This commit fixes a potential denial of service vulnerability in logrus.Writer() that could be triggered by logging text longer than 64kb without newlines.

writer.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"io"
 	"runtime"
+	"strings"
 )
 
 // Writer at INFO level. See WriterLevel for details.
@@ -20,15 +21,18 @@ func (logger *Logger) WriterLevel(level Level) *io.PipeWriter {
 	return NewEntry(logger).WriterLevel(level)
 }
 
+// Writer returns an io.Writer that writes to the logger at the info log level
 func (entry *Entry) Writer() *io.PipeWriter {
 	return entry.WriterLevel(InfoLevel)
 }
 
+// WriterLevel returns an io.Writer that writes to the logger at the given log level
 func (entry *Entry) WriterLevel(level Level) *io.PipeWriter {
 	reader, writer := io.Pipe()
 
 	var printFunc func(args ...interface{})
 
+	// Determine which log function to use based on the specified log level
 	switch level {
 	case TraceLevel:
 		printFunc = entry.Trace
@@ -48,23 +52,51 @@ func (entry *Entry) WriterLevel(level Level) *io.PipeWriter {
 		printFunc = entry.Print
 	}
 
+	// Start a new goroutine to scan the input and write it to the logger using the specified print function.
+	// It splits the input into chunks of up to 64KB to avoid buffer overflows.
 	go entry.writerScanner(reader, printFunc)
+
+	// Set a finalizer function to close the writer when it is garbage collected
 	runtime.SetFinalizer(writer, writerFinalizer)
 
 	return writer
 }
 
+// writerScanner scans the input from the reader and writes it to the logger
 func (entry *Entry) writerScanner(reader *io.PipeReader, printFunc func(args ...interface{})) {
 	scanner := bufio.NewScanner(reader)
+
+	// Set the buffer size to the maximum token size to avoid buffer overflows
+	scanner.Buffer(make([]byte, bufio.MaxScanTokenSize), bufio.MaxScanTokenSize)
+
+	// Define a split function to split the input into chunks of up to 64KB
+	chunkSize := 64 * 1024 // 64KB
+	splitFunc := func(data []byte, atEOF bool) (int, []byte, error) {
+		if len(data) > chunkSize {
+			return chunkSize, data[:chunkSize], nil
+		}
+
+		return len(data), data, nil
+	}
+
+	//Use the custom split function to split the input
+	scanner.Split(splitFunc)
+
+	// Scan the input and write it to the logger using the specified print function
 	for scanner.Scan() {
-		printFunc(scanner.Text())
+		printFunc(strings.TrimRight(scanner.Text(), "\r\n"))
 	}
+
+	// If there was an error while scanning the input, log an error
 	if err := scanner.Err(); err != nil {
 		entry.Errorf("Error while reading from Writer: %s", err)
 	}
+
+	// Close the reader when we are done
 	reader.Close()
 }
 
+// WriterFinalizer is a finalizer function that closes then given writer when it is garbage collected
 func writerFinalizer(writer *io.PipeWriter) {
 	writer.Close()
 }