Re: RFR: 8255739: x509Certificate returns � for invalid subjectAlternativeNames

[Michael StJohns]

On 1/18/2022 4:10 PM, Sean Mullan wrote:
> On Thu, 6 Jan 2022 20:28:22 GMT, Sean Mullan<mullan at openjdk.org>  wrote:
>
>>> Could you please review the JDK-8255739 bug fix?
>>>
>>> I think sun.security.x509.SubjectAlternativeNameExtension() should throw an exception for incorrect SubjectAlternativeNames instead of returning the substituted characters, which is explained in the description of BugDB.
>>>
>>> I modified DerValue.readStringInternal() not to read incorrect SubjectAlternativeNames and throw an IOException. sun.security.x509.X509CertInfo.parse() catch the IOExcepton and ignore it if SAN is a non-ciritical extension like the behavior of the IOException in readStringInternal(). So I added a test with -Djava.security.debug=x509 to confirm that.
>> I understand the reasons for making the code more robust and detecting invalid DER encodings, but this may have a non-trivial compatibility risk. In general, I think detecting invalid encodings is generally the right thing to do, but compatibility needs to be considered. Sometimes other implementations have encoding bugs that we need to workaround, etc. This change affects not only certificates but other security components that use DER in the JDK. Certificates already treat non-critical extensions that are badly encoded as not a failure, so there is some compatibility built-in already. But I think it makes sense to look at other code that calls into the DerValue methods and evaluate the potential compatibility risk. At a minimum, a CSR must be filed. As a compromise, it may make sense to (at least initially) reduce the compatibility risk by allowing the caller (ex: `sun.security.x509.DNSName`) to decide if it wants a stricter parsing of the DER-encoded string.
>>
>> I would like @wangweij or @valeriepeng to also review this.
>>
>> With respect to the test, it seems like overkill to launch a java process inside the test to run each test. Instead, I would just have separate methods for each test and run them in the same process as the main test.
>> @seanjmullan @wangweij I have commented on what you pointed out, so could you please reply?
> I need another couple of days to look at this issue again before I can reply.
>
> -------------
>
> PR:https://git.openjdk.java.net/jdk/pull/6928

Hi -

Bouncycastle started enforcing properly encoded  INTEGERs a while back 
and that caused one of my programs to start failing due to a TPM X509 
endorsement certificate just having the TPM serial number stuffed into 
the certificate serial number without normalizing it to the appropriate 
INTEGER encoding.  BC provided a work around (setting 
"org.bouncycastle.asn1.allow_unsafe_integer") which gave me time to 
re-code around the problem.  If you're going to break things, it may be 
useful to provide a work around similar to what they did.

In any event, DerValue.java uses "new String(byteArrayValue, 
charsetType)" to produce the various String values including in 
getIA5String().  I.e.,

> public String(byte[] bytes,
>                Charset  charset)
> Constructs a new |String| by decoding the specified array of bytes 
> using the specified charset. The length of the new |String| is a 
> function of the charset, and hence may not be equal to the length of 
> the byte array.
>
> _*This method always replaces malformed-input and unmappable-character 
> sequences with this charset's default replacement string.*_ The 
> |CharsetDecoder| class should be used when more control over the 
> decoding process is required.
>
Perhaps it might make sense to update the various places where this is 
used in DerValue to CharsetDecoder and to use 
charsetDecoder.onMalformedInput() and 
charsetDecoder.onUnmappableCharacter() to set the appropriate action 
related to parsing the byte array into a String of a given charset?  
That action could be set based on the presence of the bypass property.

I don't think the change as proposed is backward-compatible safe enough, 
nor does it really address the general issue of poorly encoded DER 
String values in a certificate.

Mike

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