fix(crashtracking): handle new lines in client submitted exception message (#1836)

# What does this PR do?

Escapes new lines from API consumer submitted unhandled exception message, then unescapes it when writing the report. This is necessary, because API consumers can submit arbitrary exception messages,  and if they contain new lines, the receiver state machine parsing breaks as it depends on chunks of data being sent as lines.

# Motivation

This [crash log](https://app.datadoghq.com/logs?query=service%3Ainstrumentation-telemetry-data%20%28%40tags.severity%3Acrash%20OR%20severity%3Acrash%20OR%20signum%3A%2A%20OR%20%40error.is_crash%3Atrue%29%20-%40metadata.tags%3A%22crash_datadog%3Atrue%22%20-%22Process%20was%20terminated%20due%20to%20an%20unhandled%20exception%22%20source%3Aruby&agg_m=count&agg_m_source=base&agg_q=%40metadata.family&agg_t=count&cf_lbyyhhwhyjj5l3rs65cb3w=aiugo4c9e5i04jdlqn4i&clustering_pattern_field_path=message&cols=source%2C%40tracer_version%2C%40language_version%2C%40org&event=AwAAAZ0xDw1VSu-b3AAAABhBWjB4RHcxVkFBQkxSUWRlaE1Rb1B3QUEAAAAkZDE5ZDMxMGYtNGI0OC00NDQ5LWI5NmMtY2QwZjJkNjE0NDExAAAfZw&flat_group_bys=true&fromUser=true&messageDisplay=inline&refresh_mode=sliding&sort_m=count&sort_t=count&storage=live&stream_sort=desc&top_n=10&top_o=top&view=spans&viz=stream&x_missing=true&from_ts=1772048747006&to_ts=1774640747006&live=true) has no message because the exception message being sent has [new lines](https://github.com/rails/rails/blob/8ec9ba082fd08f7db0c601056d86356b0b5e4d25/activerecord/lib/active_record/errors.rb#L354-L364) in it

# Additional Notes

I've looked at other places where API consumers submit raw strings that we just pass in raw, and I cannot find other plausible places where this could be an issue

# How to test the change?

Bin_test updated to include a new line in the input to the unhandled exception API

Co-authored-by: gyuheon.oh <gyuheon.oh@datadoghq.com>

Author: gyuheon0h

bin_tests/src/bin/crashtracker_bin_test.rs

@@ -177,7 +177,7 @@ mod unix {
 
                 crashtracker::report_unhandled_exception(
                     Some("RuntimeException"),
-                    Some("an exception occured"),
+                    Some("\n an exception \n occured \n"),
                     stacktrace,
                 )?;
 

bin_tests/tests/crashtracker_bin_test.rs

@@ -138,7 +138,7 @@ fn test_crash_tracking_bin_unhandled_exception() {
         PayloadValidator::new(payload)
             .validate_counters()?
             .validate_error_kind("UnhandledException")?
-            .validate_error_message_contains("Process was terminated due to an unhandled exception of type 'RuntimeException'. Message: an exception occured")?
+            .validate_error_message_contains("Process was terminated due to an unhandled exception of type 'RuntimeException'. Message: \n an exception \n occured \n")?
             // The two frames emitted in the bin: test_function1 and test_function2
             .validate_callstack_functions(&["test_function1", "test_function2"])?;
 

libdd-crashtracker/src/collector/crash_handler.rs

@@ -421,7 +421,15 @@ pub fn report_unhandled_exception(
     let tid = libdd_common::threading::get_current_thread_id() as libc::pid_t;
 
     let error_type_str = exception_type.unwrap_or("<unknown>");
-    let error_message_str = exception_message.unwrap_or("<no message>");
+
+    // This allocates but this is okay because we are not in a signal handler.
+    // This is necessary, because user defined exception messages can have newlines
+    // and the receiver state machine parsing depends on newlines for different sections
+    // of the crash report.
+    let error_message_str = exception_message
+        .unwrap_or("<no message>")
+        .replace('\n', "\\n")
+        .replace('\r', "\\r");
     let message = format!(
         "Process was terminated due to an unhandled exception of type '{error_type_str}'. \
          Message: {error_message_str}"

libdd-crashtracker/src/receiver/receive_report.rs

@@ -268,7 +268,8 @@ fn process_line(
 
         StdinState::Message if line.starts_with(DD_CRASHTRACK_END_MESSAGE) => StdinState::Waiting,
         StdinState::Message => {
-            builder.with_message(line.to_string())?;
+            let unescaped = line.replace("\\n", "\n").replace("\\r", "\r");
+            builder.with_message(unescaped)?;
             StdinState::Message
         }