/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.content.pm;
import android.os.Parcel;
import android.os.Parcelable;
import java.io.UnsupportedEncodingException;
import java.security.SecureRandom;
import java.util.Random;
/**
* An identity that uniquely identifies a particular device. In this
* implementation, the identity is represented as a 64-bit integer encoded to a
* 13-character string using RFC 4648's Base32 encoding without the trailing
* padding. This makes it easy for users to read and write the code without
* confusing 'I' (letter) with '1' (one) or 'O' (letter) with '0' (zero).
*
* @hide
*/
public class VerifierDeviceIdentity implements Parcelable {
/**
* Encoded size of a long (64-bit) into Base32. This format will end up
* looking like XXXX-XXXX-XXXX-X (length ignores hyphens) when applied with
* the GROUP_SIZE below.
*/
private static final int LONG_SIZE = 13;
/**
* Size of groupings when outputting as strings. This helps people read it
* out and keep track of where they are.
*/
private static final int GROUP_SIZE = 4;
private final long mIdentity;
private final String mIdentityString;
/**
* Create a verifier device identity from a long.
*
* @param identity device identity in a 64-bit integer.
* @throws
*/
public VerifierDeviceIdentity(long identity) {
mIdentity = identity;
mIdentityString = encodeBase32(identity);
}
private VerifierDeviceIdentity(Parcel source) {
final long identity = source.readLong();
mIdentity = identity;
mIdentityString = encodeBase32(identity);
}
/**
* Generate a new device identity.
*
* @return random uniformly-distributed device identity
*/
public static VerifierDeviceIdentity generate() {
final SecureRandom sr = new SecureRandom();
return generate(sr);
}
/**
* Generate a new device identity using a provided random number generator
* class. This is used for testing.
*
* @param rng random number generator to retrieve the next long from
* @return verifier device identity based on the input from the provided
* random number generator
*/
static VerifierDeviceIdentity generate(Random rng) {
long identity = rng.nextLong();
return new VerifierDeviceIdentity(identity);
}
private static final char ENCODE[] = {
'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', '2', '3', '4', '5', '6', '7',
};
private static final char SEPARATOR = '-';
private static final String encodeBase32(long input) {
final char[] alphabet = ENCODE;
/*
* Make a character array with room for the separators between each
* group.
*/
final char encoded[] = new char[LONG_SIZE + (LONG_SIZE / GROUP_SIZE)];
int index = encoded.length;
for (int i = 0; i < LONG_SIZE; i++) {
/*
* Make sure we don't put a separator at the beginning. Since we're
* building from the rear of the array, we use (LONG_SIZE %
* GROUP_SIZE) to make the odd-size group appear at the end instead
* of the beginning.
*/
if (i > 0 && (i % GROUP_SIZE) == (LONG_SIZE % GROUP_SIZE)) {
encoded[--index] = SEPARATOR;
}
/*
* Extract 5 bits of data, then shift it out.
*/
final int group = (int) (input & 0x1F);
input >>>= 5;
encoded[--index] = alphabet[group];
}
return String.valueOf(encoded);
}
// TODO move this out to its own class (android.util.Base32)
private static final long decodeBase32(byte[] input) throws IllegalArgumentException {
long output = 0L;
int numParsed = 0;
final int N = input.length;
for (int i = 0; i < N; i++) {
final int group = input[i];
/*
* This essentially does the reverse of the ENCODED alphabet above
* without a table. A..Z are 0..25 and 2..7 are 26..31.
*/
final int value;
if ('A' <= group && group <= 'Z') {
value = group - 'A';
} else if ('2' <= group && group <= '7') {
value = group - ('2' - 26);
} else if (group == SEPARATOR) {
continue;
} else if ('a' <= group && group <= 'z') {
/* Lowercase letters should be the same as uppercase for Base32 */
value = group - 'a';
} else if (group == '0') {
/* Be nice to users that mistake O (letter) for 0 (zero) */
value = 'O' - 'A';
} else if (group == '1') {
/* Be nice to users that mistake I (letter) for 1 (one) */
value = 'I' - 'A';
} else {
throw new IllegalArgumentException("base base-32 character: " + group);
}
output = (output << 5) | value;
numParsed++;
if (numParsed == 1) {
if ((value & 0xF) != value) {
throw new IllegalArgumentException("illegal start character; will overflow");
}
} else if (numParsed > 13) {
throw new IllegalArgumentException("too long; should have 13 characters");
}
}
if (numParsed != 13) {
throw new IllegalArgumentException("too short; should have 13 characters");
}
return output;
}
@Override
public int hashCode() {
return (int) mIdentity;
}
@Override
public boolean equals(Object other) {
if (!(other instanceof VerifierDeviceIdentity)) {
return false;
}
final VerifierDeviceIdentity o = (VerifierDeviceIdentity) other;
return mIdentity == o.mIdentity;
}
@Override
public String toString() {
return mIdentityString;
}
public static VerifierDeviceIdentity parse(String deviceIdentity)
throws IllegalArgumentException {
final byte[] input;
try {
input = deviceIdentity.getBytes("US-ASCII");
} catch (UnsupportedEncodingException e) {
throw new IllegalArgumentException("bad base-32 characters in input");
}
return new VerifierDeviceIdentity(decodeBase32(input));
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeLong(mIdentity);
}
public static final Parcelable.Creator<VerifierDeviceIdentity> CREATOR
= new Parcelable.Creator<VerifierDeviceIdentity>() {
public VerifierDeviceIdentity createFromParcel(Parcel source) {
return new VerifierDeviceIdentity(source);
}
public VerifierDeviceIdentity[] newArray(int size) {
return new VerifierDeviceIdentity[size];
}
};
}
|
