An invalid data access can be triggered with an HTTP POST request to a CGI
script specifying both `Transfer-Encoding: chunked` and a large negative
`Content-Length`.
The negative content length is assigned to `r->content_length` in
`client_parse_header` and passed as a negative read length to
`ustream_consume` in `client_poll_post_data` which will set the internal
ustream buffer pointer to an invalid address, causing out of bounds memory
reads later on in the code flow.
A similar implicit unsigned to signed conversion happens when parsing
chunk sizes emitted by a CGI program.
Address these issues by rejecting negative values in `r->content_length`
after assigning the `strtoul()` result.
Reported-by: Jan-Niklas Sohn <jan-niklas.sohn@gmx.de>
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
}
} else if (!strcmp(data, "content-length")) {
r->content_length = strtoul(val, &err, 0);
- if (err && *err) {
+ if ((err && *err) || r->content_length < 0) {
uh_header_error(cl, 400, "Bad Request");
return;
}
ustream_consume(cl->us, sep + 2 - buf);
/* invalid chunk length */
- if (sep && *sep) {
+ if ((sep && *sep) || r->content_length < 0) {
r->content_length = 0;
r->transfer_chunked = 0;
break;