1890189 - Only lowercase directives are honored for Cache-Control header

Status: RESOLVED FIXED

(Core :: Networking: Cache, defect, P2)

Description

[mail]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:124.0) Gecko/20100101 Firefox/124.0

Steps to reproduce:

I've been developing a web application where the framework generates HTTP response headers as follows for static resources to ensure ETag is honored:

cache-control: No-Cache
last-modified: Sat, 24 Feb 2024 12:42:28 GMT
etag: "12787-1708778548"

In Chromium, the cache-control directive is honored and I can observe a request always being made to determine whether the resource is still cached or not. In Firefox however, the default heuristic caching behavior still applies and requests are not always being made. I managed to work around this by instructing the framework to use lowercase directives as follows:

cache-control: no-cache

After this change, the caching behavior in Firefox is the same as in Chromium.

This strikes me as unexpected, given the documentation on MDN at https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control:

Caching directives are case-insensitive. However, lowercase is recommended because some implementations do not recognize uppercase directives.

Actual results:

Caching directive is only honored when using a lowercase directive:

cache-control: no-cache

Expected results:

Caching directive is honored no matter the casing. Therefore, both

cache-control: no-cache

and

cache-control: No-Cache

should result in the same caching behavior, consistent with MDN documentation of directives being case-insensitive.

Comment 1

[Valentin Gosu [:valentin] (he/him)]

Thank you for the bug report.
This is definitely something we should rectify, and I think it should be easy to do so.
We need to change CacheControlParser to use custom tokens like we do here

Comment 2

[Valentin Gosu [:valentin] (he/him)]

This might actually affect performance - when we don't cache things properly.

Comment 3

[Valentin Gosu [:valentin] (he/him)]

(In reply to Valentin Gosu [:valentin] (he/him) from comment #1)

Thank you for the bug report.
This is definitely something we should rectify, and I think it should be easy to do so.
We need to change CacheControlParser to use custom tokens like we do here

Instead of using CheckWord, we need to add the custom tokens and check them like this instead.

Comment 4

[Sunil Mayya]

Attachment: Bug 1890189: Add test to verify cache-control header parising is case-insensitive. r=#necko

Comment 5

[Sunil Mayya]

Attachment: Bug 1890189: make cache control parsing case insensitive. r=#necko

Depends on D216486

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2767e60da4f2
Add test to verify cache-control header parising is case-insensitive. r=necko-reviewers,kershaw
https://hg.mozilla.org/integration/autoland/rev/ae2a7f70cc15
make cache control parsing case insensitive. r=necko-reviewers,kershaw

Comment 7

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/2767e60da4f2
https://hg.mozilla.org/mozilla-central/rev/ae2a7f70cc15