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25 
26 package javax.crypto.spec;
27 
28 import 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  */
63 public 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      */
PBEKeySpec(char[] password)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      */
PBEKeySpec(char[] password, byte[] salt, int iterationCount, int keyLength)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      */
PBEKeySpec(char[] password, byte[] salt, int iterationCount)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      */
clearPassword()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      */
getPassword()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      */
getSalt()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      */
getIterationCount()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      */
getKeyLength()237     public final int getKeyLength() {
238         return keyLength;
239     }
240 }
241