Advanced TLS Fetcher

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

src/config/defaults.rs

@@ -71,6 +71,22 @@ pub(crate) fn default_tls_fetch_scope() -> String {
     String::new()
 }
 
+pub(crate) fn default_tls_fetch_attempt_timeout_ms() -> u64 {
+    5_000
+}
+
+pub(crate) fn default_tls_fetch_total_budget_ms() -> u64 {
+    15_000
+}
+
+pub(crate) fn default_tls_fetch_strict_route() -> bool {
+    true
+}
+
+pub(crate) fn default_tls_fetch_profile_cache_ttl_secs() -> u64 {
+    600
+}
+
 pub(crate) fn default_mask_port() -> u16 {
     443
 }

src/config/load.rs

@@ -1,6 +1,6 @@
 #![allow(deprecated)]
 
-use std::collections::{BTreeSet, HashMap};
+use std::collections::{BTreeSet, HashMap, HashSet};
 use std::hash::{DefaultHasher, Hash, Hasher};
 use std::net::{IpAddr, SocketAddr};
 use std::path::{Path, PathBuf};
@@ -977,6 +977,28 @@ impl ProxyConfig {
         // Normalize optional TLS fetch scope: whitespace-only values disable scoped routing.
         config.censorship.tls_fetch_scope = config.censorship.tls_fetch_scope.trim().to_string();
 
+        if config.censorship.tls_fetch.profiles.is_empty() {
+            config.censorship.tls_fetch.profiles = TlsFetchConfig::default().profiles;
+        } else {
+            let mut seen = HashSet::new();
+            config
+                .censorship
+                .tls_fetch
+                .profiles
+                .retain(|profile| seen.insert(*profile));
+        }
+
+        if config.censorship.tls_fetch.attempt_timeout_ms == 0 {
+            return Err(ProxyError::Config(
+                "censorship.tls_fetch.attempt_timeout_ms must be > 0".to_string(),
+            ));
+        }
+        if config.censorship.tls_fetch.total_budget_ms == 0 {
+            return Err(ProxyError::Config(
+                "censorship.tls_fetch.total_budget_ms must be > 0".to_string(),
+            ));
+        }
+
         // Merge primary + extra TLS domains, deduplicate (primary always first).
         if !config.censorship.tls_domains.is_empty() {
             let mut all = Vec::with_capacity(1 + config.censorship.tls_domains.len());
@@ -2459,6 +2481,94 @@ mod tests {
         let _ = std::fs::remove_file(path);
     }
 
+    #[test]
+    fn tls_fetch_defaults_are_applied() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_defaults_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let cfg = ProxyConfig::load(&path).unwrap();
+        assert_eq!(
+            cfg.censorship.tls_fetch.profiles,
+            TlsFetchConfig::default().profiles
+        );
+        assert!(cfg.censorship.tls_fetch.strict_route);
+        assert_eq!(cfg.censorship.tls_fetch.attempt_timeout_ms, 5_000);
+        assert_eq!(cfg.censorship.tls_fetch.total_budget_ms, 15_000);
+        assert_eq!(cfg.censorship.tls_fetch.profile_cache_ttl_secs, 600);
+        let _ = std::fs::remove_file(path);
+    }
+
+    #[test]
+    fn tls_fetch_profiles_are_deduplicated_preserving_order() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+            [censorship.tls_fetch]
+            profiles = ["compat_tls12", "modern_chrome_like", "compat_tls12", "legacy_minimal"]
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_profiles_dedup_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let cfg = ProxyConfig::load(&path).unwrap();
+        assert_eq!(
+            cfg.censorship.tls_fetch.profiles,
+            vec![
+                TlsFetchProfile::CompatTls12,
+                TlsFetchProfile::ModernChromeLike,
+                TlsFetchProfile::LegacyMinimal
+            ]
+        );
+        let _ = std::fs::remove_file(path);
+    }
+
+    #[test]
+    fn tls_fetch_attempt_timeout_zero_is_rejected() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+            [censorship.tls_fetch]
+            attempt_timeout_ms = 0
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_attempt_timeout_zero_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let err = ProxyConfig::load(&path).unwrap_err().to_string();
+        assert!(err.contains("censorship.tls_fetch.attempt_timeout_ms must be > 0"));
+        let _ = std::fs::remove_file(path);
+    }
+
+    #[test]
+    fn tls_fetch_total_budget_zero_is_rejected() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+            [censorship.tls_fetch]
+            total_budget_ms = 0
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_total_budget_zero_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let err = ProxyConfig::load(&path).unwrap_err().to_string();
+        assert!(err.contains("censorship.tls_fetch.total_budget_ms must be > 0"));
+        let _ = std::fs::remove_file(path);
+    }
+
     #[test]
     fn invalid_ad_tag_is_disabled_during_load() {
         let toml = r#"

src/config/types.rs

@@ -1367,6 +1367,82 @@ pub enum UnknownSniAction {
     Mask,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum TlsFetchProfile {
+    ModernChromeLike,
+    ModernFirefoxLike,
+    CompatTls12,
+    LegacyMinimal,
+}
+
+impl TlsFetchProfile {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            TlsFetchProfile::ModernChromeLike => "modern_chrome_like",
+            TlsFetchProfile::ModernFirefoxLike => "modern_firefox_like",
+            TlsFetchProfile::CompatTls12 => "compat_tls12",
+            TlsFetchProfile::LegacyMinimal => "legacy_minimal",
+        }
+    }
+}
+
+fn default_tls_fetch_profiles() -> Vec<TlsFetchProfile> {
+    vec![
+        TlsFetchProfile::ModernChromeLike,
+        TlsFetchProfile::ModernFirefoxLike,
+        TlsFetchProfile::CompatTls12,
+        TlsFetchProfile::LegacyMinimal,
+    ]
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TlsFetchConfig {
+    /// Ordered list of ClientHello profiles used for adaptive fallback.
+    #[serde(default = "default_tls_fetch_profiles")]
+    pub profiles: Vec<TlsFetchProfile>,
+
+    /// When true and upstream route is configured, TLS fetch fails closed on
+    /// upstream connect errors and does not fallback to direct TCP.
+    #[serde(default = "default_tls_fetch_strict_route")]
+    pub strict_route: bool,
+
+    /// Timeout per one profile attempt in milliseconds.
+    #[serde(default = "default_tls_fetch_attempt_timeout_ms")]
+    pub attempt_timeout_ms: u64,
+
+    /// Total wall-clock budget in milliseconds across all profile attempts.
+    #[serde(default = "default_tls_fetch_total_budget_ms")]
+    pub total_budget_ms: u64,
+
+    /// Adds GREASE-style values into selected ClientHello extensions.
+    #[serde(default)]
+    pub grease_enabled: bool,
+
+    /// Produces deterministic ClientHello randomness for debugging/tests.
+    #[serde(default)]
+    pub deterministic: bool,
+
+    /// TTL for winner-profile cache entries in seconds.
+    /// Set to 0 to disable profile cache.
+    #[serde(default = "default_tls_fetch_profile_cache_ttl_secs")]
+    pub profile_cache_ttl_secs: u64,
+}
+
+impl Default for TlsFetchConfig {
+    fn default() -> Self {
+        Self {
+            profiles: default_tls_fetch_profiles(),
+            strict_route: default_tls_fetch_strict_route(),
+            attempt_timeout_ms: default_tls_fetch_attempt_timeout_ms(),
+            total_budget_ms: default_tls_fetch_total_budget_ms(),
+            grease_enabled: false,
+            deterministic: false,
+            profile_cache_ttl_secs: default_tls_fetch_profile_cache_ttl_secs(),
+        }
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct AntiCensorshipConfig {
     #[serde(default = "default_tls_domain")]
@@ -1385,6 +1461,10 @@ pub struct AntiCensorshipConfig {
     #[serde(default = "default_tls_fetch_scope")]
     pub tls_fetch_scope: String,
 
+    /// Fetch strategy for TLS front metadata bootstrap and periodic refresh.
+    #[serde(default)]
+    pub tls_fetch: TlsFetchConfig,
+
     #[serde(default = "default_true")]
     pub mask: bool,
 
@@ -1492,6 +1572,7 @@ impl Default for AntiCensorshipConfig {
             tls_domains: Vec::new(),
             unknown_sni_action: UnknownSniAction::Drop,
             tls_fetch_scope: default_tls_fetch_scope(),
+            tls_fetch: TlsFetchConfig::default(),
             mask: default_true(),
             mask_host: None,
             mask_port: default_mask_port(),