CVE-2017-13089 wget stack smash

How it was found

The http.c:skip_short_body() function is called in some circumstances, such as when processing redirects. When the response is sent chunked in wget before 1.19.2, the chunk parser uses strtol() to read each chunk's length, but doesn't check that the chunk length is a non-negative number. The code then tries to skip the chunk in pieces of 512 bytes by using the MIN() macro, but ends up passing the negative chunk length to connect.c:fd_read(). As fd_read() takes an int argument, the high 32 bits of the chunk length are discarded, leaving fd_read() with a completely attacker controlled length argument.

Reproduction: To reproduce, use two terminals. In the first terminal: $ nc -l -p 8080 <wget-stack-smash.reply In the second terminal: $ wget http://127.0.0.1:8080/foo

Depending on how wget is compiled, this will either simply segfault or complain about the stack being smashed (on debian due to being compiled the stack protector.)

External links: https://nvd.nist.gov/vuln/detail/CVE-2017-13089 http://www.securityfocus.com/bid/101592 http://git.savannah.gnu.org/cgit/wget.git/commit/?id=d892291fb8ace4c3b734ea5125770989c215df3f http://www.securitytracker.com/id/1039661 https://www.viestintavirasto.fi/en/cybersecurity/vulnerabilities/2017/haavoittuvuus-2017-037.html