[#1025] - Shiro's InvalidRequestFilter blocks valid paths with encoded slashes

[haster]

fixes #1025
Adds a 3-valued enum for path-traversal-blockmode. Default is NORMAL, which only blocks actual paths. STRICT also blocks encoded slashes ('/') and periods ('.'). NO_BLOCK disables.

This enables a mode to block actual path traversal while still allowing for encoded URLs and such to be present as path parameter.

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[bdemers]

Thanks for the PR @haster! (and sorry for the delay with the response)

I can see the desire to make this more flexible, but we need to make sure we retain backwards compatibility with the current versions of Shiro.
e.g. restore the boolean getter's, (though we could deprecate it too)

I think the default value should be what you have defined as STRICT (secure by default)

Possibly enum values of ENABLED, LAX, and DISABLED? Where LAX, (or something better named), is your current NORMAL?

  /**
     * 
     * @deprecated Use {@link #getBlockTraversal()}
     */
    @Deprecated
public boolean isBlockTraversal() {
  // we could even add a log warning here 🤷
  return this.pathTraversalBlockMode != DISABLED;
}

Thoughts / suggestions? (other ideas for the term LAX)?

[ansidev]

Are there any updates on this issue?

[lprimak]

@haster what do you think about @bdemers suggestions?

[lprimak]

There are still issues with this PR that remain unresolved, and it seems the author has abandoned it.
We are happy to accept improvements to this PR or another PR to resolve the outstanding issues