Fallback to HTTP when an upgraded site sees 404 etc

[arthuredelstein]

As an improvement to #27141, can we detect when a site that has been upgraded to HTTPS from HTTP shows a top-level error code such as 404? In that case, we should fall back to HTTP again.

For QA testing:

We will direct the browser to visit a non-existent page over HTTP. The browser will attempt HTTPS behind the scenes, and when it gets a 404 code, it should automatically fall back to HTTP.

1. Enter http://upgradable.arthuredelstein.net/nonexistent.html in the address bar (or click on the link).
2. Here are two possible results:

• PASS: Final page shows a 404 error and uses http:// in the address bar.
• FAIL: Final page shows a 404 error and uses https:// in the address bar.

(This change landed in 1.52.60)

[pes10k]

cc @goodov @iefremov @bridiver we might need your help or guidance in how to do this in a chromium-friendly way

[goodov]

I think in most cases the connection will just fail. We can detect this by expecting an error page (in a throttle?), check if the http->https change was made by us and reverse it.

We can also add some info/button to the error page to return to http if a user wants this explicitly, i.e. not do this automatically.

[kjozwiak]

The above requires 1.51.107 or higher for 1.51.x verification 👍

[stephendonner]

Verified PASSED using

Brave	1.51.107 Chromium: 113.0.5672.63 (Official Build) (x86_64)
Revision	0e1a4471d5ae5bf128b1bd8f4d627c8cbd55f70c-refs/branch-heads/5672@{#912}
OS	macOS Version 13.4 (Build 22F5049e)

Steps:

1. installed 1.51.107
2. launched Brave
3. loaded http://upgradable.arthuredelstein.net/nonexistent.html
4. clicked on the Shields icon to note the settings
5. confirmed I got an HTTP 404 error
6. confirmed I remained on http://upgradable.arthuredelstein.net/nonexistent.html
7. clicked to toggle Upgrade connections to HTTPS to Only connect with HTTPS
8. confirmed I remained on http://upgradable.arthuredelstein.net/nonexistent.html
9. confirmed Continue to site and Go back buttons, which worked

example	example	example	example

---

Verification PASSED on

Brave | 1.51.107 Chromium: 113.0.5672.63 (Official Build) (64-bit)
-- | --
Revision | 0e1a4471d5ae5bf128b1bd8f4d627c8cbd55f70c-refs/branch-heads/5672@{#912}
OS | Windows 10 Version 21H2 (Build 19044.2846)

Steps:

1. installed 1.51.107
2. launched Brave
3. loaded http://upgradable.arthuredelstein.net/nonexistent.html
4. clicked on the Shields icon to note the settings
5. confirmed I got an HTTP 404 error
6. confirmed I remained on http://upgradable.arthuredelstein.net/nonexistent.html
7. clicked to toggle Upgrade connections to HTTPS to Only connect with HTTPS
8. confirmed I remained on http://upgradable.arthuredelstein.net/nonexistent.html
9. confirmed Continue to site and Go back buttons, which worked

example	example	example	example

---

Verification passed on

Brave	1.51.107 Chromium: 113.0.5672.63 (Official Build) (64-bit)
Revision	0e1a4471d5ae5bf128b1bd8f4d627c8cbd55f70c-refs/branch-heads/5672@{#912}
OS	Ubuntu 18.04 LTS

[kjozwiak]

Verification PASSED on Pixel 6 running Android 14 using the following build(s):

Brave | 1.51.107 Chromium: 113.0.5672.63 (Official Build) (32-bit)
--- | ---
Revision | 0e1a4471d5ae5bf128b1bd8f4d627c8cbd55f70c-refs/branch-heads/5672@{#912}
OS | Android 13; Build/UPB1.230309.014; 33; UpsideDownCake

Went through the STR/Cases outlined via #28013 (comment) and ensured everything was working as expected:

• ensured that loading http://upgradable.arthuredelstein.net/nonexistent.html falls back to HTTP:// due to the 404

Example	Example	Example	Example	Example

---

Verification PASSED on Samsung Galaxy Tab S8 Ultra running Android 13 using the following build(s):

Brave | 1.51.107 Chromium: 113.0.5672.63 (Official Build) (32-bit)
--- | ---
Revision | 0e1a4471d5ae5bf128b1bd8f4d627c8cbd55f70c-refs/branch-heads/5672@{#912}
OS | Android 13; Build/TP1A.220624.014; 33; REL

Went through the STR/Cases outlined via #28013 (comment) and ensured everything was working as expected:

• ensured that loading http://upgradable.arthuredelstein.net/nonexistent.html falls back to HTTP:// due to the 404

Example	Example	Example	Example	Example