[Mono-bugs] [Bug 487520] New: Incorrect key usage encoding in Mono.Security.X509.Extensions.KeyUsageExtension

[bugzilla_noreply at novell.com]

https://bugzilla.novell.com/show_bug.cgi?id=487520


           Summary: Incorrect key usage encoding in
                    Mono.Security.X509.Extensions.KeyUsageExtension
    Classification: Mono
           Product: Mono: Runtime
           Version: 2.2.x
          Platform: 32bit
        OS/Version: Windows Server 2003
            Status: NEW
          Severity: Normal
          Priority: P5 - None
         Component: misc
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: muncho at mail.ru
         QAContact: mono-bugs at lists.ximian.com
          Found By: ---


Created an attachment (id=281034)
 --> (https://bugzilla.novell.com/attachment.cgi?id=281034)
Bug demonstration

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.2; en-US; rv:1.9.0.7)
Gecko/2009021910 Firefox/3.0.7 (.NET CLR 3.5.30729)

The KeyUsageExtension.Encode method incorrectly counts the number of unused
bits in the key usage value.

Instead of 

byte unused = 16;
if (ku > 0) {
    // count the unused bits
    for (unused = 15; unused > 0; unused--) {
        if ((ku & 0x8000) == 0x8000)
            break;
        ku <<= 1;
    }

the code should be

byte unused = 0;
if (ku > 0) {
    // count the unused bits
    for (unused = 0; unused < 16; unused++)
    {
        if ((ku & 1) == 1)
            break;
        ku >>= 1;
    }

That conforms to the result produced by the Microsoft implementation of .NET.

The effect of the error is incorrect key usage saved in the certificate.

Reproducible: Always

Steps to Reproduce:
1. Compile and run MonoBug.cs
2.
3.
Actual Results:  
Key usage is reported to be
Digital Signature (80)


Expected Results:  
Key usage should be

Digital Signature, Key Encipherment, Data Encipherment, Key Agreement,
Certificate Signing (bc)

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