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https://issues.apache.org/jira/browse/WW-5705?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lukasz Lenart resolved WW-5705.
-------------------------------
Resolution: Fixed
> StringIndexOutOfBoundsException authorizing a parameter name that begins with
> a nesting character
> -------------------------------------------------------------------------------------------------
>
> Key: WW-5705
> URL: https://issues.apache.org/jira/browse/WW-5705
> Project: Struts 2
> Issue Type: Bug
> Affects Versions: 7.2.1, 7.3.0
> Reporter: Lukasz Lenart
> Priority: Major
> Fix For: 7.4.0
>
>
> {{StrutsParameterAuthorizer#isAuthorized}} derives the root property of a
> parameter name by cutting at the first nesting character ({{.}}, {{[}} or
> {{(}}), then lower-cases its first character:
> {code:java}int nestingIndex = indexOfAny(parameterName, NESTING_CHARS_STR);
> String rootProperty = nestingIndex == -1 ? parameterName :
> parameterName.substring(0, nestingIndex);
> String normalisedRootProperty = Character.toLowerCase(rootProperty.charAt(0))
> + rootProperty.substring(1);
> {code}
> When the name _begins_ with a nesting character, {{nestingIndex}} is 0,
> {{substring(0, 0)}} yields an empty string, and {{charAt(0)}} throws
> {{StringIndexOutOfBoundsException}}. The exception escapes the interceptor.
> h2. Reachability
> * {{ParametersInterceptor}} is *not* affected: {{isAcceptableName()}} applies
> {{ACCEPTED_PATTERNS}}, which requires a leading word character, before
> authorization.
> * The JSON plugin *is*: {{JSONInterceptor}} authorizes at
> {{isAcceptableNode()}}, whereas the accepted-pattern check runs later, in
> {{isAcceptableLeafName()}}, and only for leaf keys.
> * The REST plugin's {{ContentTypeInterceptor}} authorizes body-derived paths
> with no accepted- or excluded-pattern check beforehand.
> Reproduced with the container's own {{StrutsParameterAuthorizer}}, under the
> shipped default {{struts.parameters.requireAnnotations=true}}, with a JSON
> body whose root key is {{.foo}} - the exception escapes
> {{JSONInterceptor.intercept()}}.
> h2. Affected versions
> The expression dates from WW-5352 (6.4.0), but nothing reached it with such a
> name until WW-5624 wired the JSON and REST body channels through the
> authorizer in 7.2.0.
> 6.x is not affected: {{requireAnnotations}} has no default there, there is no
> {{ParameterAuthorizer}} at all, and {{ParametersInterceptor}} - its only
> caller - filters names through the accepted patterns first.
> h2. Impact
> A failed request. No authorization bypass, no amplification, nothing persists
> beyond the single request. Triaged as an ordinary robustness bug rather than
> a vulnerability.
> h2. Fix
> A name beginning with a nesting character names no root property, so
> authorization rejects it before normalisation rather than computing one.
> The change is already included in the WW-5698 pull request
> https://github.com/apache/struts/pull/1872 (commit {{2f3ce9601}}), since that
> PR routes ModelDriven parameters through the same expression. It can be split
> into its own PR if the release notes should attribute it separately.
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