pcli: fix terminal input in pcli threshold

Cargo.toml

@@ -213,6 +213,7 @@ tendermint-config                = { version = "0.34.0" }
 tendermint-light-client-verifier = { version = "0.34.0" }
 tendermint-proto                 = { version = "0.34.0" }
 tendermint-rpc                   = { version = "0.34.0" }
+termion                          = { version = "3" }
 thiserror                        = { version = "1.0" }
 tokio                            = { version = "1.3" }
 tokio-stream                     = { version = "0.1.8" }

crates/bin/pcli/Cargo.toml

@@ -97,6 +97,7 @@ tokio-util = {workspace = true}
 toml = {workspace = true, features = ["preserve_order"]}
 tonic = {workspace = true, features = ["tls-webpki-roots", "tls"]}
 tower = {workspace = true, features = ["full"]}
+termion = {workspace = true}
 tracing = {workspace = true}
 tracing-subscriber = {workspace = true, features = ["env-filter", "ansi"]}
 url = {workspace = true, features = ["serde"]}

crates/bin/pcli/src/terminal.rs

@@ -1,6 +1,7 @@
+use std::io::{Read, Write};
+
 use anyhow::Result;
 use penumbra_custody::threshold::{SigningRequest, Terminal};
-use tokio::io::{self, AsyncBufReadExt};
 use tonic::async_trait;
 
 /// For threshold custody, we need to implement this weird terminal abstraction.
@@ -40,11 +41,37 @@ impl Terminal for ActualTerminal {
     }
 
     async fn next_response(&self) -> Result<Option<String>> {
-        let stdin = io::stdin();
-        let mut stdin = io::BufReader::new(stdin);
+        // Use raw mode to allow reading more than 1KB/4KB of data at a time
+        // See https://unix.stackexchange.com/questions/204815/terminal-does-not-accept-pasted-or-typed-lines-of-more-than-1024-characters
+        use termion::raw::IntoRawMode;
+        tracing::debug!("about to enter raw mode for long pasted input");
+
+        // In raw mode, the input is not mirrored into the terminal, so we need
+        // to read char-by-char and echo it back.
+        let mut stdout = std::io::stdout().into_raw_mode()?;
+
+        let mut bytes = Vec::with_capacity(8192);
+        for b in std::io::stdin().bytes() {
+            let b = b?;
+            // In raw mode, the enter key might generate \r or \n, check either.
+            if b == b'\n' || b == b'\r' {
+                break;
+            }
+            bytes.push(b);
+            stdout.write(&[b]).unwrap();
+            // Flushing may not be the most efficient but performance isn't critical here.
+            stdout.flush()?;
+        }
+        // Drop _stdout to restore the terminal to normal mode
+        std::mem::drop(stdout);
+        // We consumed a newline of some kind but didn't echo it, now print
+        // one out so subsequent output is guaranteed to be on a new line.
+        println!("");
+
+        tracing::debug!("exited raw mode and returned to cooked mode");
 
-        let mut line = String::new();
-        stdin.read_line(&mut line).await?;
+        let line = String::from_utf8(bytes)?;
+        tracing::debug!(?line, "read response line");
 
         if line.is_empty() {
             return Ok(None);