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esp_http_server : Bugfix in parsing of empty header values

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This MR is intended to fix incorrect parsing of HTTP requests when empty header values are present.

The issue is was due to asymmetric behavior of `http_parser` library, which in case of:

    non-empty header values : invokes callbacks with the pointer to the start of a value
    empty header values : invokes callbacks with pointer to the start of next header or section

Since HTTP server relies on this pointer (along with length of the value) to locate the end of a value, and replace the line terminators (CRLFs) with null characters, the second case needed to be handled correctly.

Closes IDFGH-1539

Closes https://github.com/espressif/esp-idf/issues/3803
This commit is contained in:
Chinmay
2019-09-09 12:05:40 +05:30
committed by bot
parent 9f3f7009c0
commit 38b1c93764
4 changed files with 160 additions and 2 deletions
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17
components/esp_http_server/src/httpd_parse.c
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@@ -267,6 +267,23 @@ static esp_err_t cb_header_value(http_parser *parser, const char *at, size_t len
parser_data->last.at = at;
parser_data->last.length = 0;
parser_data->status = PARSING_HDR_VALUE;
if (length == 0) {
/* As per behavior of http_parser, when length > 0,
* `at` points to the start of CRLF. But, in the
* case when header value is empty (zero length),
* then `at` points to the position right after
* the CRLF. Since for our purpose we need `last.at`
* to point to exactly where the CRLF starts, it
* needs to be adjusted by the right offset */
char *at_adj = (char *)parser_data->last.at;
/* Find the end of header field string */
while (*(--at_adj) != ':');
/* Now skip leading spaces' */
while (*(++at_adj) == ' ');
/* Now we are at the right position */
parser_data->last.at = at_adj;
}
} else if (parser_data->status != PARSING_HDR_VALUE) {
ESP_LOGE(TAG, LOG_FMT("unexpected state transition"));
parser_data->error = HTTPD_500_INTERNAL_SERVER_ERROR;