[SECURITY ADVISORY] curl: NTLM password overflow via integer overflow

[Daniel Stenberg]

NTLM password overflow via integer overflow
===========================================

Project curl Security Advisory, September 5th 2018 -
[Permalink](https://curl.haxx.se/docs/CVE-2018-14618.html)

VULNERABILITY
-------------

libcurl contains a buffer overrun in the NTLM authentication code.

The internal function `Curl_ntlm_core_mk_nt_hash` multiplies the `length` of
the password by two (SUM) to figure out how large temporary storage area to
allocate from the heap.

The `length` value is then subsequently used to iterate over the password and
generate output into the allocated storage buffer. On systems with a 32 bit
`size_t`, the math to calculate SUM triggers an integer overflow when the
password length exceeds 2GB (2^31 bytes). This integer overflow usually causes
a very small buffer to actually get allocated instead of the intended very
huge one, making the use of that buffer end up in a heap buffer overflow.

(This bug is almost identical to
[CVE-2017-8816](https://curl.haxx.se/docs/CVE-2017-8816.html).)

We are not aware of any exploit of this flaw.

INFO
----

This bug was introduced in commit
[be285cde3f](https://github.com/curl/curl/commit/be285cde3f), April 2006.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CVE-2018-14618 to this issue.

CWE-131: Incorrect Calculation of Buffer Size

AFFECTED VERSIONS
-----------------

This issue is only present on 32 bit systems. It also requires the password
field to use more than 2GB of memory, which should be rare.

- Affected versions: libcurl 7.15.4 to and including 7.61.0
- Not affected versions: libcurl < 7.15.4 and >= 7.61.1

curl is used by many applications, but not always advertised as such.

THE SOLUTION
------------

In libcurl version 7.61.1, the integer overflow is avoided.

A [patch for
CVE-2018-14618](https://github.com/curl/curl/commit/57d299a499155d4b327e341c6024e293b0418243.patch)
is available.

RECOMMENDATIONS
---------------

We suggest you take one of the following actions immediately, in order of
preference:

A - Upgrade curl to version 7.61.1

B - Apply the patch to your version and rebuild

C - Put length restrictions on the password you can pass to libcurl

TIME LINE
---------

It was [publicly reported](https://github.com/curl/curl/issues/2756) to the
curl project on July 18, 2018. We contacted ***@openwall on August 27.

curl 7.61.1 was released on September 5 2018, coordinated with the publication
of this advisory.

CREDITS
-------

Reported by Zhaoyang Wu. Patch by Daniel Stenberg.

Thanks a lot!