From 4eb076ec19bf58cf4063b4cdb4cf370473892203 Mon Sep 17 00:00:00 2001
From: Mateusz Walkiewicz <mwalkiewicz@unoperate.com>
Date: Thu, 1 Aug 2024 13:42:08 +0200
Subject: [PATCH] DNS-over-HTTPS resolver

---
 Cargo.lock                                    |  1 +
 crates/erc20_payment_lib_common/Cargo.toml    |  1 +
 .../src/dns_over_https_resolver.rs            | 73 +++++++++++++++++++
 crates/erc20_payment_lib_common/src/lib.rs    |  1 +
 crates/erc20_rpc_pool/src/rpc_pool/pool.rs    | 14 +++-
 5 files changed, 89 insertions(+), 1 deletion(-)
 create mode 100644 crates/erc20_payment_lib_common/src/dns_over_https_resolver.rs

diff --git a/Cargo.lock b/Cargo.lock
index 6cfeaff9..6968c6e6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1206,6 +1206,7 @@ dependencies = [
  "metrics-runtime",
  "rand",
  "regex",
+ "reqwest",
  "rust_decimal",
  "rustc-hex",
  "secp256k1",
diff --git a/crates/erc20_payment_lib_common/Cargo.toml b/crates/erc20_payment_lib_common/Cargo.toml
index ecda14c9..0ef0fe30 100644
--- a/crates/erc20_payment_lib_common/Cargo.toml
+++ b/crates/erc20_payment_lib_common/Cargo.toml
@@ -29,6 +29,7 @@ rustc-hex = { workspace = true }
 secp256k1 = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
+reqwest = { workspace = true, features = ["json"] }
 sha3 = { workspace = true }
 sqlx = { workspace = true }
 structopt = { workspace = true }
diff --git a/crates/erc20_payment_lib_common/src/dns_over_https_resolver.rs b/crates/erc20_payment_lib_common/src/dns_over_https_resolver.rs
new file mode 100644
index 00000000..8e867efd
--- /dev/null
+++ b/crates/erc20_payment_lib_common/src/dns_over_https_resolver.rs
@@ -0,0 +1,73 @@
+use reqwest;
+use serde;
+use std::env;
+use std::io::ErrorKind as IoErrorKind;
+
+#[derive(serde::Deserialize)]
+struct DnsOverHttpsResponse {
+    #[serde(rename(deserialize = "Answer"))]
+    pub answer: Vec<DnsOverHttpsAnswer>,
+}
+
+#[derive(serde::Deserialize)]
+struct DnsOverHttpsAnswer {
+    pub data: String,
+}
+
+fn strip_quotes(data: &String) -> String {
+    let v1 = match data.strip_prefix('"') {
+        None => data.as_str(),
+        Some(x) => x,
+    };
+    String::from(match v1.strip_suffix('"') {
+        None => v1,
+        Some(x) => x,
+    })
+}
+
+pub enum DnsOverHttpsServer {
+    Google,
+    Cloudflare,
+}
+
+impl DnsOverHttpsServer {
+    pub fn get_dns_url(self: &DnsOverHttpsServer) -> &str {
+        match self {
+            DnsOverHttpsServer::Google => "https://dns.google/resolve",
+            DnsOverHttpsServer::Cloudflare => "https://cloudflare-dns.com/dns-query",
+        }
+    }
+}
+
+pub async fn resolve_dns_record_https(
+    record: &str,
+    record_type: &str,
+    dns_server: DnsOverHttpsServer,
+) -> std::io::Result<Vec<String>> {
+    let result = reqwest::Client::new()
+        .get(dns_server.get_dns_url())
+        .query(&[("name", record), ("type", record_type)])
+        .header(reqwest::header::ACCEPT, "application/dns-json")
+        .send()
+        .await
+        .map_err(|_| std::io::Error::new(IoErrorKind::Other, "Couldn't fetch DNS record."))?
+        .json::<DnsOverHttpsResponse>()
+        .await
+        .map_err(|_| std::io::Error::new(IoErrorKind::Other, "Couldn't fetch DNS record."))?
+        .answer
+        .iter()
+        .map(|a| strip_quotes(&a.data))
+        .collect();
+    Ok(result)
+}
+
+pub async fn resolve_txt_record_to_string_array_https(
+    record: &str,
+    dns_server: DnsOverHttpsServer,
+) -> std::io::Result<Vec<String>> {
+    resolve_dns_record_https(record, "TXT", dns_server).await
+}
+
+pub fn should_use_dns_over_https() -> bool {
+    matches!(env::var("YA_USE_HTTPS_DNS_RESOLVER"), Ok(value) if value == "1")
+}
diff --git a/crates/erc20_payment_lib_common/src/lib.rs b/crates/erc20_payment_lib_common/src/lib.rs
index 206f6739..5340003f 100644
--- a/crates/erc20_payment_lib_common/src/lib.rs
+++ b/crates/erc20_payment_lib_common/src/lib.rs
@@ -1,4 +1,5 @@
 mod db;
+pub mod dns_over_https_resolver;
 pub mod error;
 mod events;
 mod metrics;
diff --git a/crates/erc20_rpc_pool/src/rpc_pool/pool.rs b/crates/erc20_rpc_pool/src/rpc_pool/pool.rs
index eeabc890..cd74ec93 100644
--- a/crates/erc20_rpc_pool/src/rpc_pool/pool.rs
+++ b/crates/erc20_rpc_pool/src/rpc_pool/pool.rs
@@ -20,6 +20,10 @@ use uuid::Uuid;
 use web3::transports::Http;
 use web3::Web3;
 
+use erc20_payment_lib_common::dns_over_https_resolver::{
+    resolve_txt_record_to_string_array_https, should_use_dns_over_https, DnsOverHttpsServer,
+};
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct Web3ExternalEndpointList {
@@ -122,7 +126,7 @@ pub struct Web3RpcPool {
     pub endpoint_verifier: Arc<EndpointsVerifier>,
 }
 
-pub async fn resolve_txt_record_to_string_array(record: &str) -> std::io::Result<Vec<String>> {
+pub async fn resolve_txt_record_to_string_array_dns(record: &str) -> std::io::Result<Vec<String>> {
     let resolver: TokioAsyncResolver =
         TokioAsyncResolver::tokio(ResolverConfig::google(), ResolverOpts::default());
 
@@ -136,6 +140,14 @@ pub async fn resolve_txt_record_to_string_array(record: &str) -> std::io::Result
         .collect::<Vec<_>>())
 }
 
+pub async fn resolve_txt_record_to_string_array(record: &str) -> std::io::Result<Vec<String>> {
+    if should_use_dns_over_https() {
+        resolve_txt_record_to_string_array_https(record, DnsOverHttpsServer::Google).await
+    } else {
+        resolve_txt_record_to_string_array_dns(record).await
+    }
+}
+
 pub struct ChooseBestEndpointsResult {
     pub allowed_endpoints: Vec<Index>,
     pub is_resolving: bool,