Advisory #: 66
Title: Remote command injection in Ruby Gem kelredd-pruview 0.3.8
Author: Larry W. Cashdollar, @_larry0
Date: 2013-04-04
CWE: CWE-78 OS Command Injections
Download Site:
Vendor: Kelly D. Redding
Vendor Notified: 2013-04-04
Vendor Contact:
Description: A gem to ease generating image previews (thumbnails) of various files.
Remote commands can be executed if the file name contains shell meta characters. ./kelredd-pruview-0.3.0/lib/pruview/document.rb In the following code snippet, we see the user input isn't sanitized for shell metacharacters. A malicious file with special characters in the filename could be used to execute commands as the local user. 69 run_system_command("convert -format jpg \"{source}[0]\" \"{@tempfile.path}\"", "Error processing postscript document") 85 colorspace = run_system_command("identify #{GLOBAL_CMD_ARGS} -format \"%r\" #{image.path}", "Error reading document colorspace") function run_system_comand() passes user supplied input to the command line. 141 def run_system_command(command, error_message) 142 output = `{command}` 143 raise "{error_message}: error given {$?}\n{output}" if $? != 0 144 return output 145 end In kelredd-pruview-0.3.0/lib/pruview/video.rb: Also the video encoding and scaling features are vulnerable as well: 27 run("#{FLVTOOL} -U #{target}", "Unable to add meta-data for #{target}.") 51 run(build_command(@source, target, width, height, get_info(info_yml), scale_static), "Una ble to convert #{@source} to #{target}.") Run is defined as: 140 def run(command, error_message = "Unknown error.") 141 raise "Ffmpeg error: " + error_message + " - command: '#{command}'" if !system(command) 142 end User controlled data is being sent to the command line with out any shell meta charatcers being escaped. In kelredd-pruview-0.3.0/lib/pruview/video_image.rb: 13 run(build_command(source, "-ss 00:00:#{duration * 0.1}", 'mjpeg', target), "Unable to get preview image for #{target}") 30 def self.build_command(source, time_str, format, target) 31 command = %Q{#{Video::FFMPEG} -i "#{source}"} 32 command += " #{time_str}" 33 command += " -f #{format}" if !format.empty? 34 command += " -an -y #{target}" 35 end where function run() is defined as: 37 def, error_message = "Unknown error.") 38 raise "Ffmpeg error: " + error_message + " - command: '#{command}'" if !system(command) 39 end In line 38 user supplied data is passed to the command line.
Exploit Code:
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