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Binary data that is expected to be a valid string may be read and converted to a string by exception FIO11-EX0.

Noncompliant Code Example

This noncompliant code example reads a byte array and converts it into a String using the platform's default character encoding. When the default encoding differs from the encoding that was used to produce the byte array, the resulting String is likely to be incorrect. Undefined behavior can occur when some of the input lacks a valid character representation in the default encoding.

FileInputStream fis = null;
try {
  fis = new FileInputStream("SomeFile");
  DataInputStream dis = new DataInputStream(fis);
  byte[] data = new byte[1024];
  dis.readFully(data);
  String result = new String(data);
} catch (IOException x) {
  // handle error
} finally {
  if (fis != null) {
    try {
      fis.close();
    } catch (IOException x) {
      // Forward to handler
    }
  }
}

Compliant Solution

This compliant solution explicitly specifies the intended character encoding in the second argument to the String constructor.

FileInputStream fis = null;
try {
  fis = new FileInputStream("SomeFile");
  DataInputStream dis = new DataInputStream(fis);
  byte[] data = new byte[1024];
  dis.readFully(data);
  String encoding = "SomeEncoding"; // for example, "UTF-16LE"
  String result = new String(data, encoding);
} catch (IOException x) {
  // handle error
} finally {
  if (fis != null) {
    try {
      fis.close();
    } catch (IOException x) {
      // Forward to handler
    }
  }
}

Exceptions

IDS13-EX0: An explicit character encoding may be omitted on the receiving side when the data is produced by a Java application that uses the same platform and default character encoding and is communicated over a secure communication channel (see MSC00-J for more information).

Risk Assessment

Failure to specify the character encoding while performing file or network I/O can result in corrupted data.

Automated Detection

Sound automated detection of this vulnerability is not feasible.

Bibliography