Re: [PATCH v4 1/8] http: read HTTP WWW-Authenticate response headers

> 
> On Mon, Dec 12 2022, Matthew John Cheetham via GitGitGadget wrote:
> 
>> From: Matthew John Cheetham <mjcheetham@outlook.com>
>> [...]
>>  /* Initialize a credential structure, setting all fields to empty. */
>> diff --git a/http.c b/http.c
>> index 8a5ba3f4776..c4e9cd73e14 100644
>> --- a/http.c
>> +++ b/http.c
>> @@ -183,6 +183,82 @@ size_t fwrite_buffer(char *ptr, size_t eltsize, size_t nmemb, void *buffer_)
>>  	return nmemb;
>>  }
>>  
>> +static size_t fwrite_wwwauth(char *ptr, size_t eltsize, size_t nmemb, void *p)
>> +{
>> +	size_t size = eltsize * nmemb;
> 
> Just out of general paranoia: use st_mult() here, not "*" (checks for
> overflows)?

>> +	struct strvec *values = &http_auth.wwwauth_headers;
>> +	struct strbuf buf = STRBUF_INIT;
>> +	const char *val;
>> +	const char *z = NULL;
> 
> Why NULL-init the "z" here, but not the "val"? Both look like they
> should be un-init'd. We also tend to call a throw-away char pointer "p",
> not "z", but anyway (more below).... 
> 
>> +
>> +	/*
>> +	 * Header lines may not come NULL-terminated from libcurl so we must
>> +	 * limit all scans to the maximum length of the header line, or leverage
>> +	 * strbufs for all operations.
>> +	 *
>> +	 * In addition, it is possible that header values can be split over
>> +	 * multiple lines as per RFC 2616 (even though this has since been
>> +	 * deprecated in RFC 7230). A continuation header field value is
>> +	 * identified as starting with a space or horizontal tab.
>> +	 *
>> +	 * The formal definition of a header field as given in RFC 2616 is:
>> +	 *
>> +	 *   message-header = field-name ":" [ field-value ]
>> +	 *   field-name     = token
>> +	 *   field-value    = *( field-content | LWS )
>> +	 *   field-content  = <the OCTETs making up the field-value
>> +	 *                    and consisting of either *TEXT or combinations
>> +	 *                    of token, separators, and quoted-string>
>> +	 */
>> +
>> +	strbuf_add(&buf, ptr, size);
>> +
>> +	/* Strip the CRLF that should be present at the end of each field */
>> +	strbuf_trim_trailing_newline(&buf);
>> +
>> +	/* Start of a new WWW-Authenticate header */
>> +	if (skip_iprefix(buf.buf, "www-authenticate:", &val)) {
>> +		while (isspace(*val))
>> +			val++;
> 
> As we already have a "struct strbuf" here, maybe we can instead
> consistently use the strbuf functions, e.g. strbuf_ltrim() in this case.

> I haven't reviewed this in detail, maybe it's not easy or worth it
> here...
> 
>> +
>> +		strvec_push(values, val);
>> +		http_auth.header_is_last_match = 1;
>> +		goto exit;
>> +	}
>> +
>> +	/*
>> +	 * This line could be a continuation of the previously matched header
>> +	 * field. If this is the case then we should append this value to the
>> +	 * end of the previously consumed value.
>> +	 */
>> +	if (http_auth.header_is_last_match && isspace(*buf.buf)) {
>> +		const char **v = values->v + values->nr - 1;
> 
> It makes no difference to the compiler, but perhaps using []-indexing
> here is more idiomatic, for getting the nth member of this strvec?

>> +		char *append = xstrfmt("%s%.*s", *v, (int)(size - 1), ptr + 1);
>> +
>> +		free((void*)*v);
> 
> Is this reaching into the strvec & manually memory-managing it
> unavoidable, or can we use strvec_pop() etc?

>> +		*v = append;
>> +
>> +		goto exit;
>> +	}
>> +
>> +	/* This is the start of a new header we don't care about */
>> +	http_auth.header_is_last_match = 0;
>> +
>> +	/*
>> +	 * If this is a HTTP status line and not a header field, this signals
>> +	 * a different HTTP response. libcurl writes all the output of all
>> +	 * response headers of all responses, including redirects.
>> +	 * We only care about the last HTTP request response's headers so clear
>> +	 * the existing array.
>> +	 */
>> +	if (skip_iprefix(buf.buf, "http/", &z))
> 
> ...Don't you want to just skip this "z" variable altogether and use
> istarts_with() instead? All you seem to care about is whether it starts
> with it, not what the offset is.
>