//! This module exposes utilities for building DNSSEC proofs by directly querying a recursive
//! resolver.
-use std::cmp;
+use core::{cmp, ops};
+use alloc::vec;
+use alloc::vec::Vec;
+
+#[cfg(feature = "std")]
use std::net::{SocketAddr, TcpStream};
+#[cfg(feature = "std")]
use std::io::{Read, Write, Error, ErrorKind};
#[cfg(feature = "tokio")]
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"))
+// In testing use a rather small buffer to ensure we hit the allocation paths sometimes. In
+// production, we should generally never actually need to go to heap as DNS messages are rarely
+// larger than a KiB or two.
+#[cfg(any(test, fuzzing))]
+const STACK_BUF_LIMIT: u16 = 32;
+#[cfg(not(any(test, fuzzing)))]
+const STACK_BUF_LIMIT: u16 = 2048;
+
+/// A buffer for storing queries and responses.
+#[derive(Clone, PartialEq, Eq)]
+pub struct QueryBuf {
+ buf: [u8; STACK_BUF_LIMIT as usize],
+ heap_buf: Vec<u8>,
+ len: u16,
+}
+impl QueryBuf {
+ /// Generates a new buffer of the given length, consisting of all zeros.
+ pub fn new_zeroed(len: u16) -> Self {
+ let heap_buf = if len > STACK_BUF_LIMIT { vec![0; len as usize] } else { Vec::new() };
+ Self {
+ buf: [0; STACK_BUF_LIMIT as usize],
+ heap_buf,
+ len
+ }
+ }
+ /// Extends the size of this buffer by appending the given slice.
+ ///
+ /// If the total length of this buffer exceeds [`u16::MAX`] after appending, the buffer's state
+ /// is undefined, however pushing data beyond [`u16::MAX`] will not panic.
+ pub fn extend_from_slice(&mut self, sl: &[u8]) {
+ let new_len = self.len.saturating_add(sl.len() as u16);
+ let was_heap = self.len > STACK_BUF_LIMIT;
+ let is_heap = new_len > STACK_BUF_LIMIT;
+ if was_heap != is_heap {
+ self.heap_buf = vec![0; new_len as usize];
+ self.heap_buf[..self.len as usize].copy_from_slice(&self.buf[..self.len as usize]);
+ }
+ let target = if is_heap {
+ self.heap_buf.resize(new_len as usize, 0);
+ &mut self.heap_buf[self.len as usize..]
+ } else {
+ &mut self.buf[self.len as usize..new_len as usize]
+ };
+ target.copy_from_slice(sl);
+ self.len = new_len;
+ }
+ /// Converts this query into its bytes on the heap
+ pub fn into_vec(self) -> Vec<u8> {
+ if self.len > STACK_BUF_LIMIT {
+ self.heap_buf
+ } else {
+ self.buf[..self.len as usize].to_vec()
+ }
+ }
+}
+impl ops::Deref for QueryBuf {
+ type Target = [u8];
+ fn deref(&self) -> &[u8] {
+ if self.len > STACK_BUF_LIMIT {
+ &self.heap_buf
+ } else {
+ &self.buf[..self.len as usize]
+ }
+ }
+}
+impl ops::DerefMut for QueryBuf {
+ fn deref_mut(&mut self) -> &mut [u8] {
+ if self.len > STACK_BUF_LIMIT {
+ &mut self.heap_buf
+ } else {
+ &mut self.buf[..self.len as usize]
+ }
+ }
}
-fn build_query(domain: &Name, ty: u16) -> Vec<u8> {
- // TODO: Move to not allocating for the query
- 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());
+// We don't care about transaction IDs as we're only going to accept signed data.
+// Further, if we're querying over DoH, the RFC says we SHOULD use a transaction ID of 0 here.
+const TXID: u16 = 0;
+
+fn build_query(domain: &Name, ty: u16) -> QueryBuf {
+ let mut query = QueryBuf::new_zeroed(0);
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
query
}
-fn send_query(stream: &mut TcpStream, domain: &Name, ty: u16) -> Result<(), Error> {
- let query = build_query(domain, ty);
- stream.write_all(&query)?;
- Ok(())
-}
-
-#[cfg(feature = "tokio")]
-async fn send_query_async(stream: &mut TokioTcpStream, domain: &Name, ty: u16) -> Result<(), Error> {
- let query = build_query(domain, ty);
- stream.write_all(&query).await?;
- Ok(())
-}
-
#[cfg(fuzzing)]
/// Read some input and parse it as if it came from a server, for fuzzing.
pub fn fuzz_response(response: &[u8]) {
let _ = handle_response(response, &mut proof, &mut names);
}
-fn handle_response(resp: &[u8], proof: &mut Vec<u8>, rrsig_key_names: &mut Vec<Name>) -> Result<u32, Error> {
+fn handle_response(resp: &[u8], proof: &mut Vec<u8>, rrsig_key_names: &mut Vec<Name>) -> Result<u32, ()> {
let mut read: &[u8] = resp;
- if emap(read_u16(&mut read))? != TXID { return Err(Error::new(ErrorKind::Other, "bad txid")); }
+ if read_u16(&mut read)? != TXID { return Err(()); }
// 2 byte transaction ID
- let flags = emap(read_u16(&mut read))?;
+ let flags = read_u16(&mut read)?;
if flags & 0b1000_0000_0000_0000 == 0 {
- return Err(Error::new(ErrorKind::Other, "Missing response flag"));
+ return Err(());
}
if flags & 0b0111_1010_0000_0111 != 0 {
- return Err(Error::new(ErrorKind::Other, "Server indicated error or provided bunk flags"));
+ return Err(());
}
if flags & 0b10_0000 == 0 {
- return Err(Error::new(ErrorKind::Other, "Server indicated data could not be authenticated"));
+ return Err(());
}
- 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))?;
- if answers == 0 { return Err(Error::new(ErrorKind::Other, "No answers")); }
- let _authorities = emap(read_u16(&mut read))?;
- let _additional = emap(read_u16(&mut read))?;
+ let questions = read_u16(&mut read)?;
+ if questions != 1 { return Err(()); }
+ let answers = read_u16(&mut read)?;
+ if answers == 0 { return Err(()); }
+ let _authorities = read_u16(&mut read)?;
+ let _additional = read_u16(&mut read)?;
for _ in 0..questions {
- emap(read_wire_packet_name(&mut read, resp))?;
- emap(read_u16(&mut read))?; // type
- emap(read_u16(&mut read))?; // class
+ read_wire_packet_name(&mut read, resp)?;
+ read_u16(&mut read)?; // type
+ read_u16(&mut read)?; // class
}
// Only read the answers (skip authorities and additional) as that's all we care about.
let mut min_ttl = u32::MAX;
for _ in 0..answers {
- let (rr, ttl) = emap(parse_wire_packet_rr(&mut read, &resp))?;
+ let (rr, ttl) = parse_wire_packet_rr(&mut read, &resp)?;
write_rr(&rr, ttl, proof);
min_ttl = cmp::min(min_ttl, ttl);
if let RR::RRSig(rrsig) = rr { rrsig_key_names.push(rrsig.key_name); }
Ok(min_ttl)
}
-fn read_response(stream: &mut TcpStream, proof: &mut Vec<u8>, rrsig_key_names: &mut Vec<Name>) -> Result<u32, 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)?;
- handle_response(&resp, proof, rrsig_key_names)
+#[cfg(fuzzing)]
+/// Read a stream of responses and handle them it as if they came from a server, for fuzzing.
+pub fn fuzz_proof_builder(mut response_stream: &[u8]) {
+ let (mut builder, _) = ProofBuilder::new(&"example.com.".try_into().unwrap(), Txt::TYPE);
+ while builder.awaiting_responses() {
+ let len = if let Ok(len) = read_u16(&mut response_stream) { len } else { return };
+ let mut buf = QueryBuf::new_zeroed(len);
+ if response_stream.len() < len as usize { return; }
+ buf.copy_from_slice(&response_stream[..len as usize]);
+ response_stream = &response_stream[len as usize..];
+ let _ = builder.process_response(&buf);
+ }
+ let _ = builder.finish_proof();
+}
+
+const MAX_REQUESTS: usize = 10;
+/// A simple state machine which will generate a series of queries and process the responses until
+/// it has built a DNSSEC proof.
+///
+/// A [`ProofBuilder`] driver starts with [`ProofBuilder::new`], fetching the state machine and
+/// initial query. As long as [`ProofBuilder::awaiting_responses`] returns true, responses should
+/// be read from the resolver. For each query response read from the DNS resolver,
+/// [`ProofBuilder::process_response`] should be called, and each fresh query returned should be
+/// sent to the resolver. Once [`ProofBuilder::awaiting_responses`] returns false,
+/// [`ProofBuilder::finish_proof`] should be called to fetch the resulting proof.
+pub struct ProofBuilder {
+ proof: Vec<u8>,
+ min_ttl: u32,
+ dnskeys_requested: Vec<Name>,
+ pending_queries: usize,
+ queries_made: usize,
+}
+
+impl ProofBuilder {
+ /// Constructs a new [`ProofBuilder`] and an initial query to send to the recursive resolver to
+ /// begin the proof building process.
+ ///
+ /// Given a correctly-functioning resolver the proof will ultimately be able to prove the
+ /// contents of any records with the given `ty`pe at the given `name` (as long as the given
+ /// `ty`pe is supported by this library).
+ ///
+ /// You can find constants for supported standard types in the [`crate::rr`] module.
+ pub fn new(name: &Name, ty: u16) -> (ProofBuilder, QueryBuf) {
+ let initial_query = build_query(name, ty);
+ (ProofBuilder {
+ proof: Vec::new(),
+ min_ttl: u32::MAX,
+ dnskeys_requested: Vec::with_capacity(MAX_REQUESTS),
+ pending_queries: 1,
+ queries_made: 1,
+ }, initial_query)
+ }
+
+ /// Returns true as long as further responses are expected from the resolver.
+ ///
+ /// As long as this returns true, responses should be read from the resolver and passed to
+ /// [`Self::process_response`]. Once this returns false, [`Self::finish_proof`] should be used
+ /// to (possibly) get the final proof.
+ pub fn awaiting_responses(&self) -> bool {
+ self.pending_queries > 0 && self.queries_made <= MAX_REQUESTS
+ }
+
+ /// Processes a query response from the recursive resolver, returning a list of new queries to
+ /// send to the resolver.
+ pub fn process_response(&mut self, resp: &QueryBuf) -> Result<Vec<QueryBuf>, ()> {
+ if self.pending_queries == 0 { return Err(()); }
+
+ let mut rrsig_key_names = Vec::new();
+ let min_ttl = handle_response(&resp, &mut self.proof, &mut rrsig_key_names)?;
+ self.min_ttl = cmp::min(self.min_ttl, min_ttl);
+ self.pending_queries -= 1;
+
+ rrsig_key_names.sort_unstable();
+ rrsig_key_names.dedup();
+
+ let mut new_queries = Vec::with_capacity(2);
+ for key_name in rrsig_key_names.drain(..) {
+ if !self.dnskeys_requested.contains(&key_name) {
+ new_queries.push(build_query(&key_name, DnsKey::TYPE));
+ self.pending_queries += 1;
+ self.queries_made += 1;
+ self.dnskeys_requested.push(key_name.clone());
+
+ if key_name.as_str() != "." {
+ new_queries.push(build_query(&key_name, DS::TYPE));
+ self.pending_queries += 1;
+ self.queries_made += 1;
+ }
+ }
+ }
+ if self.queries_made <= MAX_REQUESTS {
+ Ok(new_queries)
+ } else {
+ Ok(Vec::new())
+ }
+ }
+
+ /// Finalizes the proof, if one is available, and returns it as well as the TTL that should be
+ /// used to cache the proof (i.e. the lowest TTL of all records which were used to build the
+ /// proof).
+ pub fn finish_proof(self) -> Result<(Vec<u8>, u32), ()> {
+ if self.pending_queries > 0 || self.queries_made > MAX_REQUESTS {
+ Err(())
+ } else {
+ Ok((self.proof, self.min_ttl))
+ }
+ }
+}
+
+#[cfg(feature = "std")]
+fn send_query(stream: &mut TcpStream, query: &[u8]) -> Result<(), Error> {
+ stream.write_all(&(query.len() as u16).to_be_bytes())?;
+ stream.write_all(&query)?;
+ Ok(())
+}
+
+#[cfg(feature = "tokio")]
+async fn send_query_async(stream: &mut TokioTcpStream, query: &[u8]) -> Result<(), Error> {
+ stream.write_all(&(query.len() as u16).to_be_bytes()).await?;
+ stream.write_all(&query).await?;
+ Ok(())
+}
+
+#[cfg(feature = "std")]
+fn read_response(stream: &mut TcpStream) -> Result<QueryBuf, Error> {
+ let mut len_bytes = [0; 2];
+ stream.read_exact(&mut len_bytes)?;
+ let mut buf = QueryBuf::new_zeroed(u16::from_be_bytes(len_bytes));
+ stream.read_exact(&mut buf)?;
+ Ok(buf)
}
#[cfg(feature = "tokio")]
-async fn read_response_async(stream: &mut TokioTcpStream, proof: &mut Vec<u8>, rrsig_key_names: &mut Vec<Name>) -> Result<u32, Error> {
- let mut len = [0; 2];
- stream.read_exact(&mut len).await?;
- let mut resp = vec![0; u16::from_be_bytes(len) as usize];
- stream.read_exact(&mut resp).await?;
- handle_response(&resp, proof, rrsig_key_names)
+async fn read_response_async(stream: &mut TokioTcpStream) -> Result<QueryBuf, Error> {
+ let mut len_bytes = [0; 2];
+ stream.read_exact(&mut len_bytes).await?;
+ let mut buf = QueryBuf::new_zeroed(u16::from_be_bytes(len_bytes));
+ stream.read_exact(&mut buf).await?;
+ Ok(buf)
}
+#[cfg(feature = "std")]
macro_rules! build_proof_impl {
- ($stream: ident, $send_query: ident, $read_response: ident $(, $async_ok: tt)?) => { {
+ ($stream: ident, $send_query: ident, $read_response: ident, $domain: expr, $ty: expr $(, $async_ok: tt)?) => { {
// We require the initial query to have already gone out, and assume our resolver will
// return any CNAMEs all the way to the final record in the response. From there, we just
// have to take any RRSIGs in the response and walk them up to the root. We do so
// iteratively, sending DNSKEY and DS lookups after every response, deduplicating requests
// using `dnskeys_requested`.
- let mut res = Vec::new(); // The actual proof stream
- let mut min_ttl = u32::MAX; // Min TTL of any answer record
- const MAX_REQUESTS: usize = 20;
- let mut rrsig_key_names = Vec::with_capacity(4); // Last response's RRSIG key_names
- let mut dnskeys_requested = Vec::with_capacity(MAX_REQUESTS);
- let mut pending_queries = 1;
- let mut queries_made = 1;
- while pending_queries != 0 && queries_made <= MAX_REQUESTS {
- let response_min_ttl = $read_response(&mut $stream, &mut res, &mut rrsig_key_names)
+ let (mut builder, initial_query) = ProofBuilder::new($domain, $ty);
+ $send_query(&mut $stream, &initial_query)
+ $(.await?; $async_ok)??; // Either await?; Ok(())?, or just ?
+ while builder.awaiting_responses() {
+ let response = $read_response(&mut $stream)
$(.await?; $async_ok)??; // Either await?; Ok(())?, or just ?
- pending_queries -= 1;
- min_ttl = cmp::min(min_ttl, response_min_ttl);
- rrsig_key_names.sort_unstable();
- rrsig_key_names.dedup();
- for key_name in rrsig_key_names.drain(..) {
- if !dnskeys_requested.contains(&key_name) {
- $send_query(&mut $stream, &key_name, DnsKey::TYPE)
- $(.await?; $async_ok)??; // Either await?; Ok(())?, or just ?
- pending_queries += 1;
- queries_made += 1;
- dnskeys_requested.push(key_name.clone());
-
- if key_name.as_str() != "." {
- $send_query(&mut $stream, &key_name, DS::TYPE)
- $(.await?; $async_ok)??; // Either await?; Ok(())?, or just ?
- pending_queries += 1;
- queries_made += 1;
- }
- }
+ let new_queries = builder.process_response(&response)
+ .map_err(|()| Error::new(ErrorKind::Other, "Bad response"))?;
+ for query in new_queries {
+ $send_query(&mut $stream, &query)
+ $(.await?; $async_ok)??; // Either await?; Ok(())?, or just ?
}
}
- if queries_made > MAX_REQUESTS {
- Err(Error::new(ErrorKind::Other, "Too many requests required"))
- } else {
- Ok((res, min_ttl))
- }
+ builder.finish_proof()
+ .map_err(|()| Error::new(ErrorKind::Other, "Too many requests required"))
} }
}
+#[cfg(feature = "std")]
fn build_proof(resolver: SocketAddr, domain: &Name, ty: u16) -> Result<(Vec<u8>, u32), Error> {
let mut stream = TcpStream::connect(resolver)?;
- send_query(&mut stream, domain, ty)?;
- build_proof_impl!(stream, send_query, read_response)
+ build_proof_impl!(stream, send_query, read_response, domain, ty)
}
#[cfg(feature = "tokio")]
async fn build_proof_async(resolver: SocketAddr, domain: &Name, ty: u16) -> Result<(Vec<u8>, u32), Error> {
let mut stream = TokioTcpStream::connect(resolver).await?;
- send_query_async(&mut stream, domain, ty).await?;
- build_proof_impl!(stream, send_query_async, read_response_async, { Ok::<(), Error>(()) })
+ build_proof_impl!(stream, send_query_async, read_response_async, domain, ty, { Ok::<(), Error>(()) })
}
/// Builds a DNSSEC proof for an A record by querying a recursive resolver, returning the proof as
///
/// Note that this proof is NOT verified in any way, you need to use the [`crate::validation`]
/// module to validate the records contained.
+#[cfg(feature = "std")]
pub fn build_a_proof(resolver: SocketAddr, domain: &Name) -> Result<(Vec<u8>, u32), Error> {
build_proof(resolver, domain, A::TYPE)
}
///
/// Note that this proof is NOT verified in any way, you need to use the [`crate::validation`]
/// module to validate the records contained.
+#[cfg(feature = "std")]
pub fn build_aaaa_proof(resolver: SocketAddr, domain: &Name) -> Result<(Vec<u8>, u32), Error> {
build_proof(resolver, domain, AAAA::TYPE)
}
///
/// Note that this proof is NOT verified in any way, you need to use the [`crate::validation`]
/// module to validate the records contained.
+#[cfg(feature = "std")]
pub fn build_txt_proof(resolver: SocketAddr, domain: &Name) -> Result<(Vec<u8>, u32), Error> {
build_proof(resolver, domain, Txt::TYPE)
}
///
/// Note that this proof is NOT verified in any way, you need to use the [`crate::validation`]
/// module to validate the records contained.
+#[cfg(feature = "std")]
pub fn build_tlsa_proof(resolver: SocketAddr, domain: &Name) -> Result<(Vec<u8>, u32), Error> {
build_proof(resolver, domain, TLSA::TYPE)
}
build_proof_async(resolver, domain, TLSA::TYPE).await
}
-#[cfg(all(feature = "validation", test))]
+#[cfg(all(feature = "validation", feature = "std", test))]
mod tests {
use super::*;
use crate::validation::*;
use std::net::ToSocketAddrs;
use std::time::SystemTime;
-
#[test]
fn test_cloudflare_txt_query() {
let sockaddr = "8.8.8.8:53".to_socket_addrs().unwrap().next().unwrap();
projects / dnssec-prover / blobdiff