esapi-java-legacy/src/main/java/org/owasp/esapi/Encoder.java at 1.4 · Java1Dev/esapi-java-legacy

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 * OWASP Enterprise Security API (ESAPI)
 * This file is part of the Open Web Application Security Project (OWASP)
 * Enterprise Security API (ESAPI) project. For details, please see
 * <a href="http://www.owasp.org/index.php/ESAPI">http://www.owasp.org/index.php/ESAPI</a>.
 * Copyright (c) 2007 - The OWASP Foundation
 * The ESAPI is published by OWASP under the BSD license. You should read and accept the
 * LICENSE before you use, modify, and/or redistribute this software.
 * @author Jeff Williams <a href="http://www.aspectsecurity.com">Aspect Security</a>
 * @created 2007
package org.owasp.esapi;
import java.io.IOException;
import org.owasp.esapi.codecs.Codec;
import org.owasp.esapi.errors.EncodingException;
 * The Encoder interface contains a number of methods for decoding input and encoding output
 * so that it will be safe for a variety of interpreters. To prevent
 * double-encoding, all encoding methods should first check to see that the
 * input does not already contain encoded characters. There are a few methods
 * related to decoding that are used for canonicalization purposes. See the
 * Validator class for more information as the Validators rely heavily on these decoders for 
 * canonicalizing data before validating it.
 * <img src="doc-files/Encoder.jpg">
 * All of the methods must use a "whitelist" or "positive" security model.
 * For the encoding methods, this means that all characters should be encoded, except for a specific list of
 * "immune" characters that are known to be safe. For the decoding methods, all encoded characters should be 
 * decoded and if any doubly encoded characters (using the same encoding scheme or two different encoding schemes)
 * should be rejected. 
 * @author Jeff Williams (jeff.williams .at. aspectsecurity.com) <a
 *         href="http://www.aspectsecurity.com">Aspect Security</a>
 * @since June 1, 2007
public interface Encoder {
	/** Standard character sets */
	public final static char[] CHAR_LOWERS = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
	public final static char[] CHAR_UPPERS = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
	public final static char[] CHAR_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
	public final static char[] CHAR_SPECIALS = { '.', '-', '_', '!', '@', '$', '^', '*', '=', '~', '|', '+', '?' };
	public final static char[] CHAR_LETTERS = StringUtilities.union(CHAR_LOWERS, CHAR_UPPERS);
	public final static char[] CHAR_ALPHANUMERICS = StringUtilities.union(CHAR_LETTERS, CHAR_DIGITS);
	 * Password character set, is alphanumerics (without l, i, I, o, O, and 0)
	 * selected specials like + (bad for URL encoding, | is like i and 1,
	 * etc...)
	public final static char[] CHAR_PASSWORD_LOWERS = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'm', 'n', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };
	public final static char[] CHAR_PASSWORD_UPPERS = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
	public final static char[] CHAR_PASSWORD_DIGITS = { '2', '3', '4', '5', '6', '7', '8', '9' };
	public final static char[] CHAR_PASSWORD_SPECIALS = { '_', '.', '!', '@', '$', '*', '=', '-', '?' };
	public final static char[] CHAR_PASSWORD_LETTERS = StringUtilities.union( CHAR_PASSWORD_LOWERS, CHAR_PASSWORD_UPPERS );
	 * This method performs canonicalization on data received to ensure that it
	 * has been reduced to its most basic form before validation. For example,
	 * URL-encoded data received from ordinary "application/x-www-url-encoded"
	 * forms so that it may be validated properly.
	 * Canonicalization is simply the operation of reducing a possibly encoded
	 * string down to its simplest form. This is important, because attackers
	 * frequently use encoding to change their input in a way that will bypass
	 * validation filters, but still be interpreted properly by the target of
	 * the attack. Note that data encoded more than once is not something that a
	 * normal user would generate and should be regarded as an attack.
	 * For input that comes from an HTTP servlet request, there are generally
	 * two types of encoding to be concerned with. The first is
	 * "applicaton/x-www-url-encoded" which is what is typically used in most
	 * forms and URI's where characters are encoded in a %xy format. The other
	 * type of common character encoding is HTML entity encoding, which uses
	 * several formats:
	 * <PRE>&lt;</PRE>,
	 * <PRE>&#117;</PRE>, and
	 * <PRE>&#x3a;</PRE>.
	 * Note that all of these formats may possibly render properly in a
	 * browser without the trailing semicolon.
	 * Double-encoding is a particularly thorny problem, as applying ordinary decoders
	 * may introduce encoded characters, even characters encoded with a different
	 * encoding scheme. For example %26lt; is a < character which has been entity encoded
	 * and then the first character has been url-encoded. Implementations should
	 * throw an IntrusionException when double-encoded characters are detected.
	 * Note that there is also "multipart/form" encoding, which allows files and
	 * other binary data to be transmitted. Each part of a multipart form can
	 * itself be encoded according to a "Content-Transfer-Encoding" header. See
	 * the HTTPUtilties.getSafeFileUploads() method.
	 * For more information on form encoding, please refer to the <a
	 * href="http://www.w3.org/TR/html4/interact/forms.html#h-17.13.4">W3C
	 * specifications</a>.
	 * This method is equivalent to calling <pre>Encoder.canonicalize(input, true);</pre>
	 * @see <a href="http://www.w3.org/TR/html4/interact/forms.html#h-17.13.4">W3C specifications</a>
	 * @param input the text to canonicalize
	 * @return a String containing the canonicalized text
	 * @throws EncodingException if canonicalization fails
	String canonicalize(String input) throws EncodingException;
	 * This method performs canonicalization on data received to ensure that it
	 * has been reduced to its most basic form before validation. For example,
	 * URL-encoded data received from ordinary "application/x-www-url-encoded"
	 * forms so that it may be validated properly.
	 * Canonicalization is simply the operation of reducing a possibly encoded
	 * string down to its simplest form. This is important, because attackers
	 * frequently use encoding to change their input in a way that will bypass
	 * validation filters, but still be interpreted properly by the target of
	 * the attack. Note that data encoded more than once is not something that a
	 * normal user would generate and should be regarded as an attack.
	 * For input that comes from an HTTP servlet request, there are generally
	 * two types of encoding to be concerned with. The first is
	 * "applicaton/x-www-url-encoded" which is what is typically used in most
	 * forms and URI's where characters are encoded in a %xy format. The other
	 * type of common character encoding is HTML entity encoding, which uses
	 * several formats:
	 * <PRE>&lt;</PRE>,
	 * <PRE>&#117;</PRE>, and
	 * <PRE>&#x3a;</PRE>.
	 * Note that all of these formats may possibly render properly in a
	 * browser without the trailing semicolon.
	 * Double-encoding is a particularly thorny problem, as applying ordinary decoders
	 * may introduce encoded characters, even characters encoded with a different
	 * encoding scheme. For example %26lt; is a < character which has been entity encoded
	 * and then the first character has been url-encoded. Implementations should
	 * throw an IntrusionException when double-encoded characters are detected.
	 * Note that there is also "multipart/form" encoding, which allows files and
	 * other binary data to be transmitted. Each part of a multipart form can
	 * itself be encoded according to a "Content-Transfer-Encoding" header. See
	 * the HTTPUtilties.getSafeFileUploads() method.
	 * For more information on form encoding, please refer to the 
	 * <a href="http://www.w3.org/TR/html4/interact/forms.html#h-17.13.4">W3C specifications</a>.
	 * @see <a href="http://www.w3.org/TR/html4/interact/forms.html#h-17.13.4">W3C specifications</a>
	 * @param input 
	 * 		the text to canonicalize
	 * @param strict 
	 * 		true if checking for double encoding is desired, false otherwise
	 * @return a String containing the canonicalized text
	 * @throws EncodingException 
	 * 		if canonicalization fails
	String canonicalize(String input, boolean strict) throws EncodingException;
	 * Encode data for use in Cascading Style Sheets (CSS) content.
	 * @see <a href="http://www.w3.org/TR/CSS21/syndata.html#escaped-characters">CSS Syntax [w3.org]</a>
	 * @param input 
	 * 		the text to encode for CSS
	 * @return input encoded for CSS
	String encodeForCSS(String input);
	 * Encode data for use in HTML using HTML entity encoding
	 * Note that the following characters:
	 * 00�08, 0B�0C, 0E�1F, and 7F�9F 
	 * <p>cannot be used in HTML. 
	 * @see <a href="http://en.wikipedia.org/wiki/Character_encodings_in_HTML">HTML Encodings [wikipedia.org]</a> 
	 * @see <a href="http://www.w3.org/TR/html4/sgml/sgmldecl.html">SGML Specification [w3.org]</a>
     * @see <a href="http://www.w3.org/TR/REC-xml/#charsets">XML Specification [w3.org]</a>
	 * @param input 
	 * 		the text to encode for HTML
	 * @return input encoded for HTML
	String encodeForHTML(String input);
	 * Encode data for use in HTML attributes.
	 * @param input 
	 * 		the text to encode for an HTML attribute
	 * @return input encoded for use as an HTML attribute
	String encodeForHTMLAttribute(String input);
	 * Encode data for insertion inside a data value in JavaScript. Putting user data directly
	 * inside a script is quite dangerous. Great care must be taken to prevent putting user data
	 * directly into script code itself, as no amount of encoding will prevent attacks there.
	 * @param input 
	 * 		the text to encode for JavaScript
	 * @return input encoded for use in JavaScript
	String encodeForJavaScript(String input);
	 * Encode data for insertion inside a data value in a Visual Basic script. Putting user data directly
	 * inside a script is quite dangerous. Great care must be taken to prevent putting user data
	 * directly into script code itself, as no amount of encoding will prevent attacks there.
	 * This method is not recommended as VBScript is only supported by Internet Explorer
	 * @param input 
	 * 		the text to encode for VBScript
	 * @return input encoded for use in VBScript
	String encodeForVBScript(String input);
	 * Encode input for use in a SQL query, according to the selected codec 
	 * (appropriate codecs include the MySQLCodec and OracleCodec).
	 * This method is not recommended. The use of the PreparedStatement 
	 * interface is the preferred approach. However, if for some reason 
	 * this is impossible, then this method is provided as a weaker 
	 * alternative. 
	 * The best approach is to make sure any single-quotes are double-quoted.
	 * Another possible approach is to use the {escape} syntax described in the
	 * JDBC specification in section 1.5.6.
	 * However, this syntax does not work with all drivers, and requires
	 * modification of all queries.
	 * @see <a href="http://java.sun.com/j2se/1.4.2/docs/guide/jdbc/getstart/statement.html">JDBC Specification</a>
	 * @param codec 
	 * 		a Codec that declares which database 'input' is being encoded for (ie. MySQL, Oracle, etc.)
	 * @param input 
	 * 		the text to encode for SQL
	 * @return input encoded for use in SQL
	String encodeForSQL(Codec codec, String input);
	 * Encode for an operating system command shell according to the selected codec (appropriate codecs include the WindowsCodec and UnixCodec). 
     * Please note the following recommendations before choosing to use this method: 
     * 1)      It is strongly recommended that applications avoid making direct OS system calls if possible as such calls are not portable, and they are potentially unsafe. Please use language provided features if at all possible, rather than native OS calls to implement the desired feature.
     * 2)      If an OS call cannot be avoided, then it is recommended that the program to be invoked be invoked directly (e.g., System.exec("nameofcommand" + "parameterstocommand");) as this avoids the use of the command shell. The "parameterstocommand" should of course be validated before passing them to the OS command.
     * 3)      If you must use this method, then we recommend validating all user supplied input passed to the command shell as well, in addition to using this method in order to make the command shell invocation safe.
     * An example use of this method would be: System.exec("dir " + ESAPI.encodeForOS(WindowsCodec, "parameter(s)tocommandwithuserinput");
	 * @param codec 
	 * 		a Codec that declares which operating system 'input' is being encoded for (ie. Windows, Unix, etc.)
	 * @param input 
	 * 		the text to encode for the command shell
	 * @return input encoded for use in command shell
	String encodeForOS(Codec codec, String input);
	 * Encode data for use in LDAP queries.
	 * @param input 
	 * 		the text to encode for LDAP
	 * @return input encoded for use in LDAP
	String encodeForLDAP(String input);
	 * Encode data for use in an LDAP distinguished name.
	 *  @param input 
	 *  		the text to encode for an LDAP distinguished name
	 *  @return input encoded for use in an LDAP distinguished name
	String encodeForDN(String input);
	 * Encode data for use in an XPath query.
	 * NB: The reference implementation encodes almost everything and may over-encode. 
	 * The difficulty with XPath encoding is that XPath has no built in mechanism for escaping
	 * characters. It is possible to use XQuery in a parameterized way to
	 * prevent injection. 
	 * For more information, refer to <a
	 * href="http://www.ibm.com/developerworks/xml/library/x-xpathinjection.html">this
	 * article</a> which specifies the following list of characters as the most
	 * dangerous: ^&"*';<>(). <a
	 * href="http://www.packetstormsecurity.org/papers/bypass/Blind_XPath_Injection_20040518.pdf">This
	 * paper</a> suggests disallowing ' and " in queries.
	 * @see <a href="http://www.ibm.com/developerworks/xml/library/x-xpathinjection.html">XPath Injection [ibm.com]</a>
	 * @see <a href="http://www.packetstormsecurity.org/papers/bypass/Blind_XPath_Injection_20040518.pdf">Blind XPath Injection [packetstormsecurity.org]</a>
	 * @param input
	 *      the text to encode for XPath
	 * @return 
	 * 		input encoded for use in XPath
	String encodeForXPath(String input);
	 * Encode data for use in an XML element. The implementation should follow the <a
	 * href="http://www.w3schools.com/xml/xml_encoding.asp">XML Encoding
	 * Standard</a> from the W3C.
	 * The use of a real XML parser is strongly encouraged. However, in the
	 * hopefully rare case that you need to make sure that data is safe for
	 * inclusion in an XML document and cannot use a parse, this method provides
	 * a safe mechanism to do so.
	 * @see <a href="http://www.w3schools.com/xml/xml_encoding.asp">XML Encoding Standard</a>
	 * @param input
	 * 			the text to encode for XML
	 * @return
	 *			input encoded for use in XML
	String encodeForXML(String input);
	 * Encode data for use in an XML attribute. The implementation should follow
	 * the <a href="http://www.w3schools.com/xml/xml_encoding.asp">XML Encoding
	 * Standard</a> from the W3C.
	 * The use of a real XML parser is highly encouraged. However, in the
	 * hopefully rare case that you need to make sure that data is safe for
	 * inclusion in an XML document and cannot use a parse, this method provides
	 * a safe mechanism to do so.
	 * @see <a href="http://www.w3schools.com/xml/xml_encoding.asp">XML Encoding Standard</a>
	 * @param input
	 * 			the text to encode for use as an XML attribute
	 * @return 
	 * 			input encoded for use in an XML attribute
	String encodeForXMLAttribute(String input);
	 * Encode for use in a URL. This method performs <a
	 * href="http://en.wikipedia.org/wiki/Percent-encoding">URL encoding</a>
	 * on the entire string.
	 * @see <a href="http://en.wikipedia.org/wiki/Percent-encoding">URL encoding</a>
	 * @param input 
	 * 		the text to encode for use in a URL
	 * @return input 
	 * 		encoded for use in a URL
	 * @throws EncodingException 
	 * 		if encoding fails
	String encodeForURL(String input) throws EncodingException;
	 * Decode from URL. Implementations should first canonicalize and
	 * detect any double-encoding. If this check passes, then the data is decoded using URL
	 * decoding.
	 * @param input 
	 * 		the text to decode from an encoded URL
	 * @return 
	 * 		the decoded URL value
	 * @throws EncodingException 
	 * 		if decoding fails
	String decodeFromURL(String input) throws EncodingException;
	 * Encode for Base64.
	 * @param input 
	 * 		the text to encode for Base64
	 * @param wrap
	 * 		the encoder will wrap lines every 64 characters of output
	 * @return input encoded for Base64
	String encodeForBase64(byte[] input, boolean wrap);
	 * Decode data encoded with BASE-64 encoding.
	 * @param input 
	 * 		the Base64 text to decode
	 * @return input 
	 * 		decoded from Base64
	 * @throws IOException
	byte[] decodeFromBase64(String input) throws IOException;
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