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15 * accompanied this code).
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24 */
25
26package javax.crypto.spec;
27
28import java.security.spec.KeySpec;
29
30/**
31 * A user-chosen password that can be used with password-based encryption
32 * (<i>PBE</i>).
33 *
34 * <p>The password can be viewed as some kind of raw key material, from which
35 * the encryption mechanism that uses it derives a cryptographic key.
36 *
37 * <p>Different PBE mechanisms may consume different bits of each password
38 * character. For example, the PBE mechanism defined in
39 * <a href="http://www.ietf.org/rfc/rfc2898.txt">
40 * PKCS #5</a> looks at only the low order 8 bits of each character, whereas
41 * PKCS #12 looks at all 16 bits of each character.
42 *
43 * <p>You convert the password characters to a PBE key by creating an
44 * instance of the appropriate secret-key factory. For example, a secret-key
45 * factory for PKCS #5 will construct a PBE key from only the low order 8 bits
46 * of each password character, whereas a secret-key factory for PKCS #12 will
47 * take all 16 bits of each character.
48 *
49 * <p>Also note that this class stores passwords as char arrays instead of
50 * <code>String</code> objects (which would seem more logical), because the
51 * String class is immutable and there is no way to overwrite its
52 * internal value when the password stored in it is no longer needed. Hence,
53 * this class requests the password as a char array, so it can be overwritten
54 * when done.
55 *
56 * @author Jan Luehe
57 * @author Valerie Peng
58 *
59 * @see javax.crypto.SecretKeyFactory
60 * @see PBEParameterSpec
61 * @since 1.4
62 */
63public class PBEKeySpec implements KeySpec {
64
65    private char[] password;
66    private byte[] salt = null;
67    private int iterationCount = 0;
68    private int keyLength = 0;
69
70    /**
71     * Constructor that takes a password. An empty char[] is used if
72     * null is specified.
73     *
74     * <p> Note: <code>password</code> is cloned before it is stored in
75     * the new <code>PBEKeySpec</code> object.
76     *
77     * @param password the password.
78     */
79    public PBEKeySpec(char[] password) {
80        if ((password == null) || (password.length == 0)) {
81            this.password = new char[0];
82        } else {
83            this.password = password.clone();
84        }
85    }
86
87
88    /**
89     * Constructor that takes a password, salt, iteration count, and
90     * to-be-derived key length for generating PBEKey of variable-key-size
91     * PBE ciphers.  An empty char[] is used if null is specified for
92     * <code>password</code>.
93     *
94     * <p> Note: the <code>password</code> and <code>salt</code>
95     * are cloned before they are stored in
96     * the new <code>PBEKeySpec</code> object.
97     *
98     * @param password the password.
99     * @param salt the salt.
100     * @param iterationCount the iteration count.
101     * @param keyLength the to-be-derived key length.
102     * @exception NullPointerException if <code>salt</code> is null.
103     * @exception IllegalArgumentException if <code>salt</code> is empty,
104     * i.e. 0-length, <code>iterationCount</code> or
105     * <code>keyLength</code> is not positive.
106     */
107    public PBEKeySpec(char[] password, byte[] salt, int iterationCount,
108        int keyLength) {
109        if ((password == null) || (password.length == 0)) {
110            this.password = new char[0];
111        } else {
112            this.password = password.clone();
113        }
114        if (salt == null) {
115            throw new NullPointerException("the salt parameter " +
116                                            "must be non-null");
117        } else if (salt.length == 0) {
118            throw new IllegalArgumentException("the salt parameter " +
119                                                "must not be empty");
120        } else {
121            this.salt = salt.clone();
122        }
123        if (iterationCount<=0) {
124            throw new IllegalArgumentException("invalid iterationCount value");
125        }
126        if (keyLength<=0) {
127            throw new IllegalArgumentException("invalid keyLength value");
128        }
129        this.iterationCount = iterationCount;
130        this.keyLength = keyLength;
131    }
132
133
134    /**
135     * Constructor that takes a password, salt, iteration count for
136     * generating PBEKey of fixed-key-size PBE ciphers. An empty
137     * char[] is used if null is specified for <code>password</code>.
138     *
139     * <p> Note: the <code>password</code> and <code>salt</code>
140     * are cloned before they are stored in the new
141     * <code>PBEKeySpec</code> object.
142     *
143     * @param password the password.
144     * @param salt the salt.
145     * @param iterationCount the iteration count.
146     * @exception NullPointerException if <code>salt</code> is null.
147     * @exception IllegalArgumentException if <code>salt</code> is empty,
148     * i.e. 0-length, or <code>iterationCount</code> is not positive.
149     */
150    public PBEKeySpec(char[] password, byte[] salt, int iterationCount) {
151        if ((password == null) || (password.length == 0)) {
152            this.password = new char[0];
153        } else {
154            this.password = password.clone();
155        }
156        if (salt == null) {
157            throw new NullPointerException("the salt parameter " +
158                                            "must be non-null");
159        } else if (salt.length == 0) {
160            throw new IllegalArgumentException("the salt parameter " +
161                                                "must not be empty");
162        } else {
163            this.salt = salt.clone();
164        }
165        if (iterationCount<=0) {
166            throw new IllegalArgumentException("invalid iterationCount value");
167        }
168        this.iterationCount = iterationCount;
169    }
170
171    /**
172     * Clears the internal copy of the password.
173     *
174     */
175    public final void clearPassword() {
176        if (password != null) {
177            for (int i = 0; i < password.length; i++) {
178                password[i] = ' ';
179            }
180            password = null;
181        }
182    }
183
184    /**
185     * Returns a copy of the password.
186     *
187     * <p> Note: this method returns a copy of the password. It is
188     * the caller's responsibility to zero out the password information after
189     * it is no longer needed.
190     *
191     * @exception IllegalStateException if password has been cleared by
192     * calling <code>clearPassword</code> method.
193     * @return the password.
194     */
195    public final char[] getPassword() {
196        if (password == null) {
197            throw new IllegalStateException("password has been cleared");
198        }
199        return password.clone();
200    }
201
202    /**
203     * Returns a copy of the salt or null if not specified.
204     *
205     * <p> Note: this method should return a copy of the salt. It is
206     * the caller's responsibility to zero out the salt information after
207     * it is no longer needed.
208     *
209     * @return the salt.
210     */
211    public final byte[] getSalt() {
212        if (salt != null) {
213            return salt.clone();
214        } else {
215            return null;
216        }
217    }
218
219    /**
220     * Returns the iteration count or 0 if not specified.
221     *
222     * @return the iteration count.
223     */
224    public final int getIterationCount() {
225        return iterationCount;
226    }
227
228    /**
229     * Returns the to-be-derived key length or 0 if not specified.
230     *
231     * <p> Note: this is used to indicate the preference on key length
232     * for variable-key-size ciphers. The actual key size depends on
233     * each provider's implementation.
234     *
235     * @return the to-be-derived key length.
236     */
237    public final int getKeyLength() {
238        return keyLength;
239    }
240}
241