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<p>Thank you Mike for the additional analysis!</p>
<p>I would like to avoid any significant modifications to the code
at this moment, as I have only limited resources to test them.</p>
<p>The last proposed patch [1] takes a conservative approach and
just increases the limit of the iterations.</p>
<p>So, this is highly unlikely to break any existing code.</p>
<p>Given that this patch was confirmed to resolve a problem in at
least one existing scenario, I'd like to go ahead with this fix
unless there are strong objections.</p>
<p>I agree that it may make sense to revisit this code and make sure
it conform to the standards and real hardware, but I think it
should be done separately from this issue.</p>
<p>Another reason to keep the fix as simple as possible is that
we're planning for backporting the fix to the earlier releases of
the JDK, so I'd rather keep it low-risk.<br>
</p>
<p>With kind regards,</p>
<p>Ivan<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2/12/20 9:43 PM, Michael StJohns
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:5bed26e1-be4e-da41-0d7a-059ca33e3deb@comcast.net">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<div class="moz-cite-prefix">Hi - <br>
</div>
<br>
<p>I needed to go take a quick look at 7816-3 to figure out what's
what.</p>
<p>Basically, this code is a bit problematic. <br>
</p>
<p>1) Since this code doesn't support extended length APDUs for
T=0, you should never have to do multiple calls to get the
responses - e.g. the max response handled here should be 256
bytes. But this is the only case in which the GetResponse code
should actually be active??? T=1 uses low level mapping of
I-Blocks rather than an APDU mapping. And looking at pcsc.c -
you've got 8192 as the maximum size for a per-call return from
SCardTransmit, and I'm not sure what SCardTransmit will do - I'm
wondering if its returning the 6Cxx error code.<br>
</p>
<p>2) The iteration count should probably be set from the Le value
in the transmitted CommandAPDU rather than set to a fixed
value. Or even better, don't use an iteration count, but simply
count down from the specified Le and stop when negative.</p>
<p>I'm very confused now. <br>
</p>
<p>What protocol is the customer using? What's the actual APDU
they're sending to get the data? (Mostly curious about Lc and Le
here).<br>
</p>
<p>If you changed the iteration loop to parse the Le field and use
that to count down received data, would that break things?<br>
</p>
<p>Mike<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2/12/2020 11:23 PM, Valerie Peng
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:3c87015d-3d01-2450-7691-42cc4f35ed26@oracle.com">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8">
<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/"
moz-do-not-send="true">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)"
moz-do-not-send="true">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/"
moz-do-not-send="true">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"
moz-do-not-send="true">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/"
moz-do-not-send="true">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>
</blockquote>
<p>l<br>
</p>
</blockquote>
<pre class="moz-signature" cols="72">--
With kind regards,
Ivan Gerasimov</pre>
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