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authorJo-Philipp Wich <jo@mein.io>2019-12-22 22:32:00 +0100
committerJo-Philipp Wich <jo@mein.io>2019-12-22 22:32:00 +0100
commit5f9ae5738372aaa3a6be2f0a278933563d3f191a (patch)
treec3ce3c43aad6d8dda52567b131031b89b9197ec3
parent6b03f9605323df23d12e3876feb466f53f8d50c4 (diff)
client: fix invalid data access through invalid content-length values
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>
-rw-r--r--client.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/client.c b/client.c
index 5913553..92f7609 100644
--- a/client.c
+++ b/client.c
@@ -346,7 +346,7 @@ static void client_parse_header(struct client *cl, char *data)
}
} 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;
}
@@ -444,7 +444,7 @@ void client_poll_post_data(struct client *cl)
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;