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//! Support for encoding the network document meta-format
//!
//! Implements writing documents according to
//! [dir-spec.txt](https://spec.torproject.org/dir-spec).
//! section 1.2 and 1.3.
//! This facility processes output that complies with the meta-document format,
//! (`dir-spec.txt` section 1.2) -
//! unless `raw` methods are called with improper input.
//! However, no checks are done on keyword presence/absence, multiplicity, or ordering,
//! so the output may not necessarily conform to the format of the particular intended document.
//! It is the caller's responsibility to call `.item()` in the right order,
//! with the right keywords and arguments.
// TODO Plan for encoding signed documents:
//
// * Derive an encoder function for Foo; the encoder gives you Encoded<Foo>.
// * Write code ad-hoc to construct FooSignatures.
// * Call encoder-core-provided method on Encoded to add the signatures
// Method(s) on Encoded<Foo> are provided centrally to let you get the &str to hash it.
// Nothing cooked is provided to help with the signature encoding layering violation:
// the central encoding derives do not provide any way to obtain a partly-encoded
// signature item so that it can be added to the hash.
// So the signing code must recapitulate some of the item encoding. This will generally
// be simply a const str (or similar) with the encoded item name and any parameters,
// in precisely the form that needs to be appended to the hash.
// This does leave us open to bugs where the hashed data doesn't match what ends up
// being encoded, but since it's a fixed string, such a bug couldn't survive a smoke test.
// If there are items where the layering violation involves encoding
// of variable parameters, this would need further work, either ad-hoc,
// or additional traits/macrology/etc. if there's enough cases where it's needed.
mod multiplicity;
#[macro_use]
mod derive;
mod impls;
use std::cmp;
use std::collections::BTreeSet;
use std::fmt::Write;
use std::iter;
use std::marker::PhantomData;
use base64ct::{Base64, Base64Unpadded, Encoding};
use educe::Educe;
use itertools::Itertools;
use paste::paste;
use rand::{CryptoRng, RngCore};
use tor_bytes::EncodeError;
use tor_error::internal;
use void::Void;
use crate::KeywordEncodable;
use crate::parse::tokenize::tag_keywords_ok;
use crate::types::misc::Iso8601TimeSp;
// Exports used by macros, which treat this module as a prelude
#[doc(hidden)]
pub use {
crate::netdoc_ordering_check,
derive::{DisplayHelper, RestMustComeLastMarker},
multiplicity::{
MultiplicityMethods, MultiplicitySelector, OptionalityMethods,
SingletonMultiplicitySelector,
},
std::fmt::{self, Display},
std::result::Result,
tor_error::{Bug, into_internal},
};
/// Encoder, representing a partially-built document.
///
/// For example usage, see the tests in this module, or a descriptor building
/// function in tor-netdoc (such as `hsdesc::build::inner::HsDescInner::build_sign`).
#[derive(Debug, Clone)]
pub struct NetdocEncoder {
/// The being-built document, with everything accumulated so far
/// If an [`ItemEncoder`] exists, it will add a newline when it's dropped.
/// `Err` means bad values passed to some builder function.
/// Such errors are accumulated here for the benefit of handwritten document encoders.
built: Result<String, Bug>,
}
/// Encoder for an individual item within a being-built document
/// Returned by [`NetdocEncoder::item()`].
#[derive(Debug)]
pub struct ItemEncoder<'n> {
/// The document including the partial item that we're building
/// We will always add a newline when we're dropped
doc: &'n mut NetdocEncoder,
/// Position within a (perhaps partially-) built document
/// This is provided mainly to allow the caller to perform signature operations
/// on the part of the document that is to be signed.
/// (Sometimes this is only part of it.)
/// There is no enforced linkage between this and the document it refers to.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]
pub struct Cursor {
/// The offset (in bytes, as for `&str`)
/// Can be out of range if the corresponding `NetdocEncoder` is contains an `Err`.
offset: usize,
/// Types that can be added as argument(s) to item keyword lines
/// Implemented for strings, and various other types.
/// This is a separate trait so we can control the formatting of (eg) [`Iso8601TimeSp`],
/// without having a method on `ItemEncoder` for each argument type.
// TODO consider renaming this to ItemArgumentEncodable to mirror all the other related traits.
pub trait ItemArgument {
/// Format as a string suitable for including as a netdoc keyword line argument
/// The implementation is responsible for checking that the syntax is legal.
/// For example, if `self` is a string, it must check that the string is
/// in legal as a single argument.
/// Some netdoc values (eg times) turn into several arguments; in that case,
/// one `ItemArgument` may format into multiple arguments, and this method
/// is responsible for writing them all, with the necessary spaces.
fn write_arg_onto(&self, out: &mut ItemEncoder<'_>) -> Result<(), Bug>;
impl NetdocEncoder {
/// Start encoding a document
pub fn new() -> Self {
NetdocEncoder {
built: Ok(String::new()),
/// Adds an item to the being-built document
/// The item can be further extended with arguments or an object,
/// using the returned `ItemEncoder`.
pub fn item(&mut self, keyword: impl KeywordEncodable) -> ItemEncoder {
self.raw(&keyword.to_str());
ItemEncoder { doc: self }
/// Internal name for `push_raw_string()`
fn raw(&mut self, s: &dyn Display) {
self.write_with(|b| {
write!(b, "{}", s).expect("write! failed on String");
Ok(())
});
/// Extend the being-built document with a fallible function `f`
/// Doesn't call `f` if the building has already failed,
/// and handles the error if `f` fails.
fn write_with(&mut self, f: impl FnOnce(&mut String) -> Result<(), Bug>) {
let Ok(build) = &mut self.built else {
return;
match f(build) {
Ok(()) => (),
Err(e) => {
self.built = Err(e);
/// Adds raw text to the being-built document
/// `s` is added as raw text, after the newline ending the previous item.
/// If `item` is subsequently called, the start of that item
/// will immediately follow `s`.
/// It is the responsibility of the caller to obey the metadocument syntax.
/// In particular, `s` should end with a newline.
/// No checks are performed.
/// Incorrect use might lead to malformed documents, or later errors.
pub fn push_raw_string(&mut self, s: &dyn Display) {
self.raw(s);
/// Return a cursor, pointing to just after the last item (if any)
pub fn cursor(&self) -> Cursor {
let offset = match &self.built {
Ok(b) => b.len(),
Err(_) => usize::MAX,
Cursor { offset }
/// Obtain the text of a section of the document
/// Useful for making a signature.
pub fn slice(&self, begin: Cursor, end: Cursor) -> Result<&str, Bug> {
self.built
.as_ref()
.map_err(Clone::clone)?
.get(begin.offset..end.offset)
.ok_or_else(|| internal!("NetdocEncoder::slice out of bounds, Cursor mismanaged"))
/// Obtain the document so far in textual form
pub fn text_sofar(&self) -> Result<&str, Bug> {
self.built.as_deref().map_err(Clone::clone)
/// Build the document into textual form
pub fn finish(self) -> Result<String, Bug> {
impl Default for NetdocEncoder {
fn default() -> Self {
// We must open-code this because the actual encoder contains Result, which isn't Default
NetdocEncoder::new()
impl<T: crate::NormalItemArgument> ItemArgument for T {
fn write_arg_onto(&self, out: &mut ItemEncoder<'_>) -> Result<(), Bug> {
(*self.to_string()).write_arg_onto(out)
impl<'n> ItemEncoder<'n> {
/// Add a single argument.
/// Convenience method that defers error handling, for use in infallible contexts.
/// Consider whether to use `ItemArgument::write_arg_onto` directly, instead.
/// If the argument is not in the correct syntax, a `Bug`
/// error will be reported (later).
// This is not a hot path. `dyn` for smaller code size.
pub fn arg(mut self, arg: &dyn ItemArgument) -> Self {
self.add_arg(arg);
self
/// Add a single argument, to a borrowed `ItemEncoder`
// Needed for implementing `ItemArgument`
pub(crate) fn add_arg(&mut self, arg: &dyn ItemArgument) {
let () = arg
.write_arg_onto(self)
.unwrap_or_else(|err| self.doc.built = Err(err));
/// Add zero or more arguments, supplied as a single string.
/// `args` should zero or more valid argument strings,
/// separated by (single) spaces.
/// This is not (properly) checked.
pub fn args_raw_string(&mut self, args: &dyn Display) {
let args = args.to_string();
if !args.is_empty() {
self.args_raw_nonempty(&args);
/// Add one or more arguments, supplied as a single string, without any checking
fn args_raw_nonempty(&mut self, args: &dyn Display) {
self.doc.raw(&format_args!(" {}", args));
/// Add an `ItemObjectEncodable` to the item
// Note that the `ItemValueEncodable` derive macro (in `derive.rs`)
// also implements this functionality.
pub fn object(self, object: &dyn ItemObjectEncodable) {
let label = object.label();
let mut buf = vec![];
object
.write_object_onto(&mut buf)
self.object_bytes(label, buf);
/// Add an object to the item, given the keyword and a `tor_bytes::WriteableOnce`
/// Checks that `keywords` is in the correct syntax.
/// Doesn't check that it makes semantic sense for the position of the document.
/// `data` will be PEM (base64) encoded.
// If keyword is not in the correct syntax, a `Bug` is stored in self.doc.
pub fn object_bytes(
self,
keywords: &str,
// Writeable isn't dyn-compatible
data: impl tor_bytes::WriteableOnce,
) {
use crate::parse::tokenize::object::*;
self.doc.write_with(|out| {
if keywords.is_empty() || !tag_keywords_ok(keywords) {
return Err(internal!("bad object keywords string {:?}", keywords));
let data = {
let mut bytes = vec![];
data.write_into(&mut bytes)?;
Base64::encode_string(&bytes)
let mut data = &data[..];
writeln!(out, "\n{BEGIN_STR}{keywords}{TAG_END}").expect("write!");
while !data.is_empty() {
let (l, r) = if data.len() > BASE64_PEM_MAX_LINE {
data.split_at(BASE64_PEM_MAX_LINE)
} else {
(data, "")
writeln!(out, "{l}").expect("write!");
data = r;
// final newline will be written by Drop impl
write!(out, "{END_STR}{keywords}{TAG_END}").expect("write!");
/// Finish encoding this item
/// The item will also automatically be finished if the `ItemEncoder` is dropped.
pub fn finish(self) {}
impl Drop for ItemEncoder<'_> {
fn drop(&mut self) {
self.doc.raw(&'\n');
/// Ordering, to be used when encoding network documents
/// Implemented for anything `Ord`.
/// Can also be implemented manually, for if a type cannot be `Ord`
/// (perhaps for trait coherence reasons).
pub trait EncodeOrd {
/// Compare `self` and `other`
/// As `Ord::cmp`.
fn encode_cmp(&self, other: &Self) -> cmp::Ordering;
impl<T: Ord> EncodeOrd for T {
fn encode_cmp(&self, other: &Self) -> cmp::Ordering {
self.cmp(other)
/// Documents (or sub-documents) that can be encoded in the netdoc metaformat
pub trait NetdocEncodable {
/// Append the document onto `out`
fn encode_unsigned(&self, out: &mut NetdocEncoder) -> Result<(), Bug>;
/// Collections of fields that can be encoded in the netdoc metaformat
/// Whole documents have structure; a `NetdocEncodableFields` does not.
pub trait NetdocEncodableFields {
fn encode_fields(&self, out: &mut NetdocEncoder) -> Result<(), Bug>;
/// Items that can be encoded in network documents
pub trait ItemValueEncodable {
/// Write the item's arguments, and any object, onto `out`
/// `out` will have been freshly returned from [`NetdocEncoder::item`].
fn write_item_value_onto(&self, out: ItemEncoder) -> Result<(), Bug>;
/// An Object value that be encoded into a netdoc
pub trait ItemObjectEncodable {
/// The label (keyword(s) in `BEGIN` and `END`)
fn label(&self) -> &str;
/// Represent the actual value as bytes.
/// The caller, not the object, is responsible for base64 encoding.
// This is not a tor_bytes::Writeable supertrait because tor_bytes's writer argument
// is generic, which prevents many deisrable manipulations of an `impl Writeable`.
fn write_object_onto(&self, b: &mut Vec<u8>) -> Result<(), Bug>;
/// Builders for network documents.
/// This trait is a bit weird, because its `Self` type must contain the *private* keys
/// necessary to sign the document!
/// So it is implemented for "builders", not for documents themselves.
/// Some existing documents can be constructed only via these builders.
/// The newer approach is for documents to be transparent data, at the Rust level,
/// and to derive an encoder.
/// TODO this derive approach is not yet implemented!
/// Actual document types, which only contain the information in the document,
/// don't implement this trait.
pub trait NetdocBuilder {
/// Build the document into textual form.
fn build_sign<R: RngCore + CryptoRng>(self, rng: &mut R) -> Result<String, EncodeError>;
/// implement [`ItemValueEncodable`] for a particular tuple size
macro_rules! item_value_encodable_for_tuple {
{ $($i:literal)* } => { paste! {
impl< $( [<T$i>]: ItemArgument, )* > ItemValueEncodable for ( $( [<T$i>], )* ) {
fn write_item_value_onto(
&self,
#[allow(unused)]
mut out: ItemEncoder,
) -> Result<(), Bug> {
$(
<[<T$i>] as ItemArgument>::write_arg_onto(&self.$i, &mut out)?;
)*
} }
item_value_encodable_for_tuple! {}
item_value_encodable_for_tuple! { 0 }
item_value_encodable_for_tuple! { 0 1 }
item_value_encodable_for_tuple! { 0 1 2 }
item_value_encodable_for_tuple! { 0 1 2 3 }
item_value_encodable_for_tuple! { 0 1 2 3 4 }
item_value_encodable_for_tuple! { 0 1 2 3 4 5 }
item_value_encodable_for_tuple! { 0 1 2 3 4 5 6 }
item_value_encodable_for_tuple! { 0 1 2 3 4 5 6 7 }
item_value_encodable_for_tuple! { 0 1 2 3 4 5 6 7 8 }
item_value_encodable_for_tuple! { 0 1 2 3 4 5 6 7 8 9 }
#[cfg(test)]
mod test {
// @@ begin test lint list maintained by maint/add_warning @@
#![allow(clippy::bool_assert_comparison)]
#![allow(clippy::clone_on_copy)]
#![allow(clippy::dbg_macro)]
#![allow(clippy::mixed_attributes_style)]
#![allow(clippy::print_stderr)]
#![allow(clippy::print_stdout)]
#![allow(clippy::single_char_pattern)]
#![allow(clippy::unwrap_used)]
#![allow(clippy::unchecked_time_subtraction)]
#![allow(clippy::useless_vec)]
#![allow(clippy::needless_pass_by_value)]
//! <!-- @@ end test lint list maintained by maint/add_warning @@ -->
use super::*;
use std::str::FromStr;
use crate::types::misc::Iso8601TimeNoSp;
use base64ct::{Base64Unpadded, Encoding};
#[test]
fn time_formats_as_args() {
use crate::doc::authcert::AuthCertKwd as ACK;
use crate::doc::netstatus::NetstatusKwd as NK;
let t_sp = Iso8601TimeSp::from_str("2020-04-18 08:36:57").unwrap();
let t_no_sp = Iso8601TimeNoSp::from_str("2021-04-18T08:36:57").unwrap();
let mut encode = NetdocEncoder::new();
encode.item(ACK::DIR_KEY_EXPIRES).arg(&t_sp);
encode
.item(NK::SHARED_RAND_PREVIOUS_VALUE)
.arg(&"3")
.arg(&"bMZR5Q6kBadzApPjd5dZ1tyLt1ckv1LfNCP/oyGhCXs=")
.arg(&t_no_sp);
let doc = encode.finish().unwrap();
println!("{}", doc);
assert_eq!(
doc,
r"dir-key-expires 2020-04-18 08:36:57
shared-rand-previous-value 3 bMZR5Q6kBadzApPjd5dZ1tyLt1ckv1LfNCP/oyGhCXs= 2021-04-18T08:36:57
"
);
fn authcert() {
use crate::doc::authcert::{AuthCert, UncheckedAuthCert};
// c&p from crates/tor-llcrypto/tests/testvec.rs
let pk_rsa = {
let pem = "
MIGJAoGBANUntsY9boHTnDKKlM4VfczcBE6xrYwhDJyeIkh7TPrebUBBvRBGmmV+
PYK8AM9irDtqmSR+VztUwQxH9dyEmwrM2gMeym9uXchWd/dt7En/JNL8srWIf7El
qiBHRBGbtkF/Re5pb438HC/CGyuujp43oZ3CUYosJOfY/X+sD0aVAgMBAAE";
Base64Unpadded::decode_vec(&pem.replace('\n', "")).unwrap()
encode.item(ACK::DIR_KEY_CERTIFICATE_VERSION).arg(&3);
.item(ACK::FINGERPRINT)
.arg(&"9367f9781da8eabbf96b691175f0e701b43c602e");
.item(ACK::DIR_KEY_PUBLISHED)
.arg(&Iso8601TimeSp::from_str("2020-04-18 08:36:57").unwrap());
.item(ACK::DIR_KEY_EXPIRES)
.arg(&Iso8601TimeSp::from_str("2021-04-18 08:36:57").unwrap());
.item(ACK::DIR_IDENTITY_KEY)
.object_bytes("RSA PUBLIC KEY", &*pk_rsa);
.item(ACK::DIR_SIGNING_KEY)
.item(ACK::DIR_KEY_CROSSCERT)
.object_bytes("ID SIGNATURE", []);
.item(ACK::DIR_KEY_CERTIFICATION)
.object_bytes("SIGNATURE", []);
eprintln!("{}", doc);
r"dir-key-certificate-version 3
fingerprint 9367f9781da8eabbf96b691175f0e701b43c602e
dir-key-published 2020-04-18 08:36:57
dir-key-expires 2021-04-18 08:36:57
dir-identity-key
-----BEGIN RSA PUBLIC KEY-----
qiBHRBGbtkF/Re5pb438HC/CGyuujp43oZ3CUYosJOfY/X+sD0aVAgMBAAE=
-----END RSA PUBLIC KEY-----
dir-signing-key
dir-key-crosscert
-----BEGIN ID SIGNATURE-----
-----END ID SIGNATURE-----
dir-key-certification
-----BEGIN SIGNATURE-----
-----END SIGNATURE-----
let _: UncheckedAuthCert = AuthCert::parse(&doc).unwrap();