Note that, like BER/1, DER streams are streams of explicitly * tagged data values. Accordingly, this programming interface does * not expose any variant of the java.io.InputStream interface, since * that kind of input stream holds untagged data values and using that * I/O model could prevent correct parsing of the DER data. * *
At this time, this class supports only a subset of the types of DER
* data encodings which are defined. That subset is sufficient for parsing
* most X.509 certificates.
*
*
* @author David Brownell
* @author Amit Kapoor
* @author Hemma Prafullchandra
*/
public class DerInputStream {
/*
* This version only supports fully buffered DER. This is easy to
* work with, though if large objects are manipulated DER becomes
* awkward to deal with. That's where BER is useful, since BER
* handles streaming data relatively well.
*/
DerInputBuffer buffer;
/** The DER tag of the value; one of the tag_ constants. */
public byte tag;
/**
* Create a DER input stream from a data buffer. The buffer is not
* copied, it is shared. Accordingly, the buffer should be treated
* as read-only.
*
* @param data the buffer from which to create the string (CONSUMED)
*/
public DerInputStream(byte[] data) throws IOException {
init(data, 0, data.length, true);
}
/**
* Create a DER input stream from part of a data buffer with
* additional arg to control whether DER checks are enforced.
* The buffer is not copied, it is shared. Accordingly, the
* buffer should be treated as read-only.
*
* @param data the buffer from which to create the string (CONSUMED)
* @param offset the first index of data which will
* be read as DER input in the new stream
* @param len how long a chunk of the buffer to use,
* starting at "offset"
* @param allowBER whether to allow constructed indefinite-length
* encoding as well as tolerate leading 0s
*/
public DerInputStream(byte[] data, int offset, int len,
boolean allowBER) throws IOException {
init(data, offset, len, allowBER);
}
/**
* Create a DER input stream from part of a data buffer.
* The buffer is not copied, it is shared. Accordingly, the
* buffer should be treated as read-only.
*
* @param data the buffer from which to create the string (CONSUMED)
* @param offset the first index of data which will
* be read as DER input in the new stream
* @param len how long a chunk of the buffer to use,
* starting at "offset"
*/
public DerInputStream(byte[] data, int offset, int len) throws IOException {
init(data, offset, len, true);
}
/*
* private helper routine
*/
private void init(byte[] data, int offset, int len, boolean allowBER) throws IOException {
if ((offset+2 > data.length) || (offset+len > data.length)) {
throw new IOException("Encoding bytes too short");
}
// check for indefinite length encoding
if (DerIndefLenConverter.isIndefinite(data[offset+1])) {
if (!allowBER) {
throw new IOException("Indefinite length BER encoding found");
} else {
byte[] inData = new byte[len];
System.arraycopy(data, offset, inData, 0, len);
DerIndefLenConverter derIn = new DerIndefLenConverter();
buffer = new DerInputBuffer(derIn.convert(inData), allowBER);
}
} else {
buffer = new DerInputBuffer(data, offset, len, allowBER);
}
buffer.mark(Integer.MAX_VALUE);
}
DerInputStream(DerInputBuffer buf) {
buffer = buf;
buffer.mark(Integer.MAX_VALUE);
}
/**
* Creates a new DER input stream from part of this input stream.
*
* @param len how long a chunk of the current input stream to use,
* starting at the current position.
* @param do_skip true if the existing data in the input stream should
* be skipped. If this value is false, the next data read
* on this stream and the newly created stream will be the
* same.
*/
public DerInputStream subStream(int len, boolean do_skip)
throws IOException {
DerInputBuffer newbuf = buffer.dup();
newbuf.truncate(len);
if (do_skip) {
buffer.skip(len);
}
return new DerInputStream(newbuf);
}
/**
* Return what has been written to this DerInputStream
* as a byte array. Useful for debugging.
*/
public byte[] toByteArray() {
return buffer.toByteArray();
}
/*
* PRIMITIVES -- these are "universal" ASN.1 simple types.
*
* INTEGER, ENUMERATED, BIT STRING, OCTET STRING, NULL
* OBJECT IDENTIFIER, SEQUENCE (OF), SET (OF)
* UTF8String, PrintableString, T61String, IA5String, UTCTime,
* GeneralizedTime, BMPString.
* Note: UniversalString not supported till encoder is available.
*/
/**
* Get an integer from the input stream as an integer.
*
* @return the integer held in this DER input stream.
*/
public int getInteger() throws IOException {
if (buffer.read() != DerValue.tag_Integer) {
throw new IOException("DER input, Integer tag error");
}
return buffer.getInteger(getDefiniteLength(buffer));
}
/**
* Get a integer from the input stream as a BigInteger object.
*
* @return the integer held in this DER input stream.
*/
public BigInteger getBigInteger() throws IOException {
if (buffer.read() != DerValue.tag_Integer) {
throw new IOException("DER input, Integer tag error");
}
return buffer.getBigInteger(getDefiniteLength(buffer), false);
}
/**
* Returns an ASN.1 INTEGER value as a positive BigInteger.
* This is just to deal with implementations that incorrectly encode
* some values as negative.
*
* @return the integer held in this DER value as a BigInteger.
*/
public BigInteger getPositiveBigInteger() throws IOException {
if (buffer.read() != DerValue.tag_Integer) {
throw new IOException("DER input, Integer tag error");
}
return buffer.getBigInteger(getDefiniteLength(buffer), true);
}
/**
* Get an enumerated from the input stream.
*
* @return the integer held in this DER input stream.
*/
public int getEnumerated() throws IOException {
if (buffer.read() != DerValue.tag_Enumerated) {
throw new IOException("DER input, Enumerated tag error");
}
return buffer.getInteger(getDefiniteLength(buffer));
}
/**
* Get a bit string from the input stream. Padded bits (if any)
* will be stripped off before the bit string is returned.
*/
public byte[] getBitString() throws IOException {
if (buffer.read() != DerValue.tag_BitString)
throw new IOException("DER input not an bit string");
return buffer.getBitString(getDefiniteLength(buffer));
}
/**
* Get a bit string from the input stream. The bit string need
* not be byte-aligned.
*/
public BitArray getUnalignedBitString() throws IOException {
if (buffer.read() != DerValue.tag_BitString) {
throw new IOException("DER input not a bit string");
}
int length = getDefiniteLength(buffer);
if (length == 0) {
return new BitArray(0);
}
/*
* First byte = number of excess bits in the last octet of the
* representation.
*/
length--;
int excessBits = buffer.read();
if (excessBits < 0) {
throw new IOException("Unused bits of bit string invalid");
}
int validBits = length*8 - excessBits;
if (validBits < 0) {
throw new IOException("Valid bits of bit string invalid");
}
byte[] repn = new byte[length];
if ((length != 0) && (buffer.read(repn) != length)) {
throw new IOException("Short read of DER bit string");
}
return new BitArray(validBits, repn);
}
/**
* Returns an ASN.1 OCTET STRING from the input stream.
*/
public byte[] getOctetString() throws IOException {
if (buffer.read() != DerValue.tag_OctetString)
throw new IOException("DER input not an octet string");
int length = getDefiniteLength(buffer);
byte[] retval = new byte[length];
if ((length != 0) && (buffer.read(retval) != length))
throw new IOException("Short read of DER octet string");
return retval;
}
/**
* Returns the asked number of bytes from the input stream.
*/
public void getBytes(byte[] val) throws IOException {
if ((val.length != 0) && (buffer.read(val) != val.length)) {
throw new IOException("Short read of DER octet string");
}
}
/**
* Reads an encoded null value from the input stream.
*/
public void getNull() throws IOException {
if (buffer.read() != DerValue.tag_Null || buffer.read() != 0)
throw new IOException("getNull, bad data");
}
/**
* Reads an X.200 style Object Identifier from the stream.
*/
public ObjectIdentifier getOID() throws IOException {
return new ObjectIdentifier(this);
}
/**
* Return a sequence of encoded entities. ASN.1 sequences are
* ordered, and they are often used, like a "struct" in C or C++,
* to group data values. They may have optional or context
* specific values.
*
* @param startLen guess about how long the sequence will be
* (used to initialize an auto-growing data structure)
* @return array of the values in the sequence
*/
public DerValue[] getSequence(int startLen) throws IOException {
tag = (byte)buffer.read();
if (tag != DerValue.tag_Sequence)
throw new IOException("Sequence tag error");
return readVector(startLen);
}
/**
* Return a set of encoded entities. ASN.1 sets are unordered,
* though DER may specify an order for some kinds of sets (such
* as the attributes in an X.500 relative distinguished name)
* to facilitate binary comparisons of encoded values.
*
* @param startLen guess about how large the set will be
* (used to initialize an auto-growing data structure)
* @return array of the values in the sequence
*/
public DerValue[] getSet(int startLen) throws IOException {
tag = (byte)buffer.read();
if (tag != DerValue.tag_Set)
throw new IOException("Set tag error");
return readVector(startLen);
}
/**
* Return a set of encoded entities. ASN.1 sets are unordered,
* though DER may specify an order for some kinds of sets (such
* as the attributes in an X.500 relative distinguished name)
* to facilitate binary comparisons of encoded values.
*
* @param startLen guess about how large the set will be
* (used to initialize an auto-growing data structure)
* @param implicit if true tag is assumed implicit.
* @return array of the values in the sequence
*/
public DerValue[] getSet(int startLen, boolean implicit)
throws IOException {
tag = (byte)buffer.read();
if (!implicit) {
if (tag != DerValue.tag_Set) {
throw new IOException("Set tag error");
}
}
return (readVector(startLen));
}
/*
* Read a "vector" of values ... set or sequence have the
* same encoding, except for the initial tag, so both use
* this same helper routine.
*/
protected DerValue[] readVector(int startLen) throws IOException {
DerInputStream newstr;
byte lenByte = (byte)buffer.read();
int len = getLength(lenByte, buffer);
if (len == -1) {
// indefinite length encoding found
int readLen = buffer.available();
int offset = 2; // for tag and length bytes
byte[] indefData = new byte[readLen + offset];
indefData[0] = tag;
indefData[1] = lenByte;
DataInputStream dis = new DataInputStream(buffer);
dis.readFully(indefData, offset, readLen);
dis.close();
DerIndefLenConverter derIn = new DerIndefLenConverter();
buffer = new DerInputBuffer(derIn.convert(indefData), buffer.allowBER);
if (tag != buffer.read())
throw new IOException("Indefinite length encoding" +
" not supported");
len = DerInputStream.getDefiniteLength(buffer);
}
if (len == 0)
// return empty array instead of null, which should be
// used only for missing optionals
return new DerValue[0];
/*
* Create a temporary stream from which to read the data,
* unless it's not really needed.
*/
if (buffer.available() == len)
newstr = this;
else
newstr = subStream(len, true);
/*
* Pull values out of the stream.
*/
Vectorreset will return here.
*/
public void mark(int value) { buffer.mark(value); }
/**
* Return to the position of the last mark
* call. A mark is implicitly set at the beginning of
* the stream when it is created.
*/
public void reset() { buffer.reset(); }
/**
* Returns the number of bytes available for reading.
* This is most useful for testing whether the stream is
* empty.
*/
public int available() { return buffer.available(); }
}