Add support for building proofs using a local recursive resolver

diff --git a/Cargo.toml b/Cargo.toml
index 2177bb9f2af210bcf08a85a54be91d9c498bbcc3..86ddb6b0f88a89b422c2870a2a4d143fd4f24731 100644 (file)
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,9 @@ categories = ["cryptography", "no-std"]
 edition = "2021"
 rust-version = "1.60.0"
 
+[features]
+std = []
+
 [dependencies]
 ring = { version = "0.17", default-features = false, features = ["alloc"] }
 hex_lit = { version = "0.1", default-features = false, features = ["rust_v_1_46"] }

diff --git a/src/lib.rs b/src/lib.rs
index 5a54a8cb56b3572ee06d2f4a17ed15f86d0ccf3a..14104e50d6b534e34383d7fbe224013fc9db2d8f 100644 (file)
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,7 +16,7 @@
 
 #![deny(missing_docs)]
 
-#![no_std]
+#![cfg_attr(not(feature = "std"), no_std)]
 extern crate alloc;
 
 use alloc::vec::Vec;

diff --git a/src/query.rs b/src/query.rs
new file mode 100644 (file)
index 0000000..65da2f0
--- /dev/null
+++ b/src/query.rs
@@ -0,0 +1,145 @@
+//! This module exposes utilities for building DNSSEC proofs by directly querying a recursive
+//! resolver.
+
+use std::net::{SocketAddr, TcpStream};
+use std::io::{Read, Write, Error, ErrorKind};
+
+use crate::write_rr;
+use crate::rr::*;
+use crate::ser::*;
+
+// We don't care about transaction IDs as we're only going to accept signed data. Thus, we use
+// this constant instead of a random value.
+const TXID: u16 = 0x4242;
+
+fn emap<V>(v: Result<V, ()>) -> Result<V, Error> {
+       v.map_err(|_| Error::new(ErrorKind::Other, "Bad Response"))
+}
+
+fn send_query(stream: &mut TcpStream, domain: Name, ty: u16) -> Result<(), Error> {
+       let mut query = Vec::with_capacity(1024);
+       let query_msg_len: u16 = 2 + 2 + 8 + 2 + 2 + name_len(&domain) + 11;
+       query.extend_from_slice(&query_msg_len.to_be_bytes());
+       query.extend_from_slice(&TXID.to_be_bytes());
+       query.extend_from_slice(&[0x01, 0x20]); // Flags: Recursive, Authenticated Data
+       query.extend_from_slice(&[0, 1, 0, 0, 0, 0, 0, 1]); // One question, One additional
+       write_name(&mut query, &domain);
+       query.extend_from_slice(&ty.to_be_bytes());
+       query.extend_from_slice(&1u16.to_be_bytes()); // INternet class
+       query.extend_from_slice(&[0, 0, 0x29]); // . OPT
+       query.extend_from_slice(&0u16.to_be_bytes()); // 0 UDP payload size
+       query.extend_from_slice(&[0, 0]); // EDNS version 0
+       query.extend_from_slice(&0x8000u16.to_be_bytes()); // Accept DNSSEC RRs
+       query.extend_from_slice(&0u16.to_be_bytes()); // No additional data
+       stream.write_all(&query)?;
+       Ok(())
+}
+
+fn read_response(stream: &mut TcpStream) -> Result<Vec<RR>, Error> {
+       let mut len = [0; 2];
+       stream.read_exact(&mut len)?;
+       let mut resp = vec![0; u16::from_be_bytes(len) as usize];
+       stream.read_exact(&mut resp)?;
+
+       let mut read: &[u8] = &resp;
+       if emap(read_u16(&mut read))? != TXID { return Err(Error::new(ErrorKind::Other, "bad txid")); }
+       // 2 byte transaction ID
+       let flags = emap(read_u16(&mut read))?;
+       if flags & 0b1000_0000_0000_0000 == 0 {
+               return Err(Error::new(ErrorKind::Other, "Missing response flag"));
+       }
+       if flags & 0b0111_1010_0000_0111 != 0 {
+               return Err(Error::new(ErrorKind::Other, "Server indicated error or provided bunk flags"));
+       }
+       if flags & 0b10_0000 == 0 {
+               return Err(Error::new(ErrorKind::Other, "Server indicated data could not be authenticated"));
+       }
+       let questions = emap(read_u16(&mut read))?;
+       if questions != 1 { return Err(Error::new(ErrorKind::Other, "server responded to multiple Qs")); }
+       let answers = emap(read_u16(&mut read))?;
+       let _authorities = emap(read_u16(&mut read))?;
+       let _additional = emap(read_u16(&mut read))?;
+
+       for _ in 0..questions {
+               emap(read_name(&mut read))?;
+               emap(read_u16(&mut read))?; // type
+               emap(read_u16(&mut read))?; // class
+       }
+
+       // Only read the answers (skip authorities and additional) as that's all we care about.
+       let mut res = Vec::new();
+       for _ in 0..answers {
+               res.push(emap(parse_wire_packet_rr(&mut read, &resp))?);
+       }
+       Ok(res)
+}
+
+fn build_proof(resolver: SocketAddr, domain: Name, ty: u16) -> Result<Vec<u8>, Error> {
+       let mut stream = TcpStream::connect(resolver)?;
+       let mut res = Vec::new();
+       send_query(&mut stream, domain, ty)?;
+       let mut reached_root = false;
+       for _ in 0..10 {
+               let resp = read_response(&mut stream)?;
+               for rr in resp {
+                       write_rr(&rr, 0, &mut res);
+                       if rr.name().as_str() == "." {
+                               reached_root = true;
+                       } else {
+                               if let RR::RRSig(rrsig) = rr {
+                                       if rrsig.name == rrsig.key_name {
+                                               send_query(&mut stream, rrsig.key_name, DS::TYPE)?;
+                                       } else {
+                                               send_query(&mut stream, rrsig.key_name, DnsKey::TYPE)?;
+                                       }
+                               }
+                       }
+               }
+               if reached_root { break; }
+       }
+
+       if !reached_root { Err(Error::new(ErrorKind::Other, "Too many requests required")) }
+       else { Ok(res) }
+}
+
+/// Builds a DNSSEC proof for an A record by querying a recursive resolver
+pub fn build_a_proof(resolver: SocketAddr, domain: Name) -> Result<Vec<u8>, Error> {
+       build_proof(resolver, domain, A::TYPE)
+}
+
+/// Builds a DNSSEC proof for an AAAA record by querying a recursive resolver
+pub fn build_aaaa_proof(resolver: SocketAddr, domain: Name) -> Result<Vec<u8>, Error> {
+       build_proof(resolver, domain, AAAA::TYPE)
+}
+
+/// Builds a DNSSEC proof for a TXT record by querying a recursive resolver
+pub fn build_txt_proof(resolver: SocketAddr, domain: Name) -> Result<Vec<u8>, Error> {
+       build_proof(resolver, domain, Txt::TYPE)
+}
+
+/// Builds a DNSSEC proof for a TLSA record by querying a recursive resolver
+pub fn build_tlsa_proof(resolver: SocketAddr, domain: Name) -> Result<Vec<u8>, Error> {
+       build_proof(resolver, domain, TLSA::TYPE)
+}
+
+#[cfg(test)]
+mod tests {
+       use super::*;
+       use crate::*;
+
+       use rand::seq::SliceRandom;
+
+       use std::net::ToSocketAddrs;
+
+       #[test]
+       fn test_txt_query() {
+               let sockaddr = "8.8.8.8:53".to_socket_addrs().unwrap().next().unwrap();
+               let query_name = "matt.user._bitcoin-payment.mattcorallo.com.".try_into().unwrap();
+               let proof = build_txt_proof(sockaddr, query_name).unwrap();
+
+               let mut rrs = parse_rr_stream(&proof).unwrap();
+               rrs.shuffle(&mut rand::rngs::OsRng);
+               let verified_rrs = verify_rr_stream(&rrs).unwrap();
+               assert_eq!(verified_rrs.len(), 1);
+       }
+}