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Fix padding handling for 64 byte challenges #5

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Fix padding handling for 64 byte challenges #5

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17 changes: 17 additions & 0 deletions src/net/cooperi/ykotpapplet/YkOtpApplet.java
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Original file line number Diff line number Diff line change
Expand Up @@ -278,6 +278,23 @@ public class YkOtpApplet extends Applet implements ExtendedLength
return;
}

// Yubikey considers the last byte as padding
// if and only if the challenge size is 64 bytes
// but then also all preceding bytes of the same value
if(lc == (short)64) {
lc--;
for(i = (byte)62; i>=(byte)0; i--) {
if(buffer[(byte)apdu.getOffsetCdata() + i] != buffer[(byte)apdu.getOffsetCdata() + 63]) {
break;
}
lc--;
}
if(lc == 0) {
ISOException.throwIt(ISO7816.SW_DATA_INVALID);
return;
}
}

if (hmacSha1 == null) {
Util.arrayCopyNonAtomic(slot.ipad, (short)0,
hmacBuf, (short)0, (short)64);
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