org.apache.hadoop.io

Class SecureIOUtils

java.lang.Object

org.apache.hadoop.io.SecureIOUtils

public class SecureIOUtils
extends Object

This class provides secure APIs for opening and creating files on the local disk. The main issue this class tries to handle is that of symlink traversal.
An example of such an attack is:

1. Malicious user removes his task's syslog file, and puts a link to the jobToken file of a target user.
2. Malicious user tries to open the syslog file via the servlet on the tasktracker.
3. The tasktracker is unaware of the symlink, and simply streams the contents of the jobToken file. The malicious user can now access potentially sensitive map outputs, etc. of the target user's job.

A similar attack is possible involving task log truncation, but in that case due to an insecure write to a file.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	SecureIOUtils.AlreadyExistsException Signals that an attempt to create a file at a given pathname has failed because another file already existed at that path.

Constructor Summary

Constructors

Constructor and Description
SecureIOUtils()

Method Summary

Modifier and Type	Method and Description
static FileOutputStream	createForWrite(File f, int permissions) Open the specified File for write access, ensuring that it does not exist.
protected static RandomAccessFile	forceSecureOpenForRandomRead(File f, String mode, String expectedOwner, String expectedGroup)
protected static FileInputStream	forceSecureOpenForRead(File f, String expectedOwner, String expectedGroup)
protected static FSDataInputStream	forceSecureOpenFSDataInputStream(File file, String expectedOwner, String expectedGroup) Same as openFSDataInputStream except that it will run even if security is off.
static RandomAccessFile	openForRandomRead(File f, String mode, String expectedOwner, String expectedGroup)
static FileInputStream	openForRead(File f, String expectedOwner, String expectedGroup) Open the given File for read access, verifying the expected user/group constraints if security is enabled.
static FSDataInputStream	openFSDataInputStream(File file, String expectedOwner, String expectedGroup) Opens the FSDataInputStream on the requested file on local file system, verifying the expected user/group constraints if security is enabled.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SecureIOUtils

public SecureIOUtils()

Method Detail

openForRandomRead

public static RandomAccessFile openForRandomRead(File f,
                                                 String mode,
                                                 String expectedOwner,
                                                 String expectedGroup)
                                          throws IOException

Parameters:

f - file that we are trying to open

mode - mode in which we want to open the random access file

expectedOwner - the expected user owner for the file

expectedGroup - the expected group owner for the file

Returns:

Open the given File for random read access, verifying the expected user/ group constraints if security is enabled. Note that this function provides no additional security checks if hadoop security is disabled, since doing the checks would be too expensive when native libraries are not available.

Throws:

IOException - if an IO error occurred or if the user/group does not match when security is enabled.

forceSecureOpenForRandomRead

@VisibleForTesting
protected static RandomAccessFile forceSecureOpenForRandomRead(File f,
                                                                                  String mode,
                                                                                  String expectedOwner,
                                                                                  String expectedGroup)
                                                                           throws IOException

Parameters:

f - input f.

mode - input mode.

expectedOwner - input expectedOwner.

expectedGroup - input expectedGroup.

Returns:

Same as openForRandomRead except that it will run even if security is off. This is used by unit tests.

Throws:

IOException - raised on errors performing I/O.

openFSDataInputStream

public static FSDataInputStream openFSDataInputStream(File file,
                                                      String expectedOwner,
                                                      String expectedGroup)
                                               throws IOException

Opens the FSDataInputStream on the requested file on local file system, verifying the expected user/group constraints if security is enabled.

Parameters:

file - absolute path of the file

expectedOwner - the expected user owner for the file

expectedGroup - the expected group owner for the file

Returns:

FSDataInputStream.

Throws:

IOException - if an IO Error occurred or the user/group does not match if security is enabled

forceSecureOpenFSDataInputStream

@VisibleForTesting
protected static FSDataInputStream forceSecureOpenFSDataInputStream(File file,
                                                                                       String expectedOwner,
                                                                                       String expectedGroup)
                                                                                throws IOException

Same as openFSDataInputStream except that it will run even if security is off. This is used by unit tests.

Parameters:

file - input file.

expectedOwner - input expectedOwner.

expectedGroup - input expectedGroup.

Returns:

FSDataInputStream.

Throws:

IOException - raised on errors performing I/O.

openForRead

public static FileInputStream openForRead(File f,
                                          String expectedOwner,
                                          String expectedGroup)
                                   throws IOException

Open the given File for read access, verifying the expected user/group constraints if security is enabled.

Parameters:

f - the file that we are trying to open

expectedOwner - the expected user owner for the file

expectedGroup - the expected group owner for the file

Returns:

Note that this function provides no additional checks if Hadoop security is disabled, since doing the checks would be too expensive when native libraries are not available.

Throws:

IOException - if an IO Error occurred, or security is enabled and the user/group does not match

forceSecureOpenForRead

@VisibleForTesting
protected static FileInputStream forceSecureOpenForRead(File f,
                                                                           String expectedOwner,
                                                                           String expectedGroup)
                                                                    throws IOException

Parameters:

f - input f.

expectedOwner - input expectedOwner.

expectedGroup - input expectedGroup.

Returns:

Same as openForRead() except that it will run even if security is off. This is used by unit tests.

Throws:

IOException - raised on errors performing I/O.

createForWrite

public static FileOutputStream createForWrite(File f,
                                              int permissions)
                                       throws IOException

Open the specified File for write access, ensuring that it does not exist.

Parameters:

f - the file that we want to create

permissions - we want to have on the file (if security is enabled)

Returns:

createForWrite FileOutputStream.

Throws:

SecureIOUtils.AlreadyExistsException - if the file already exists

IOException - if any other error occurred