[jboss-jira] [JBoss JIRA] (ELY-618) Dead code in DEREncoder

[Ilia Vassilev (JIRA)]

    [ https://issues.jboss.org/browse/ELY-618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13588786#comment-13588786 ] 

Ilia Vassilev commented on ELY-618:
-----------------------------------

[~fjuma] Correct me if I'm wrong, but the whole logic in DEREncoder is designed for tag numbers <= 30 (single octet). According to the spec [1],  tag numbers > 30 needs multiple octets and the implementation in {{DEREncoder.writeTag()}} method is intended to do this. Unfortunately, the logic only works on single octet tags (tag number <= 30). The good think is that all of the tags in {{ASN1.java}} are single octet and work fine with the current implementation. The public methods {{startExplicit(int number), startExplicit(int clazz, int number), encodeImplicit(int number), encodeImplicit(int clazz, int number)}} take tag number but the implementation will only work on tags <= 30. If we decide to keep the current implementation (tag number <= 30), we can remove some of the logic in {{DEREncoder.writeTag()}} method and add checks in the public methods. To implement the full spec, some redesign is needed.   

[1] https://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf (page 4)

> Dead code in DEREncoder
> -----------------------
>
>                 Key: ELY-618
>                 URL: https://issues.jboss.org/browse/ELY-618
>             Project: WildFly Elytron
>          Issue Type: Bug
>    Affects Versions: 1.1.0.Beta7
>            Reporter: Ondrej Lukas
>            Assignee: Ilia Vassilev
>              Labels: static_analysis
>
> There is an unintentional dead code in writeTag method of org.wildfly.security.asn1.DEREncoder. Variable {{tagNumber}} can be assigned to 31 as its maximal value from {{int tagNumber = tag & TAG_NUMBER_MASK;}} (because {{TAG_NUMBER_MASK = 0x1f}}) on line 576 [1] which means that condition {{if (tagNumber < 128)}} on line 582 is always true. It causes that else branch is never executed.
> [1] https://github.com/wildfly-security/wildfly-elytron/blob/4453ea40a7a617b62f039153f7ebfb903c619406/src/main/java/org/wildfly/security/asn1/DEREncoder.java#L576



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