From b151237a7f8651ed8694748832af05786a7eccfd Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Fri, 7 Jul 2023 14:19:55 +0100
Subject: [PATCH] rng ranges: Use gen_range_infallible() for Duration::ZERO..=T

---
 Cargo.lock                                | 1 +
 crates/arti-testing/Cargo.toml            | 1 +
 crates/arti-testing/src/rt/badtcp.rs      | 5 +++--
 crates/tor-circmgr/src/timeouts/pareto.rs | 2 +-
 crates/tor-dirmgr/src/state.rs            | 5 ++---
 crates/tor-guardmgr/src/util.rs           | 3 ++-
 6 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 8e23bff21..99e3eb44d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -330,6 +330,7 @@ dependencies = [
  "rand 0.8.5",
  "serde",
  "tokio",
+ "tor-basic-utils",
  "tor-checkable",
  "tor-config",
  "tor-dirmgr",
diff --git a/crates/arti-testing/Cargo.toml b/crates/arti-testing/Cargo.toml
index 828f94fdc..3d9c4bf01 100644
--- a/crates/arti-testing/Cargo.toml
+++ b/crates/arti-testing/Cargo.toml
@@ -37,6 +37,7 @@ pin-project = "1"
 rand = "0.8"
 serde = { version = "1.0.103", features = ["derive"] }
 tokio = { version = "1.7", features = ["signal", "macros"] }
+tor-basic-utils = { path = "../tor-basic-utils", version = "0.7.1" }
 tor-checkable = { path = "../tor-checkable", version = "0.5.1", features = ["experimental-api"] }
 tor-config = { path = "../tor-config", version = "0.9.2" }
 tor-dirmgr = { package = "tor-dirmgr", path = "../tor-dirmgr", version = "0.10.2", features = ["dirfilter"] }
diff --git a/crates/arti-testing/src/rt/badtcp.rs b/crates/arti-testing/src/rt/badtcp.rs
index f950275aa..34258dfbb 100644
--- a/crates/arti-testing/src/rt/badtcp.rs
+++ b/crates/arti-testing/src/rt/badtcp.rs
@@ -8,7 +8,7 @@ use anyhow::anyhow;
 use async_trait::async_trait;
 use futures::io::{AsyncRead, AsyncWrite};
 use pin_project::pin_project;
-use rand::{thread_rng, Rng};
+use rand::thread_rng;
 use std::io::{Error as IoError, ErrorKind as IoErrorKind, Result as IoResult};
 use std::net::SocketAddr;
 use std::pin::Pin;
@@ -16,6 +16,7 @@ use std::str::FromStr;
 use std::sync::{Arc, Mutex};
 use std::task::{Context, Poll};
 use std::time::Duration;
+use tor_basic_utils::RngExt as _;
 
 /// An action that we can take upon trying to make a TCP connection.
 #[derive(Debug, Copy, Clone)]
@@ -154,7 +155,7 @@ impl<R: Runtime> TcpProvider for BrokenTcpProvider<R> {
                 Ok(BreakableTcpStream::Present(conn))
             }
             Action::Fail(dur, kind) => {
-                let d = thread_rng().gen_range(Duration::from_secs(0)..=dur);
+                let d = thread_rng().gen_range_infallible(..=dur);
                 self.inner.sleep(d).await;
                 Err(IoError::new(kind, anyhow::anyhow!("intentional failure")))
             }
diff --git a/crates/tor-circmgr/src/timeouts/pareto.rs b/crates/tor-circmgr/src/timeouts/pareto.rs
index 90a6d1b50..f654dc516 100644
--- a/crates/tor-circmgr/src/timeouts/pareto.rs
+++ b/crates/tor-circmgr/src/timeouts/pareto.rs
@@ -657,7 +657,7 @@ mod test {
     use super::*;
     use crate::timeouts::TimeoutEstimator;
     use tor_basic_utils::test_rng::testing_rng;
-    use tor_basic_utils::{RngExt as _};
+    use tor_basic_utils::RngExt as _;
 
     /// Return an action to build a 3-hop circuit.
     fn b3() -> Action {
diff --git a/crates/tor-dirmgr/src/state.rs b/crates/tor-dirmgr/src/state.rs
index 7d83a59af..862374507 100644
--- a/crates/tor-dirmgr/src/state.rs
+++ b/crates/tor-dirmgr/src/state.rs
@@ -10,13 +10,13 @@
 //! [`bootstrap`](crate::bootstrap) module for functions that actually
 //! load or download directory information.
 
-use rand::Rng;
 use std::collections::{HashMap, HashSet};
 use std::fmt::Debug;
 use std::mem;
 use std::sync::{Arc, Mutex};
 use std::time::{Duration, SystemTime};
 use time::OffsetDateTime;
+use tor_basic_utils::RngExt as _;
 use tor_error::{internal, warn_report};
 use tor_netdir::{MdReceiver, NetDir, PartialNetDir};
 use tor_netdoc::doc::authcert::UncheckedAuthCert;
@@ -1151,8 +1151,7 @@ impl<R: Runtime> DirState for GetMicrodescsState<R> {
 /// is `lifetime`.
 fn pick_download_time(lifetime: &Lifetime) -> SystemTime {
     let (lowbound, uncertainty) = client_download_range(lifetime);
-    let zero = Duration::new(0, 0);
-    lowbound + rand::thread_rng().gen_range(zero..=uncertainty)
+    lowbound + rand::thread_rng().gen_range_infallible(..=uncertainty)
 }
 
 /// Based on the lifetime for a consensus, return the time range during which
diff --git a/crates/tor-guardmgr/src/util.rs b/crates/tor-guardmgr/src/util.rs
index 75966e4d0..9e846dc7f 100644
--- a/crates/tor-guardmgr/src/util.rs
+++ b/crates/tor-guardmgr/src/util.rs
@@ -2,6 +2,7 @@
 
 use rand::Rng;
 use std::time::{Duration, SystemTime};
+use tor_basic_utils::RngExt as _;
 
 /// Return a random time within the range `when-max ..= when`.
 ///
@@ -12,7 +13,7 @@ use std::time::{Duration, SystemTime};
 /// an attempt to make some kinds of traffic analysis attacks a bit
 /// harder for an attacker who can read our state after the fact.
 pub(crate) fn randomize_time<R: Rng>(rng: &mut R, when: SystemTime, max: Duration) -> SystemTime {
-    let offset = rng.gen_range(Duration::ZERO..=max);
+    let offset = rng.gen_range_infallible(..=max);
     let random = when
         .checked_sub(offset)
         .unwrap_or(SystemTime::UNIX_EPOCH)