t, triggeringPrincipal) {
    if (!uriString) {
      return "";
    }

    // Strip leading and trailing whitespace, then try to create a
    // URI from the dropped string. If that succeeds, we're
    // dropping a URI and we need to do a security check to make
    // sure the source document can load the dropped URI.
    uriString = uriString.replace(/^\s*|\s*$/g, "");

    // Apply URI fixup so that this validation prevents bad URIs even if the
    // similar fixup is applied later, especialy fixing typos up will convert
    // non-URI to URI.
    // We don't know if the uri comes from a private context, but luckily we
    // are only using fixedURI, so there's no risk to use the wrong search
    // engine.
    let fixupFlags =
      Ci.nsIURIFixup.FIXUP_FLAG_FIX_SCHEME_TYPOS |
      Ci.nsIURIFixup.FIXUP_FLAG_ALLOW_KEYWORD_LOOKUP;
    let info = Services.uriFixup.getFixupURIInfo(uriString, fixupFlags);
    if (!info.fixedURI || info.keywordProviderName) {
      // Loading a keyword search should always be fine for all cases.
      return uriString;
    }
    let uri = info.fixedURI;

    let secMan = Services.scriptSecurityManager;
    let flags = secMan.STANDARD;
    if (disallowInherit) {
      flags |= secMan.DISALLOW_INHERIT_PRINCIPAL;
    }

    secMan.checkLoadURIWithPrincipal(triggeringPrincipal, uri, flags);

    // Once we validated, return the URI after fixup, instead of the original
    // uriString.
    return uri.spec;
  },

  _getTriggeringPrincipalFromDataTransfer(
    aDataTransfer,
    fallbackToSystemPrincipal
  ) {
    let sourceNode = aDataTransfer.mozSourceNode;
    if (
      sourceNode &&
      (sourceNode.localName !== "browser" ||
        sourceNode.namespaceURI !==
          "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul")
    ) {
      // Use sourceNode's principal only if the sourceNode is not browser.
      //
      // If sourceNode is browser, the actual triggering principal may be
      // differ than sourceNode's principal, since sourceNode's principal is
      // top level document's one and the drag may be triggered from a frame
      // with different principal.
      if (sourceNode.nodePrincipal) {
        return sourceNode.nodePrincipal;
      }
    }

    // First, fallback to mozTriggeringPrincipalURISpec that is set when the
    // drop comes from another content process.
    let principalURISpec = aDataTransfer.mozTriggeringPrincipalURISpec;
    if (!principalURISpec) {
      // Fallback to either system principal or file principal, supposing
      // the drop comes from outside of the browser, so that drops of file
      // URIs are always allowed.
      //
      // TODO: Investigate and describe the difference between them,
      //       or use only one principal. (Bug 1367038)
      if (fallbackToSystemPrincipal) {
        return Services.scriptSecurityManager.getSystemPrincipal();
      }

      principalURISpec = "file:///";
    }
    return Services.scriptSecurityManager.createContentPrincipal(
      Services.io.newURI(principalURISpec),
      {}
    );
  },

  getTriggeringPrincipal(aEvent) {
    let dataTransfer = aEvent.dataTransfer;
    return this._getTriggeringPrincipalFromDataTransfer(dataTransfer, true);
  },

  getPolicyContainer(aEvent) {
    let sourceNode = aEvent.dataTransfer.mozSourceNode;
    if (aEvent.dataTransfer.policyContainer !== null) {
      return aEvent.dataTransfer.policyContainer;
    }

    if (
      sourceNode &&
      (sourceNode.localName !== "browser" ||
        sourceNode.namespaceURI !==
          "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul")
    ) {
      // Use sourceNode's policyContainer only if the sourceNode is not browser.
      //
      // If sourceNode is browser, the actual triggering policyContainer may be differ than sourceNode's policyContainer,
      // since sourceNode's policyContainer is top level document's one and the drag may be triggered from a
      // frame with different policyContainer.
      return sourceNode.policyContainer;
    }
    return null;
  },

  canDropLink(aEvent, aAllowSameDocument) {
    if (this._eventTargetIsDisabled(aEvent)) {
      return false;
    }

    let dataTransfer = aEvent.dataTransfer;
    let types = dataTransfer.types;
    if (
      !types.includes("application/x-moz-file") &&
      !types.includes("text/x-moz-url") &&
      !types.includes("text/uri-list") &&
      !types.includes("text/x-moz-text-internal") &&
      !types.includes("text/plain")
    ) {
      return false;
    }

    if (aAllowSameDocument) {
      return true;
    }

    // If this is an external drag, allow drop.
    let sourceTopWC = dataTransfer.sourceTopWindowContext;
    if (!sourceTopWC) {
      return true;
    }

    // If drag source and drop target are in the same top window, don't allow.
    let eventWC =
      aEvent.originalTarget.ownerGlobal.browsingContext.currentWindowContext;
    if (eventWC && sourceTopWC == eventWC.topWindowContext) {
      return false;
    }

    return true;
  },

  dropLinks(aEvent, aDisallowInherit) {
    if (aEvent && this._eventTargetIsDisabled(aEvent)) {
      return [];
    }

    let dataTransfer = aEvent.dataTransfer;
    let links = this._getDropLinks(dataTransfer);
    let triggeringPrincipal = this._getTriggeringPrincipalFromDataTransfer(
      dataTransfer,
      false
    );

    for (let link of links) {
      try {
        link.url = this._validateURI(
          dataTransfer,
          link.url,
          aDisallowInherit,
          triggeringPrincipal
        );
      } catch (ex) {
        // Prevent the drop entirely if any of the links are invalid even if
        // one of them is valid.
        aEvent.stopPropagation();
        aEvent.preventDefault();
        throw ex;
      }
    }

    return links;
  },

  validateURIsForDrop(aEvent, aURIs, aDisallowInherit) {
    let dataTransfer = aEvent.dataTransfer;
    let triggeringPrincipal = this._getTriggeringPrincipalFromDataTransfer(
      dataTransfer,
      false
    );

    for (let uri of aURIs) {
      this._validateURI(
        dataTransfer,
        uri,
        aDisallowInherit,
        triggeringPrincipal
      );
    }
  },

  queryLinks(aDataTransfer) {
    return this._getDropLinks(aDataTransfer);
  },

  _eventTargetIsDisabled(aEvent) {
    let ownerDoc = aEvent.originalTarget.ownerDocument;
    if (!ownerDoc || !ownerDoc.defaultView) {
      return false;
    }

    return ownerDoc.defaultView.windowUtils.isNodeDisabledForEvents(
      aEvent.originalTarget
    );
  },
};
PK