send EC public key in chunks and remove buffer length check

src/xyz/wendland/javacard/pki/isoapplet/IsoApplet.java

@@ -879,12 +879,23 @@ private void sendECPublicKey(APDU apdu, ECPublicKey key) throws InvalidArguments
  short len, r;
  byte[] buf = apdu.getBuffer();
 
+ short le = apdu.setOutgoing();
+
  // Return pubkey. See ISO7816-8 table 3.
  len = (short)(7 // We have: 7 tags,
  + (key.getSize() >= LENGTH_EC_FP_512 ? 9 : 7) // 7 length fields, of which 2 are 2 byte fields when using 521 bit curves,
  + 8 * field_bytes + 4); // 4 * field_len + 2 * 2 field_len + cofactor (2 bytes) + 2 * uncompressed tag
+
  pos += UtilTLV.writeTagAndLen((short)0x7F49, len, buf, pos);
 
+ // Total size = sizeof(Start-TLV) + len = pos + len
+ short toSend = (short)(len + pos);
+ if (toSend < le) {
+ apdu.setOutgoingLength(toSend);
+ } else if (toSend > le) {
+ ISOException.throwIt(ISO7816.SW_WRONG_LENGTH);
+ }
+
  // Prime - "P"
  len = field_bytes;
  pos += UtilTLV.writeTagAndLen((short)0x81, len, buf, pos);
@@ -897,7 +908,10 @@ private void sendECPublicKey(APDU apdu, ECPublicKey key) throws InvalidArguments
  } else if (r > len) {
  throw InvalidArgumentsException.getInstance();
  }
+ // Send the data after each field to avoid buffer overflows
  pos += len;
+ apdu.sendBytes((short)0, pos);
+ pos = (short)0;
 
  // First coefficient - "A"
  len = field_bytes;
@@ -910,6 +924,8 @@ private void sendECPublicKey(APDU apdu, ECPublicKey key) throws InvalidArguments
  throw InvalidArgumentsException.getInstance();
  }
  pos += len;
+ apdu.sendBytes((short)0, pos);
+ pos = (short)0;
 
  // Second coefficient - "B"
  len = field_bytes;
@@ -922,6 +938,8 @@ private void sendECPublicKey(APDU apdu, ECPublicKey key) throws InvalidArguments
  throw InvalidArgumentsException.getInstance();
  }
  pos += len;
+ apdu.sendBytes((short)0, pos);
+ pos = (short)0;
 
  // Generator - "PB"
  len = (short)(1 + 2 * field_bytes);
@@ -934,6 +952,8 @@ private void sendECPublicKey(APDU apdu, ECPublicKey key) throws InvalidArguments
  throw InvalidArgumentsException.getInstance();
  }
  pos += len;
+ apdu.sendBytes((short)0, pos);
+ pos = (short)0;
 
  // Order - "Q"
  len = field_bytes;
@@ -946,6 +966,8 @@ private void sendECPublicKey(APDU apdu, ECPublicKey key) throws InvalidArguments
  throw InvalidArgumentsException.getInstance();
  }
  pos += len;
+ apdu.sendBytes((short)0, pos);
+ pos = (short)0;
 
  // Public key - "PP"
  len = (short)(1 + 2 * field_bytes);
@@ -964,9 +986,7 @@ private void sendECPublicKey(APDU apdu, ECPublicKey key) throws InvalidArguments
  pos += UtilTLV.writeTagAndLen((short)0x87, len, buf, pos);
  Util.setShort(buf, pos, key.getK());
  pos += 2;
-
- // buf now contains the complete public key.
- apdu.setOutgoingAndSend((short)0, pos);
+ apdu.sendBytes((short)0, pos);
  }
 
  /**

src/xyz/wendland/javacard/pki/isoapplet/UtilTLV.java

@@ -197,9 +197,6 @@ public static short writeTagAndLen(short tag, short len, byte[] out, short outOf
  if(len < 0) {
  throw InvalidArgumentsException.getInstance();
  }
- if((short)(tagLen + getLengthFieldLength(len)) > (short)(outLen - outOffset)) {
- throw NotEnoughSpaceException.getInstance();
- }
 
  if(tagLen == 1) {
  out[pos] = (byte)(tag & (short)0x00FF);