pub fn to_proxy(&self) -> Result<Option<Proxy>> {
        Ok(match self.clone() {
            ProxyConfig::None => None,
            ProxyConfig::Global { url } => Some(Proxy::all(url)?),
            ProxyConfig::ByDomain(proxies) => Some(Proxy::custom(move |url| {
                proxies.iter().find_map(|proxy| proxy.for_url(url)).cloned() // first matching proxy
            })),
        })
    }
}
impl Default for ProxyConfig {
    fn default() -> Self {
        ProxyConfig::None
    }
}

#[derive(Clone, Debug, Deserialize)]
pub struct PartialProxyConfig {
    #[serde(deserialize_with = "crate::utils::deserialize_from_str")]
    url: Url,
    #[serde(default)]
    include: Vec<WildCardedDomain>,
    #[serde(default)]
    exclude: Vec<WildCardedDomain>,
}
impl PartialProxyConfig {
    pub fn for_url(&self, url: &Url) -> Option<&Url> {
        let domain = url.domain()?;
        let mut included_because = None; // most specific reason it was included
        let mut excluded_because = None; // most specific reason it was excluded
        if self.include.is_empty() {
            // treat empty include list as `*`
            included_because = Some(&WildCardedDomain::WildCard)
        }
        for wc_domain in &self.include {
            if wc_domain.matches(domain) {
                match included_because {
                    Some(prev) if !wc_domain.more_specific_than(prev) => (),
                    _ => included_because = Some(wc_domain),
                }
            }
        }
        for wc_domain in &self.exclude {
            if wc_domain.matches(domain) {
                match excluded_because {
                    Some(prev) if !wc_domain.more_specific_than(prev) => (),
                    _ => excluded_because = Some(wc_domain),
                }
            }
        }
        match (included_because, excluded_because) {
            (Some(a), Some(b)) if a.more_specific_than(b) => Some(&self.url), // included for a more specific reason than excluded
            (Some(_), None) => Some(&self.url),
            _ => None,
        }
    }
}

/// A domain name, that optionally allows a * as its first subdomain.
#[derive(Clone, Debug)]
pub enum WildCardedDomain {
    WildCard,
    WildCarded(String),
    Exact(String),
}
impl WildCardedDomain {
    pub fn matches(&self, domain: &str) -> bool {
        match self {
            WildCardedDomain::WildCard => true,
            WildCardedDomain::WildCarded(d) => domain.ends_with(d),
            WildCardedDomain::Exact(d) => domain == d,
        }
    }
    pub fn more_specific_than(&self, other: &Self) -> bool {
        match (self, other) {
            (WildCardedDomain::WildCard, WildCardedDomain::WildCard) => false,
            (_, WildCardedDomain::WildCard) => true,
            (WildCardedDomain::Exact(a), WildCardedDomain::WildCarded(_)) => other.matches(a),
            (WildCardedDomain::WildCarded(a), WildCardedDomain::WildCarded(b)) => {
                a != b && a.ends_with(b)
            }
            _ => false,
        }
    }
}
impl std::str::FromStr for WildCardedDomain {
    type Err = std::convert::Infallible;
    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        // maybe do some domain validation?
        Ok(if s.starts_with("*.") {
            WildCardedDomain::WildCarded(s[1..].to_owned())
        } else if s == "*" {
            WildCardedDomain::WildCarded("".to_owned())
        } else {
            WildCardedDomain::Exact(s.to_owned())
        })
    }
}
impl<'de> serde::de::Deserialize<'de> for WildCardedDomain {
    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
    where
        D: serde::de::Deserializer<'de>,
    {
        crate::utils::deserialize_from_str(deserializer)
    }
}