/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 com.android.internal.net;
import android.util.Log;
import java.io.IOException;
import javax.security.auth.x500.X500Principal;
/**
* A simple distinguished name(DN) parser.
*
* <p>This class is based on org.apache.harmony.security.x509.DNParser. It's customized to remove
* external references which are unnecessary for our requirements.
*
* <p>This class is only meant for extracting a string value from a DN. e.g. it doesn't support
* values in the hex-string style.
*
* <p>This class is used by {@link DomainNameValidator} only. However, in order to make this
* class visible from unit tests, it's made public.
*
* @hide
*/
public final class DNParser {
private static final String TAG = "DNParser";
/** DN to be parsed. */
private final String dn;
// length of distinguished name string
private final int length;
private int pos, beg, end;
// tmp vars to store positions of the currently parsed item
private int cur;
// distinguished name chars
private char[] chars;
/**
* Exception message thrown when we failed to parse DN, which shouldn't happen because we
* only handle DNs that {@link X500Principal#getName} returns, which shouldn't be malformed.
*/
private static final String ERROR_PARSE_ERROR = "Failed to parse DN";
/**
* Constructor.
*
* @param principal - {@link X500Principal} to be parsed
*/
public DNParser(X500Principal principal) {
this.dn = principal.getName(X500Principal.RFC2253);
this.length = dn.length();
}
// gets next attribute type: (ALPHA 1*keychar) / oid
private String nextAT() throws IOException {
// skip preceding space chars, they can present after
// comma or semicolon (compatibility with RFC 1779)
for (; pos < length && chars[pos] == ' '; pos++) {
}
if (pos == length) {
return null; // reached the end of DN
}
// mark the beginning of attribute type
beg = pos;
// attribute type chars
pos++;
for (; pos < length && chars[pos] != '=' && chars[pos] != ' '; pos++) {
// we don't follow exact BNF syntax here:
// accept any char except space and '='
}
if (pos >= length) {
// unexpected end of DN
throw new IOException(ERROR_PARSE_ERROR);
}
// mark the end of attribute type
end = pos;
// skip trailing space chars between attribute type and '='
// (compatibility with RFC 1779)
if (chars[pos] == ' ') {
for (; pos < length && chars[pos] != '=' && chars[pos] == ' '; pos++) {
}
if (chars[pos] != '=' || pos == length) {
// unexpected end of DN
throw new IOException(ERROR_PARSE_ERROR);
}
}
pos++; //skip '=' char
// skip space chars between '=' and attribute value
// (compatibility with RFC 1779)
for (; pos < length && chars[pos] == ' '; pos++) {
}
// in case of oid attribute type skip its prefix: "oid." or "OID."
// (compatibility with RFC 1779)
if ((end - beg > 4) && (chars[beg + 3] == '.')
&& (chars[beg] == 'O' || chars[beg] == 'o')
&& (chars[beg + 1] == 'I' || chars[beg + 1] == 'i')
&& (chars[beg + 2] == 'D' || chars[beg + 2] == 'd')) {
beg += 4;
}
return new String(chars, beg, end - beg);
}
// gets quoted attribute value: QUOTATION *( quotechar / pair ) QUOTATION
private String quotedAV() throws IOException {
pos++;
beg = pos;
end = beg;
while (true) {
if (pos == length) {
// unexpected end of DN
throw new IOException(ERROR_PARSE_ERROR);
}
if (chars[pos] == '"') {
// enclosing quotation was found
pos++;
break;
} else if (chars[pos] == '\\') {
chars[end] = getEscaped();
} else {
// shift char: required for string with escaped chars
chars[end] = chars[pos];
}
pos++;
end++;
}
// skip trailing space chars before comma or semicolon.
// (compatibility with RFC 1779)
for (; pos < length && chars[pos] == ' '; pos++) {
}
return new String(chars, beg, end - beg);
}
// gets hex string attribute value: "#" hexstring
private String hexAV() throws IOException {
if (pos + 4 >= length) {
// encoded byte array must be not less then 4 c
throw new IOException(ERROR_PARSE_ERROR);
}
beg = pos; // store '#' position
pos++;
while (true) {
// check for end of attribute value
// looks for space and component separators
if (pos == length || chars[pos] == '+' || chars[pos] == ','
|| chars[pos] == ';') {
end = pos;
break;
}
if (chars[pos] == ' ') {
end = pos;
pos++;
// skip trailing space chars before comma or semicolon.
// (compatibility with RFC 1779)
for (; pos < length && chars[pos] == ' '; pos++) {
}
break;
} else if (chars[pos] >= 'A' && chars[pos] <= 'F') {
chars[pos] += 32; //to low case
}
pos++;
}
// verify length of hex string
// encoded byte array must be not less then 4 and must be even number
int hexLen = end - beg; // skip first '#' char
if (hexLen < 5 || (hexLen & 1) == 0) {
throw new IOException(ERROR_PARSE_ERROR);
}
// get byte encoding from string representation
byte[] encoded = new byte[hexLen / 2];
for (int i = 0, p = beg + 1; i < encoded.length; p += 2, i++) {
encoded[i] = (byte) getByte(p);
}
return new String(chars, beg, hexLen);
}
// gets string attribute value: *( stringchar / pair )
private String escapedAV() throws IOException {
beg = pos;
end = pos;
while (true) {
if (pos >= length) {
// the end of DN has been found
return new String(chars, beg, end - beg);
}
switch (chars[pos]) {
case '+':
case ',':
case ';':
// separator char has beed found
return new String(chars, beg, end - beg);
case '\\':
// escaped char
chars[end++] = getEscaped();
pos++;
break;
case ' ':
// need to figure out whether space defines
// the end of attribute value or not
cur = end;
pos++;
chars[end++] = ' ';
for (; pos < length && chars[pos] == ' '; pos++) {
chars[end++] = ' ';
}
if (pos == length || chars[pos] == ',' || chars[pos] == '+'
|| chars[pos] == ';') {
// separator char or the end of DN has beed found
return new String(chars, beg, cur - beg);
}
break;
default:
chars[end++] = chars[pos];
pos++;
}
}
}
// returns escaped char
private char getEscaped() throws IOException {
pos++;
if (pos == length) {
throw new IOException(ERROR_PARSE_ERROR);
}
switch (chars[pos]) {
case '"':
case '\\':
case ',':
case '=':
case '+':
case '<':
case '>':
case '#':
case ';':
case ' ':
case '*':
case '%':
case '_':
//FIXME: escaping is allowed only for leading or trailing space char
return chars[pos];
default:
// RFC doesn't explicitly say that escaped hex pair is
// interpreted as UTF-8 char. It only contains an example of such DN.
return getUTF8();
}
}
// decodes UTF-8 char
// see http://www.unicode.org for UTF-8 bit distribution table
private char getUTF8() throws IOException {
int res = getByte(pos);
pos++; //FIXME tmp
if (res < 128) { // one byte: 0-7F
return (char) res;
} else if (res >= 192 && res <= 247) {
int count;
if (res <= 223) { // two bytes: C0-DF
count = 1;
res = res & 0x1F;
} else if (res <= 239) { // three bytes: E0-EF
count = 2;
res = res & 0x0F;
} else { // four bytes: F0-F7
count = 3;
res = res & 0x07;
}
int b;
for (int i = 0; i < count; i++) {
pos++;
if (pos == length || chars[pos] != '\\') {
return 0x3F; //FIXME failed to decode UTF-8 char - return '?'
}
pos++;
b = getByte(pos);
pos++; //FIXME tmp
if ((b & 0xC0) != 0x80) {
return 0x3F; //FIXME failed to decode UTF-8 char - return '?'
}
res = (res << 6) + (b & 0x3F);
}
return (char) res;
} else {
return 0x3F; //FIXME failed to decode UTF-8 char - return '?'
}
}
// Returns byte representation of a char pair
// The char pair is composed of DN char in
// specified 'position' and the next char
// According to BNF syntax:
// hexchar = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
// / "a" / "b" / "c" / "d" / "e" / "f"
private int getByte(int position) throws IOException {
if ((position + 1) >= length) {
// to avoid ArrayIndexOutOfBoundsException
throw new IOException(ERROR_PARSE_ERROR);
}
int b1, b2;
b1 = chars[position];
if (b1 >= '0' && b1 <= '9') {
b1 = b1 - '0';
} else if (b1 >= 'a' && b1 <= 'f') {
b1 = b1 - 87; // 87 = 'a' - 10
} else if (b1 >= 'A' && b1 <= 'F') {
b1 = b1 - 55; // 55 = 'A' - 10
} else {
throw new IOException(ERROR_PARSE_ERROR);
}
b2 = chars[position + 1];
if (b2 >= '0' && b2 <= '9') {
b2 = b2 - '0';
} else if (b2 >= 'a' && b2 <= 'f') {
b2 = b2 - 87; // 87 = 'a' - 10
} else if (b2 >= 'A' && b2 <= 'F') {
b2 = b2 - 55; // 55 = 'A' - 10
} else {
throw new IOException(ERROR_PARSE_ERROR);
}
return (b1 << 4) + b2;
}
/**
* Parses the DN and returns the attribute value for an attribute type.
*
* @param attributeType attribute type to look for (e.g. "ca")
* @return value of the attribute that first found, or null if none found
*/
public String find(String attributeType) {
try {
// Initialize internal state.
pos = 0;
beg = 0;
end = 0;
cur = 0;
chars = dn.toCharArray();
String attType = nextAT();
if (attType == null) {
return null;
}
while (true) {
String attValue = "";
if (pos == length) {
return null;
}
switch (chars[pos]) {
case '"':
attValue = quotedAV();
break;
case '#':
attValue = hexAV();
break;
case '+':
case ',':
case ';': // compatibility with RFC 1779: semicolon can separate RDNs
//empty attribute value
break;
default:
attValue = escapedAV();
}
if (attributeType.equalsIgnoreCase(attType)) {
return attValue;
}
if (pos >= length) {
return null;
}
if (chars[pos] == ',' || chars[pos] == ';') {
} else if (chars[pos] != '+') {
throw new IOException(ERROR_PARSE_ERROR);
}
pos++;
attType = nextAT();
if (attType == null) {
throw new IOException(ERROR_PARSE_ERROR);
}
}
} catch (IOException e) {
// Parse error shouldn't happen, because we only handle DNs that
// X500Principal.getName() returns, which shouldn't be malformed.
Log.e(TAG, "Failed to parse DN: " + dn);
return null;
}
}
}
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