Escape control characters in message sign preview. (#2517)

Author: fnando

cmd/crates/soroban-test/tests/it/message.rs

@@ -212,4 +212,8 @@ fn message_sign_escapes_control_characters_in_preview() {
         !stderr.contains('\x1b'),
         "stderr should not contain raw ESC bytes, got: {stderr:?}"
     );
+    assert!(
+        stderr.contains("\\x1b"),
+        "stderr should contain escaped ESC as \\x1b, got: {stderr:?}"
+    );
 }

cmd/soroban-cli/src/commands/message/sign.rs

@@ -9,7 +9,7 @@ use crate::{
     config::{locator, secret},
     print::Print,
     signer::{self, Signer},
-    utils::strip_control_escapes,
+    utils::escape_control_characters,
 };
 
 use super::SEP53_PREFIX;
@@ -93,7 +93,7 @@ impl Cmd {
         };
         print.infoln(format!(
             "Message: {}",
-            strip_control_escapes(&message_display)
+            escape_control_characters(&message_display)
         ));
         println!("{signature_base64}");
         Ok(())

cmd/soroban-cli/src/utils.rs

@@ -171,8 +171,20 @@ pub fn is_hex_string(s: &str) -> bool {
     s.chars().all(|s| s.is_ascii_hexdigit())
 }
 
-pub fn strip_control_escapes(s: &str) -> String {
-    s.chars().filter(|c| !c.is_control()).collect()
+pub fn escape_control_characters(s: &str) -> String {
+    use std::fmt::Write as _;
+    let mut result = String::with_capacity(s.len());
+    for c in s.chars() {
+        if c.is_control() {
+            let mut buf = [0u8; 4];
+            for &byte in c.encode_utf8(&mut buf).as_bytes() {
+                write!(result, "\\x{byte:02x}").unwrap();
+            }
+        } else {
+            result.push(c);
+        }
+    }
+    result
 }
 
 pub fn contract_id_hash_from_asset(