[Cryptography Team] Debugging SSL on Linux
Robert Withers
reefedjib at yahoo.com
Tue Mar 20 20:42:42 UTC 2007
Ron and Norbert,
I found that SSL failed to establish a connection on the Mac, and I
suspect the same is actually true on Windows, on close inspection.
The resulting MIMEDocument has an error when evaluating the example:
> 'https://home.selfish.org' asUrl retrieveContents.
I debugged into the SSLSocket and found where the ProtocolCap was
getting killed. This occurred when processing the SSLCertificateMsg,
with a certificate chain of 2 certificates. The new code I added to
verify certificates is having a problem verifying certificate 1 with
certificate 2.
Digging a little further showed that there are 3 problems, the 2nd
and 3rd hidden by the 1st.
The 1st problem is the comparison if cert1's issuer with cert2's
subject. One part of these X509Names is a Pkcs9EmailAddress, which
is wrapping a ASN1IA5String. This class (ASN1IA5String) is missing
an #= operation, and so they are claiming they are not equal. I
fixed this.
The 2nd and 3rd problems are ASN1 encoding/decoding problems.
The 2nd problem is an issue with tag 12 being encoded as 19, the
default for a String.
the source bytes encoded with this code
| bytes |
bytes := #(160 18 12 16 104 111 109 101 46 115 101 108 102 105 115
104 46 111 114 103) asByteArray.
(ASN1Value fromAsnDer: bytes readStream) encodeAsnDer.
encode as
#(160 18 19 16 104 111 109 101 46 115 101 108 102 105 115 104 46 111
114 103)
check the third byte to see the problem. Since the TBSCertificate
are reencoded for signature checking, the ASN1 hierarchy must be able
to reencode precisely. So I added several classes for different
types of strings (ASN1PrintableString, ASN1UniversalString, and
ASN1BMPString) and updated the tag table to use them. This solves
this problem, but there are still holes in the ASN1 tag framework.
The 3rd problem is an ASN1 decoding problem with an
ASN1ExplicitContextValue class, that is embedded in a
CertificateExtension. Here is the ExplicitContextValue part, which
seems to be malformed:
| bytes ext |
bytes := #(160 30 6 8 43 6 1 5 5 7 8 5 160 18 12 16 104 111 109 101
46 115 101 108 102 105 115 104 46 111 114 103) asByteArray.
ext := (ASN1Value fromAsnDer: bytes readStream).
ext encodeAsnDer
resulting in:
a ByteArray (160 10 6 8 43 6 1 5 5 7 8 5)
Notice the 2nd byte. Now this being embedded means that the part
that dropped off is actualy captured in the certExtension, and when
he certExtension encdes itself, here is the fragment that it encodes:
a ByteArray (160 10 6 8 43 6 1 5 5 7 8 5 160 18 12 16 104 111 109
101 46 115 101 108 102 105 115 104 46 111 114 103)
The original bytes gave a length of 30, which captured 2 values and I
didn't think a ExplicitContextValue could do that. The encoded bytes
have a length of 10 which is just the first element. When it
decodes, instead of grabbing the bytes specified by length it just
decodes the next ASN1Value, the first chunk. So here is how it
breaks down:
<{160} [30] (
<{6} [8] (43 6 1 5 5 7 8 5)>
<{160} [18] (
<{12} [16] (104 111 109 101 46 115 101 108 102 105 115 104 46 111
114 103)>
)>
)>
Now, either an ExplicitContextValue can have 2 values like this, and
we need to change some code, or this is malformed. Please advise if
we can change ExplicitContextValue to handle this.
If it is malformed, then because we are re-encoding the ASN1 bytes to
do signatures, and since I added the Certificate Extensions, this is
now breaking. Either we need to save the original bytes to do
signatures with, and avoid re-encoding, or else this correctly
fails. Saving the original bytes of ASN1 is a major rewrite.
Sorry I couldn't get this site working for you right away, but we
will need to resolve this issue in the design, first.
Robert
On Mar 20, 2007, at 11:01 AM, Ron Teitelbaum wrote:
> Hello everyone,
>
>
>
> Can anyone help debugging SSL on Linux?
>
>
>
> This is from Norbert:
>
>
>
> I'm using it on linux with squeak vm 3.9-8 #5 Tue Oct 10 11:56:09
> PDT 2006 gcc 4.0.3 Squeak3.9alpha of 4 July 2005 [latest update:
> #7021] Linux ubuntu 2.6.15-27-386 #1 PREEMPT Sat Sep 16 01:51:59
> UTC 2006 i686 GNU/Linux default plugin location: /usr/local/lib/
> squeak/3.9-8/*.so and a stock 3.9 7067 image. I tried using a fresh
> copy of the image but the errors stay the same errors.
>
>
>
> I tried using the url that Norbert gave and it worked fine on Windows.
>
>
>
> 'https://home.selfish.org' asUrl retrieveContents.
>
>
>
> Could someone try this on Linux and see if they can help provide
> info as to what is going wrong. I suspect that the client hello is
> causing the server to disconnect. Maybe an Endian issue?
>
>
>
> Thanks,
>
>
> Ron Teitelbaum
> Squeak Cryptography Team Leader
>
> _______________________________________________
> Cryptography mailing list
> Cryptography at lists.squeakfoundation.org
> http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/
> cryptography
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