[Cryptography Team] Debugging SSL on Linux

[Robert Withers]

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
>
> _______________________________________________
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> Cryptography at lists.squeakfoundation.org
> http://lists.squeakfoundation.org/cgi-bin/mailman/listinfo/ 
> cryptography

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