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Fix path_info_len underflow in manage-script-name with trailing-slash mountpoints #2774

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Fix path_info_len underflow in manage-script-name with trailing-slash mountpoints #2774

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14 changes: 12 additions & 2 deletions core/protocol.c
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Original file line number Diff line number Diff line change
Expand Up @@ -793,8 +793,18 @@ int uwsgi_parse_vars(struct wsgi_request *wsgi_req) {
best_found = mountpoint_len;
wsgi_req->script_name = uwsgi_apps[i].mountpoint;
wsgi_req->script_name_len = uwsgi_apps[i].mountpoint_len;
wsgi_req->path_info = orig_path_info + wsgi_req->script_name_len;
wsgi_req->path_info_len = orig_path_info_len - wsgi_req->script_name_len;
/* When the request path equals the mountpoint without its
* trailing slash (e.g. GET /footris against /footris/),
* orig_path_info_len < script_name_len. Guard against the
* uint16_t underflow that would otherwise set path_info_len
* to 65535 and trigger an out-of-bounds read. */
if (orig_path_info_len >= (int)wsgi_req->script_name_len) {
wsgi_req->path_info = orig_path_info + wsgi_req->script_name_len;
wsgi_req->path_info_len = orig_path_info_len - wsgi_req->script_name_len;
} else {
wsgi_req->path_info = orig_path_info + orig_path_info_len;
wsgi_req->path_info_len = 0;
}

wsgi_req->hvec[wsgi_req->script_name_pos].iov_base = wsgi_req->script_name;
wsgi_req->hvec[wsgi_req->script_name_pos].iov_len = wsgi_req->script_name_len;
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