public static ECDSASignature decodeFromDER(byte[] bytes) {
ASN1InputStream decoder = null;
try {
decoder = new ASN1InputStream(bytes);
DLSequence seq = (DLSequence) decoder.readObject();
if (seq == null) throw new RuntimeException("Reached past end of ASN.1 stream.");
ASN1Integer r, s;
try {
r = (ASN1Integer) seq.getObjectAt(0);
s = (ASN1Integer) seq.getObjectAt(1);
} catch (ClassCastException e) {
throw new IllegalArgumentException(e);
}
// OpenSSL deviates from the DER spec by interpreting these values as unsigned, though they
// should not be
// Thus, we always use the positive versions. See: http://r6.ca/blog/20111119T211504Z.html
return new ECDSASignature(r.getPositiveValue(), s.getPositiveValue());
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
if (decoder != null)
try {
decoder.close();
} catch (IOException x) {
}
}
}
/**
* Convert an inline encoded hex string rendition of an ASN.1 object back into its corresponding
* ASN.1 object.
*
* @param str the hex encoded object
* @param off the index at which the encoding starts
* @return the decoded object
*/
protected ASN1Primitive convertHexEncoded(String str, int off) throws IOException {
str = Strings.toLowerCase(str);
byte[] data = new byte[(str.length() - off) / 2];
for (int index = 0; index != data.length; index++) {
char left = str.charAt((index * 2) + off);
char right = str.charAt((index * 2) + off + 1);
if (left < 'a') {
data[index] = (byte) ((left - '0') << 4);
} else {
data[index] = (byte) ((left - 'a' + 10) << 4);
}
if (right < 'a') {
data[index] |= (byte) (right - '0');
} else {
data[index] |= (byte) (right - 'a' + 10);
}
}
ASN1InputStream aIn = new ASN1InputStream(data);
return aIn.readObject();
}