Re: [PATCH 1/1] http: don't send C or POSIX in Accept-Language

> The LANGUAGE environment variable is not specified by POSIX, but a
> variety of programs using GNU gettext accept it.  The Linux manpages
> state that it can contain a colon-separated list of locales.
> 
> However, not all locales are valid as languages.  The C and POSIX
> locales, for instance, are not languages and are not registered with
> IANA, nor are they a part of ISO 639.  In fact, "C" is too short to
> match the ABNF production for a language, which must be at least two
> characters in length.
> 
> Nonetheless, many users provide these values in the LANGUAGE environment
> variable for unknown reasons and if they do, we do not want to send a
> malformed Accept-Language header to the server.  If there are no other
> valid language tags, then send no header; otherwise, send only the valid
> tags, ignoring "C" and "POSIX" wherever they may appear, as well as any
> variants (such as the "C.UTF-8" locale found on some Linux systems).

> We do not reject all possible invalid language tags since doing so
> would require bundling a copy of the IANA database and would risk poor
> behavior in the face of uncommon languages or values that are not
> registered but meet the production for private use or other restricted
> interchange.  However, these two values are widely used in the LANGUAGE
> header, are well-known and widely used non-language locales, and have
> been seen in the wild on the server side.
> 
> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> ---
>  http.c                     |  8 ++++++++
>  t/t5541-http-push-smart.sh | 18 ++++++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/http.c b/http.c
> index d88e79fbde..a96df4fcdb 100644
> --- a/http.c
> +++ b/http.c
> @@ -2022,6 +2022,14 @@ static void write_accept_language(struct strbuf *buf)
>  			s++;
>  
>  		if (tag.len) {
> +			/*
> +			 * These are not valid languages: do not send them to
> +			 * the server.
> +			 */
> +			if (!strcmp(tag.buf, "C") || !strcmp(tag.buf, "POSIX")) {
> +				strbuf_reset(&tag);
> +				continue;
> +			}

>  			num_langs++;
>  			REALLOC_ARRAY(language_tags, num_langs);
>  			language_tags[num_langs - 1] = strbuf_detach(&tag, NULL);
> diff --git a/t/t5541-http-push-smart.sh b/t/t5541-http-push-smart.sh
> index 538b603f03..96a6833e67 100755
> --- a/t/t5541-http-push-smart.sh
> +++ b/t/t5541-http-push-smart.sh
> @@ -86,6 +86,24 @@ test_expect_success 'push to remote repository (standard) with sending Accept-La
>  	GIT_TRACE_CURL=true LANGUAGE="ko_KR.UTF-8" git push -v -v 2>err &&
>  	! grep "Expect: 100-continue" err &&
>  
> +	grep "=> Send header: Accept-Language:" err >err.language &&
> +	test_cmp exp err.language &&
> +
> +	test_commit C-is-not-a-language &&
> +	GIT_TRACE_CURL=true LANGUAGE="C" git push -v -v 2>err &&
> +
> +	! grep "=> Send header: Accept-Language:" err >err.language &&
> +	test_must_be_empty err.language &&
> +
> +	test_commit POSIX-is-not-a-language-either &&
> +	GIT_TRACE_CURL=true LANGUAGE="POSIX" git push -v -v 2>err &&
> +
> +	! grep "=> Send header: Accept-Language:" err >err.language &&
> +	test_must_be_empty err.language &&

> +
> +	test_commit ignore-C-and-POSIX-as-languages-wherever-provided &&
> +	GIT_TRACE_CURL=true LANGUAGE="C.UTF-8:ko_KR.UTF-8:POSIX" git push -v -v 2>err &&
> +
>  	grep "=> Send header: Accept-Language:" err >err.language &&
>  	test_cmp exp err.language
>  '