Firefox Accounts renders blank-ish screen if dom.storage.enabled is false

[pdehaan]

Found in https://accounts.stage.mozaws.net/ver.json (commit 310bd7d)

{
    "version": "0.25.0",
    "commit": "310bd7d9e6906dc6124cd536c33e4ee9bdd0ebc5",
    "l10n": "87cc8f9eb4",
    "tosPp": "a9ad0e4ed4"
}

---

Steps to reproduce:

1. Launch Firefox.
2. Go to about:config.
3. Search for dom.storage.enabled and set it to false.
4. Open a new tab and browse to https://accounts.stage.mozaws.net/
5. Open the Dev Tools and switch to "Console"
6. Weep uncontrollably.

---

Actual results:

Figure 1. Thats no good!

TypeError: t is null
— via 1da513a8.main.js:14

If I try and read the cryptic minimized content, I see the following (3) instances of t.:

1. t.setItem(a,JSON.stringify(c)) (/app/scripts/vendor/crosstab.js:247?)
2. var b=t.getItem(a) (/app/scripts/vendor/crosstab.js:256?)
3. t.removeItem(u.keys[a]) (/app/scripts/vendor/crosstab.js:414?)

---

Expected results:

We should check for local/session storage and possibly fail fast(er) if dom.storage is disabled.
Thankfully it looks like all the errors are coming from vendor/crosstab.js, I think elsewhere the localStorage and sessionStorage calls are wrapped in try/catch blocks.

[ckarlof]

Yeah, we detect localStorage enabled in lib/config-loader.js, but the introduction of crosstab.js introduced this regression. @shane-tomlinson, take a look? We should also add metrics to measure how often localStorage and cookies are disabled.

/cc @kparlante

[shane-tomlinson]

Search for dom.storage.enabled and set it to false.

Tinfoilers...

[shane-tomlinson]

I'm trying to think if we require access to local/sessionStorage, or if FxA will work acceptably, albeit with a slightly degraded experience, with dom.storage.enabled set to false.

If we are unable to store data, the repercussions are:

• No way to remember the user's previous session and user must sign in from scratch.
• No way to pass session information from the verification tab and the password reset tab after the user completes the password reset.

IIUC, a Sync user with dom.storage.enabled set to false should be alright, the unwrapBKey and keyFetchToken are sent to the browser upon verification and should not be stored anyways.

[shane-tomlinson]

There are multiple problems when dom.storage.enabled is set to false.

1. crosstab blows up on initialization.
2. with crosstab completely disabled, reloading /cookies_disabled shows a blank screen.

[jrgm]

Search for dom.storage.enabled and set it to false.
Tinfoilers...

This came from https://bugzilla.mozilla.org/show_bug.cgi?id=1093915#c4, with the user reporting that they had a blank screen, and indicating that they had taken no action to set it to false intentionally.

[kparlante]

Yeah, we detect localStorage enabled in lib/config-loader.js, but the introduction of crosstab.js introduced this regression. @shane-tomlinson, take a look? We should also add metrics to measure how often localStorage and cookies are disabled.

screen.cookies_disabled and error.cookies_disabled error are relatively rare, and mostly occur on iPhones. Here's a week's worth: https://kibana.fxa.us-west-2.prod.mozaws.net/#dashboard/temp/AUmgR8wzemn6F9h2haem

If I'm reading the code correctly, this screen gets shown for either localStorage or cookies disabled:

fxa-content-server/app/scripts/lib/config-loader.js

Line 64 in b380ce4

areCookiesEnabled: function (force) {

[shane-tomlinson]

If I'm reading the code correctly, this screen gets shown for either localStorage or cookies disabled:

fxa-content-server/app/scripts/lib/config-loader.js

Line 64 in b380ce4

areCookiesEnabled: function (force) {

You are correct. @ryanfeeley and I talked about creating separate messages/screens for cookies and localStorage, but we felt the average user would have almost no clue what localStorage means. My intuition says the most common cause for a disabled localStorage is disabled cookies, but we do not have metrics around that and intuition is usually wrong.

We should make the metrics report for what caused the failure more specific.