Merge #676: Posts: CVE-2017-18350 disclosure

8664825 Posts: CVE-2017-18350 disclosure (Luke Dashjr)

Pull request description:

  Not sure if this warrants a bitcoincore.org post or not...

ACKs for top commit:
  harding:
    Tested ACK 8664825 .  Thanks!

Tree-SHA512: 6190e293a39e80557bcf4cf10c4212a052ca6628a6143dc8ce7a48abc02c1b03f5879f282fddbac012151e09a8f00c4757fdfb3b58b02dade884fcf82d512637

Author: harding

_posts/en/posts/2019-11-08-CVE-2017-18350.md

@@ -0,0 +1,55 @@
+---
+title: CVE-2017-18350 Disclosure
+name: cve-2017-18350-disclosure
+id: en-2017-18350-disclosure
+lang: en
+type: posts
+layout: post
+
+## If this is a new post, reset this counter to 1.
+version: 1
+
+## Only true if release announcement or security annoucement.  English posts only
+announcement: 1
+
+excerpt: >
+  Disclosure of the details of CVE-2017-18350, a fix for which was
+  released on November 6th, 2017 in Bitcoin Core version 0.15.1.
+---
+{{page.excerpt}}
+
+Technical Details
+==========
+CVE-2017-18350 is a buffer overflow vulnerability which allows a malicious SOCKS proxy server to overwrite the program stack on systems with a signed `char` type (including common 32-bit and 64-bit x86 PCs).
+
+The vulnerability was introduced in [60a87bce873 (SOCKS5 support)](https://github.com/bitcoin/bitcoin/commit/60a87bce873ce1f76a80b7b8546e83a0cd4e07a5) and first released in Bitcoin Core v0.7.0rc1 in 2012 Aug 27. A fix was hidden in [d90a00eabed ("Improve and document SOCKS code")](https://github.com/bitcoin/bitcoin/commit/d90a00eabed0f3f1acea4834ad489484d0012372) released in v0.15.1, 2017 Nov 6.
+
+To be vulnerable, the node must be configured to use such a malicious proxy in the first place. Note that using *any* proxy over an insecure network (such as the Internet) is potentially a vulnerability since the connection could be intercepted for such a purpose.
+
+Upon a connection request from the node, the malicious proxy would respond with an acknowledgement of a different target domain name than the one requested. Normally this acknowledgement is entirely ignored, but if the length uses the high bit (ie, a length 128-255 inclusive), it will be interpreted by vulnerable versions as a negative number instead. When the negative number is passed to the recv() system call to read the domain name, it is converted back to an unsigned/positive number, but at a much wider size (typically 32-bit), resulting in an effectively infinite read into and beyond the 256-byte dummy stack buffer.
+
+To fix this vulnerability, the dummy buffer was changed to an explicitly unsigned data type, avoiding the conversion to/from a negative number.
+
+Attribution
+===========
+Credit goes to [practicalswift](https://twitter.com/practicalswift) for discovering and providing the initial fix for the vulnerability, and Wladimir J. van der Laan for a disguised version of the fix as well as general cleanup to the at-risk code.
+
+Timeline
+========
+
+- 2012-04-01: Vulnerability introduced in PR #1141.
+- 2012-05-08: Vulnerability merged to master git repository.
+- 2012-08-27: Vulnerability published in v0.7.0rc1.
+- 2012-09-17: Vulnerability released in v0.7.0.
+- ...
+- 2017-09-21: practicalswift discloses vulnerability to security team.
+- 2017-09-23: Wladimir opens PR #11397 to quietly fix vulnerability.
+- 2017-09-27: Fix merged to master git repository.
+- 2017-10-18: Fix merged to 0.15 git repository.
+- 2017-11-04: Fix published in v0.15.1rc1.
+- 2017-11-09: Fix released in v0.15.1.
+- ...
+- 2019-06-22: Vulnerability existence disclosed to bitcoin-dev ML.
+- 2019-11-08: Vulnerability details disclosure to bitcoin-dev ML.
+
+{% include references.md %}