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<p>Hi, Ivan,</p>
<p><span style="left: 729.868px; top: 57.2085px; font-size: 18.4px;
font-family: sans-serif; transform: scaleX(1.00278);">I share
your thought/confusion on the current impl as </span>I am also
not familiar with <span style="left: 729.868px; top: 57.2085px;
font-size: 18.4px; font-family: sans-serif; transform:
scaleX(1.00278);">ISO/IEC 7816-4. <br>
</span></p>
<p><span style="left: 729.868px; top: 57.2085px; font-size: 18.4px;
font-family: sans-serif; transform: scaleX(1.00278);">Based on
my reading of this standard and the CardImpl code, it looks like
the while-true loop is for retrieving additional response data.
Per the standard and javadoc, max length of the response data is
65536. Given that SW2 is only one byte, it would probably only
return at most 256 byte response data at a time. Thus, the
iteration count would be at most 256.<br>
</span></p>
<span style="left: 729.868px; top: 57.2085px; font-size: 18.4px;
font-family: sans-serif; transform: scaleX(1.00278);"></span>
<p>So far we are on the same page. <br>
</p>
<p>With the latest webrev (webrev.01), it seems that the loop will
only be run 255 instead of 256 times as k is incremented before
comparison. Thus, I think we should fix the check.<br>
</p>
<p>Valerie<br>
</p>
<div class="moz-cite-prefix">On 2/11/2020 12:18 PM, Ivan Gerasimov
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:e1380ad6-c05c-9a40-8dd1-76049d3ed221@oracle.com">Hi
Valerie!
<br>
<br>
To be honest, the all these limitations are not quite clear to me.
<br>
<br>
If the command is using an extended Le word to specify the
expected length of the response data, then this length can be at
most 65536.
<br>
<br>
If a short Le was used, then the length can be at most 256.
<br>
<br>
However, if we received 0x61 in the SW1, that means that more data
bytes are available and they can be retrieved by issuing another
transmit call with a short Le. This next call can again
potentially result in 0x61 in SW1, and so on.
<br>
<br>
In the standard, I cannot see any explicit limitations on the
number of retries. So, I see it as it might be possible to
retrieve more data than 65536 bytes.
<br>
<br>
On the other hand, in the specification for CommandAPDU [1] we
have hardcoded limit for the maximum response length, which is
65536. So, even if it were possible to retrieve larger data,
there's no point to try, as the current API prohibits it.
<br>
<br>
Assuming that the 0x61 response can only be received when a short
Le is used, the maximum RESPONSE_ITERATOR should be set to 256,
and an exception should be thrown once that number is exceeded.
<br>
<br>
I've updated the webrev in-place accordingly.
<br>
<br>
[0] <a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~igerasim/8163251/01/webrev/">http://cr.openjdk.java.net/~igerasim/8163251/01/webrev/</a>
<br>
<br>
[1]
<a class="moz-txt-link-freetext" href="https://docs.oracle.com/en/java/javase/13/docs/api/java.smartcardio/javax/smartcardio/CommandAPDU.html#%3Cinit%3E(int,int,int,int,int)">https://docs.oracle.com/en/java/javase/13/docs/api/java.smartcardio/javax/smartcardio/CommandAPDU.html#%3Cinit%3E(int,int,int,int,int)</a><br>
<br>
With kind regards,
<br>
<br>
Ivan
<br>
<br>
<br>
On 2/10/20 6:40 PM, Valerie Peng wrote:
<br>
<blockquote type="cite">Hi Ivan,
<br>
<br>
You removed the "=", so the actual iteration count is reduced by
one.
<br>
<br>
Should the iteration count be 256 or 257? If the actual count
should be 257, then may be the check needs to be changed to k++
from ++k?
<br>
<br>
Valerie
<br>
<br>
On 2/10/2020 5:07 PM, Ivan Gerasimov wrote:
<br>
<blockquote type="cite">Thank you Michael!
<br>
<br>
It's a good point about maximum length.
<br>
<br>
Here's the updated webrev with the new System property dropped
and the increased number of iterations:
<br>
<br>
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~igerasim/8163251/01/webrev/">http://cr.openjdk.java.net/~igerasim/8163251/01/webrev/</a>
<br>
<br>
With kind regards,
<br>
Ivan
<br>
<br>
<br>
On 2/10/20 4:18 PM, Michael StJohns wrote:
<br>
<blockquote type="cite">On 2/10/2020 6:49 PM, Ivan Gerasimov
wrote:
<br>
<blockquote type="cite">Hello!
<br>
<br>
Current implementation of the method
javax.smartcardio.CardChannel.transmit() has an internal
limitation on the maximum allowed amount of the
transmitted data.
<br>
<br>
This limitation is dictated by the maximum number of
iterations to transmit data from a card: Each iteration
can transmit up to 256 bytes of data, and we have a
hardcoded limit of 32 iterations.
<br>
<br>
Over time, we've received requests to increase this limit,
as there are occasions when the effective limit of 8k is
not enough.
<br>
<br>
Would you please help review a proposal: First, it is
proposed to increase the default limit of iteration to 128
(so that up to 32k of data can be transmitted); Second,
the limit of iterations is made configurable via a System
property. This limit can be increased up to 4096 (so that
the total amount of transmitted data can be made up to
1m).
<br>
<br>
BUGURL: <a class="moz-txt-link-freetext" href="https://bugs.openjdk.java.net/browse/JDK-8163251">https://bugs.openjdk.java.net/browse/JDK-8163251</a>
<br>
WEBREV:
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~igerasim/8163251/00/webrev/">http://cr.openjdk.java.net/~igerasim/8163251/00/webrev/</a>
<br>
<br>
If there is an agreement on the proposal, I'll file a CSR
to document a new System property.
<br>
<br>
Thanks in advance!
<br>
<br>
</blockquote>
Given that the maximum length for an extended APDU is 64K
(65536) (hmm +7 for the header and +2 for LE), and for its
return is 64K + 2 bytes, I'm not quite sure why you'd up
the number to 4096/1M - I'd set the default and fixed value
to 257 (64K) and leave it at that.
<br>
<br>
Mike
<br>
<br>
<br>
<br>
<br>
<br>
</blockquote>
</blockquote>
</blockquote>
</blockquote>
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