Header Content is split on Comma

[DavZim]

All header values are split on comma.
This breaks for example the If-Modified-Since functionality of ETags as it uses the (ugly but sadly standard) "Tue, 15 Mar 2022 10:27:07 GMT" format.

According to this not all headers should be split on comma.

This is not present when RestRserve::Request and app$process_request(req) is used for some reasons.

Is this intended or a bug/not-yet-implemented-feature?

If confirmed, I am happy to help.

Replication

Replicate the issue with the following:

library(RestRserve)

print_headers = Middleware$new( 
  process_request = function(.req, .res) print(.req$headers),
  process_response = function(.req, .res) {},
  id = "print_headers"
)
app = Application$new()
app$append_middleware(print_headers)
app$add_get("/foo", FUN = function(.req, .res) .res$body = 42)

# Test using RestRserve::Request works
req = Request$new(
  path = "/static/example-text-file",
  method = "GET",
  headers = list("If-Modified-Since" = "Tue, 15 Mar 2022 10:27:07 GMT")
)

# the header is not split on the comma! We get one date - CORRECT!
rs = app$process_request(req)
#> $`if-modified-since`
#> [1] "Tue, 15 Mar 2022 10:27:07 GMT"

# start the server
backend = BackendRserve$new()
backend$start(app, http_port = 8080)

Now we can see the issue either by using curl:

curl http://localhost:8080/foo -H "If-Modified-Since: Tue, 15 Mar 2022 10:27:07 GMT"

which results in

#> $`if-modified-since`
#> [1] "Tue"                      "15 Mar 2022 10:27:07 GMT"

Note that providing the header as "If-Modified-Since: \"Tue, 15 ...\"" does not change the outcome.

or by using httr:

httr::GET("http://localhost:8080/foo",
          httr::add_headers("If-Modified-Since" = "Tue, 15 Mar 2022 10:27:07 GMT"))

which also results in

#> $`if-modified-since`
#> [1] "Tue"                      "15 Mar 2022 10:27:07 GMT"

[dselivanov]

wild wild http =) Yes, seems not all http headers should be split on comma. Would be great if you could investigate.

[artemklevtsov]

Is there any RFC where this is clearly described?
We can skip split headers by default as made in some other frameworks. Otherwise we should support whitelist of the header names.

[DavZim]

I will have a look at it.

Do you know why the RestRserve::Request is handled differently than the curl request?

[dselivanov]

Not sure - need to see source code

[artemklevtsov]

Here:
https://github.com/rexyai/RestRserve/blob/master/src/parse_headers.cpp#L36-L42

[DavZim]

A quick note on why the two (BackendRserve$new()... vs Application$process_request) handle the headers differently (for the moment I am looking at the way middleware handles the headers in process_request) from what I understand at the moment:

• Application does not call the function cpp_parse_headers around here
• The cpp_parse_headers function is called in BackendRserve here

This makes it hard to test as I don't know of a way to test the library with BackendRserve, therefore the error is not possible to trigger in the test environment.

Regardless, I will work on making the cpp_parse_headers code dependent on header names.