* 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.
*
* @version 1.35
*
* @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;
/**
* 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) {
buffer = new DerInputBuffer(data);
buffer.mark(Integer.MAX_VALUE);
}
/**
* 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) {
buffer = new DerInputBuffer(data, offset, len);
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.
* @throws IOException
*/
public byte[] toByteArray() throws IOException {
return buffer.toByteArray();
}
/*
* PRIMITIVES -- these are "universal" ASN.1 simple types.
*
* INTEGER, BIT STRING, OCTET STRING, NULL
* OBJECT IDENTIFIER, SEQUENCE (OF), SET (OF)
* PrintableString, T61String, IA5String, UTCTime
*/
/**
* Get an (unsigned) integer from the input stream.
*/
public BigInt getInteger() throws IOException {
if (buffer.read() != DerValue.tag_Integer)
throw new IOException("DER input, Integer tag error");
return buffer.getUnsigned(getLength(buffer));
}
/**
* Get a bit string from the input stream. Only octet-aligned
* bitstrings (multiples of eight bits in length) are handled
* by this method.
*/
public byte[] getBitString() throws IOException {
if (buffer.read() != DerValue.tag_BitString)
throw new IOException("DER input not an bit string");
int length = getLength(buffer);
/*
* This byte affects alignment and padding (for the last byte).
* Use getUnalignedBitString() for none 8-bit aligned bit strings.
*/
if (buffer.read() != 0)
return null;
length--;
/*
* Just read the data into an aligned, padded octet buffer.
*/
byte[] retval = new byte[length];
if (buffer.read(retval) != length)
throw new IOException("short read of DER bit string");
return retval;
}
/**
* 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 = getLength(buffer) - 1;
/*
* First byte = number of excess bits in the last octet of the
* representation.
*/
int validBits = length * 8 - buffer.read();
byte[] repn = new byte[length];
if (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 = getLength(buffer);
byte[] retval = new byte[length];
if (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) {
if (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 {
int b = buffer.read();
if (b != DerValue.tag_Sequence)
throw new IOException("Sequence tag error " + b);
return readVector(startLen);
}
public void skipSequence(int startLen) throws IOException {
int b = buffer.read();
if (b != DerValue.tag_Sequence)
throw new IOException("Sequence tag error " + b);
int len = getLength(buffer);
buffer.skip(len);
}
/**
* 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 {
if (buffer.read() != 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 {
int tag = 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 {
int len = getLength(buffer);
DerInputStream newstr;
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();
}
}