Re: [PATCH] http: parse HTTP headers case-insensitive

[Heinrich Schuchardt]

On 1/15/22 00:46, Jamo wrote:
> According to https://www.ietf.org/rfc/rfc2616.txt 4.2, header names
> shall be case insensitive and we are now forced to read headers like
> "Content-Length" capitalized.
>
> The problem with that is when a HTTP server responds with a
> "content-length" header in lowercase, GRUB gets stuck because HTTP
> module doesn't know the length of the transmission and the call never
> ends.

This seems to be v2 of the patch.

To make reviewing easier , please, consider the following for future 
submissions:

Put the version number into the subject line:

    [PATCH v2] http: parse HTTP headers case-insensitive

and add a description of the change between the patches after triple 
hyphens:

---
v2:
        typos fixed

No need to resend this time.

> ---
>   grub-core/net/http.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/grub-core/net/http.c b/grub-core/net/http.c
> index b616cf40b..d3ba8c799 100644
> --- a/grub-core/net/http.c
> +++ b/grub-core/net/http.c
> @@ -130,7 +130,7 @@ parse_line (grub_file_t file, http_data_t data, char *ptr, 
> grub_size_t len)
>         data->first_line_recv = 1;
>         return GRUB_ERR_NONE;
>       }
> -  if (grub_memcmp (ptr, "Content-Length: ", sizeof ("Content-Length: ") - 1)
> +  if (grub_strncasecmp (ptr, "Content-Length: ", sizeof ("Content-Length: ") - 
> 1)

This comparison might still be too restrictive: The RFC 2616 
specification says:

"The field value MAY be preceded by any amount of LWS (linear white 
space), though a single SP is preferred."

LWS  = [CRLF] 1*( SP | HT )

So the header might look like

"Content-length:\t  3495".

or like

"Content-length:3495".

So here you should not test for the space but only for the string 
"Content-Length:".

>         == 0 && !data->size_recv)
>       {
>         ptr += sizeof ("Content-Length: ") - 1;
> @@ -138,8 +138,8 @@ parse_line (grub_file_t file, http_data_t data, char *ptr, 
> grub_size_t len)
>         data->size_recv = 1;
>         return GRUB_ERR_NONE;
>       }
> -  if (grub_memcmp (ptr, "Transfer-Encoding: chunked",
> -                  sizeof ("Transfer-Encoding: chunked") - 1) == 0)
> +  if (grub_strncasecmp (ptr, "Transfer-Encoding: chunked",
> +                       sizeof ("Transfer-Encoding: chunked") - 1) == 0)

Here you need two comparisons and a function to skip the optional 
whitespace between the tokens. You should check that "chunked" is 
followed by LWS.

"Transfer-Encoding: chunkedMeat" should not match.
"Transfer-Encoding:chunked\t" should match.

Best regards

Heinrich

>       {
>         data->chunked = 1;
>         return GRUB_ERR_NONE;