Bug 1912129: Reduce time precision for EXSLT date time function. r=timhuang

lineno = "176"

["browser_exslt_timezone_load.js"]

["browser_exslt_time_precision.js"]

/**

 * Bug 1912129 - A test case for verifying EXSLT date will report second-precise

 *               time fingerprinting resistance is enabled.

 */

function getTime(tab) {

  const extractTime = function () {

    const xslText = `

    <xsl:stylesheet version="1.0"

                    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"

                    xmlns:date="http://exslt.org/dates-and-times"

                    extension-element-prefixes="date">

      <xsl:output method="text" />

      <xsl:template match="/">

        <xsl:value-of select="date:date-time()" />

      </xsl:template>

    </xsl:stylesheet>`;

    const parser = new DOMParser();

    const xsltProcessor = new XSLTProcessor();

    const xslStylesheet = parser.parseFromString(xslText, "application/xml");

    xsltProcessor.importStylesheet(xslStylesheet);

    const xmlDoc = parser.parseFromString("<test />", "application/xml");

    const styledDoc = xsltProcessor.transformToDocument(xmlDoc);

    const time = styledDoc.firstChild.textContent;

    return time;

  };

  const extractTimeExpr = `(${extractTime.toString()})();`;

  return SpecialPowers.spawn(

    tab.linkedBrowser,

    [extractTimeExpr],

    async funccode => content.eval(funccode)

  );

}

add_task(async function test_new_window() {

  await SpecialPowers.pushPrefEnv({

    set: [

      ["privacy.fingerprintingProtection", true],

      ["privacy.fingerprintingProtection.overrides", "+ReduceTimerPrecision"],

    ],

  });

  // Open a tab for extracting the time from XSLT.

  const tab = await BrowserTestUtils.openNewForegroundTab({

    gBrowser,

    opening: TEST_PATH + "file_dummy.html",

    forceNewProcess: true,

  });

  for (let i = 0; i < 10; i++) {

    // eslint-disable-next-line mozilla/no-arbitrary-setTimeout

    await new Promise(res => setTimeout(res, 25));

    // The regex could be a lot shorter (e.g. /\.(\d{3})/) but I wrote the whole

    // thing to make sure the time is in the expected format and to allow us

    // to re-use this regex in the future if we need to.

    // Note: Date format is not locale dependent.

    const regex = /\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.(\d{3})[-+]\d{2}:\d{2}/;

    const time = await getTime(tab);

    const [, milliseconds] = time.match(regex);

    is(milliseconds, "000", "Date's precision was reduced to seconds.");

  }

  BrowserTestUtils.removeTab(tab);

  await SpecialPowers.popPrefEnv();

});

      Document* sourceDoc = getSourceDocument(aContext);

      NS_ENSURE_STATE(sourceDoc);

      PR_ExplodeTime(

          PR_Now(),

      PRTimeParamFn timezone =

          sourceDoc->ShouldResistFingerprinting(RFPTarget::JSDateTimeUTC)

              ? PR_GMTParameters

              : PR_LocalTimeParameters,

          &prtime);

              : PR_LocalTimeParameters;

      PRTime time =

          sourceDoc->ShouldResistFingerprinting(RFPTarget::ReduceTimerPrecision)

              ? (PRTime)nsRFPService::ReduceTimePrecisionAsSecs(

                    (double)PR_Now() / PR_USEC_PER_SEC, 0,

                    RTPCallerType::ResistFingerprinting) *

                    PR_USEC_PER_SEC

              : PR_Now();

      PR_ExplodeTime(time, timezone, &prtime);

      int32_t offset =

          (prtime.tm_params.tp_gmt_offset + prtime.tm_params.tp_dst_offset) /